U.S. patent application number 09/887194 was filed with the patent office on 2003-02-20 for recombinant constructs and their use in reducing gene expression.
Invention is credited to Glassman, Kimberly F., Gordon-Kamm, William J., Kinney, Anthony J., Lowe, Keith S., Nichols, Scott E., Stecca, Kevin L..
Application Number | 20030036197 09/887194 |
Document ID | / |
Family ID | 22797209 |
Filed Date | 2003-02-20 |
United States Patent
Application |
20030036197 |
Kind Code |
A1 |
Glassman, Kimberly F. ; et
al. |
February 20, 2003 |
Recombinant constructs and their use in reducing gene
expression
Abstract
Recombinant constructs useful for reducing the expression of
endogenous mRNA and any substantially similar endogenous mRNA are
disclosed. In particular, a recombinant construct comprising, inter
alia, a suitable nucleic acid sequence and its reverse complement
can be used to alter the expression of any homologous, endogenous
RNA (i.e., the target RNA) which is in proximity to this suitable
nucleic acid sequence.
Inventors: |
Glassman, Kimberly F.;
(Ankeny, IA) ; Gordon-Kamm, William J.;
(Urbandale, IA) ; Kinney, Anthony J.; (Wilmington,
DE) ; Lowe, Keith S.; (Johnston, IA) ;
Nichols, Scott E.; (West Chester, PA) ; Stecca, Kevin
L.; (Bear, DE) |
Correspondence
Address: |
E I DU PONT DE NEMOURS AND COMPANY
LEGAL PATENT RECORDS CENTER
BARLEY MILL PLAZA 25/1128
4417 LANCASTER PIKE
WILMINGTON
DE
19805
US
|
Family ID: |
22797209 |
Appl. No.: |
09/887194 |
Filed: |
June 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60213961 |
Jun 23, 2000 |
|
|
|
Current U.S.
Class: |
435/455 ;
435/320.1 |
Current CPC
Class: |
C12N 15/825 20130101;
C12N 15/8218 20130101; C12N 15/8216 20130101; C12N 15/8246
20130101; C12N 15/8251 20130101; C12N 15/8247 20130101; C12N
15/8245 20130101 |
Class at
Publication: |
435/455 ;
435/320.1 |
International
Class: |
C12N 015/00; C12N
015/87 |
Claims
What is claimed is:
1. A recombinant construct comprising a promoter operably linked to
a DNA sequence which, when expressed by a host produces an RNA
having: (a) homology to at least one target mRNA expressed by the
host, (b) two complementary RNA regions which are unrelated to any
endogenous RNA in the host, and which are in proximity to (a),
wherein the expressed RNA reduces the expression of the target mRNA
or any substantially similar endogenous mRNA.
2. A recombinant construct comprising a promoter operably linked to
a DNA sequence which, when expressed by a host, produces an RNA
having: (a) homology to at least one target mRNA expressed by the
host, (b) an RNA region unrelated to any endogenous RNA in the host
and located 5' to (a), and (c) the reverse complement of the RNA in
(b) located 3' to (a), wherein the expressed RNA reduces the
expression of the target mRNA or any substantially similar
endogenous mRNA.
3. A recombinant construct comprising a promoter operably linked to
a DNA sequence which, when expressed by a host, produces an RNA
having: (a) homology to at least one target mRNA expressed by the
host, and (b) two complementary RNA regions which are unrelated to
any endogenous RNA in the host, and which are located 5' to (a),
wherein the expressed RNA reduces the expression of the target mRNA
or any substantially similar endogenous mRNA.
4. A recombinant construct comprising a promoter operably linked to
a DNA sequence which, when expressed by a host, produces an RNA
having: (a) homology to at least one target mRNA expressed by the
host, and (b) two complementary RNA regions which are unrelated to
any endogenous RNA in the host, and which are located 3' to (a),
wherein the expressed RNA reduces the expression of the target mRNA
or any substantially similar endogenous mRNA.
5. A recombinant construct comprising a promoter operably linked to
a DNA sequence which, when expressed by a host, produces an RNA
having: (a) homology to at least one target mRNA expressed by the
host, and (b) two complementary RNA regions which are unrelated to
any endogenous RNA in the host, and which are located within (a),
wherein the expressed RNA reduces the expression of the target mRNA
or any substantially similar endogenous mRNA.
6. The recombinant construct of any of claims 1-5 wherein the RNA
region or regions which are unrelated to any endogenous RNA in the
host comprise a synthetic, non-naturally occurring RNA
sequence.
7. The recombinant construct of any of claims 1-5 wherein the RNA
region or regions which are unrelated to any endogenous RNA in the
host do not comprise plant viral RNA.
8. A method for reducing expression of a target mRNA or any
substantially similar endogenous mRNA which comprises: (a)
transforming a host with any of the recombinant constructs of
claims 1-5; and (b) selecting hosts which have reduced expression
of the target mRNA or any substantially similar endogenous
mRNA.
9. A method for reducing expression of a target mRNA or any
substantially similar endogenous mRNA which comprises: (a)
transforming a host with the recombinant construct of claim 6; and
(b) selecting hosts which have reduced expression of the target
mRNA or any substantially similar endogenous mRNA.
10. A method for reducing expression of a target mRNA or any
substantially similar endogenous mRNA which comprises: (a)
transforming a host with the recombinant construct of claim 7; and
(b) selecting hosts which have reduced expression of the target
mRNA or any substantially similar endogenous mRNA.
11. An RNA comprising: (a) homology to at least one target mRNA
expressed by a host, (b) two complementary RNA regions which are
unrelated to any endogenous RNA in the host, and which are in
proximity to (a), wherein the RNA, when introduced into the host,
reduces the expression of the target mRNA or any substantially
similar endogenous mRNA.
12. An RNA comprising: (a) homology to at least one target mRNA
expressed by a host, (b) an RNA region unrelated to any endogenous
RNA in the host and located 5' to (a), and (c) the reverse
complement of the RNA in (b) located 3' to (a), wherein the RNA,
when introduced into the host, reduces the expression of the target
mRNA or any substantially similar endogenous mRNA.
13. An RNA comprising: (a) homology to at least one target mRNA
expressed by the host, and (b) two complementary RNA regions which
are unrelated to any endogenous RNA in the host, and which are
located 5' to (a), wherein the RNA, when introduced into the host,
reduces the expression of the target mRNA or any substantially
similar endogenous mRNA.
14. An RNA comprising: (a) homology to at least one target mRNA
expressed by the host, and (b) two complementary RNA regions which
are unrelated to any endogenous RNA in the host, and which are
located 3' to (a), wherein the RNA, when introduced into the host,
reduces the expression of the target mRNA or any substantially
similar endogenous mRNA.
15. An RNA comprising: (a) homology to at least one target mRNA
expressed by the host, and (b) two complementary RNA regions which
are unrelated to any endogenous RNA in the host, and which are
located within (a), wherein the RNA, when introduced into the host,
reduces the expression of the target mRNA or any substantially
similar endogenous mRNA.
16. The RNA of any of claims 11-15 wherein the RNA region or
regions which are unrelated to any endogenous RNA in the host
comprise a synthetic, non-naturally occurring RNA sequence.
17. The RNA of any of claims 11-15 wherein the RNA region or
regions which are unrelated to any endogenous RNA in the host do
not comprise plant viral RNA.
18. A method for reducing expression of a target mRNA or any
substantially similar endogenous mRNA which comprises: (a)
introducing into a host any of the RNA of claims 11-15; and (b)
selecting hosts which have reduced expression of the target mRNA or
any substantially similar endogenous mRNA.
19. A method for reducing expression of a target mRNA or any
substantially similar endogenous mRNA which comprises: (a)
introducing into a host the recombinant construct of claim 16; and
(b) selecting hosts which have reduced expression of the target
mRNA or any substantially similar endogenous mRNA.
20. A method for reducing expression of a target mRNA or any
substantially similar endogenous mRNA which comprises: (a)
introducing into a host the recombinant construct of claim 17; and
(b) selecting hosts which have reduced expression of the target
mRNA or any substantially similar endogenous mRNA.
21. A recombinant construct comprising a promoter operably linked
to a DNA sequence which, when expressed by a host produces an RNA
having: (a) homology to at least one target mRNA expressed by the
host, (b) two complementary RNA regions which are encoded by any
nucleic acid sequence in the genome of the host provided that said
sequence does not encode the target mRNA or any sequence that is
substantially similar to the target mRNA and said regions are in
proximity to (a), wherein the expressed RNA reduces the expression
of the target mRNA or any substantially similar endogenous
mRNA.
22. A recombinant construct comprising a promoter operably linked
to a DNA sequence which, when expressed by a host, produces an RNA
having: (a) homology to at least one target mRNA expressed by the
host, (b) an RNA region encoded by any nucleic acid sequence in the
genome of the host provided that said sequence does not encode the
target mRNA or any sequence that is substantially similar to the
target mRNA and located 5' to (a), and (c) the reverse complement
of the nucleic acid in (b) located 3' to (a), wherein the expressed
RNA reduces the expression of the target mRNA or any substantially
similar endogenous mRNA.
23. A recombinant construct comprising a promoter operably linked
to a DNA sequence which, when expressed by a host, produces an RNA
having: (a) homology to at least one target mRNA expressed by the
host, and (b) two complementary RNA regions which are encoded by
any nucleic acid sequence in the genome of the host provided that
said sequence does not encode the target mRNA or any sequence that
is substantially similar to the target mRNA, and which regions are
located 5' to (a), wherein the expressed RNA reduces the expression
of the target mRNA or any substantially similar endogenous
mRNA.
24. A recombinant construct comprising a promoter operably linked
to a DNA sequence which, when expressed by a host, produces an RNA
having: (a) homology to at least one target mRNA expressed by the
host, and (b) two complementary RNA regions which are encoded by
any nucleic acid sequence in the genome of the host provided that
said sequence does not encode the target mRNA or any sequence that
is substantially similar to the target mRNA, and which regions are
located 3' to (a), wherein the expressed RNA reduces the expression
of the target mRNA or any substantially similar endogenous
mRNA.
25. A recombinant construct comprising a promoter operably linked
to a DNA sequence which, when expressed by a host, produces an RNA
having: (a) homology to at least one target mRNA expressed by the
host, and (b) two complementary RNA regions which are encoded by
any nucleic acid sequence in the genome of the host provided that
said sequence does not encode the target mRNA or any sequence that
is substantially similar to the target mRNA, and which regions are
located within (a), wherein the expressed RNA reduces the
expression of the target mRNA or any substantially similar
endogenous mRNA.
26. The recombinant constructs of claims 21-25 wherein the nucleic
acid sequence in the genome of the host is a sequence which is not
expressed by the host.
27. The recombinant constructs of claims 21-25 wherein the nucleic
acid sequence in the genome of the host is sequence which is
expressed by the host.
28. A method for reducing expression of a target mRNA or any
substantially similar endogenous mRNA which comprises: (a)
transforming a host with any of the recombinant constructs of
claims 21-25; and (b) selecting hosts which have reduced expression
of the target mRNA or any substantially similar endogenous
mRNA.
29. A method for reducing expression of a target mRNA or any
substantially similar endogenous mRNA which comprises: (a)
transforming a host with the recombinant construct of claim 26; and
(b) selecting hosts which have reduced expression of the target
mRNA or any substantially similar endogenous mRNA.
30. A method for reducing expression of a target mRNA or any
substantially similar endogenous mRNA which comprises: (a)
transforming a host with the recombinant construct of claim 27; and
(b) selecting hosts which have reduced expression of the target
mRNA or any substantially similar endogenous mRNA.
31. An RNA comprising: (a) homology to at least one target mRNA
expressed by a host, (b) two complementary RNA regions which are
encoded by any nucleic acid sequence in the genome of the host
provided that said sequence does not encode the target mRNA or any
sequence that is substantially similar to the target mRNA and which
regions are in proximity to (a), wherein the RNA, when introduced
into the host, reduces the expression of the target mRNA or any
substantially similar endogenous mRNA.
32. An RNA comprising: (a) homology to at least one target mRNA
expressed by a host, (b) an RNA region encoded by any nucleic acid
sequence in the genome of the host provided that said sequence does
not encode the target mRNA or any sequence that is substantially
similar to the target mRNA and is located 5' to (a), and (c) the
reverse complement of the RNA in (b) located 3' to (a), wherein the
RNA, when introduced into the host, reduces the expression of the
target mRNA or any substantially similar endogenous mRNA.
33. An RNA comprising: (a) homology to at least one target mRNA
expressed by the host, and (b) two complementary RNA regions which
are encoded by any nucleic acid sequence in the genome of the host
provided that said sequence does not encode the target mRNA or any
sequence that is substantially similar to the target mRNA and which
regions are located 5' to (a), wherein the RNA, when introduced
into the host, reduces the expression of the target mRNA or any
substantially similar endogenous mRNA.
34. An RNA comprising: (a) homology to at least one target mRNA
expressed by the host, and (b) two complementary RNA regions which
are encoded by any nucleic acid sequence in the genome of the host
provided that said sequence does not encode the target mRNA or any
sequence that is substantially similar to the target mRNA, and
which regions are located 3' to (a), wherein the RNA, when
introduced into the host, reduces the expression of the target mRNA
or any substantially similar endogenous mRNA.
35. An RNA comprising: (a) homology to at least one target mRNA
expressed by the host, and (b) two complementary RNA regions which
are encoded by any nucleic acid sequence in the genome of the host
provided that said sequence does not encode the target mRNA or any
sequence that is substantially similar to the target mRNA, and
which are located within (a), wherein the RNA, when introduced into
the host, reduces the expression of the target mRNA or any
substantially similar endogenous mRNA.
36. The RNA of any of claims 31-35 wherein the nucleic acid
sequence in the genome of the host is a sequence which is not
expressed by the host.
37. The RNA of any of claims 31-35 wherein the nucleic acid
sequence in the genome of the host is a sequence which is expressed
by the host.
38. A method for reducing expression of a target mRNA or any
substantially similar endogenous mRNA which comprises: (a)
introducing into a host any of the RNA of claims 31-35; and (b)
selecting hosts which have reduced expression of the target mRNA or
any substantially similar endogenous mRNA.
39. A method for reducing expression of a target mRNA or any
substantially similar endogenous mRNA which comprises: (a)
introducing into a host the RNA of claim 36; and (b) selecting
hosts which have reduced expression of the target mRNA or any
substantially similar endogenous mRNA.
40. A method for reducing expression of a target mRNA or any
substantially similar endogenous mRNA which comprises: (a)
introducing into a host the RNA of claim 37; and (b) selecting
hosts which have reduced expression of the target mRNA or any
substantially similar endogenous mRNA.
41. A method for identifying or screening an essential plant gene
which comprises: (a) transforming a plant cell with a recombinant
construct comprising a constitutive promoter wherein said construct
is capable of reducing expression of an essential plant gene with a
high degree of frequency; (b) quantifying all transformed plant
cells from step (a); (c) quantifying all transformed plant cells
from a control which does not reduce expression of an essential
plant gene; and (d) comparing the quantification of transformed
plant cells selected from step (b) with the quantification of
transformed plants cells selected from step (c) wherein the
quantification of transformed plants cells selected from step (c)
should substantially exceed the quantification of transformed plant
cells selected from step (b).
42. A method for identifying or screening an essential plant gene
which comprises: (a) transforming a plant cell with the recombinant
construct of any of claims 1-5 which further comprises a
constitutive promoter which is capable of reducing expression of an
essential plant gene with a high degree of frequency; (b)
quantifying all transformed plant cells from step (a); (c)
quantifying all transformed plant cells from a control which does
not reduce expression of an essential plant gene; and (d) comparing
the quantification of transformed plant cells selected from step
(b) with the quantification of transformed plants cells selected
from step (c) wherein the quantification of transformed plants
cells selected from step (c) should substantially exceed the
quantification of transformed plant cells selected from step
(b).
43. A method for identifying or screening an essential plant gene
which comprises: (a) transforming a plant cell with the recombinant
construct of any of claim 6 which further comprises a constitutive
promoter which is capable of reducing expression of an essential
plant gene with a high degree of frequency; (b) quantifying all
transformed plant cells from step (a); (c) quantifying all
transformed plant cells from a control which does not reduce
expression of an essential plant gene; and (d) comparing the
quantification of transformed plant cells selected from step (b)
with the quantification of transformed plants cells selected from
step (c) wherein the quantification of transformed plants cells
selected from step (c) should substantially exceed the
quantification of transformed plant cells selected from step
(b).
44. A method for identifying or screening an essential plant gene
which comprises: (a) transforming a plant cell with the recombinant
construct of any of claim 7 which further comprises a constitutive
promoter which is capable of reducing expression of an essential
plant gene with a high degree of frequency; (b) quantifying all
transformed plant cells from step (a); (c) quantifying all
transformed plant cells from a control which does not reduce
expression of an essential plant gene; and (d) comparing the
quantification of transformed plant cells selected from step (b)
with the quantification of transformed plants cells selected from
step (c) wherein the quantification of transformed plants cells
selected from step (c) should substantially exceed the
quantification of transformed plant cells selected from step
(b).
45. The recombinant construct of claims 1-5 wherein the DNA
sequences encoding the two complementary RNA sequences are
comprised within any of the sequences set forth in SEQ ID NOs: 12,
13, or 34.
Description
FIELD OF THE INVENTION
[0001] This invention relates to reducing gene expression and, in
particular, to recombinant constructs useful for reducing the
expression of endogenous mRNA and any substantially similar
endogenous mRNA.
BACKGROUND OF THE INVENTION
[0002] Plant development is a complex physiological and biochemical
process requiring the coordinated expression of many genes. The
production of new plant varieties with improved nutritional or
disease-resistant traits can be achieved by modifying this
coordinated pattern of gene expression. Recombinant DNA techniques
have made it possible to alter the expression patterns of
individual, specific plant genes without directly affecting the
expression of other plant genes. In this way, the expression
pattern of an individual gene can be either enhanced or diminished
in the whole plant, in specific tissues, or in developmental
stages. Thus, it is now routine to construct transgenes with
defined promoters and terminators and express them in a variety of
organisms.
[0003] However, there are some reports in the literature that some
introduced transgenes do not have the expected expression patterns.
These unexpected expression patterns are seen in organisms as
diverse as nematodes and plants. For example, some plants receiving
transgenic copies of an endogenous gene under the control of a
strong promoter, sometimes fail to accumulate mRNA for that gene.
Furthermore, all mRNA from endogenous genes having sequence
homology to the transgene also fail to accumulate mRNA, effectively
eliminating the expression of the endogenous gene product. This was
discovered originally when chalcone synthase transgenes in petunia
caused suppression of the endogenous chalcone synthase genes
(Napoli et al (1990) Plant Cell 2:279-289).
[0004] The phenomenon was referred to as "cosuppression" since
expression of both the endogenous gene and the introduced transgene
were suppressed (for reviews see Vaucheret et al (1998) Plant J
16:651-659; and Gura (2000) Nature 404:804-808). Cosuppression
technology constitutes the subject matter of U.S. Pat. No.
5,231,020 which issued to Jorgensen et al on Jul. 27, 1999.
Cosuppression is also referred to as "gene silencing" or
post-transcriptional gene silencing (PTGS) by plant biologists,
"RNA interference" by those studying worms and flies (Montgomery
and Fire (1998) TIG 14:255-258; Fire et al (1998) Nature
391:806-811; Hammond et al (2000) Nature 404:293-296; and PCT
Application No. WO 99/32619 published Jul. 1, 1999), and "quelling"
by researchers working with fungi (Romano and Macino (1992) Mol
Microbiol 6:3343-3353).
[0005] The mechanisms by which the expression of a specific gene is
inhibited by either antisense or sense RNA genes are not clearly
understood and the frequencies of obtaining the desired down
regulation in a transgenic plant are generally low and vary with
the gene, the strength of its promoter and specificity, the method
of transformation, and the complexity of transgene insertion
events. (Grant (1999) Cell 96:303-306; and Selker (1999) Cell
97:157-160.).
[0006] The speculation is that PTGS is an ancient self-defense
mechanism evolved to combat infection by viruses and transposons.
It appears that this pathogen-derived resistance is triggered by
the presence in the host's cells of double-stranded RNA (dsRNA) or
some other aberrant nucleic acid, which are indicative of a viral
assault. Normally, the RNA moving freely around a cell should be
single-stranded messenger RNA (mRNA) which is the intermediate
between host genes and the proteins they encode. When the aberrant
RNA invades then any mRNAs matching the invading nucleic acid's
sequence are shut down. If the trigger is homologous to part of the
host's genetic sequence, then both the host and viral genes are
silenced (Baulcombe (1996) Plant Cell 8:1833-1844). WO 99/15682
which published on Apr. 1, 1999 and WO 98/36083 which published on
Aug. 20, 1998 describe gene silencing materials and methods. These
publications describe, inter alia, the silencing of plant genomic
gene expression by introducing expression constructs containing
plant viral nucleic acid sequences coupled to whole, or partial,
gene sequences homologous to the target genes to be silenced.
[0007] WO 99/53050, which published on Oct. 21, 1999, describes
chimeric constructs encoding RNA molecules directed towards a
target nucleic acid which are comprised of sense and antisense
sequences, such that the expressed RNA is capable of forming an
intramolecular double-stranded RNA structure. The expression of
these RNA in transgenic organisms results in gene silencing of the
all homologous target nucleic acid sequences within the cell.
[0008] U.S. Pat. No. 5,942,657, issued to Bird et al on Aug. 25,
1999, and WO 93/23551, which published on Nov. 25, 1993, describe
coordinated inhibition of plant gene expression in which two or
more genes are inhibited by introducing a single control gene
having distinct DNA regions homologous to each of the target genes
and a promoter operable in plants adapted to transcribe from such
distinct regions RNA that inhibits expression of each of the target
genes.
[0009] The present invention describes the use of suitable DNA
sequences or RNA sequences derived therefrom, as is discussed
below, in ways which here-to-fore have not been previously
described. These sequences, and their reverse complements, can be
used to reduce the expression of any endogenous genomic sequence
that shares substantial similarity to nucleic acid fragment which
is in proximity to the DNA sequence or RNA sequence derived
therefrom. The details of this phenomenon are described herein.
SUMMARY OF THE INVENTION
[0010] This invention concerns a recombinant construct comprising a
promoter operably linked to a DNA sequence which, when expressed by
a host produces an RNA having:
[0011] (a) homology to at least one target mRNA expressed by the
host,
[0012] (b) two complementary RNA regions which are unrelated to any
endogenous RNA in the host, and which are in proximity to (a),
[0013] wherein the expressed RNA reduces the expression of the
target mRNA or any substantially similar endogenous mRNA.
[0014] In a second embodiment, this invention concerns a
recombinant construct comprising a promoter operably linked to a
DNA sequence which, when expressed by a host, produces an RNA
having:
[0015] (a) homology to at least one target mRNA expressed by the
host,
[0016] (b) an RNA region unrelated to any endogenous RNA in the
host and located 5' to (a), and
[0017] (c) the reverse complement of the RNA in (b) located 3' to
(a),
[0018] wherein the expressed RNA reduces the expression of the
target mRNA or any substantially similar endogenous mRNA.
[0019] In a third embodiment, this invention concerns a recombinant
construct comprising a promoter operably linked to a DNA sequence
which, when expressed by a host, produces an RNA having:
[0020] (a) homology to at least one target mRNA expressed by the
host, and
[0021] (b) two complementary RNA regions which are unrelated to any
endogenous RNA in the host, and which are located 5' to (a),
[0022] wherein the expressed RNA reduces the expression of the
target mRNA or any substantially similar endogenous mRNA.
[0023] In a fourth embodiment, this invention concerns a
recombinant construct comprising a promoter operably linked to a
DNA sequence which, when expressed by a host, produces an RNA
having:
[0024] (a) homology to at least one target mRNA expressed by the
host, and
[0025] (b) two complementary RNA regions which are unrelated to any
endogenous RNA in the host, and which are located 3' to (a),
[0026] wherein the expressed RNA reduces the expression of the
target mRNA or any substantially similar endogenous mRNA.
[0027] In a fifth embodiment, this invention concerns a recombinant
construct comprising a promoter operably linked to a DNA sequence
which, when expressed by a host, produces an RNA having:
[0028] (a) homology to at least one target mRNA expressed by the
host, and
[0029] (b) two complementary RNA regions which are unrelated to any
endogenous RNA in the host, and which are located within (a),
[0030] wherein the expressed RNA reduces the expression of the
target mRNA or any substantially similar endogenous mRNA.
[0031] In another aspect of any of the foregoing recombinant
constructs, the RNA region or regions which are unrelated to any
endogenous RNA in the host comprise a synthetic, non-naturally
occurring RNA sequence.
[0032] In still another aspect of any of the foregoing recombinant
constructs, the RNA region or regions which are unrelated to any
endogenous RNA in the host do not comprise plant viral RNA.
[0033] In a sixth embodiment, this invention concerns a method for
reducing expression of a target mRNA or any substantially similar
endogenous mRNA which comprises:
[0034] (a) transforming a host with any of the above-described
recombinant constructs; and
[0035] (b) selecting hosts which have reduced expression of the
target mRNA or any substantially similar endogenous mRNA.
[0036] In a seventh, embodiment, this invention concerns a
recombinant construct comprising an RNA having:
[0037] (a) homology to at least one target mRNA expressed by a
host,
[0038] (b) two complementary RNA regions which are unrelated to any
endogenous RNA in the host, and which are in proximity to (a),
[0039] wherein the RNA, when introduced into the host, reduces the
expression of the target mRNA or any substantially similar
endogenous mRNA.
[0040] In an eighth embodiment, this invention concerns a
recombinant construct comprising an RNA having:
[0041] (a) homology to at least one target mRNA expressed by a
host,
[0042] (b) an RNA region unrelated to any endogenous RNA in the
host and located 5' to (a), and
[0043] (c) the reverse complement of the RNA in (b) located 3' to
(a),
[0044] wherein the RNA, when introduced into the host, reduces the
expression of the target mRNA or any substantially similar
endogenous mRNA.
[0045] In a ninth embodiment, this invention concerns a recombinant
construct comprising an RNA having:
[0046] (a) homology to at least one target mRNA expressed by the
host, and
[0047] (b) two complementary RNA regions which are unrelated to any
endogenous RNA in the host, and which are located 5' to (a),
[0048] wherein the RNA, when introduced into the host, reduces the
expression of the target mRNA or any substantially similar
endogenous mRNA.
[0049] In a tenth embodiment, this invention concerns a recombinant
construct comprising an RNA having:
[0050] (a) homology to at least one target mRNA expressed by the
host, and
[0051] (b) two complementary RNA regions which are unrelated to any
endogenous RNA in the host, and which are located 3' to (a),
[0052] wherein the RNA, when introduced into the host, reduces the
expression of the target mRNA or any substantially similar
endogenous mRNA.
[0053] In an eleventh embodiment, this invention concerns a
recombinant construct comprising an RNA having:
[0054] (a) homology to at least one target mRNA expressed by the
host, and
[0055] (b) two complementary RNA regions which are unrelated to any
endogenous RNA in the host, and which are located within (a),
[0056] wherein the RNA, when introduced into the host, reduces the
expression of the target mRNA or any substantially similar
endogenous mRNA.
[0057] In another aspect of any of the foregoing RNAs, the RNA
region or regions which are unrelated to any endogenous RNA in the
host comprise a synthetic, non-naturally occurring RNA
sequence.
[0058] In still another aspect of any of the foregoing recombinant
constructs, the RNA region or regions which are unrelated to any
endogenous RNA in the host do not comprise plant viral RNA.
[0059] In a twelfth embodiment, this invention concerns a method
for reducing expression of a target mRNA or any substantially
similar endogenous mRNA which comprises:
[0060] (a) introducing into a host any of the above-described RNAs;
and
[0061] (b) selecting hosts which have reduced expression of the
target mRNA or any substantially similar endogenous mRNA.
[0062] In a thirteenth embodiment this invention concerns, a
recombinant construct comprising a promoter operably linked to a
DNA sequence which, when expressed by a host produces an RNA
having:
[0063] (a) homology to at least one target mRNA expressed by the
host,
[0064] (b) two complementary RNA regions which are encoded by any
nucleic acid sequence in the genome of the host provided that said
sequence does not encode the target mRNA or any sequence that is
substantially similar to the target mRNA and said regions are in
proximity to (a),
[0065] wherein the expressed RNA reduces the expression of the
target mRNA or any substantially similar endogenous mRNA.
[0066] In a fourteenth embodiment this invention concerns, a
recombinant construct comprising a promoter operably linked to a
DNA sequence which, when expressed by a host produces an RNA
having:
[0067] (a) homology to at least one target mRNA expressed by the
host,
[0068] (b) an RNA region encoded by any nucleic acid sequence in
the genome of the host provided that said sequence does not encode
the target mRNA or any sequence that is substantially similar to
the target mRNA and located 5' to (a), and
[0069] (c) the reverse complement of the nucleic acid in (b)
located 3' to (a),
[0070] wherein the expressed RNA reduces the expression of the
target mRNA or any substantially similar endogenous mRNA.
[0071] In a fifteenth embodiment this invention concerns, a
recombinant construct comprising a promoter operably linked to a
DNA sequence which, when expressed by a host produces an RNA
having:
[0072] (a) homology to at least one target mRNA expressed by the
host, and
[0073] (b) two complementary RNA regions which are encoded by any
nucleic acid sequence in the genome of the host provided that said
sequence does not encode the target mRNA or any sequence that is
substantially similar to the target mRNA, and which regions are
located 5' to (a),
[0074] wherein the expressed RNA reduces the expression of the
target mRNA or any substantially similar endogenous mRNA.
[0075] In a sixteenth embodiment this invention concerns, a
recombinant construct comprising a promoter operably linked to a
DNA sequence which, when expressed by a host produces an RNA
having:
[0076] (a) homology to at least one target mRNA expressed by the
host, and
[0077] (b) two complementary RNA regions which are encoded by any
nucleic acid sequence in the genome of the host provided that said
sequence does not encode the target mRNA or any sequence that is
substantially similar to the target mRNA, and which regions are
located 3' to (a),
[0078] wherein the expressed RNA reduces the expression of the
target mRNA or any substantially similar endogenous mRNA.
[0079] In a seventeenth embodiment this invention concerns, a
recombinant construct comprising a promoter operably linked to a
DNA sequence which, when expressed by a host produces an RNA
having:
[0080] (a) homology to at least one target mRNA expressed by the
host, and
[0081] (b) two complementary RNA regions which are encoded by any
nucleic acid sequence in the genome of the host provided that said
sequence does not encode the target mRNA or any sequence that is
substantially similar to the target mRNA, and which regions are
located within (a),
[0082] wherein the expressed RNA reduces the expression of the
target mRNA or any substantially similar endogenous mRNA.
[0083] In another aspect of any of the foregoing recombinant
constructs, the RNA region or regions which are unrelated to any
endogenous RNA in the host comprise a synthetic, non-naturally
occurring RNA sequence.
[0084] In still another aspect of any of the foregoing recombinant
constructs, the RNA region or regions which are unrelated to any
endogenous RNA in the host do not comprise plant viral RNA.
[0085] In an eighteenth embodiment this invention concerns, a
method for reducing expression of a target mRNA or any
substantially similar endogenous mRNA which comprises:
[0086] (a) transforming a host with any of the above-described
recombinant constructs; and
[0087] (b) selecting hosts which have reduced expression of the
target mRNA or any substantially similar endogenous mRNA.
[0088] In a nineteenth embodiment this invention concerns an RNA
comprising:
[0089] (a) homology to at least one target mRNA expressed by a
host,
[0090] (b) two complementary RNA regions which are encoded by any
nucleic acid sequence in the genome of the host provided that said
sequence does not encode the target mRNA or any sequence that is
substantially similar to the target mRNA and which regions are in
proximity to (a),
[0091] wherein the RNA, when introduced into the host, reduces the
expression of the target mRNA or any substantially similar
endogenous mRNA.
[0092] In a twentieth embodiment this invention concerns an RNA
comprising:
[0093] (a) homology to at least one target mRNA expressed by a
host,
[0094] (b) an RNA region encoded by any nucleic acid sequence in
the genome of the host provided that said sequence does not encode
the target mRNA or any sequence that is substantially similar to
the target mRNA and is located 5' to (a), and
[0095] (c) the reverse complement of the RNA in (b) located 3' to
(a),
[0096] wherein the RNA, when introduced into the host, reduces the
expression of the target mRNA or any substantially similar
endogenous mRNA.
[0097] In a twenty-first embodiment this invention concerns an RNA
comprising:
[0098] (a) homology to at least one target mRNA expressed by the
host, and
[0099] (b) two complementary RNA regions which are encoded by any
nucleic acid sequence in the genome of the host provided that said
sequence does not encode the target mRNA or any sequence that is
substantially similar to the target mRNA and which regions are
located 5' to (a),
[0100] wherein the RNA, when introduced into the host, reduces the
expression of the target mRNA or any substantially similar
endogenous mRNA.
[0101] In a twenty-second embodiment this invention concerns an RNA
comprising:
[0102] (a) homology to at least one target mRNA expressed by the
host, and
[0103] (b) two complementary RNA regions which are encoded by any
nucleic acid sequence in the genome of the host provided that said
sequence does not encode the target mRNA or any sequence that is
substantially similar to the target mRNA, and which regions are
located 3' to (a),
[0104] wherein the RNA, when introduced into the host, reduces the
expression of the target mRNA or any substantially similar
endogenous mRNA.
[0105] In a twenty-third embodiment this invention concerns an RNA
comprising:
[0106] (a) homology to at least one target mRNA expressed by the
host, and
[0107] (b) two complementary RNA regions which are encoded by any
nucleic acid sequence in the genome of the host provided that said
sequence does not encode the target mRNA or any sequence that is
substantially similar to the target mRNA, and which are located
within (a),
[0108] wherein the RNA, when introduced into the host, reduces the
expression of the target mRNA or any substantially similar
endogenous mRNA.
[0109] In another aspect of any of the foregoing RNAs, the RNA
region or regions which are unrelated to any endogenous RNA in the
host comprise a synthetic, non-naturally occurring RNA
sequence.
[0110] In still another aspect of any of the foregoing recombinant
constructs, the RNA region or regions which are unrelated to any
endogenous RNA in the host do not comprise plant viral RNA.
[0111] In a twenty-fourth embodiment this invention concerns a
method for reducing expression of a target mRNA or any
substantially similar endogenous mRNA which comprises:
[0112] (a) introducing into a host any of the above-described RNAs;
and
[0113] (b) selecting hosts which have reduced expression of the
target mRNA or any substantially similar endogenous mRNA.
[0114] In a twenty-fifth embodiment, this invention concerns a
method for identifying or screening an essential plant gene which
comprises:
[0115] (a) transforming a plant cell with a recombinant construct
comprising a constitutive promoter wherein said construct is
capable of reducing expression of an essential plant gene with a
high degree of frequency;
[0116] (b) quantifying all transformed plant cells from step
(a);
[0117] (c) quantifying all transformed plant cells from a control
which does not reduce expression of an essential plant gene;
and
[0118] (d) comparing the quantification of transformed plant cells
selected from step (b) with the quantification of transformed
plants cells selected from step (c) wherein the quantification of
transformed plants cells selected from step (c) should
substantially exceed the quantification of transformed plant cells
selected from step (b).
[0119] In a twenty-sixth embodiment, this invention concerns a
method for identifying or screening an essential plant gene which
comprises:
[0120] (a) transforming a plant cell with any of the recombinant
constructs of the invention comprising a promoter operably linked
to a DNA sequence and which further comprises a constitutive
promoter which is capable of reducing expression of an essential
plant gene with a high degree of frequency;
[0121] (b) quantifying all transformed plant cells from step
(a);
[0122] (c) quantifying all transformed plant cells from a control
which does not reduce expression of an essential plant gene;
and
[0123] (d) comparing the quantification of transformed plant cells
selected from step (b) with the quantification of transformed
plants cells selected from step (c) wherein the quantification of
transformed plants cells selected from step (c) should
substantially exceed the quantification of transformed plant cells
selected from step (b).
BRIEF DESCRIPTION OF THE DRAWING AND SEQUENCE LISTINGS
[0124] The invention can be more fully understood from the
following detailed description and the accompanying drawings and
Sequence Listing which form a part of this application.
[0125] FIG. 1 depicts the results of chimerism in experiments on
antisense, "classical co-suppression", and complementary region
reduction of expression for the soybean gene Fad2, a fatty acid
desaturase. Chimerism is a measure of the percentage of individuals
isolated in individual transformed lines that exhibit the phenotype
characteristic of the desired trait.
[0126] FIG. 2 shows total soybean sugars visualized after TLC
separation. The raffinose and stachyose sugars are the lowest band
in each lane. The "Low 4" lane is isolated from a soybean line
known to have very low levels of raffinose/stachyose sugars. The
two "GAS-EL" lines both have lower levels of raffinose/stachyose
than are found in the surrounding lines indicating that the
GAS1/GAS2 fragments contained within the EL construct are
suppressing galactinol synthase activity in these lines.
[0127] The attached Sequence Listing (SEQ ID NOs:1-35) describe
oligonucleotide sequences used in the design of various plasmids
described herein, or the sequence of the complementary regions
found in some of the plasmids.
[0128] SEQ ID NO:1 is the sequence of an oligonucleotide primer
used in a polymerase chain reaction (PCR) amplification of the
soybean Fad2-1 gene for insertion into plasmid pKS67 to produce
plasmid pKS91.
[0129] SEQ ID NO:2 is the sequence of an oligonucleotide primer
used in a PCR amplification of the soybean Fad2-1 gene for
insertion into plasmid pKS67 to produce plasmid pKS91.
[0130] SEQ ID NO:3 is the sequence of an oligonucleotide primer
used in a PCR amplification of the soybean Fad2-1 gene for
insertion into plasmid pKS67 to produce plasmid pKS91.
[0131] SEQ ID NO:4 is the sequence of an oligonucleotide primer
used in a PCR amplification of the soybean Fad2-1 gene for
insertion into plasmid pKS67 to produce plasmid pKS91.
[0132] SEQ ID NO:5 is the sequence of an oligonucleotide primer
used in a PCR amplification of the soybean Fad2-1 gene for
insertion into plasmid pKS67 to produce plasmid pKS91.
[0133] SEQ ID NO:6 is the sequence of an oligonucleotide primer
used in a PCR amplification of the soybean Fad2-1 gene for
insertion into plasmid pKS67 to produce plasmid pKS91.
[0134] SEQ ID NO:7 is a linker oligonucleotide used to insert
various restriction enzyme sites into the plasmid pKS17 to form the
plasmid pKS102.
[0135] SEQ ID NO:8 is the sequence of an oligonucleotide primer
used in a PCR amplification of the soybean Cer3 gene for insertion
into plasmid pKS67 to form plasmid pKS100.
[0136] SEQ ID NO:9 is the sequence of an oligonucleotide primer
used in a PCR amplification of the soybean Cer3 gene for insertion
into plasmid pKS67 to form plasmid pKS100.
[0137] SEQ ID NO:10 is the sequence of an oligonucleotide primer
used in a PCR amplification of the soybean Cer3 gene for insertion
into plasmid pKS67 to form plasmid pKS100.
[0138] SEQ ID NO:11 is the sequence of an oligonucleotide primer
used in a PCR amplification of the soybean Cer3 gene for insertion
into plasmid pKS67 to form plasmid pKS100.
[0139] SEQ ID NO:12 represents the 1.times. complementary repeat
designated ELVISLIVES found in plasmids pKS106 and pKS124.
[0140] SEQ ID NO:13 represents the 2.times. complementary repeat
designated ELVISLIVES found in plasmids pKS133.
[0141] SEQ ID NO:14 is the sequence of an oligonucleotide primer
used in a PCR amplification of the ELVISLIVES complementary
region.
[0142] SEQ ID NO:15 is the sequence of an oligonucleotide primer
used in a PCR amplification of the ELVISLIVES complementary
region.
[0143] SEQ ID NO:16 is the sequence of an oligonucleotide primer
used in a PCR amplification of the soybean Fad2-1 gene to produce
the 599 nucleotide fragment inserted into plasmid pKS106 to produce
the plasmid pKS111.
[0144] SEQ ID NO:17 is the sequence of an oligonucleotide primer
used in a PCR amplification of the soybean Fad2-1 gene to produce
the 599 nucleotide fragment inserted into plasmid pKS106 to produce
the plasmid pKS111.
[0145] SEQ ID NO:18 is the sequence of the common 5'
oligonucleotide primer used in a PCR amplification of the soybean
Fad2-1 gene for use in testing size requirements for target
sequences.
[0146] SEQ ID NO:19 is the sequence of a 3' oligonucleotide primer
used in a PCR amplification of the soybean Fad2-1 gene for
production of the 25 bp fragment.
[0147] SEQ ID NO:20 is the sequence of a 3' oligonucleotide primer
used in a PCR amplification of the soybean Fad2-1 gene for
production of the 75 bp fragment.
[0148] SEQ ID NO:21 is the sequence of a 3' oligonucleotide primer
used in a PCR amplification of the soybean Fad2-1 gene for
production of the 150 bp fragment.
[0149] SEQ ID NO:22 is the sequence of a 3' oligonucleotide primer
used in a PCR amplification of the soybean Fad2-1 gene for
production of the 300 bp fragment.
[0150] SEQ ID NO:23 is the sequence of a 3' oligonucleotide primer
used in a PCR amplification of the soybean Fad2-1 gene for
production of the 600 bp fragment.
[0151] SEQ ID NO:24 represents the 2.times. ELVISLIVES
complementary repeat region from pBS68 which contains 2.times.
ELVISLIVES complementary regions surrounding the 599 nucleotide
Fad2-1 NotI fragment from pKS111 and a 969 nucleotide fragment from
a soybean delta-9 desaturase.
[0152] SEQ ID NO:25 is the sequence of a 5' oligonucleotide primer
used in a PCR amplification of the Lea promoter.
[0153] SEQ ID NO:26 is the sequence of a 3' oligonucleotide primer
used in a PCR amplification of the Lea promoter.
[0154] SEQ ID NO:27 is the sequence of a 5' oligonucleotide primer
used in a PCR amplification of the phaseolin 3'-end.
[0155] SEQ ID NO:28 is the sequence of a 3' oligonucleotide primer
used in a PCR amplification of the phaseolin 3'-end.
[0156] SEQ ID NO:29 represents the 2.times. ELVISLIVES
complementary repeat region from pKS149 that contains fragments
from two soybean galactinol synthase genes GAS1 and GAS2 (411 and
435 nucleotides, respectively). The region is functionally attached
to a late-soybean-embryo promoter (LEA) and a phaseolin 3'
terminator region. This entire region is then cloned into the BamHI
site of pKS136, which contains a 2.times. ELVISLIVES complementary
repeat region controlled by a soybean Kti promoter and terminator
region.
[0157] SEQ ID NO:30 represents the DNA sequence of the soybean
galactinol synthase gene GAS1.
[0158] SEQ ID NO:31 represents the putative translation product DNA
sequence of SEQ ID NO:30 the soybean galactinol synthase gene
GAS1.
[0159] SEQ ID NO:32 represents the DNA sequence of the soybean
galactinol synthase gene GAS2.
[0160] SEQ ID NO:33 represents the putative translation product DNA
sequence of SEQ ID NO:32 the soybean galactinol synthase gene
GAS2.
[0161] SEQ ID NO:34 represents the complementary region SHH3 from
plasmid PHP17962, used in the construction of plasmid PHP17894
containing the phytoene desaturase fragment. The complementary
regions are from 8-212 and 305-509, respectively. Restriction
endonuclease sites for EcoRV, KpnI, KspI, SphI, and NcoI can be
used as cloning sites between the complementary regions.
[0162] SEQ ID NO:35 represents the DNA sequence of the soybean
acetolactate synthase (ALS) gene.
[0163] SEQ ID NO:36 is the sequence of a 3' oligonucleotide primer
used in a PCR amplification of the soybean Fad2-1 gene for
production of the 50 bp fragment.
DETAILED DESCRIPTION OF THE INVENTION
[0164] In the context of this disclosure, a number of terms shall
be utilized.
[0165] The term "host" refers to any organism, or cell thereof,
whether human or non-human into which a recombinant construct can
be stably or transiently introduced in order to reduce gene
expression.
[0166] As used herein, an "isolated nucleic acid fragment" is a
polymer of RNA or DNA that is single- or double-stranded,
optionally containing synthetic, non-natural or altered nucleotide
bases. An isolated nucleic acid fragment in the form of a polymer
of DNA may be comprised of one or more segments of cDNA, genomic
DNA or synthetic DNA. Nucleotides (usually found in their
5'-monophosphate form) are referred to by their single letter
designation as follows: "A" for adenylate or deoxyadenylate (for
RNA or DNA, respectively), "C" for cytidylate or deoxycytidylate,
"G" for guanylate or deoxyguanylate, "U" for uridylate, "T" for
deoxythymidylate, "R" for purines (A or G), "Y" for pyrimidines (C
or T), "K" for g or T, "H" for A or C or T, "I" for inosine, and
"N" for any nucleotide.
[0167] The terms "subfragment that is functionally equivalent" and
"functionally equivalent subfragment" are used interchangeably
herein. These terms refer to a portion or subsequence of an
isolated nucleic acid fragment in which the ability to alter gene
expression or produce a certain phenotype is retained whether or
not the fragment or subfragment encodes an active enzyme. For
example, the fragment or subfragment can be used in the design of
chimeric genes to produce the desired phenotype in a transformed
plant. Chimeric genes can be designed for use in co-suppression or
antisense by linking a nucleic acid fragment or subfragment
thereof, whether or not it encodes an active enzyme, in the
appropriate orientation relative to a plant promoter sequence.
[0168] The terms "homology", "homologous", "substantially similar"
and "corresponding substantially" are used interchangeably herein.
They refer to nucleic acid fragments wherein changes in one or more
nucleotide bases does not affect the ability of the nucleic acid
fragment to mediate gene expression or produce a certain phenotype.
These terms also refer to modifications of the nucleic acid
fragments of the instant invention such as deletion or insertion of
one or more nucleotides that do not substantially alter the
functional properties of the resulting nucleic acid fragment
relative to the initial, unmodified fragment. It is therefore
understood, as those skilled in the art will appreciate, that the
invention encompasses more than the specific exemplary
sequences.
[0169] Moreover, the skilled artisan recognizes that substantially
similar nucleic acid sequences encompassed by this invention are
also defined by their ability to hybridize, under moderately
stringent conditions (for example, 0.5.times.SSC, 0.1% SDS,
60.degree. C.) with the sequences exemplified herein, or to any
portion of the nucleotide sequences reported herein and which are
functionally equivalent to the promoter of the invention.
Stringency conditions can be adjusted to screen for moderately
similar fragments, such as homologous sequences from distantly
related organisms, to highly similar fragments, such as genes that
duplicate functional enzymes from closely related organisms.
Post-hybridization washes determine stringency conditions. One set
of preferred conditions involves a series of washes starting with
6.times.SSC, 0.5% SDS at room temperature for 15 min, then repeated
with 2.times.SSC, 0.5% SDS at 45.degree. C. for 30 min, and then
repeated twice with 0.2.times.SSC, 0.5% SDS at 50.degree. C. for 30
min. A more preferred set of stringent conditions involves the use
of higher temperatures in which the washes are identical to those
above except for the temperature of the final two 30 min washes in
0.2.times.SSC, 0.5% SDS was increased to 60.degree. C. Another
preferred set of highly stringent conditions involves the use of
two final washes in 0.1.times.SSC, 0.1% SDS at 65.degree. C.
[0170] With respect to the degree of substantial similarity between
the target (endogenous) mRNA and the RNA region in the construct
having homology to the target mRNA, such sequences should be at
least 25 nucleotides in length, preferably at least 50 nucleotides
in length, more preferably at least 100 nucleotides in length,
again more preferably at least 200 nucleotides in length, and most
preferably at least 300 nucleotides in length; and should be at
least 80% identical, preferably at least 85% identical, more
preferably at least 90% identical, and most preferably at least 95%
identical.
[0171] Sequence alignments and percent similarity calculations may
be determined using a variety of comparison methods designed to
detect homologous sequences including, but not limited to, the
Megalign program of the LASARGENE bioinformatics computing suite
(DNASTAR Inc., Madison, Wis.). Multiple alignment of the sequences
are performed using the Clustal method of alignment (Higgins and
Sharp (1989) CABIOS. 5:151-153) with the default parameters (GAP
PENALTY=10, GAP LENGTH PENALTY=10). Default parameters for pairwise
alignments and calculation of percent identity of protein sequences
using the Clustal method are KTUPLE=1, GAP PENALTY=3, WINDOW=5 and
DIAGONALS SAVED=5. For nucleic acids these parameters are KTUPLE=2,
GAP PENALTY=5, WINDOW=4 and DIAGONALS SAVED=4.
[0172] "Gene" refers to a nucleic acid fragment that expresses a
specific protein, including regulatory sequences preceding (5'
non-coding sequences) and following (3' non-coding sequences) the
coding sequence. "Native gene" refers to a gene as found in nature
with its own regulatory sequences. "Chimeric gene" refers any gene
that is not a native gene, comprising regulatory and coding
sequences that are not found together in nature. Accordingly, a
chimeric gene may comprise regulatory sequences and coding
sequences that are derived from different sources, or regulatory
sequences and coding sequences derived from the same source, but
arranged in a manner different than that found in nature. A
"foreign" gene refers to a gene not normally found in the host
organism, but that is introduced into the host organism by gene
transfer. Foreign genes can comprise native genes inserted into a
non-native organism, or chimeric genes. A "transgene" is a gene
that has been introduced into the genome by a transformation
procedure.
[0173] The term "essential plant genes" as used herein refers to
genes encoding a product that is required for normal plant growth,
development, and/or viability. In addition to ALS, examples of
essential plant genes would include, but not be limited to,
rate-limiting enzymes in amino acid, nucleic acid, or lipid
biosynthesis. It is also believed that many genes with unknown
function may be essential. Suppression of essential plant genes by
chemical or genetic means will result in altered growth and/or
development. If an essential gene is unique in the genome of the
plant, suppression may lead to plant death, which is the basis of
many plant herbicides.
[0174] "Coding sequence" refers to a DNA sequence that codes for a
specific amino acid sequence. "Regulatory sequences" refer to
nucleotide sequences located upstream (5' non-coding sequences),
within, or downstream (3' non-coding sequences) of a coding
sequence, and which influence the transcription, RNA processing or
stability, or translation of the associated coding sequence.
Regulatory sequences may include, but are not limited to,
promoters, translation leader sequences, introns, and
polyadenylation recognition sequences.
[0175] "Promoter" refers to a DNA sequence capable of controlling
the expression of a coding sequence or functional RNA. The promoter
sequence consists of proximal and more distal upstream elements,
the latter elements often referred to as enhancers. Accordingly, an
"enhancer" is a DNA sequence which can stimulate promoter activity
and may be an innate element of the promoter or a heterologous
element inserted to enhance the level or tissue-specificity of a
promoter. Promoters may be derived in their entirety from a native
gene, or be composed of different elements derived from different
promoters found in nature, or even comprise synthetic DNA segments.
It is understood by those skilled in the art that different
promoters may direct the expression of a gene in different tissues
or cell types, or at different stages of development, or in
response to different environmental conditions. Promoters which
cause a gene to be expressed in most cell types at most times are
commonly referred to as "constitutive promoters". New promoters of
various types useful in plant cells are constantly being
discovered; numerous examples may be found in the compilation by
Okamuro and Goldberg, (1989) Biochemistry of Plants 15:1-82. It is
further recognized that since in most cases the exact boundaries of
regulatory sequences have not been completely defined, DNA
fragments of some variation may have identical promoter
activity.
[0176] An "intron" is an intervening sequence in a gene that does
not encode a portion of the protein sequence. Thus, such sequences
are transcribed into RNA but are then excised and are not
translated. The term is also used for the excised RNA sequences. An
"exon" is a portion of the sequence of a gene that is transcribed
and is found in the mature messenger RNA derived from the gene, but
is not necessarily a part of the sequence that encodes the final
gene product.
[0177] The "translation leader sequence" refers to a DNA sequence
located between the promoter sequence of a gene and the coding
sequence. The translation leader sequence is present in the fully
processed mRNA upstream of the translation start sequence. The
translation leader sequence may affect processing of the primary
transcript to mRNA, mRNA stability or translation efficiency.
Examples of translation leader sequences have been described
(Turner, R. and Foster, G. D. (1995) Molecular Biotechnology
3:225).
[0178] The "3' non-coding sequences" refer to DNA sequences located
downstream of a coding sequence and include polyadenylation
recognition sequences and other sequences encoding regulatory
signals capable of affecting mRNA processing or gene expression.
The polyadenylation signal is usually characterized by affecting
the addition of polyadenylic acid tracts to the 3' end of the mRNA
precursor. The use of different 3' non-coding sequences is
exemplified by Ingelbrecht et al, (1989) Plant Cell 1:671-680.
[0179] "RNA transcript" refers to the product resulting from RNA
polymerase-catalyzed transcription of a DNA sequence. When the RNA
transcript is a perfect complementary copy of the DNA sequence, it
is referred to as the primary transcript or it may be a RNA
sequence derived from post-transcriptional processing of the
primary transcript and is referred to as the mature RNA. "Messenger
RNA (mRNA)" refers to the RNA that is without introns and that can
be translated into protein by the cell. "cDNA" refers to a DNA that
is complementary to and synthesized from a mRNA template using the
enzyme reverse transcriptase. The cDNA can be single-stranded or
converted into the double-stranded form using the Klenow fragment
of DNA polymerase I. "Sense" RNA refers to RNA transcript that
includes the mRNA and can be translated into protein within a cell
or in vitro. "Antisense RNA" refers to an RNA transcript that is
complementary to all or part of a target primary transcript or mRNA
and that blocks the expression of a target gene (U.S. Pat. No.
5,107,065). The complementarity of an antisense RNA may be with any
part of the specific gene transcript, i.e., at the 5' non-coding
sequence, 3' non-coding sequence, introns, or the coding sequence.
"Functional RNA" refers to antisense RNA, ribozyme RNA, or other
RNA that may not be translated but yet has an effect on cellular
processes. The terms "complement" and "reverse complement" are used
interchangeably herein with respect to mRNA transcripts, and are
meant to define the antisense RNA of the message.
[0180] The term "target mRNA" refers to any mRNA whose expression
in the host is to be reduced.
[0181] The term "endogenous RNA" refers to any RNA which is encoded
by any nucleic acid sequence present in the genome of the host
prior to transformation with the recombinant construct of the
present invention, whether naturally-occurring or non-naturally
occurring, i.e., introduced by recombinant means, mutagenesis,
etc.
[0182] The term "non-naturally occurring" means artificial, not
consistent with what is normally found in nature.
[0183] The term "operably linked" refers to the association of
nucleic acid sequences on a single nucleic acid fragment so that
the function of one is regulated by the other. For example, a
promoter is operably linked with a coding sequence when it is
capable of regulating the expression of that coding sequence (i.e.,
that the coding sequence is under the transcriptional control of
the promoter). Coding sequences can be operably linked to
regulatory sequences in a sense or antisense orientation. In
another example, the complementary RNA regions of the invention can
be operably linked, either directly or indirectly, 5' to the target
mRNA, or 3' to the target mRNA, or within the target mRNA, or a
first complementary region is 5' and its complement is 3' to the
target mRNA.
[0184] The term "expression", as used herein, refers to the
production of a functional end-product. Expression of a gene
involves transcription of the gene and translation of the mRNA into
a precursor or mature protein. "Antisense inhibition" refers to the
production of antisense RNA transcripts capable of suppressing the
expression of the target protein. "Co-suppression" refers to the
production of sense RNA transcripts capable of suppressing the
expression of identical or substantially similar foreign or
endogenous genes (U.S. Pat. No. 5,231,020).
[0185] "Mature" protein refers to a post-translationally processed
polypeptide; i.e., one from which any pre- or propeptides present
in the primary translation product have been removed. "Precursor"
protein refers to the primary product of translation of mRNA; i.e.,
with pre- and propeptides still present. Pre- and propeptides may
be but are not limited to intracellular localization signals.
[0186] "Stable transformation" refers to the transfer of a nucleic
acid fragment into a genome of a host organism, including both
nuclear and organellar genomes, resulting in genetically stable
inheritance. In contrast, "transient transformation" refers to the
transfer of a nucleic acid fragment into the nucleus, or
DNA-containing organelle, of a host organism resulting in gene
expression without integration or stable inheritance. Host
organisms containing the transformed nucleic acid fragments are
referred to as "transgenic" organisms. The preferred method of cell
transformation of rice, corn and other monocots is the use of
particle-accelerated or "gene gun" transformation technology (Klein
et al, (1987) Nature (London) 327:70-73; U.S. Pat. No. 4,945,050),
or an Agrobacterium-mediated method using an appropriate Ti plasmid
containing the transgene (Ishida Y. et al, 1996, Nature Biotech.
14:745-750).
[0187] Standard recombinant DNA and molecular cloning techniques
used herein are well known in the art and are described more fully
in Sambrook, J., Fritsch, E. F. and Maniatis, T. Molecular Cloning:
A Laboratory Manual; Cold Spring Harbor Laboratory Press: Cold
Spring Harbor, 1989 (hereinafter "Sambrook").
[0188] The term "recombinant" refers to an artificial combination
of two otherwise separated segments of sequence, e.g., by chemical
synthesis or by the manipulation of isolated segments of nucleic
acids by genetic engineering techniques.
[0189] "PCR" or "Polymerase Chain Reaction" is a technique for the
synthesis of large quantities of specific DNA segments, consists of
a series of repetitive cycles (Perkin Elmer Cetus Instruments,
Norwalk, Conn.). Typically, the double stranded DNA is heat
denatured, the two primers complementary to the 3' boundaries of
the target segment are annealed at low temperature and then
extended at an intermediate temperature. One set of these three
consecutive steps is referred to as a cycle.
[0190] The terms "recombinant construct", "expression construct"
and "recombinant expression construct" are used interchangeably
herein. Such construct may be itself or may be used in conjunction
with a vector. If a vector is used then the choice of vector is
dependent upon the method that will be used to transform host
plants as is well known to those skilled in the art. For example, a
plasmid vector can be used. The skilled artisan is well aware of
the genetic elements that must be present on the vector in order to
successfully transform, select and propagate host cells comprising
any of the isolated nucleic acid fragments of the invention. The
skilled artisan will also recognize that different independent
transformation events will result in different levels and patterns
of expression (Jones et al, (1985) EMBO J. 4:2411-2418; De Almeida
et al, (1989) Mol. Gen. Genetics 218:78-86), and thus that multiple
events must be screened in order to obtain lines displaying the
desired expression level and pattern. Such screening may be
accomplished by Southern analysis of DNA, Northern analysis of mRNA
expression, Western analysis of protein expression, or phenotypic
analysis.
[0191] Co-suppression constructs in plants previously have been
designed by focusing on overexpression of a nucleic acid sequence
having homology to an endogenous mRNA, in the sense orientation,
which results in the reduction of all RNA having homology to the
overexpressed sequence (see Vaucheret et al (1998) Plant J
16:651-659; and Gura (2000) Nature 404:804-808). The overall
efficiency of this phenomenon is low, and the extent of the RNA
reduction is widely variable. Recent work has described the use of
"hairpin" structures that incorporate all, or part, of an mRNA
encoding sequence in a complementary orientation that results in a
potential "stem-loop" structure for the expressed RNA (PCT
Publication WO 99/53050 published on Oct. 21, 1999). This increases
the frequency of co-suppression in the recovered transgenic plants.
Another variation describes the use of plant viral sequences to
direct the suppression, or "silencing", of proximal mRNA encoding
sequences (PCT Publication WO 98/36083 published on Aug. 20, 1998).
Both of these co-suppressing phenomena have not been elucidated
mechanistically, although recent genetic evidence has begun to
unravel this complex situation (Elmayan et al (1998) Plant Cell
10:1747-1757).
[0192] Surprisingly and unexpectedly, it has been found that
suitable nucleic acid sequences and their reverse complement can be
used to alter the expression of any homologous, endogenous RNA
(i.e., the target RNA) which is in proximity to the suitable
nucleic acid sequence and its reverse complement. As is discussed
below, the suitable nucleic acid sequence and its reverse
complement can be either unrelated to any endogenous RNA in the
host or can be encoded by any nucleic acid sequence in the genome
of the host provided that nucleic acid sequence does not encode any
target mRNA or any sequence that is substantially similar to the
target mRNA.
[0193] Thus, the present invention presents a very efficient and
robust approach to achieving single, or multiple, gene
co-suppression using single plasmid transformation. As is discussed
in greater detail below, the constructs are composed of promoters
linked to mRNA(s) coding regions, or fragments thereof, that are
targeted for suppression, and short complementary sequences that
are unrelated to the targets. The complementary sequences can be
oriented both 5', both 3', or on either side of the target
sequence. The complementary sequences are preferred to be about
40-50 nucleotides in length, or more preferably 50-100 nucleotides
in length, or most preferably at least or greater than 100-300
nucleotides. The complementary sequences are unrelated to the
target, but can come from any other source. Preferred embodiments
of these sequences include, but are not limited to, plant
sequences, bacterial sequences, animal sequences, viral or phage
sequences, or completely artificial, i.e. non-naturally occurring,
sequences not known to occur in any organism (see "ELVISLIVES"
below). All sequences can be compared to other known sequences, or
each other, using any one of a number of sequence alignment
programs as set forth below in Example 4.
[0194] The term "high degree of frequency" as used herein, with
respect to the suppression efficiency, refers to the percentage of
transformed lines that exhibit the target suppressed phenotype.
High frequency percentages are expected to be in a range of at
least 15-95% and any integer percentage found within the range.
Preferred embodiments would include at least 15%, 20%, 25%, 30%,
35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, and
95%.
[0195] The present invention concerns a recombinant construct
comprising a promoter operably linked to a DNA sequence which, when
expressed by a host produces an RNA having:
[0196] (a) homology to at least one target mRNA expressed by the
host,
[0197] (b) two complementary RNA regions which are unrelated to any
endogenous RNA in the host, and which are in proximity to (a),
[0198] wherein the expressed RNA reduces the expression of the
target mRNA or any substantially similar endogenous mRNA.
[0199] In another aspect the present invention concerns a
recombinant construct comprising a promoter operably linked to a
DNA sequence which, when expressed by a host produces an RNA
having:
[0200] (a) homology to at least one target mRNA expressed by the
host,
[0201] (b) two complementary RNA regions which are encoded by any
nucleic acid sequence in the genome of the host provided that said
sequence does not encode the target mRNA or any sequence that is
substantially similar to the target mRNA and said regions are in
proximity to (a),
[0202] wherein the expressed RNA reduces the expression of the
target mRNA or any substantially similar endogenous mRNA.
[0203] Any promoter can be used to practice the invention. There
can be mentioned a beta-conglycinin promoter, a Kunitz soybean
Trypsin Inhibitor (KSTI or Kti) promoter, a Gly m Bd 28K promoter,
T7 promoter, a 35S promoter and a beta-phaseolin promoter. The
preferred promoter is that of the .alpha.'-subunit of
beta-conglycinin (referred to herein as the beta-conglycinin
promoter). Co-suppressed plants that contain recombinant expression
constructs with the promoter of the .alpha.'-subunit of
beta-conglycinin will often exhibit suppression of both the .alpha.
and .alpha.' subunits of beta-congylcinin (as described in PCT
Publication No. WO 97/47731, published on Dec. 18, 1997, the
disclosure of which is hereby incorporated by reference).
Particularly preferred promoters are those that allow seed-specific
expression. This may be especially useful since seeds are the
primary source consumable protein and oil, and also since
seed-specific expression will avoid any potential deleterious
effect in non-seed tissues.
[0204] Examples of seed-specific promoters include, but are not
limited to, the promoters of seed storage proteins, which can
represent up to 90% of total seed protein in many plants. The seed
storage proteins are strictly regulated, being expressed almost
exclusively in seeds in a highly tissue-specific and stage-specific
manner (Higgins et al, (1984) Ann. Rev. Plant Physiol. 35:191-221;
Goldberg et al, (1989) Cell 56:149-160). Moreover, different seed
storage proteins may be expressed at different stages of seed
development.
[0205] Expression of seed-specific genes has been studied in great
detail (See reviews by Goldberg et al, (1989) Cell 56:149-160 and
Higgins et al, (1984) Ann. Rev. Plant Physiol. 35:191-221). There
are currently numerous examples of seed-specific expression of seed
storage protein genes in transgenic dicotyledonous plants. These
include genes from dicotyledonous plants for bean .beta.-phaseolin
(Sengupta-Gopalan et al, (1985) Proc. Natl. Acad. Sci. USA 82:
3320-3324; Hoffman et al, (1988) Plant Mol. Biol. 11: 717-729),
bean lectin (Voelker et al, (1987) EMBO J. 6: 3571-3577), soybean
lectin (Okamuro et al, (1986) Proc. Natl. Acad. Sci. USA 83:
8240-8244), soybean Kunitz trypsin inhibitor (Perez-Grau et al,
(1989) Plant Cell 1: 095-1109), soybean b-conglycinin (Beachy et
al, (1985) EMBO J. 4: 3047-3053; pea vicilin (Higgins et al, (1988)
Plant Mol. Biol. 11:683-695), pea convicilin (Newbigin et al,
(1990) Planta 180:461-470), pea legumin (Shirsat et al, (1989) Mol.
Gen. Genetics 215:326-331); rapeseed napin (Radke et al, (1988)
Theor. Appl. Genet. 75:685-694) as well as genes from
monocotyledonous plants such as for maize 15 kD zein (Hoffman et
al, (1987) EMBO J. 6:3213-3221), maize 18 kD oleosin (Lee at al.,
(1991) Proc. Natl. Acad. Sci. USA 88:6181-6185), barley
.beta.-hordein (Marris et al, (1988) Plant Mol. Biol. 10:359-366)
and wheat glutenin (Colot et al, (1987) EMBO J. 6:3559-3564).
Moreover, promoters of seed-specific genes operably linked to
heterologous coding sequences in chimeric gene constructs also
maintain their temporal and spatial expression pattern in
transgenic plants. Such examples include use of Arabidopsis
thaliana 2S seed storage protein gene promoter to express
enkephalin peptides in Arabidopsis and Brassica napus seeds
(Vandekerckhove et al, (1989) Bio/Technology 7:929-932), bean
lectin and bean .beta.-phaseolin promoters to express luciferase
(Riggs et al, (1989) Plant Sci. 63:47-57), and wheat glutenin
promoters to express chloramphenicol acetyl transferase (Colot et
al, (1987) EMBO J. 6:3559-3564).
[0206] As was noted above any type of promoter such as
constitutive, tissue-preferred or inducible promoters can be used
to practice the invention. Examples of constitutive promoters
include the cauliflower mosaivirus (CaMV) 35S transcription
initiation region, the 1'- or 2'- promoter derived from T-DNA of
Agrobacterium tumefaciens, the ubiquitin 1 promoter, the Smas
promoter, the cinnamyl alcohol dehydrogenase promoter (U.S. Pat.
No. 5,683,439), the Nos promoter, the pEmu promoter, the rubisco
promoter, the GRP1-8 promoter and other transcription initiation
regions from various plant genes known to those of skill.
[0207] Examples of inducible promoters are the Adh1 promoter which
is inducible by hypoxia or cold stress, the Hsp70 promoter which is
inducible by heat stress, and the PPDK promoter which is inducible
by light. Also useful are promoters that are chemically
inducible.
[0208] Examples of promoters under developmental control include
promoters that initiate transcription preferentially in certain
tissues, such as leaves, roots, fruit, seeds, or flowers. An
exemplary promoter is the anther specific promoter 5126 (U.S. Pat.
Nos. 5,689,049 and 5,689,051). In addition to those mentioned
above, other examples of seed-specific promoters include, but are
not limited to, 27 kD gamma zein promoter and waxy promoter,
Boronat, A., Martinez, M. C., Reina, M., Puigdomenech, P. and
Palau, J.; Isolation and sequencing of a 28 kD glutelin-2 gene from
maize: Common elements in the 5' flanking regions among zein and
glutelin genes; Plant Sci. 47, 95-102 (1986) and Reina, M., Ponte,
I., Guillen, P., Boronat, A. and Palau, J., Sequence analysis of a
genomic clone encoding a Zc2 protein from Zea mays W64 A, Nucleic
Acids Res. 18 (21), 6426 (1990). See the following site relating to
the waxy promoter: Kloesgen, R. B., Gierl, A., Schwarz-Sommer, Z.
S. and Saedler, H., Molecular analysis of the waxy locus of Zea
mays, Mol. Gen. Genet. 203, 237-244 (1986). Promoters that express
in the embryo, pericarp, and endosperm are disclosed in PCT
Application No. WO 00/11177 published Mar. 2, 2000, and PCT
Application No. WO 00/12733 published Mar. 9, 2000. The disclosures
each of these are incorporated herein by reference in their
entirety.
[0209] Either heterologous or non-heterologous (i.e., endogenous)
promoters can be used to practice the invention.
[0210] The promoter is then operably linked using conventional
means well known to those skilled in the art to a DNA sequence
which, when expressed by a host produces an RNA meeting certain
criteria.
[0211] The host can be any organism, or cell thereof, into which
the recombinant construct of this invention can be stably or
transiently introduced in order to alter gene expression. Examples
of suitable hosts include, but are not limited to, a plant, animal,
protozoan, bacterium, virus or fungus. The plant may be a monocot,
dicot or gymnosperm; the animal may be a vertebrate or
invertebrate. Preferred microbes are those used in agriculture or
by industry. Fungi include organisms in both the mold and yeast
morphologies.
[0212] Plants include Arabidopsis; field crops (e.g., alfalfa,
barley, bean, corn, cotton, flax, pea, rape, rice, rye, safflower,
sorghum, soybean, sunflower, tobacco, and wheat); vegetable crops
(e.g., asparagus, beet, broccoli, cabbage, carrot, cauliflower,
celery, cucumber, eggplant, lettuce, onion, pepper, potato,
pumpkin, radish, spinach, squash, taro, tomato, and zucchini);
fruit and nut crops (e.g., almond, apple, apricot, banana,
blackberry, blueberry, cacao, cherry, coconut, cranberry, date,
fajoa, filbert, grape, grapefruit, guava, kiwi, lemon, lime, mango,
melon, nectarine, orange, papaya, passion fruit, peach, peanut,
pear, pineapple, pistachio, plum, raspberry, strawberry, tangerine,
walnut, and watermelon); etc.
[0213] Examples of human or non-human vertebrate animals include
mammals, fish, cattle, goat, pig, sheep, rodent, hamster, mouse,
rat, guinea pigs, rabbits, and primate; invertebrate animals
include nematodes, other worms, Drosophila, and other insects.
Representative orders of insects include Coleoptera, Diptera,
Lepidoptera, and Homoptera.
[0214] The DNA sequence expressed by the host produces an RNA
having:
[0215] (a) homology to at least one target mRNA expressed by the
host;
[0216] (b1) two complementary RNA regions which are unrelated to
any endogenous RNA in the host, and which are in proximity to the
target mRNA, wherein the expressed RNA reduces the expression of
the target RNA or any substantially similar endogenous mRNA, or
[0217] (b2) two complementary RNA regions which are encoded by any
nucleic acid sequence in the genome of the host provided that said
sequence does not encode the target mRNA or any sequence that is
substantially similar to the target mRNA and said regions are in
proximity to (a).
[0218] The complementary RNA regions may comprise any of the
following:
[0219] (a) any nucleic acid sequence not normally present in the
genome of a host, i.e, are not related to any endogenous RNA in the
host; or
[0220] (b) any nucleic acid sequence in the genome of the host
which encodes the complementary regions provided that said sequence
does not encode the target mRNA or any sequence that is
substantially similar to the target mRNA.
[0221] With respect to (a) any nucleic acid sequence not normally
present in the genome of a host, the RNA region or regions which
are unrelated to any endogenous RNA in the host may comprise a
synthetic, non-naturally occurring RNA sequence. In still a further
aspect, these RNA region or regions, optionally, may or may not
comprise plant viral RNA.
[0222] With respect to (b) any nucleic acid sequence in the genome
of the host which encodes the complementary regions provided that
said sequence does not encode the target mRNA or any sequence that
is substantially similar to the target mRNA, this sequence
comprises transcribed or non-transcribed nucleic acid sequences
which may be present in the genome of the host, i.e., this sequence
may or may not be expressed by the host.
[0223] The complementary RNA regions described herein are in
proximity to the target mRNA. The term "in proximity" means that
the complementary regions are operably linked 5' to the target
mRNA, or 3' to the target mRNA, or within the target mRNA, or 5'
and 3' to the target mRNA, i.e., the complementary regions or
sequences can be found on either end of the target mRNA.
[0224] The complementary RNA regions can be any size that is
suitable for altering the expression of the target mRNA. The
complementary sequences are preferred to be about 40-50 nucleotides
in length, or more preferably 50-100 nucleotides in length, or most
preferably greater than 100-300 nucleotides. These complementary
sequences can be synthesized using conventional means well known to
those skilled in the art.
[0225] Examples of suitable complementary RNA regions which can be
used to practice the invention include, but are not limited to, SEQ
ID NO:12 and 13, bacterial sequences, jellyfish sequences, or any
artificial or naturally occurring sequences.
[0226] In another embodiment this invention concerns a method for
reducing expression of a target mRNA or any substantially similar
endogenous mRNA which comprises:
[0227] (a) introducing into a host any of the recombinant
constructs discussed herein, and
[0228] (b) selecting hosts which have reduced expression of the
target mRNA or any substantially similar endogenous mRNA.
[0229] Transformation methods are discussed above and are well
known to those skilled in the art.
[0230] Selection of the host having the desired phenotype will
depend upon the target mRNA whose expression is being altered. As
was noted above, the target mRNA may be any mRNA whose expression
in the host is to be altered. Typically, it should share homology
with the RNA produced by the host transformed with a recombinant
construct of the invention. The expression of more than one target
mRNA may be reduced provided that these targets share homology with
the RNA produced by the host transformed with a recombinant
construct of the invention.
[0231] In still another embodiment, this invention concerns a
recombinant construct comprising an RNA in lieu of a DNA sequence.
Thus, this RNA comprises:
[0232] (a) homology to at least one target mRNA expressed by a
host,
[0233] (b) two complementary RNA regions which are unrelated to any
endogenous RNA in the host, and which are in proximity to (a),
[0234] wherein the RNA, when introduced into the host, reduces the
expression of the target mRNA or any substantially similar
endogenous mRNA.
[0235] In another aspect, this invention concerns a recombinant
construct comprising an RNA in lieu of a DNA sequence in which the
RNA comprises:
[0236] (a) homology to at least one target mRNA expressed by a
host,
[0237] (b) two complementary RNA regions which are encoded by any
nucleic acid sequence in the genome of the host provided that said
sequence does not encode the target mRNA or any sequence that is
substantially similar to the target mRNA and which regions are in
proximity to (a),
[0238] wherein the RNA, when introduced into the host, reduces the
expression of the target mRNA or any substantially similar
endogenous mRNA.
[0239] As was discussed above the complementary RNA regions may
comprise any of the following:
[0240] (a) any nucleic acid sequence not normally present in the
genome of a host, i.e, are not related to any endogenous RNA in the
host; or
[0241] (b) any nucleic acid sequence in the genome of the host
which encodes the complementary regions provided that said sequence
does not encode the target mRNA or any sequence that is
substantially similar to the target mRNA.
[0242] With respect to (a) any nucleic acid sequence not normally
present in the genome of a host, the RNA region or regions which
are unrelated to any endogenous RNA in the host may comprise a
synthetic, non-naturally occurring RNA sequence. In still a further
aspect, these RNA region or regions, optionally, may or may not
comprise plant viral RNA.
[0243] With respect to (b) any nucleic acid sequence in the genome
of the host which encodes the complementary regions provided that
said sequence does not encode the target mRNA or any sequence that
is substantially similar to the target mRNA, this sequence
comprises transcribed or non-transcribed nucleic acid sequences
which may be present in the genome of the host.
[0244] The complementary RNA regions described herein are in
proximity to the target mRNA. The term "in proximity" means that
the complementary regions are operably linked 5' to the target
mRNA, or 3' to the target mRNA, or within the target mRNAS, or 5'
and 3' to the target mRNA, i.e., the complementary regions or
sequences can be found on either end of the target mRNA.
[0245] In addition, these RNAs can be used in a method for reducing
expression of a target mRNA or any substantially similar endogenous
mRNA which comprises:
[0246] (a) introducing into a host any of the RNAs described
herein; and
[0247] (b) selecting hosts which have reduced expression of the
target mRNA or any substantially similar endogenous mRNA.
[0248] In still a further aspect, the present invention concerns a
method for identifying or screening an essential plant gene which
comprises:
[0249] (a) transforming a plant cell with a recombinant construct
comprising a constitutive promoter wherein said construct is
capable of reducing expression of an essential plant gene with a
high degree of frequency;
[0250] (b) quantifying all transformed plant cells from step
(a);
[0251] (c) quantifying all transformed plant cells from a control
which does not reduce expression of an essential plant gene;
and
[0252] (d) comparing the quantification of transformed plant cells
selected from step (b) with the quantification of transformed
plants cells selected from step (c) wherein the quantification of
transformed plants cells selected from step (c) should
substantially exceed the quantification of transformed plant cells
selected from step (b).
[0253] Any essential plant gene can be identified or screened using
the method of the invention. An important aspect of this method is
the use of a constitutive promoter and a recombinant construct
capable of reducing expression of an essential plant gene with a
high degree of frequency.
[0254] Essential plant genes are defined above.
[0255] Constitutive promoters are defined above. Preferably, the
constitutive promoter is a high level or strong constitutive
promoter wherein expression of the gene under the control of the
promoter results in production of high levels of mRNA.
[0256] Any recombinant construct comprising a constitutive promoter
which is capable of reducing expression of an essential plant gene
with a high degree of frequency can be used to practice the
invention. In a preferred embodiment, the recombinant construct can
be any of the recombinant constructs of the invention comprising a
promoter operably linked to a DNA sequence provided that the
promoter is a constitutive promoter. The term high degree of
frequency is defined above.
[0257] Any plant cells can be transformed using standard
transformation methods as described above.
[0258] The number of plant cells transformed with a recombinant
construct comprising a constitutive promoter wherein the
recombinant construct is designed to reduce expression of an
essential plant gene is quantified and compared to the number of
plant cells transformed using a control in which expression of the
essential plant gene is not reduced. If the number of plant cells
transformed with the control substantially exceeds the number of
plant cells transformed with the recombinant construct designed to
reduce expression of an essential plant gene, then an essential
plant gene has been identified/screened. By "substantially
exceeds", it is meant at least a five-fold difference and,
preferably, a ten-fold difference. Also preferred would be a
4-fold, 6-fold, 7-fold, 8-fold, 9-fold, or greater than a 10-fold
difference. Thus, the number of plant cells transformed with the
control should be at least five-fold greater than the number of
plant cells transformed with the recombinant construct designed to
reduce expression of an essential plant gene.
EXAMPLES
[0259] The present invention is further defined in the following
Examples, in which all parts and percentages are by weight and
degrees are Celsius, unless otherwise stated. It should be
understood that these Examples, while indicating preferred
embodiments of the invention, are given by way of illustration
only. From the above discussion and these Examples, one skilled in
the art can ascertain the essential characteristics of this
invention, and without departing from the spirit and scope thereof,
can make various changes and modifications of the invention to
adapt it to various usages and conditions. The disclosures
contained within the references used herein are hereby incorporated
by reference.
Example 1
Transformation of Somatic Soybean Embryo Cultures
[0260] Generic Stable Soybean Transformation Protocol:
[0261] Soybean embryogenic suspension cultures are maintained in 35
ml liquid media (SB55 or SBP6) on a rotary shaker, 150 rpm, at
28.degree. C. with mixed fluorescent and incandescent lights on a
16:8 h day/night schedule. Cultures are subcultured every four
weeks by inoculating approximately 35 mg of tissue into 35 ml of
liquid medium.
1 TABLE 1 Stock Solutions (g/L): MS Sulfate 100X Stock MgSO.sub.4
7H.sub.2O 37.0 MnSO.sub.4 H.sub.2O 1.69 ZnSO.sub.4 7H.sub.2O 0.86
CuSO.sub.4 5H.sub.2O 0.0025 MS Halides 100X Stock CaCl.sub.2
2H.sub.2O 44.0 KI 0.083 CoCl.sub.2 6H.sub.2O 0.00125
KH.sub.2PO.sub.4 17.0 H.sub.3BO.sub.3 0.62 Na.sub.2MoO.sub.4
2H.sub.2O 0.025 MS FeEDTA 100X Stock Na.sub.2EDTA 3.724 FeSO.sub.4
7H.sub.2O 2.784 B5 Vitamin Stock 10 g m-inositol 100 mg nicotinic
acid 100 mg pyridoxine HCl 1 g thiamine SB55 (per Liter, pH 5.7) 10
ml each MS stocks 1 ml B5 Vitamin stock 0.8 g NH.sub.4NO.sub.3 3.03
3 g KNO.sub.3 1 ml 2,4-D (10 mg/mL stock) 60 g sucrose 0.667 g
asparagine SBP6 same as SB55 except 0.5 ml 2,4-D SB103 (per Liter,
pH 5.7) 1X MS Salts 6% maltose 750 mg MgCl.sub.2 0.2% Gelrite
SB71-1 (per Liter, pH 5.7) 1X B5 salts 1 ml B5 vitamin stock 3%
sucrose 750 mg MgCl.sub.2 0.2% Gelrite
[0262] Soybean embryogenic suspension cultures are transformed with
pTC3 by the method of particle gun bombardment (Klein et al (1987)
Nature 327:70). A DuPont Biolistic PDS1000/HE instrument (helium
retrofit) is used for these transformations.
[0263] To 50 ml of a 60 mg/ml 1 .mu.m gold particle suspension is
added (in order); 5 .mu.l DNA(1 .mu.g/.mu.l), 20 .mu.l spermidine
(0.1 M), and 50 .mu.l CaCl.sub.2 (2.5 M). The particle preparation
is agitated for 3 min, spun in a microfuge for 10 sec and the
supernatant removed. The DNA-coated particles are then washed once
in 400 .mu.l 70% ethanol and re suspended in 40 .mu.l of anhydrous
ethanol. The DNA/particle suspension is sonicated three times for 1
sec each. Five .mu.l of the DNA-coated gold particles are then
loaded on each macro carrier disk. For selection, a plasmid
conferring resistance to hygromycin phosphotransferase (HPT) may be
co-bombarded with the silencing construct of interest.
[0264] Approximately 300-400 mg of a four week old suspension
culture is placed in an empty 60.times.15 mm petri dish and the
residual liquid removed from the tissue with a pipette. For each
transformation experiment, approximately 5-10 plates of tissue are
normally bombarded. Membrane rupture pressure is set at 1000 psi
and the chamber is evacuated to a vacuum of 28 inches of mercury.
The tissue is placed approximately 3.5 inches away from the
retaining screen and bombarded three times. Following bombardment,
the tissue is placed back into liquid and cultured as described
above.
[0265] Eleven days post bombardment, the liquid media is exchanged
with fresh SB55 containing 50 mg/ml hygromycin. The selective media
is refreshed weekly. Seven weeks post bombardment, green,
transformed tissue is observed growing from untransformed, necrotic
embryogenic clusters. Isolated green tissue is removed and
inoculated into individual flasks to generate new, clonally
propagated, transformed embryogenic suspension cultures. Thus each
new line is treated as an independent transformation event. These
suspensions can then be maintained as suspensions of embryos
maintained in an immature developmental stage or regenerated into
whole plants by maturation and germination of individual somatic
embryos.
[0266] Independent lines of transformed embryogenic clusters are
removed from liquid culture and placed on a solid agar media
(SB103) containing no hormones or antibiotics. Embryos are cultured
for four weeks at 26.degree. C. with mixed fluorescent and
incandescent lights on a 16:8 h day/night schedule. During this
period, individual embryos are removed from the clusters and
screened for alterations in their fatty acid compositions (Example
3). Co-suppression of Fad2 results in a reduction of
polyunsaturated fatty acids and an increase in oleic acid
content.
[0267] It should be noted that any detectable phenotype, resulting
from the co-suppression of a target gene, can be screened at this
stage. This would include, but not be limited to, alterations in
protein content, carbohydrate content, growth rate, viability, or
the ability to develop normally into a soybean plant.
Example 2
Transformation of Maize
[0268] Generic Stable Maize Transformation Protocol:
[0269] Transformation of plasmid DNA in Hi-II strains of maize
follows the standard Hi-II bombardment transformation protocol
(Songstad D. D. et al, (1996) In Vitro Cell Dev. Biol. Plant
32:179-183). Cells are transformed by culturing maize immature
embryos (approximately 1-1.5 mm in length) onto 560P medium
containing N6 salts, Erikkson's vitamins, 0.69 g/l proline, 2 mg/l
2,4-D and 3% sucrose. After 4-5 days of incubation in the dark at
28.degree. C., embryos are removed from 560P medium and cultured,
scutellum up, onto 560Y medium which is equivalent to 560P but
contains 12% sucrose. Embryos are allowed to acclimate to this
medium for 3 h prior to transformation. The scutellar surface of
the immature embryos is targeted using particle bombardment with
either a mixture containing UBI:moPAT:pinII+UBI:GUS:pinII plasmids,
or with a combination of these two plasmids plus any one of the
constructs of the present invention (UBI is the ubiquitin-1
promoter, Christensen et al (1989) Plant Mol Bio 12:619-632; moPAT
refers to a "monocot-optimized phosphinothricin acyltransferase"
gene conferring resistance to the herbicide glufosinate ammonium,
referenced in PCT Application No. WO 98/30701 published on Jul. 16,
1998; the pinII (proteinase inhibitor) terminator is described in
An et al (1989) Plant Cell 1:115-122; and the GUS gene
(beta-glucuronidase) is described in Jefferson et al (1986) PNAS
83:8447-8451). Embryos are transformed using the PDS-1000 Helium
Gun from Bio-Rad at one shot per sample using 650PSI rupture disks.
DNA delivered per shot averages about 0.1667 ug. An equal number of
embryos per ear are bombarded with either the control DNA (PAT/GUS)
or the mixture of control with any one of the constructs of the
present invention. Following bombardment, all embryos are cultured
and maintained on 560L medium (N6 salts, Eriksson's vitamins, 0.5
mg/l thiamine, 20 g/l sucrose, 1 mg/l 2,4-D, 2.88 g/l proline, 2.0
g/l gelrite, and 8.5 mg/l silver nitrate). After 2-7 days
post-bombardment, all the embryos from both treatments are
transferred onto N6-based medium containing 3 mg/l bialaphos
Pioneer 560P medium described above, with no proline and with 3
mg/l bialaphos). Plates are maintained at 28.degree. C. in the dark
and are observed for colony recovery with transfers to fresh medium
occurring every two weeks.
[0270] Transient Maize Assays:
[0271] High type II callus is maintained by subculturing onto fresh
560P medium every two weeks. Healthy callus is pushed through a
0.77 mm.sup.2 nylon mesh and resuspended in MS culture medium with
2 mg/l 2,4-D at a density of 3 grams of tissue/40 ml medium. The
cell suspension are then pipetted in 4 ml aliquots (each containing
approximately 300 mg of cells) onto glass filter papers for
bombardment using a vacuum apparatus. These filters are then placed
on 560P medium and cultured in the dark at 26.degree. C. After 2-4
days the filters are removed from the culture medium and excess
liquid is removed using a vacuum apparatus. Filters with cells are
then shot (using the DuPont Biolistics PDS1000/He gun) according to
established methods (see example above) using 1 .mu.m gold
particles and 650 psi rupture disks. Immediately after bombardment
filters are returned to 560P culture medium and cultured in the
dark at 26.degree. C. All DNA's are adjusted to obtain a final
concentration of 1 .mu.g/total DNA/particle prep tube (6 shots).
The typical experiment is shot as follows:
GUS DNA+control DNA+Luciferase DNA
GUS DNA+silencing construct DNA+Luciferase DNA
[0272] Two days after bombardment cells are scraped from filters
and protein is extracted, and enzyme activity is determined, using
the luciferase assays outlined in the Dual-Luciferase Reporter
Assay protocol (Promega Corp., Madison, Wis.). The same extract is
also used to perform fluorometric GUS assays using the protocol of
Rao and Flynn (1990) Biotechniques 8:38-40. Data presented in
Example 8 below is plotted as the ratio of GUS/Luciferase
units.
Example 3
The Phenotype of Transgenic Soybean Somatic Embryos is Predictive
of Seed Phenotypes from Resultant Regenerated Plants
[0273] Mature somatic soybean embryos are a good model for zygotic
embryos. While in the globular embryo state in liquid culture,
somatic soybean embryos contain very low amounts of triacylglycerol
or storage proteins typical of maturing, zygotic soybean embryos.
At this developmental stage, the ratio of total triacylglyceride to
total polar lipid (phospholipids and glycolipid) is about 1:4, as
is typical of zygotic soybean embryos at the developmental stage
from which the somatic embryo culture was initiated. At the
globular stage as well, the mRNAs for the prominent seed proteins,
.alpha.' subunit of .beta.-conglycinin, kunitz trypsin inhibitor 3,
and seed lectin are essentially absent. Upon transfer to
hormone-free media to allow differentiation to the maturing somatic
embryo state, triacylglycerol becomes the most abundant lipid
class. As well, mRNAs for .alpha.'-subunit of .beta.-conglycinin,
kunitz trypsin inhibitor 3 and seed lectin become very abundant
messages in the total mRNA population. On this basis somatic
soybean embryo system behaves very similarly to maturing zygotic
soybean embryos in vivo, and is therefore a good and rapid model
system for analyzing the phenotypic effects of modifying the
expression of genes in the fatty acid biosynthesis pathway.
[0274] Most importantly, the model system is also predictive of the
fatty acid composition of seeds from plants derived from transgenic
embryos. This is illustrated with two different antisense
constructs in two different types of experiment that were
constructed following the protocols set forth in the PCT
Publication Nos. WO 93/11245 and WO 94/11516. Liquid culture
globular embryos were transformed with a chimeric gene comprising a
soybean microsomal .DELTA..sup.15 desaturase as described in PCT
Publication No. WO 93/11245 which was published on Jun. 10, 1993,
the disclosure of which is hereby incorporated by reference
(experiment 1,) or a soybean microsomal .DELTA..sup.12 desaturase
as described in PCT Publication No. WO 94/11516 which was published
on May 26, 1994, the disclosure of which is hereby incorporated by
reference (experiment 2). Both gene constructs were introduced in
antisense orientation under the control of a seed-specific promoter
(.beta.-conglycinin promoter) and gave rise to mature embryos. The
fatty acid content of mature somatic embryos from lines transformed
with vector only (control) and the vector containing the antisense
chimeric genes as well as of seeds of plants regenerated from them
was determined.
[0275] One set of embryos from each line was analyzed for fatty
acid content and another set of embryos from that same line was
regenerated into plants. Fatty acid analysis of single embryos was
determined either by direct trans-esterification of individual
seeds in 0.5 mL of methanolic H.sub.2SO.sub.4 (2.5%) or by hexane
extraction of bulk seed samples followed by transesterification of
an aliquot in 0.8 mL of 1% sodium methoxide in methanol. Fatty acid
methyl esters were extracted from the methanolic solutions into
hexane after the addition of an equal volume of water. In all
cases, if there was a reduced 18:3 content in a transgenic embryo
line when compared to an untransformed control, then a
corresponding reduction in 18:3 content was also observed in the
segregating seeds of the plant derived from that transformed line
(Table 2).
2TABLE 2 Percent 18:3 Content Of Embryos and Seeds of Control and
.DELTA..sup.15 Antisense Construct Transgenic Soybean Lines Embryo
Average Seed Average Transformant Line (SD, n = 10) (SD, n = 10)
Control 12.1 (2.6) 8.9 (0.8) .DELTA..sup.15 antisense, line 1 5.6
(1.2) 4.3 (1.6) .DELTA..sup.15 antisense, line 2 8.9 (2.2) 2.5
(1.8) .DELTA..sup.15 antisense, line 3 7.3 (1.1) 4.9 (1.9)
.DELTA..sup.15 antisense, line 4 7.0 (1.9) 2.4 (1.7) .DELTA..sup.15
antisense, line 5 8.5 (1.9) 4.5 (2.2) .DELTA..sup.15 antisense,
line 6 7.6 (1.6) 4.6 (1.6) *[Seeds which were segregating with
wild-type phenotype and without a copy of the transgene are not
included in these averages]
[0276] In addition, different lines containing the same antisense
construct, were used for fatty acid analysis in somatic embryos and
for regeneration into plants. About 55% of the transformed embryo
lines showed an increased 18:1 content when compared with control
lines (Table 3). Soybean seeds, of plants regenerated from
different somatic embryo lines containing the same antisense
construct, had a similar frequency (53%) of high oleate
transformants as the somatic embryos (Table 3). On occasion, an
embryo line may be chimeric. That is, 10-70% of the embryos in a
line may not contain the transgene. The remaining embryos that do
contain the transgene, have been found in all cases to be clonal.
In such a case, plants with both wild type and transgenic
phenotypes may be regenerated from a single, transgenic line, even
if most of the embryos analyzed from that line had a transgenic
phenotype. An example of this is shown in Table 4, in which, of 5
plants regenerated from a single embryo line, 3 have a high oleic
phenotype and two were wild type. In most cases, all the plants
regenerated from a single transgenic line will have seeds
containing the transgene. Thus, it was concluded that an altered
fatty acid phenotype observed in a transgenic, mature somatic
embryo line is predictive of an altered fatty acid composition of
seeds of plants derived from that line.
3TABLE 3 Oleate Levels in Somatic Embryos and Seeds of Regenerated
Soybeans Transformed With, or Without, .DELTA..sup.12 Desaturase
Antisense Construct # of # of Lines with Average* Vector Lines High
18:1 % 18:1 Somatic embryos: Control 19 0 12.0 .DELTA..sup.12
antisense 20 11 35.3 Seeds of regenerated plants: Control 6 0 18.2
.DELTA..sup.12 antisense 17 9 44.4 *average 18:1 of transgenics is
the average of all embryos or seeds transformed with the
.DELTA..sup.12 antisense construct in which at least one embryo or
seed from that line had an 18:1 content greater than 2 standard
deviations from the control value (12.0 in embryos, 18.2 in seeds).
The control average is the average of embryos or seeds which do not
contain any transgenic DNA but have been treated in an identical
manner to the transgenics.
[0277]
4TABLE 4 Analysis of Seeds From Five Independent Plants Segregating
From Plant Line 4 Plant # Average seed 18:1% Highest seed 18:1% 1
18.0 26.3 2 33.6 72.1 7 13.6 21.2 9 32.9 57.3 11 24.5 41.7 Mean of
15-20 seeds from 5 different plants regenerated from a single
embryo line. Only plants #2, 9 and 11 have seeds with a high 18:1
phenotype.
Example 4
Analysis of Nucleic Acid Sequences
[0278] Nucleic acid sequences comprising the target regions or the
complementary regions by conducting BLAST (Basic Local Alignment
Search Tool; Altschul et al (1993) J. Mol. Biol. 215:403-410; see
also www.ncbi.nlm.nih.gov/BLAST/) searches for sequences contained
in the BLAST "nr" database (comprising all non-redundant GenBank
CDS translations, sequences derived from the 3-dimensional
structure Brookhaven Protein Data Bank, the last major release of
the SWISS-PROT protein sequence database, EMBL, and DDBJ
databases). The nucleic sequences are analyzed for similarity to
all publicly available DNA sequences contained in the "nr" database
using the BLASTN algorithm provided by the National Center for
Biotechnology Information (NCBI). The DNA sequences can also be
translated in all reading frames and compared for similarity to all
publicly available protein sequences contained in the "nr" database
using the BLASTX algorithm (Gish and States (1993) Nat. Genet.
3:266-272) provided by the NCBI. For convenience, the P-value
(probability) of observing a match of a cDNA sequence to a sequence
contained in the searched databases merely by chance as calculated
by BLAST are reported herein as "pLog" values, which represent the
negative of the logarithm of the reported P-value. Accordingly, the
greater the pLog value, the greater the likelihood that the cDNA
sequence and the BLAST "hit" represent homologous proteins.
Example 5
A Comparison of Reduced Fad2 Expression Using Antisense vs.
"Classical" Co-suppression vs. "Complementary Region"
Co-suppression
[0279] The following are some comparisons of antisense, "classical"
co-suppression, and "complementary region" co-suppression (CRC) in
similar experiments involving a soybean fatty acid desaturase
(Fad). Fad2-1 is a gene locus encoding a .DELTA.-12 desaturase from
soybean that introduces a double bond into the oleic acid
side-chain to form a polyunsaturated fatty acid. Reduction in the
expression of Fad2-1 results in the accumulation of oleic acid
(18:1, or an 18 carbon fatty acid tail with a single double bond)
and a corresponding decrease in polyunsaturated fatty acid
content.
[0280] The antisense constructs have all, or a portion, of the
Fad2-1 coding region in a reverse orientation behind a strong
promoter. It is believed that expression of the "antisense" RNA
interferes with normal translation of the homologous endogenous
gene via a hybridization event. The "classical" co-suppression
construct have all, or a portion, of Fad2-1 in the normal sense
orientation behind a strong promoter. It is believed that the
expression of the "co-suppressing" RNA activates an uncharacterized
mechanism that results in the partial, or total, elimination of the
introduced RNA, as well as all RNAs having substantially similar
sequences. The CRC construct used contains a portion of the Fad2-1
coding region (300 bp) duplicated in the reverse complement
orientation, forming a complementary region specific for
Fad2-1.
[0281] The plasmids used in these experiments were made using
standard cloning methods well known to those skilled in the art
(Sambrook et al (1989) Molecular Cloning, CSHL Press, New York). A
starting plasmid pKS18HH (U.S. Pat. No.5,846,784 the contents of
which are hereby incorporated by reference) contains a hygromycin B
phosphotransferase (HPT) obtained from E. coli strain W677 under
the control of a T7 promoter and the 35S couliflower mosaic virus
promoter. Plasmid pKS18HH thus contains the T7 promoter/HPT/T7
terminator cassette for expression of the HPT enzyme in certain
strains of E. coli such as NovaBlue(DE3) [from Novagen], that are
lysogenic for lambda DE3 (which carries the T7 RNA Polymerase gene
under lacV5 control). Plasmid pKS18HH also contains the 35S/HPT/NOS
cassette for constitutive expression of the HPT enzyme in plants,
such as soybean. These two expression systems allow selection for
growth in the presence of hygromycin to be used as a means of
identifying cells that contain the plasmid in both bacterial and
plant systems. pKS18HH also contains three unique restiction
endonuclease sites suitable for the cloning other chimeric genes
into this vector. Plasmid ZBL100 (PCT Application No. WO 00/11176
published on Mar. 2, 2000) is a derivative of pKS18HH with a
reduced NOS 3' terminator. Plasmid pKS67 is a ZBL100 derivative
with the insertion of a beta-conglycinin promoter, in front of a
NotI cloning site, followed by a phaseolin 3' terminator (described
in PCT Application No. WO 94/11516, published on May 26, 1994).
PKS91 is a derivative of pKS67 with a polymerase chain reaction
(PCR) hairpin fragment of the soybean Fad2 gene inserted into the
Not I site. The primers used in PCR reactions with soybean Fad2-1
DNA as follows (all sequences are 5' to 3'):
5 PCR(A) GAATTCGCGGCCGCATGGGAGGTAGAGGTC SEQ ID NO:1
GGAAAACCATGCAACCCATTGGTACTTGCT SEQ ID NO:2 PCR(B)
AGCAAGTACCAATGGGTTGCATGGTTTTCC SEQ ID NO:3
AGCAAGTACCAATGGATACTTGTTCCTGTA SEQ ID NO:4 PCR(A/AS)
TACAGGAACAAGTATCCATTGGTACTTGCT SEQ ID NO:5
GAATTCGCGGCCGCATGGGAGGTAGAGGTC SEQ ID NO:6
[0282] The products of the three reactions (A)+(B)+(A/AS) are
ligated together, digested with the restriction enzyme Not I, and
the 1.3 kb fragment is cloned into the Not I site of KS67. The
plasmid pKS91 was used in the experiments presented in this
section. The 2.5 kb plasmid pKS17 contains pSP72 (obtained from
Promega Biosystems) and the T7 promoter/HPT/T7 3' terminator
region, and is the original vector into which the 3.2 kb BamHI-SalI
fragment containing the 35S/HPT/NOS cassette was cloned to form
pKS18HH. The plasmid pKS102 is a pKS17 derivative that is digested
with XhoI and SalI, treated with mung-bean nuclease to generate
blunt ends, and ligated to insert the following linker:
[0283] GGCGCGCCAAGCTTGGATCCGTCGACGGCGCGCC SEQ ID NO:7
[0284] The plasmid pKS83 has the 2.3 kb BamHI fragment of ML70
containing the Kti3 promoter/NotI/Kti3 3' terminator region
(described in PCT Application No. WO 94/11516, published on May 26,
1994) ligated into the BamHI site of pKS17. The plasmid pKS103 is a
derivative of pKS83 with the 1.3 kb NotI fragment of pKS91
(containing the Fad2 complementary sequence) ligated into the NotI
site.
[0285] In order to have comparable numbers of antisense lines to
compare to the more numerous co-suppression constructs, it was
necessary to include antisense experiments in which Fad 6 was
co-bombarded with Fad 2-1. Fad6 is a gene encoding .DELTA.-12
desaturase found in plastids (as opposed to Fad2 which is found in
the microsomal compartment). It was believed that suppression of
Fad2 and Fad6 simultaneously might give a stronger, or different,
phenotype than Fad2 suppression alone. However, it has since been
determined that Fad6 does not produce a phenotype, therefore the
phenotypes obtained from antisense experiments with both Fad2 and
Fad6 only reflect changes in Fad2-1 content.
[0286] Control embryos (286 individuals) had an average 18:1
content of 9% with a standard deviation (SD) of 6.2% (actual range
4-22%). Thus, an oleic acid content of 25% was chosen to represent
a positive reduction in Fad2-1 which results in increased 18:1 that
is more than 2 SDs from the mean, and higher than the highest
control value seen. If a line has at least 1 embryo with an 18:1
content of 25% or more, it is counted as an antisense or a
cosuppression event. Two experiments were combined to generate
about 30 lines.
6TABLE 5 Positive Transformed Lines With Reduced Fad2-1 Expression
Antisense Co-suppression CRC Fad2-1 lines with >25% 9 out of 31
9 out of 28 31 out of 33 18:1 content Percent total 29% 32% 94%
[0287] Another point to consider when analyzing transgenic plants
with reduced expression due to antisense or co-suppression is
chimerism. In the antisense and cosuppression experiments above the
positive events lines detected may have only contained a single
embryo out of ten with increased oleic acid content. Since all of
these experiments had 10 embryos per line analyzed it is possible
to graphically represent chimerism data by plotting actual embryo
numbers against oleic content (greater or less than 25% which would
be indicative of a tranformant reduced in .DELTA.-12 expression).
Therefore, if a line has little or no chimerism then all of its
embryos will have a suppressed phenotype as opposed to being wild
types. The data appear to be quite convincing that CRC (the grey
box) transformants give consistently higher oleic acid contents
with less chirmeric events:
[0288] Another issue is the efficiency with which a line exhibits
the reduced expression phenotype. The results from the experiments
here and in Example 6 confirm that the constructs containing the
complementary regions in proximity to the target sequence were more
effective at producing very high 18:1 content in embryos than
either antisense or "classical" co-suppression (i.e. as opposed to
complementary region containing co-suppression, CRC). The level of
suppression achieved in an experiment is reflected in the
corresponding increase of oleic acid content in the plants. The
higher the average 18:1 content, the greater the degree of
suppression. The complementary region containing constructs had
oleic acid contents of 50% which is over 5 SDs from the control
mean.
7TABLE 6 Positive Transformed Lines With High Efficiency Reduction
in Fad2-1 Expression Antisense Co-suppression CRC Fad2-1 lines with
>50% 1 out of 31 3 out of 28 29 out of 33 Percent total 3% 11%
88%
[0289] It appears that CRC is the most efficient and effective way
of producing high 18:1 content in embryos with reduced Fad2-1
content. As was shown in Example 3 there is a phenotypic
correlation between embryo oleic acid content and seed oleic acid
content in transgenic plant. Thus experiments yielding embryonic
lines with greater than 51% are most desirable since they appear to
guarantee a seed oleic of greater than 80%:
[0290] It is noted that most positive seed lines detected are close
to (or greater than) 80% oleic. Those few that aren't appear to be
derived from embryo lines with a maximum oleic content ranging from
30% to 50%. To date no lines having a positive phenotype that had
maximum embryo content of oleic acid less than 30%, and lines in
the production system with 51% or more oleic acid content have
always given rise to the best seed phenotypes. Additionally, the
top five embryo lines from production (all greater than 50% oleic)
gave the best phenotype in seed (greater than 80%) and the bottom
four embryo lines (all less than 50% oleic in embryos) all gave
less than 80% oleic acid content in seed.
Example 6
Target and Complementary Sequences can Both Co-suppress Their
Endogenous Homologs
[0291] The inclusion of a complementary region into the target
region of a co-suppression construct results in the improvement of
efficiency and uniformity in the resultant transformants (Example
5). The next step is to test if more than one gene can be
suppressed using this approach. Preliminary results using a 300
nucleotide complementary region from Fad2-1 surrounding a 600
nucleotide target from the soybean thioesterase gene results in the
suppression of both genes. This result was interesting for two
reasons. First the complementary region from Fad2 was interrupted
with thioesterase sequence, unlike the construct presented in
Example 5. Second, the non-complementary target sequence
(thioesterase) was inhibited in all lines that exhibited Fad2
reduction of expression, implying that there was equal efficiency
of target and complementary region reduction of expression.
[0292] To further test if any target sequence expression can be
efficiently repressed with any complementary region a construct was
made using Fad2-1 as the target in combination with a complementary
region from the soybean eceriferum3 (cer3) locus. Cer3 encodes one
of 21 gene products known to be involved in wax biosynthesis in
Arabidopsis thaliana (Hannoufa et al (1996) Plant J 10:459-67). The
inhibition of a single cer3 gene has no visible phenotype in
soybean. Also, cer3 is involved in a biosynthetic pathway that has
no known interactions with the fatty acid metabolic pathway
containing Fad2 activity. The plasmid pKS100 is a derivative of
pKS67. PCR reactions are run with the following primers (5'-3'
orientations) and cer3 DNA:
8 PCR(A + B) GAATTCGCGGCCGCGGCACGAGATTTGAGG SEQ ID NO:8
TTGCCCAATGTTTATGCATATGTAGAACTG SEQ ID NO:9 PCR(A/AS)
CAGTTCTACATATGCATAAACATTGGGCAA SEQ ID NO:10
GAATTCGCGGCCGCGGCACGAGATTTGAGG SEQ ID NO:11
[0293] The product of the two reactions are ligated together,
digested with NotI, and cloned into the NotI site of pKS67. Next,
the 516 bp ScaI fragment from soybean Fad2-1 is ligated into a FspI
digested pKS100 (within the Cer3 DNA, removing a small portion of
the complementary sequence) to form pBS58. Restriction enzyme
digestions were used to select the plasmid containing the Fad2
fragment in the sense or antisense orientation. It is believed that
Fad2 expression is reduced efficiently in all constructs tested in
soybeans.
Example 7
Suppression in Soybean of Fad2 by ELVISLIVES Complementary
Region
[0294] Constructs have now been made which have "synthetic
complementary regions" (SCR). Since the Fad 2 CR/TE2 target
suppressed both endogenous genes in the one line examined, and
since Cer3/Fad2 constructs suppress Fad2, it was deduced that it
may be possible to use any complementary sequence to reduce the
expression of a target. In this example the target sequence is
placed between complementary sequences that are not known to be
part of any biologically derived gene or genome (i.e. sequences
that are "synthetic" or conjured up from the mind of the inventor).
The target DNA would therefore be in the sense or antisense
orientation and the complementary RNA would be unrelated to any
known nucleic acid sequence. It is possible to design a standard
"suppression vector" into which pieces of any target gene for
suppression could be dropped. The plasmids pKS106, pKS124, and
pKS133 exemplify this. One skilled in the art will appreciate that
all of the plasmid vectors contain antibiotic selection genes such
as, but not limited to, hygromycin phosphotransferase with
promoters such as the T7 inducible promoter.
[0295] pKS106 uses the beta-conglycinin promoter while the pKS124
and 133 plasmids use the Kti promoter, both of these promoters
exhibit strong tissue specific expression in the seeds of soybean.
pKS106 uses a 3' termination region from the phaseolin gene, and
pKS124 and 133 use a Kti 3' termination region. pKS106 and 124 have
single copies of the 36 nucleotide EagI-ELVISLIVES sequence
surrounding a NotI site (the amino acids given in parentheses are
back-translated from the complementary strand): SEQ ID NO:12.
9 EagI E L V I S L I V E S NotI SEQ ID NO:12 CGGCCG GAG CTG GTC ATC
TCG CTC ATC GTC GAG TCG GCGGCCGC (S) (E) (V) (I) (L) (S) (I) (V)
(L) (E) EagI CGA CTC GAC GAT GAG CGA GAT GAC CAG CTC CGGCCG.
[0296] pKS133 has 2.times. copies of ELVISLIVES surrounding the
NotI site: SEQ ID NO:13
10 EagI E L V I S L I V E S EagI E L V I S SEQ ID NO:13
cggccggagctggtcatctcgctcatcgtcgagtcg gcggccg gagctggtcatctcg L I V
E S NotI (S) (E (V) (I) (L) (S) (I) (V) (L) (E) EagI
ctcatcgtcgagtcg gcggccgc cgactcgacgatgagcgagatgaccagctc cggccgc (S)
(E) (V) (I) (L) (S) (I) (V) (L) (E) EagI cgactcgacgatgagcgagatga-
ccagctc cggccg
[0297] The idea is that the single EL linker (SCR) can be
duplicated to increase stem lengths in increments of approximately
40 nucleotides. A series of vectors will cover the SCR lengths
between 40 bp and the 300 bp. Various target gene lengths are also
under evaluation. It is believed that certain combinations of
target lengths and complementary region lengths will give optimum
suppression of the target, although preliminary results would
indicate that the suppression phenomenon works well over a wide
range of sizes and sequences. It is also believed that the lengths
and ratios providing optimum suppression may vary somewhat given
different target sequences and/or complementary regions.
[0298] The plasmid pKS106 is made by putting the EagI fragment of
ELVISLIVES (SEQ ID NO:12) into the NotI site of pKS67. The
ELVISLIVES fragment is made by PCR using two primers and no other
DNA:
11 5'-GAATTCCGGCCGGAGCTGGTCATCTCGCTCATCGTCGAGTCGGCGGCCGCC SEQ ID
NO:14 GACTCGACGATGAGCGAGATGACCAGCTCCGGCCGGAATTC-3'
5'-GAATTCCGGCCGGAG-3' SEQ ID NO:15
[0299] The product of the PCR reaction is digested with EagI
(5'-CGGCCG-3') and then ligated into NotI digested pKS67. The
pKS111 is made by inserting a 599 nucleotide fragment from the
delta-12 desaturase gene (Fad2, nucleotides 399-997), in an
antisense orientation into the NotI site of pKS106. The Fad2
fragment is made by PCR using the following primers and Fad2 DNA as
a template:
[0300] GAATTCGCGGCCGCTGAGTGATTGCTCACGAGT SEQ ID NO:16
[0301] GAATTCGCGGCCGCTTAATCTCTGTCCATAGTT SEQ ID NO:17
[0302] The PCR product is digested with NotI (5'-GCGGCCGC-3') and
ligated into NotI digested pKS106. The total length of
complementary sequence is 47 nucleotides (with the 8 nucleotides
from the NotI site and 3 additional flanking bases). Co-suppression
of Fad2 results in a decrease in the production of polyunsaturated
fatty acids, and a corresponding increase in the accumulation of
oleic acid (18:1) in soybeans. (see Example 3 above). Oleic acid
concentrations in 18 of the 22 lines transformed with pKS111 were
2-5 times that found for the vector only controls, indicating
co-suppression in 82% of the recovered transgenic plants. It
appears that the placement of a single SCR (ELVISLIVES or EL)
surrounding a short segment of Fad2 (600 bp) is sufficient to give
co-suppression at efficiencies equal to the efficiencies achieved
using the CRC constructs of Example 5. The term "ELVISLIVES" and
"EL" are used interchangeably herein.
[0303] Additional plasmids can be used to test this example. For
example, pKS121 contains the Kti3 promoter/NotI/Kti3 3' terminator
fragment analogous to pKS83 inserted into the BamHI-SalI digested
pKS102. The EagI digested ELVISLIVES cloning site made from SEQ ID
NOs:14 and 15 is inserted into the NotI site of pKS121 to form
pKS124. The Fad2 fragment from pKS111 is ligated into NotI digested
pKS124 to form pKS132. The EagI digested EL PCR product can be
ligated into NotI digested pKS124 to form the 2.times.EL pKS133. An
additional 2.times.EL vector, pKS151, is similar to pKS133 except
for the addition of a second hygromycin phosphotransferase gene
with a 35S-CaMV promoter. Any synthetic sequence, or naturally
occurring sequence, can be used in an analogous manner. The
addition of the 599 bp soybean Fad2 fragment from pKS111 into a
NotI digested pKS133 produces pKS136.
[0304] The efficiency of Fad2 suppression using 1.times.EL (pKS132)
was compared to Fad2 suppression using the 2.times.EL (pKS136)
construct. Hygromycin resistant lines of soybean embryos were
isolated from independent transformation experiments with pKS132
and pKS136. Out of 98 lines containing pKS132, 69% displayed the
high oleic phenotype. Out of 54 lines containing pKS136, 70%
displayed the high oleic acid phenotype. Thus, both 1.times. and
2.times.EL constructs efficiently suppressed the Fad2 target
gene.
Example 8
Target Sequence Affects Suppression Efficiency
[0305] The length of the target was tested to determine the effect
on the efficiency of suppression in an EL construct. PCR reactions
were performed using the primers shown in Table 7 to create 25, 50,
75, 150, 300, and 600 fragments of Fad2 to place between 2.times.EL
complementary regions. The PCR products were cut with Not I and
ligated into pBluescript and the sequence of the fragments was
verified. Not I digested fragments were then ligated into the NotI
of pKS151.
12TABLE 7 Primers for PCR of Soybean Fad2 Primer Sequence Length
SEQ ID NO 5'-GAATTCGCGGCCGCCCAATCTA- TTGGGTTCTC-3' -- 18 common
5'-end primer position 363 in Fad2 sequence
5'-GAATTCGCGGCCGCAACCTTGGAGAACCCAAT-3 25 19 3'-end primer for 25 bp
fragment from 363-387 of Fad2
5'-GAATTCGCGGCCGCATCACCCACACACCAGTG-3' 50 36 3'-end primer for 50
bp fragment from 363-412 of Fad2 5'-GAATTCGCGGCCGCGGCATGG-
TGACCACACTC-3' 75 20 3'-end primer for 75 bp fragment from 363-437
of Fad2 5'-GAATTCGCGGCCGCTGAGAAATAAGGGACTAA-3' 150 21 3'-end primer
for 150 bp fragment from 363-512 of Fad2
5'-GAATTCGCGGCCGCGAGTGTGACGAGAAGAGA-3' 300 22 3'-end primer for 300
bp fragment from 363-662 of Fad2
5'-GAATTCGCGGCCGCTTCTGATGAATCGTAATG-3' 600 23 3'-end primer for 600
bp fragment from 363-962 of Fad2
[0306]
13TABLE 8 Effect of Target Length on Suppression by 2XEL Fad2
Target Length # Lines Tested High Oleic 25 8 0% 50 8 0% 75 8 13%
150 8 13% 300 29 34% 600 20 60%
[0307] The result in Table 8 show a clear correlation between
target length and efficiency of supression. The longest (600 bp)
fragment of Fad2 is nearly twice as likely to be suppressed in the
EL construct than a 300 bp fragment, while 50 bp and shorter
fragments
Example 9
[0308] Multiple Target Sequences Can be Suppressed by
2.times.EL
[0309] A construct was assembled to test whether multiple target
sequences can be used between EL complementary sequences to achieve
simultaneous suppression. A 969 bp fragment from a soybean delta-9
desaturase was inserted into pKS136 next to the 599 bp Fad2
fragment to form pBS68. Both desaturase fragments were flanked by
2.times.EL complementary regions (2.times.EL-Fad2-Delta
9-2.times.EL the sequence of which is shown in SEQ ID NO:24).
[0310] Delta-9 desaturase catalyzes the double-bond at the
9-position of 18-carbon fatty acids to form oleic acid (18:1) from
stearic acid (18:0), analogous to the delta-12 Fad2 which catalyzes
the 12-position double bond that converts oleic acid to linoleic
acid (18:2). Suppression of the unique Fad2 gene results in an
accumulation of oleic acid at the expense of polyunsaturated fatty
acids. Suppression of delta-9 desaturases results in an
accumulation of stearic acid at the expense of all unsaturated
fatty acids. However, there are several delta-9 desaturases in
soybean (at least three) so it is unclear how the suppression of
one member would affect oil composition. Transformation protocols
and oil composition analyses were performed as previously outlined
in Examples 1 and 3, respectively.
[0311] Transformation of soybean with pBS68 resulted in 113
hygromycin resistant lines. Of these 72 showed some oil phenotype
(64%). The phenotypes of the 72 suppressed lines were: 18 were high
stearate, 23 were high oleate, and 31 were both high oleate and
high stearate. Therefore, multiple targets can be efficiently
suppressed by a single EL construct.
Example 10
Suppression of Soybean Galactinol Synthase Genes in ELVISLIVES
Constructs
[0312] Raffinose saccharides are a group of D-galactose-containing
oligosaccharide derivatives of sucrose that are widely distributed
in plants. Raffinose saccharides are characterized by the general
formula:
[O-.beta.-D-galactopyranosyl-(1.fwdarw.6).sub.n-.alpha.-glucopyranosyl-(.-
fwdarw.2)-.beta.-D-fructofuranoside where n=0 through n=4 are known
respectively as sucrose, raffinose, stachyose, verbascose, and
ajugose.
[0313] Although abundant in many species, raffinose saccharides are
an obstacle to the efficient utilization of some
economically-important crop species. Raffinose saccharides are not
digested directly by animals, primarily because alpha-galactosidase
is not present in the intestinal mucosa [Gitzelmann et al (1965)
Pediatrics 36:231-236; Rutloffet al (1967) Nahrung 11:39-46].
However, microflora in the lower gut are readily able to ferment
the raffinose saccharides resulting in an acidification of the gut
and production of carbon dioxide, methane and hydrogen gases
[Murphy et al (1972) J. Agr. Food. Chem. 20:813-817; Cristofaro et
al (1974) in Sugars in Nutrition, H. L. Sipple and K. W. McNutt,
Eds. Academic Press, New York, Chap. 20, 313-335; Reddy et al
(1980) J. Food Science 45:1161 -1164]. The resulting flatulence can
severely limit the use of leguminous plants in animal, particularly
human, diets. It is unfortunate that the presence of raffinose
saccharides restricts the use of legumes in human diets because
many of these species are otherwise excellent sources of protein
and soluble fiber. Varieties of edible beans free of raffinose
saccharides would be more valuable for human and animal diets and
would facilitate broader access to the desirable nutritional
qualities of edible leguminous plants.
[0314] The biosynthesis of raffinose saccharides has been well
characterized [see Dey (1985) in Biochemistry of Storage
Carbohydrates in Green Plants, P. M. Dey and R. A. Dixon, Eds.
Academic Press, London, pp. 53-129]. The committed reaction of
raffinose saccharide biosynthesis involves the synthesis of
galactinol from UDP-galactose and myo-inositol. The enzyme that
catalyzes this reaction is galactinol synthase (inositol
1-alpha-galactosyltransferase; EC 2.4.1.123). Synthesis of
raffinose and higher homologues in the raffinose saccharide family
from sucrose is thought to be catalyzed by distinct
galactosyltransferases (for example, raffinose synthase and
stachyose synthase). Studies in many species suggest that
galactinol synthase is the key enzyme controlling the flux of
reduced carbon into the biosynthesis of raffinose saccharides
[Handley et al (1983) J. Amer. Soc. Hort. Sci. 108:600-605;
Saravitz, et al (1987) Plant Physiol. 83:185-189]. Altering the
activity of galactinol synthase, either as a result of
overexpression or through antisense inhibition, would change the
amount of raffinose saccharides produced in a given tissue.
[0315] Related galactinol synthase genes already known in the art
include sequences disclosed in U.S. Pat. Nos. 5,773,699 and
5,648,210, Kerr et al, "Nucleotide Sequences of Galactinol Synthase
from Zucchini and Soybean" and Sprenger and Keller (2000) Plant J
21:249-258. Presumably related sequences are also disclosed in PCT
Publication No. WO 98/50553, Lightner, "Corn Glycogenin". Two genes
encoding soybean galactinol synthases have been previously
identified (SEQ ID NOs:30 and 32, with the predicted translation
products shown in SEQ ID NOs:31 and 33; presented in U.S. Pat No.
U.S. Provisional Application No. 60/196550, filed Apr. 11, 2000).
Unlike the unique soybean Fad2 gene, it is known that there are
multiple galactinol synthase genes in soybean. Because there are
multiple genes encoding galactinol synthases, it is believed that
suppression of more than one gene may be required to detect an
effect on raffinose sugar levels.
[0316] A plasmid construct was assembled containing fragments of
two galactinol synthase soybean genes Gas1 (390 bp from 13-402 of
SEQ ID NO:30) and Gas2 (399 bp, from 129-527 of SEQ ID NO:32)
cloned in the NotI site of a 2.times.EL cassette. The promoter
region was a late embryo promoter (Lea) from soybean. The Lea
promoter (Lee et al (1992) Plant Physiol 100:2121-2122; Genbank
Accession No. M97285) was amplified from genomic A2872 soybean DNA
with the following primers:
[0317] SEQ ID NO:25 5'-ATT AAC CTC AAT TCT TCT AAG (position 25-45
of M97285)
[0318] SEQ ID NO:26 5'-TTC AAA GAT CAA TTA TTT CC (position
995-1112 M97285)
[0319] and a phaseolin 3'-end (amplified with primers shown in SEQ
ID NOs:27 and 28) was added. The entire Lea
promoter-2.times.EL-Gas1-Gas2-2.- times.EL -phaseolin 3'-end
cassette was then cloned into the BamHI site of pKS136 to create
the pKS149 vector (the sequence of the complete EL region of pKS149
is shown in SEQ ID NO:29). When introduced into plants pKS136 will
inhibit both Fad2 (controlled by the Kti promoter) and Gas genes
(controlled by the Lea promoter). Since the Kti promoter is active
in embryos, it is possible to screen the embryos for high oleic
phenotype, as described in the previous examples. Of the 119 lines
isolated as hygromycin resistant 65% were found to have a high
oleic phenotype.
[0320] These suppressed lines should also contain the Gas
suppression cassette, allowing for the assay of raffinose sugars in
the seedlings (Lea is not active during the early embryo stage).
Raffinose sugars (galactinol, raffinose, stachyose, etc.) can be
detected using thin layer chromatography. Plant samples are
extracted with hexane then dried. The dried material is then
resuspended in 80% methanol, incubated at room temperature for 1-2
hours, centrifuged, and 1-2 microliters of the supernatant is
spotted onto a TLC plate (Kieselgel 60 CF, from EM Scientific,
Gibbstown, N.J.; catalog no. 13749-6). The TLC is run in
ethylacetate:isopropanol:20% acetic acid (3:4:4) for 1-1.5 hours.
The air dried plates are sprayed with 2% sulfuric acid and heated
until the charred sugars are detected. As shown in FIG. 2 the two
lines labeled GAS-EL show reduced levels of raffinose sugars
(lowest band) when compared to a control known to have very low
raffinose sugars (Low 4). It is estimated that there is a 60%
reduction of raffinose sugars in these lines when compared to
wild-type soybean.
Example 11
ELVISLIVES Constructs can Be Used to Screen Essential Plant
Genes
[0321] Acetolactate synthase (ALS), also known as acetohydroxyacid
synthase (AHAS), catalyzes the first common step in the
biosynthesis of the branched chain amino acids isoleucine, leucine,
and valine (Keeler et al, Plant Physiol 1993 102: 1009-18).
Inhibition of native plant ALS by several classes of structurally
unrelated herbicides including sulfonylureas, imidazolinones, and
triazolopyrimidines, is lethal (Chong C K, Choi J D Biochem Biophys
Res Commun 2000 279:462-7). Hence suppression of the gene encoding
ALS in soybean should also be lethal. Thus, a well-validated
herbicide target like ALS can inserted into EL vectors to test
whether the transformation screening process can be used to
identify essential plant genes. If so, other essential plant genes
could be screened in a high-throughput method to identify novel
potential herbicide targets. The term "essential plant genes" as
used herein refers to genes encoding a product that is required for
normal plant growth, development, and/or viability. In addition to
ALS, examples of essential plant genes would include, but not be
limited to, rate-limiting enzymes in amino acid, nucleic acid, or
lipid biosynthesis. It is also believed that many genes with
unknown function may be essential.
[0322] If a soy EL-ALS-EL construct is expressed during selection
on hygromycin, very few events should be recovered, even though the
HPT gene is present. If the EL-ALS-EL transcriptional unit is not
expressed until late embryogenesis then recovery of transformation
events should be similar in number to events obtained with vector
controls, containing only the HPT gene. Constitutive expression of
EL-ALS-EL can be accomplished by using a 35S promoter (pKS161).
Expression of EL-ALS-EL restricted to late
embryogenesis/germination can be accomplished with the previously
described LEA promoter (pKS163).
[0323] To make KS161 the EL linker (SEQ ID NO:12) was cloned into
the NotI site of pKS50 to produce pKS137 (a single EL complementary
region with a 1 kb 35S CaMV promoter and a 700 bp nos 3'-end on a
plasmid with 2 HPT genes one with a T7 promoter and the second with
a 35S promoter). A 208 bp Hind III/EcoR I fragment from a soybean
ALS gene (SEQ ID NO:35, fragment is from position 891-1114) was
then cloned into the Hind III/EcoR I sites of pKS137 to produce
pKS161. To make pKS163 the EL linker (SEQ ID NO:12) was cloned into
the NotI site of pKS127 to produce KS139 (a single EL complementary
region with the Lea promoter and the phaseolin 3'-end from Example
10 on a plasmid with 2 HPT genes one with a T7 promoter and the
second with a 35S promoter). The 208 bp Hind III/EcoR I fragment
from soybean ALS gene (SEQ ID NO:35, the HindIII/EcoRI fragment is
from position 896-1103) was then cloned into the Hind III/EcoR I
sites of KS139 to produce KS 163.
[0324] KS161 and KS 163 were transformed into 821 tissue (Example
1). The transformation efficiency for this tissue is normally in
the range of 200-500 clones/gram of tissue. The results of two
separate transformation experiments with KS161 and KS163, 4 weeks
after bombardment and transfer to hygromycin-containing medium
are:
[0325] Expt. 1
[0326] KS161 (35S ALS EL) 16 clones/gram tissue
[0327] KS163 (LEA ALS EL) 247 clones/gram tissue
[0328] Expt. 2
[0329] KS161 (35S ALS EL) 43 clones/gram tissue
[0330] KS163 (LEA ALS EL) 467 clones/gram tissue
[0331] In both experiments the 35S EL-ALS vector resulted in a
>90% decrease in clone numbers, presumably because of
suppression of the endogenous ALS gene throughout embryo formation
stages. Therefore, the difference in clone numbers obtained for a
novel gene fragment inserted into a 35S-EL construct (KS137) and a
LEA-EL construct (KS139) can be used as a measure of whether the
corresponding endogenous gene is essential or not, and thus whether
or not it is a potential herbicide target. The effect of an unknown
gene fragment on transformation efficiency can be measured within a
few weeks of particle bombardment and thus this is a rapid means of
identifying new herbicide target candidates. A typical screen
consists of bombarding tissue with KS137 and KS139 as empty-vector
controls, KS161 as a positive (ALS) control and various gene
fragments, amplified by PCR to contain Hind III and EcoR I sites,
cloned into the HindIII/EcoRI sites of KS137 and KS139.
[0332] The improved frequency of suppression achieved with the EL
constructs allows for the possibility of a reliable screening
method. A significant percentage of the hygromycin recovered
transformation events must be suppressed by the target sequence
contained within pKS137 or pKS139 in order for there to be a
statistically definitive difference between the two experiments.
The term "high degree of frequency" as used herein, with respect to
the suppression efficiency, refers to the percentage of transformed
lines that exhibit the target suppressed phenotype. High frequency
percentages are expected to be in a range of at least 15-95% and
any integer percentage found within the range. Preferred
embodiments would include at least 15%, 20%, 25%, 30%, 35%, 40%,
45%, 50%, 55%, 60%, 65%, 70 %,75%, 80%, 85%, 90%, and 95%.
Example 12
Suppression of Cellulose Synthase in Maize Using EL Constructs
[0333] Cellulose synthase genes encode a family of proteins
involved in cellulose formation in plants (Pear, et al, Proc. Natl.
Acad. Sci. (USA) 93, 12637-12642; Saxena, et al, (1990), Plant
Molecular Biology 15, 673-684). Several maize genes encoding
cellulose synthases (cesA) have been recently cloned and
characterized (PCT Publication No. WO 00/09706, published on Feb.
24, 2000). Fragments from four of these genes, cesA1, cesA4, cesA5,
and cesA8, were used to test whether 1 .times.EL could direct the
suppression of these genes in maize.
[0334] One kb fragments from the 5'-end of the cDNA clones
(including 5'-UTR and ORF sequences) for cesA1, cesA4, cesA5, and
cesA8 were each cloned separately into the internal NotI site of
1.times.EL (SEQ ID NO:12) constructs. Each of these "EL-cesA-EL"
cassettes was inserted into a plasmid containing a f3.7 promoter (a
weak constitutive promoter exhibiting some preference for
stalk-specific expression), a proteinase inhibitor 3'-end (pinII
from potato, An et al (1989) Plant Cell 1: 115-122), and a
35S:BAR:pinII selection marker. A control plasmid containing an IN2
promoter driving a GUS gene with a pinll 3'-end was also made.
[0335] Results from maize transformation experiments with each of
the constructs are shown in Table 9. Twenty-five lines were
isolated for each of the four cesA gene constructs and 18 lines
were isolated for the control. The height of the plants and stalk
diameter were on average smaller in the lines containing the
suppression constructs than in the control. Ear heights were
shorter in the cesA1 and cesA5 containing lines. The average
cellulose percentage of total dry matter is normally 46% in control
plants. All of the cesA constructs had lines that were below 46%
cellulose with cesA1>cesA5>cesA8>cesA4. The lines that
exhibited low cellulose percentages were tested by DNA Southern
blot analyses to determine which contained a single-copy transgene
insertion. All had at least one line that had both low cellulose
and a single transgene.
14TABLE 9 Summary of CesA Suppression By EL Constructs height Ear
Stalk Cellulose Single Construct (cm) (cm) (mm) <46% transgene
Control 171 44 16 CesAl 150 40 14 9 3 CesA4 164 46 13 3 2 CesA5 148
41 13 7 2 CesA8 166 46 15 5 1
[0336] These results show that cellulose levels are altered in
plants containing cesA gene fragments contained within 1.times.EL
constructs. This is interpreted as meaning that cesA suppression in
maize has a detectable phenotype, and that EL-controlled
suppression is active in maize. It should be noted that the f3.7
promoter is a weak promoter compared to others used in this
application (35S-CaMV, Kti, etc.) and that cesA is a large
multigene family. These factors may have an effect on the frequency
and/or extent of suppression.
Example 13
Transient Suppression of GFP in Maize Using GUS Complementary
Region
[0337] All expression cassettes used in this example comprise a
maize ubiquitin promoter (nt 1-899), a maize ubiquitin 5'
untranslated leader sequence (nt 900-982) and a maize ubiquitin
intron 1 (nt 983-1992). In plasmid PHP7921 the coding sequence (nt
2015-2731) is GFP (green fluorescent protein) with codons optimized
for expression in maize. In plasmid PHP3953 the coding sequence (nt
2013-3821) is GUS. Both cassettes include the polyadenylation
signal sequences from the proteinase inhibitor II gene of S.
tuberosum (PINII TERM, nt 2737-3047 in PHP7921 and nt 3883-4192 in
PHP3953).
[0338] Standard recombinant DNA methodologies well known to those
skilled in the art were used throughout the construction of the
expression cassettes for this work. Orientations of fragment
insertions and the final structures of the plasmid constructs were
determined using standard agarose gel analysis and/or sequencing of
the plasmids.
[0339] Plasmid PHP7921 was used to create a complementary region
(CR) of a small portion of the GFP coding sequence as follows:
plasmid DNA was digested with XhoI and treated with the Klenow
fragment of DNA polymerase I to release a 244 bp blunt-ended
fragment representing nt 2436-2675 near the 3' end of the GFP
coding sequence. This fragment was then inserted back into PHP7921
at the HpaI site (nt 2735) just downstream of the stop codon of
GFP. A recombinant plasmid was identified that had the inserted
fragment in the reverse orientation relative to the original
sequence. This plasmid was designated PHP16391.
[0340] Expression cassettes for GUS containing a heterologous
GFP-CR were constructed as follows: the entire GFP-CR of PHP16391
was isolated as a BsrGI fragment (nt 2464-2947, 483 bp). This
fragment comprises sequences capable of forming a CR with a 214 bp
stem and a 55 nt loop. The fragment was rendered blunt-ended as
above using Klenow and inserted into the GUS expression cassette of
PHP3953 at three different sites. Plasmid PHP16561 has the GFP-CR
inserted in the BamHI site (filled in) of PHP3953 (nt 2006), just
5' to the start codon. Plasmid PHP16562 has the GFP-CR inserted in
the PacI site (T4 polymerase-treated to render blunt) at nt 3919 of
PHP3953 just 3' to the stop codon. Similarly, plasmid PHP16563 has
the GFP-CR inserted in the SnaBI site at nt 2398 of PHP3953 within
the GUS coding sequence.
[0341] High type II callus was maintained by subculturing onto
fresh 560P (N6 salts, Erikkson's vitamins, 0.69 g/l proline, 2 mg/l
2,4-D and 3% sucrose) medium every two weeks. Healthy callus was
extruded through a 0.77 mm.sup.2 nylon mesh, weighed, and
resuspended in MS culture medium with 2 mg/l 2,4-D at a density of
3 grams of tissue/40 ml medium. Cells were uniformly suspended by
pipetting the solution up-and-down through a large-bore pipette,
and 4 ml aliquots (300 mg) were then collected on glass filter
papers using a vacuum apparatus. These filters, each containing
approximately 300 mg of cells, were then placed on 560P medium and
cultured in the dark at 26.degree. C. After 2-4 days the filters
were removed from the culture medium and excess liquid was removed
using a vacuum apparatus. DNA was then delivered into the cells
using a DuPont Biolistics particle gun using a standard Hi-II
bombardment transformation protocol (Songstad D. D. et al, In Vitro
Cell Dev. Biol. Plant 32:179-183, 1996) modified by using 1 um gold
particles. Immediately after bombardment the filters were returned
to 560P culture medium and cultured in the dark at 26.degree. C.
All DNA's were combined in equal ratios to obtain a final
concentration of 1 ug of total DNA/particle preparation (0.33 ug of
each DNA combined in each preparative tube was used for 6 shots).
The experiment was shot as follows: From each treatment 10 plates
were bombarded (5 from each of two DNA preps).
15 Treatment DNA's # Control PHP3953 (GUS) + PHP10256(rLuciferase)
+ PHP7921(GFP) #2 GUS w/5'CRC PHP3953 (GUS) + PHP10256
(rLuciferase) + PHP16561(CR-GUS) #3 GUS w 3'CRC PHP3953 (GUS) +
PHP10256 (rLuciferase) + PHP16562(GUS-CR) #4 GUS w/CRC in cds
PHP3953 (GUS) + PHP10256 (rLuciferase) + PHP16563(GU-CR-S)
[0342] For analysis, the plates within a treatment were grouped
into 5 pairs (each pair containing plates shot with different DNA
preparations for the same plasmid treatment). Two days after
bombardment, all the tissue from the two paired plates was combined
and resuspended in 5 ml of culture medium. After mixing with a
wide-bore pipette, a 1 ml aliquot was transferred into a 1.5 ml
Eppendorf tube. The cells were centrifuged at 1000 RPMs for 2
minutes in a microfuge and the supernatant (culture medium)
decanted. To each tube, 150 ul of "Promega Luciferase Passive Lysis
Buffer" was added, temperature-equilibrated on ice, and the cells
were broken apart using a hand-drill powered Kontes-tube plastic
pestil (extraction and subsequent luciferase assays followed
Promega's Dual-Luciferase Reporter Assay protocol (Technical
Bulletin #TM040). The cell debris was pelleted by centrifugation in
the Microfuge at 3000 RPM for 3 minutes and the supernatant was
pipetted off. Aliquots of this extract were used for the
fluorometric quantitation of both GUS and luciferase (50 and 20 ul,
respectively). GUS enzyme activity was determined as a rate
measurement between 10 and 40 minutes after adding substrates, and
data was expressed as pmol MU/min/ml/extract (slope). Fluorometric
GUS assays were performed on a LabSystems FLUOROSKAN Ascent FL
according to the protocol of Rao and Flynn (Biotechniques 1990
8:38-40. Fluorometric analysis of luciferase activity collected
using an Analytical Luminescence Laboratory Monolight 2010,
following the manufacturer's instructions and the Promega protocol.
Assessing both markers for each replicate provided an internal
control (luciferase) against which relative GUS activity could be
rated. Thus, data was plotted as the ratio of GUS/Luciferase units
(because the absolute fluorometric units for Renilla luciferase
were so high, all the raw values for luciferase activity were
divided by 10 before using to normalize GUS activity).
16TABLE 10 Complementary Regions of GFP Reduce Target GUS Activity
in a 3' (#3) and Internal Orientation (#4) Pmol. MU/min/ml extract
slope/ Treatment rLuci Ave. Standard deviation #1 74.14 27.66 #2
82.05 20.99 #3 20.22 17.87 #4 9.67 3.02 Repeat Expt #1 86.93 6.94
#2 77.3 22.62 #3 20.03 7.32 #4 11.2 2.32
[0343] It appears from the results (see Table 10) of these
transient expression experiments that the placement of a
complementary region 5' to a target does not reduce the expression
of the target gene. However, it is believed that under optimized
conditions, or in a stable transformation experiment, placement of
a complementary region 5' to a target is sufficient to reduce
expression of the target.
Example 14
Suppression of Maize PDS by A Modified Soybean Complementary
Region
[0344] An additional suppression construct was created using a 205
bp HindIII-BstEII fragment from the soybean Kti promoter as the
complementary region surrounding a multiple cloning site. Two
copies of the Kti fragment were ligated in an inverted repeat
arrangement and subsequently modified by PCR to remove inconvenient
restriction sites and add cloning sites at both ends and in the
region between the two complementary sequences to form the SHH3
cassette (see SEQ ID NO:34). The resulting plasmid (PHP17962) was
used as a source of the SHH3 sequence. The Kti sequence is not
normally found in the maize genome, therefore no suppression of
endogenous maize genes is expected from the SHH3 region alone.
However, when a portion of an endogenous target sequence is
inserted into the cloning sites between the complementary Kti
sequences, the homologous endogenous gene transcript should be
affected.
[0345] To test the utility of the SHH3 in silencing an endogenous
gene, a 1385 bp NheI fragment representing about 80% of the coding
sequence of the phytoene desaturase gene (PDS-1) of Z. mays
(Pioneer EST cnlcz91R, Genbank Accession No. L39266) was treated
with Klenow enzyme as previously described to render the ends blunt
and then ligated into the EcoRV site of SHH3 to generate PHP17894.
The SHH3-PDS fragment was then moved as a 1865 bp HpaI fragment
into an intermediate vector construct to place it under the control
of the ubiquitin promoter: ubiquitin intron1 (U.S. Pat. No.
5,510,474 and 5,614,399) with polyadenylation signals provided by
the pinII terminator (An et al (1989) Plant Cell 1:115-122). The
resulting plant transcription unit was moved into a binary vector
(PHP15578) containing a CaMV35S--bialaphos selectable marker
element to generate PHP17914. This construct was electroporated
into competent cells of Agrobacterium tumefaciens strain LBA4404
carrying the superbinary plasmid pSB1 ((Ishida et al (1996) Nature
Biotech 14:745-750). This process generates a cointegrate plasmid
comprising the combined sequences of PHP17914 and pSB1. This
cointegrate plasmid, designated PHP17939, was used to transform
immature embryos of Z. mays as follows.
[0346] Transformation of Maize Mediated by Agrobacterium
[0347] Freshly isolated immature embryos of maize, about 10 days
after pollination (DAP), were incubated with the Agrobacterium. The
preferred genotype for transformation is the highly transformable
genotype Hi-II (Armstrong (1991) Maize Gen Coop Newsletter
65:92-93). An F.sub.1 hybrid created by crossing with an Hi-II with
an elite inbred may also be used. After Agrobacterium treatment of
immature embryos, the embryos were cultured on medium containing
toxic levels of herbicide. Only those cells which receive the
herbicide-resistance gene, and the linked gene(s), grow on
selective medium. Transgenic events so selected are propagated and
regenerated to whole plants, produce seed, and transmit transgenes
to progeny.
[0348] Preparation of Agrobacterium
[0349] The engineered Agrobacterium tumefaciens LBA4404 was
constructed as per U.S. Pat. No. 5,591,616 to contain the PDS gene
suppressed by the complementary region shown in SEQ ID NO:34 and a
selectable marker gene. Typically either BAR (D'Halluin et al
(1992) Methods Enzymol. 216:415-426) or PAT (Wohlleben et al (1988)
Gene 70:25-37) may be used as a selectable marker.
[0350] To use the engineered construct in plant transformation, a
master plate of single bacterial colonies was first prepared by
inoculating the bacteria on minimal AB medium [minimal AB medium
contains the following ingredients: 850.000 ml of deionized water;
50.000 ml of stock solution 800A; 9 g of Phytagar which is added
after Q.S. to volume; 50.000 ml of stock solution 800B #; 5.000 g
of glucose #; and 2.000 ml of spectinomycin 50/mg/ml stock #.
Directions are: dissolve ingredients in polished deionized water in
sequence; Q.S. to volume with polished deionized water less 100 ml
per liter; sterilize and cool to 60.degree. C. Ingredients
designated with a # are added after sterilizing and cooling to
temperature. Stock solution 800A contains the following
ingredients: 950.000 ml of deionized water; 60.000 g of potassium
phosphate dibasic K2HPO4; and 20.000 g of sodium phos. monobasic,
hydrous. Directions are: dissolve ingredients in polished deionized
water in sequence; adjust pH to 7.0 with potassium hydroxide; Q.S.
to volume with polished deionized water after adjusting pH; and
sterilize and cool to 60.degree. C. Stock solution 800B contains
the following ingredients: 950.000 ml of deionized water; 20.000 g
of ammonium chloride; 6.000 g of magnesium sulfate 7-H2O, MgSO4,
7H2O; 3.000 g of potassium chloride; 0.200 g of calcium chloride
(anhydrate); and 0.050 g of ferrous sulfate 7-hydrate. Directions
are: dissolve ingredients in polished deionized water in sequence;
Q.S. to volume with polished deionized water; and sterilize and
cool to 60.degree. C.] and then incubating the bacteria plate
inverted at 28.degree. C. in darkness for about 3 days. A working
plate was then prepared by selecting a single colony from the plate
of minimal A medium [minimal A medium contains the following
ingredients: 950.000 ml of deionized water; 10.500 g of potassium
phosphate dibasic K2HPO4; 4.500 g of potassium phosphate monobasic
KH2PO4; 1.000 g of ammonium sulfate; 0.500 g of sodium citrate
dihydrate; 10.000 ml of sucrose 20% solution #; and 1.000 ml of 1M
magnesium sulfate #. Directions are: dissolve ingredients in
polished deionized water in sequence; Q.S. to volume with deionized
water; sterilize and cool to 60.degree. C. Ingredients designated
with a # are added after sterilizing and cooling to temperature]
and streaking it across a plate of YP medium [minimal YP medium
contains the following ingredients: 950.000 ml of deionized water;
5.000 g of yeast extract (Difco); 10.000 g of peptone (Difco);
5.000 g of sodium chloride; 15.000 g of bacto-agar, which is added
after Q.S. to volume; and 1.000 ml of spectinomycin 50 mg/ml stock
#. Directions are: dissolve ingredients in polished deionized water
in sequence; adjust pH to 6.8 with potassium hydroxide; Q.S. to
volume with polished deionized water after adjusting pH; sterilize
and cool to 60.degree. C. Ingredients designated with a # are added
after sterilizing and cooling to temperature]. The YP-medium
bacterial plate was then incubated inverted at 28.degree. C. in
darkness for 1-2 days.
[0351] Agrobacterium for plant transfection and co-cultivation was
prepared 1 day prior to transformation. Into 30 ml of minimal A
medium in a flask was placed 50 .mu.g/ml spectinomycin, 100 .mu.M
acetosyringone, and about a 1/8 loopful of Agrobacterium from a 1
to 2-day-old working plate. The Agrobacterium was then grown at
28.degree. C. at 200 rpm in darkness overnight (about 14 hours). In
mid-log phase, the Agrobacterium was harvested and resuspended at 3
to 5.times.10.sup.8 CFU/ml in 561Q medium+100 .mu.M acetosyringone
using standard microbial techniques and standard curves.
[0352] Immature Embryo Preparation
[0353] Nine to ten days after controlled pollination of a corn
plant, developing immature embryos are opaque and 1-1.5 mm long and
are the appropriate size for Agro-infection. The husked ears were
sterilized in 50% commercial bleach and 1 drop Tween for 30
minutes, and then rinsed twice with sterile water. The immature
embryos were aseptically removed from the caryopsis and placed into
2 ml of sterile holding solution comprising of medium 561Q +100
.mu.M acetosyringone [medium 561 Q contains the following
ingredients: 950.000 ml of D-I Water, Filtered; 4.000 g of Chu (N6)
Basal Salts (Sigma C-1416); 1.000 ml of Eriksson's Vitamin Mix
(1000.times.Sigma-1511); 1.250 ml of Thiamine.HCL.4 mg/ml; 3.000 ml
of 2, 4-D 0.5 mg/ml (No. 2A); 0.690 g of L-proline; 68.500 g of
Sucrose; and 36.000 g of Glucose. Directions are: dissolve
ingredients in polished deionized water in sequence; adjust pH to
5.2 w/KOH; Q.S. to volume with polished deionized water after
adjusting pH; and filter sterilize (do not autoclave)].
[0354] Agrobacterium Infection and Co-cultivation of Embryos
[0355] Holding solution was decanted from excised immature embryos
and replaced with prepared Agrobacterium. Following gentle mixing
and incubation for about 5 minutes, the Agrobacterium was decanted
from the immature embryos. Immature embryos were then moved to a
plate of 562P medium [medium 562 P contains the following
ingredients: 950.000 ml of D-I Water, Filtered; 4.000 g of Chu (N6)
Basal Salts (Sigma C-1416); 1.000 ml of Eriksson's Vitamin Mix
(1000.times.Sigma-1511); 1.250 ml of Thiamine.HCL.4 mg/ml; 4.000 ml
of 2, 4-D 0.5 mg/ml; 0.690 g of L-proline; 30.000 g of Sucrose;
3.000 g of Gelrite, which is added after Q.S. to volume; 0.425 ml
of Silver Nitrate 2 mg/ml #; and 1.000 ml of Aceto Syringone 100 mM
#. Directions are: dissolve ingredients in polished deionized water
in sequence; adjust pH to 5.8 w/KOH; Q.S. to volume with polished
deionized water after adjusting pH; and sterilize and cool to
60.degree. C. Ingredients designated with a # are added after
sterilizing and cooling to temperature], scutellum surface upwards,
and incubated at 20.degree. C. for 3 days in darkness followed by
incubation at 28.degree. C. for 3 days in darkness on medium
562P+100 mg/ml carbenecillin (see U.S. Pat. No. 5,981,840).
[0356] Selection of Transgenic Events
[0357] Following incubation, the immature embryos were transferred
to 563O medium [medium 563 O contains the following ingredients:
950.000 ml of D-I Water, Filtered; 4.000 g of Chu (N6) Basal Salts
(Sigma C-1416); 1.000 ml of Eriksson's Vitamin Mix
(1000.times.Sigma-1511); 1.250 ml of Thiamine.HCL.4 mg/ml; 30.000 g
of Sucrose; 3.000 ml of 2, 4-D 0.5 mg/ml (No. 2A); 0.690 g of
L-proline; 0.500 g of Mes Buffer; 8.000 g of Agar (Sigma A-7049,
Purified), which is added after Q.S. to volume; 0.425 ml of Silver
Nitrate 2 mg/ml #; 3.000 ml of Bialaphos 1 mg/ml #; and 2.000 ml of
Agribio Carbenicillin 50 mg/ml #. Directions are: dissolve
ingredients in polished deionized water in sequence; adjust to pH
5.8 w/koh; Q.S. to volume with polished deionized water after
adjusting pH; sterilize and cool to 60.degree. C. Ingredients
designated with a are added after sterilizing and cooling to
temperature] for selection of events. The transforming DNA
possesses a herbicide-resistance gene, in this example the BAR
gene, which confers resistance to bialaphos. At 10 to 14-day
intervals, embryos were transferred to 5630 medium. Actively
growing putative transgenic embryogenic tissue were visible in 6-8
weeks.
Example 15
Suppression of Maize PDS by a Modified Soybean Complementary Region
Regeneration of T.sub.0 Plants
[0358] Transgenic embryogenic tissue is transferred to 288W medium
[medium 288 W contains the following ingredients: 950.000 ml of D-I
H.sub.2O; 4.300 g of MS Salts; 0.100 g of Myo-Inositol; 5.000 ml of
MS Vitamins Stock Solution (No. 36J); 1.000 ml of Zeatin.5 mg/ml;
60.000 g of Sucrose; 8.000 g of Agar (Sigma A-7049, Purified),
which is added after Q.S. to volume; 2.000 ml of IAA 0.5 mg/ml #;
1.000 ml of 0.1 Mm ABA #; 3.000 ml of Bialaphos 1 mg/ml #; and
2.000 ml of Agribio Carbenicillin 50 mg/ml #. Directions are:
dissolve ingredients in polished deionized water in sequence;
adjust to pH 5.6; Q.S. to volume with polished deionized water
after adjusting pH; sterilize and cool to 60.degree. C. Add 3.5 g/L
of Gelrite for cell biology. Ingredients designated with a # are
added after sterilizing and cooling to temperature] and incubated
at 28.degree. C. in darkness until somatic embryos matured, or
about 10 to 18 days. Individual matured somatic embryos with
well-defined scutellum and coleoptile are transferred to 272 embryo
germination medium [medium 272 contains the following ingredients:
950.000 ml of deionized water; 4.300 g of MS Salts; 0.100 g of
Myo-Inositol; 5.000 of MS Vitamins Stock Solution; 40.000 g of
Sucrose; and 1.500 g of Gelrite, which is added after Q.S. to
volume. Directions are: dissolve ingredients in polished deionized
water in sequence; adjust to pH 5.6; Q.S. to volume with polished
deionized water after adjusting pH; and sterilize and cool to
60.degree. C.] and incubated at 28.degree. C. in the light. After
shoots and roots emerge, individual plants are potted in soil and
hardened-off using typical horticultural methods. Plants are then
evaluated for the PDS-silenced phenotype.
[0359] Phytoene desaturase catalyzes a rate-limiting step in the
biosynthesis of carotenoids in plants (Misawa, et al The Plant
Journal (1993) 4(5):833-840). It is a known target of bleaching
herbicides such as norflurazon. Cosuppression of the endogenous
phytoene desaturase by the introduced SHH3-flanked PDS1 gives a
similar bleached phenotype when young plants are incubated in the
light (Thomas, et al (2001) The Plant Journal 25(4):417-425; Kumagi
et al (1995) PNAS USA 92:1679-1683; Ruiz et al (1998) Plant Cell
10:937-946).
* * * * *
References