U.S. patent application number 12/645976 was filed with the patent office on 2011-05-12 for serine hydroxymethyltransferase as target for herbicides.
This patent application is currently assigned to BASF Aktiengesellschaft. Invention is credited to Frederik Bornke, Kirsten Deist, Thomas Ehrhardt, Annette Freund, Wolfgang Lein, Marc Stitt Nigel, Andreas Reindl, Ralf-Michael Schmidt, Uwe Sonnewald.
Application Number | 20110113494 12/645976 |
Document ID | / |
Family ID | 27815823 |
Filed Date | 2011-05-12 |
United States Patent
Application |
20110113494 |
Kind Code |
A1 |
Sonnewald; Uwe ; et
al. |
May 12, 2011 |
Serine Hydroxymethyltransferase as Target for Herbicides
Abstract
The present invention relates to serine hydroxymethyltransferase
(E.C. 2.1.2.1) as novel target for herbicides, and to nucleic acid
sequences encoding a polypeptide with the biological activity of a
serine hydroxymethyltransferase, which, when not present, bring
about growth retardation symptoms and chlorotic leaves, comprising
the nucleic acid sequence SEQ ID No:3, and functional equivalents
of the abovementioned nucleic acid sequence or the nucleic acid
sequence SEQ ID NO:7 and functional equivalents of the
abovementioned nucleic acid sequence. Moreover, the present
invention relates to the use of the abovementioned nucleic acid
sequences, of functional analogs of the SEQ ID NO:3 or SEQ ID NO:7
or of polypeptides encoded by one of the abovementioned nucleic
acid sequences in a method for identifying herbicidally active
compounds which inhibit serine hydroxymethyltransferases, and to
the use of these compounds which have been identified by the method
as herbicides.
Inventors: |
Sonnewald; Uwe;
(Quedlinburg, DE) ; Bornke; Frederik;
(Quedlinburg, DE) ; Deist; Kirsten; (Westdorf,
DE) ; Nigel; Marc Stitt; (Potsdam, DE) ; Lein;
Wolfgang; (Potsdam, DE) ; Ehrhardt; Thomas;
(Speyer, DE) ; Reindl; Andreas; (Mannheim, DE)
; Schmidt; Ralf-Michael; (Kirrweiler, DE) ;
Freund; Annette; (Limburgerhof, DE) |
Assignee: |
BASF Aktiengesellschaft
Ludwigshafen
DE
|
Family ID: |
27815823 |
Appl. No.: |
12/645976 |
Filed: |
December 23, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11949874 |
Dec 4, 2007 |
7662603 |
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12645976 |
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10507989 |
Sep 16, 2004 |
7319013 |
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PCT/EP2003/002574 |
Mar 13, 2003 |
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11949874 |
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Current U.S.
Class: |
800/3 ;
435/252.3; 435/254.11; 435/254.2; 435/29; 435/7.71; 506/10; 506/9;
800/13; 800/278; 800/298; 800/300 |
Current CPC
Class: |
C12N 15/8274 20130101;
C12N 9/1014 20130101 |
Class at
Publication: |
800/3 ; 506/9;
800/298; 800/13; 435/254.2; 435/254.11; 435/252.3; 435/6; 435/7.71;
435/29; 506/10; 800/278; 800/300 |
International
Class: |
A61K 49/00 20060101
A61K049/00; C40B 30/04 20060101 C40B030/04; A01H 5/00 20060101
A01H005/00; A01K 67/00 20060101 A01K067/00; C12N 1/19 20060101
C12N001/19; C12N 1/15 20060101 C12N001/15; C12N 1/21 20060101
C12N001/21; C12Q 1/68 20060101 C12Q001/68; G01N 33/573 20060101
G01N033/573; C12Q 1/02 20060101 C12Q001/02; C40B 30/06 20060101
C40B030/06; A01H 1/06 20060101 A01H001/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 20, 2002 |
DE |
10212469.8 |
Claims
1. A method for detecting functional analogs of the SEQ ID NO: 3 or
SEQ ID NO: 7, comprising a) preparing a probe and subsequently
screening a genomic library or cDNA library of the species in
question; or b) conducting a computer search for analogous
sequences in an electronic data base.
2. A nonhuman transgenic organism comprising at least one nucleic
acid molecule, expression cassette or vector selected from the
group consisting of: a) a nucleic acid molecule selected from the
group consisting of: i) a nucleic acid sequence as shown in SEQ ID
NO:3; ii) a nucleic acid sequence encoding an amino acid sequence
as shown in SEQ ID NO:4; iii) a nucleic acid sequence with the
nucleic acid sequence shown in SEQ ID NO: 7; iv) a nucleic acid
sequence encoding an amino acid sequence as shown in SEQ ID NO:8;
and v) functional equivalents of the nucleic acid sequence SEQ ID
NO:7 with at least 95% identity to SEQ ID NO:7, b) an expression
cassette comprising genetic control sequences in operable linkage
with a nucleic acid sequence as in a), and c) a vector comprising
an expression cassette according to b), wherein said organism is
selected from the group consisting of bacteria, yeasts, fungi,
animals and plants.
3. A method for identifying herbicidally active substances
comprising a) bringing a nucleic acid molecule encoding a
polypeptide with the enzymatic activity of a serine
hydroxymethyltransferase or a polypeptide with the enzymatic
activity of a serine hydroxymethyltransferase into contact with one
or more test compounds under conditions which permit the test
compound(s) to bind to the nucleic acid molecule or the
polypeptide; and b) detecting whether the test compound binds to
the polypeptide of a); reduces or blocks the activity of the
polypeptide of a); or reduces or blocks the transcription,
translation or expression of the nucleic acid of a), as an
indication that the test compound is herbicidally active.
4. The method according to claim 3, wherein said polypeptide with
the enzymatic activity of a serine hydroxymethyltransferase has the
biological activity of a serine hydroxymethyltransferase.
5. A method of identifying herbicidally active substances as
claimed in claim 3, wherein said nucleic acid molecule is a nucleic
acid sequence selected from the group consisting of: a) a nucleic
acid sequence as shown in SEQ ID NO:3; b) a nucleic acid sequence
encoding an amino acid sequence as shown in SEQ ID NO:4; c) a
nucleic acid sequence with the nucleic acid sequence shown in SEQ
ID NO: 7; d) a nucleic acid sequence encoding an amino acid
sequence as shown in SEQ ID NO:8; e) functional equivalents of the
nucleic acid sequence SEQ ID NO:7 with at least 95% identity to SEQ
ID NO:7, and f) a nucleic acid molecule comprising a region with at
least 60% identity to SEQ ID NO:3.
6. The method according to claim 5, wherein said polypeptide is
encoded by a nucleic acid molecule selected from the group
consisting of a) a nucleic acid sequence as shown in SEQ ID NO:3;
b) a nucleic acid sequence encoding an amino acid sequence as shown
in SEQ ID NO:4; c) a nucleic acid sequence with the nucleic acid
sequence shown in SEQ ID NO: 7; d) a nucleic acid sequence encoding
an amino acid sequence as shown in SEQ ID NO:8; and e) functional
equivalents of the nucleic acid sequence SEQ ID NO:7 with at least
95% identity to SEQ ID NO:7, and f) a nucleic acid molecule
comprising a region with at least 60% identity to SEQ ID NO:3.
7. A method for identifying herbicidally active substances,
comprising a) expressing in a transgenic organism, a plant serine
hydroxymethyltransferase which is encoded by a nucleic acid
sequence selected from the group consisting of: i) a nucleic acid
sequence as shown in SEQ ID NO:3; ii) a nucleic acid sequence
encoding an amino acid sequence as shown in SEQ ID NO:4; iii) a
nucleic acid sequence with the nucleic acid sequence shown in SEQ
ID NO: 7; iv) a nucleic acid sequence encoding an amino acid
sequence as shown in SEQ ID NO:8; v) functional equivalents of the
nucleic acid sequence SEQ ID NO:7 with at least 95% identity to SEQ
ID NO:7; and vi) a nucleic acid sequence comprising a part-region
with at least 60% identity to the SEQ ID NO:3, or culturing an
organism which naturally encodes a plant serine
hydroxymethyltransferase which is encoded by a nucleic acid
sequence according to i)-vi); b) preparing a cell digest of the
transgenic or nontransgenic organism and bringing the serine
hydroxymethyltransferase in the cell digest, in partially or
homogeneously purified form, into contact with a test compound; and
c) determining whether the test compound reduces or blocks the
activity of the serine hydroxymethyltransferase, where the activity
of the serine hydroxymethyltransferase incubated with the test
compound is compared with the activity of a serine
hydroxymethyltransferase which is not incubated with a test
compound; as an indication that the test compound is herbicidally
active.
8. The method according to claim 7, wherein, in step c), the
activity of the serine hydroxymethyltransferase is determined by
the chromatographic isolation and quantification of
tetrahydrofolate and Cl-tetrahydrofolate.
9. A method for identifying herbicidally active substances,
comprising a) generating a transgenic organism as claimed in claim
2 or a transgenic organism with a nucleic acid sequence comprising
a region with at least 60% identity to SEQ ID NO:3; b) applying a
test substance to the transgenic organism generated in a) and to a
nontransgenic organism of the same type; c) determining the growth
or the viability of the transgenic and the nontransgenic organisms
after application of the test substance; and d) determining test
substances which bring about a reduced growth or a reduced
viability of the nontransgenic organism in comparison with the
growth of the transgenic organism as an indication that the test
compounds are herbicidally active.
10. The method as claimed in claim 9, wherein said transgenic
organism is a plant or a yeast.
11. The method according to claim 10, wherein said reduced growth
or a reduced viability of the nontransgenic organism in comparison
with the growth of the transgenic organism is between 10-50%.
12. A method for identifying substances with a growth-regulatory
action, comprising: a) generating a transgenic plant with a nucleic
acid sequence comprising a region with at least 60% identity with
SEQ ID NO:3; b) applying a test substance to the transgenic plant
generated in a) and to a nontransgenic plant of the same type; c)
determining the growth or the viability of the transgenic and the
nontransgenic plants after application of the test substance; and
d) selecting test substances which bring about altered growth of
the nontransgenic plant in comparison with the growth of the
transgenic plant as an indication that the test compounds are
herbicidally active.
13. The method as claimed in claim 3, wherein the substances are
identified in a high-throughput screening.
14. A method for generating modified gene products which are
encoded by variants of the nucleic acid sequence of SEQ ID NO: 7,
comprising a) expressing a protein encoded by a nucleic acid as
shown in SEQ ID NO: 7 in a heterologous system or in a cell-free
system; b) modifying the protein by randomized or directed
mutagenesis of the nucleic acid; c) measuring the interaction of
the modified gene product with the herbicide; d) identifying
derivatives of the protein which show less interaction; e) assaying
the biological activity of the protein after application of the
herbicide; and f) selecting the nucleic acid sequences which have a
modified biological activity against the herbicide.
15. A method as claimed in claim 14, further comprising introducing
the sequences selected in accordance with claim 14 f) into an
organism.
16. An organism generated by the method as claimed in claim 15.
17. An organism generated by a method for generating transgenic
plants which are resistant to herbicidally active substances which
reduce or inhibit the biological activity of a serine
hydroxymethyltransferase, comprising overexpressing in said
transgenic plants, nucleic acid sequences selected from the group
consisting of: i) a nucleic acid sequence as shown in SEQ ID NO:3;
ii) a nucleic acid sequence encoding an amino acid sequence as
shown in SEQ ID NO:4; iii) a nucleic acid sequence with the nucleic
acid sequence shown in SEQ ID NO: 7; iv) a nucleic acid sequence
encoding an amino acid sequence as shown in SEQ ID NO:8; and v)
functional equivalents of the nucleic acid sequence SEQ ID NO:7
with at least 95% identity to SEQ ID NO:7, or functional
equivalents of the nucleic acid sequence SEQ ID NO:7 with at least
88% identity to SEQ ID NO:7.
Description
[0001] This application is a divisional of Ser. No. 11/949,874
filed Dec. 4, 2007; which is a divisional of Ser. No. 10/507,989
filed Sep. 16, 2004, now U.S. Pat. No. 7,319,013 issued Jan. 15,
2008, which is a 35 U.S.C. 371 National Phase Entry Application
from PCT/EP2003/002574, filed Mar. 13, 2003, which claims the
benefit of German Patent Application No. 10212469.8 filed on Mar.
20, 2002, the disclosure of which is incorporated herein in its
entirety by reference.
[0002] The present invention relates to serine
hydroxymethyltransferase (E.C. 2.1.2.1) as novel target for
herbicides, and to nucleic acid sequences encoding a polypeptide
with the biological activity of a serine hydroxymethyltransferase,
which, when not present, bring about growth retardation symptoms
and karotic leaves, comprising the nucleic acid sequence SEQ ID
No:3, and functional equivalents of the abovementioned nucleic acid
sequence, or the nucleic acid sequence SEQ ID NO:7 and functional
equivalents of the abovementioned nucleic acid sequence. Moreover,
the present invention relates to the use of the abovementioned
nucleic acid sequences, of functional analogs of the SEQ ID NO:3 or
SEQ ID NO:7 or of polypeptides encoded by one of the abovementioned
nucleic acid sequences in a method for identifying herbicidally
active compounds which inhibit serine hydroxymethyltransferases,
and to the use of these compounds which have been identified by the
method as herbicides.
[0003] The basic principle of identifying herbicides via inhibiting
a defined target is known (for example U.S. Pat. No. 5,187,071, WO
98/33925, WO 00/77185). In general, there is a great demand for the
detection of enzymes which might constitute novel targets for
herbicides. Reasons hereof are that herbicidal active ingredients
which act on known targets show the development of resistance
problems, and the constant endeavor to identify novel herbicidal
active ingredients which are distinguished by as broad as possible
a range of action, eco friendliness and toxicological compatibility
and/or low application rates.
[0004] In practice, the detection of novel targets always entails
great difficulties since the inhibition of an enzyme which is part
of a metabolic pathway frequency has no further effect on the
plant's growth. The reason may be that the plant switches over to
alternative metabolic pathways whose existence is not known, or
that the enzyme which is being inhibited is not limiting for the
metabolic pathway. Furthermore, plant genomes are distinguished by
a high degree of functional redundance. In the Arabidopsis thaliana
genome, functionally equivalent enzymes are more frequently found
in gene families than is the case with insects or mammals (Nature,
2000, 408(6814):796-815). This hypothesis is confirmed
experimentally by the fact that large gene knock-out programs by
the insertion of T-DNA or transposons into Arabidopsis have, as
yet, yielded fewer manifested phenotypes than expected (Curr. Op.
Plant Biol. 4, 2001, pp. 111-117).
[0005] It is an object of the present invention to identify novel
targets which are essential for the growth of plants or whose
inhibition lead to reduced plant growth, and to provide methods
which are suitable for identifying herbicidally active
compounds.
[0006] We have found that this object is achieved by the provision
of serine hydroxymethyltransferase (SHMT) as novel target for
herbicides and by the provision of nucleic acid sequences encoding
polypeptide with the biological activity of an SHMT comprising
[0007] a) a nucleic acid sequence with the nucleic acid sequence
shown in SEQ ID NO:3; or [0008] b) a nucleic acid sequence which,
on the basis of the degeneracy of the genetic code, can be derived
from the amino acid sequence shown in SEQ ID NO:4 by back
translation; or [0009] c) functional equivalents of the nucleic
acid sequence SEQ ID NO:3 comprising a part-region with at least
91% identity to the SEQ ID NO:3; and of nucleic acid sequences
comprising [0010] a) a nucleic acid sequence with the nucleic acid
sequence shown in SEQ ID NO:7; or [0011] b) a nucleic acid sequence
which, on the basis of the degeneracy of the genetic code, can be
derived from the amino acid sequence shown in SEQ ID NO:8 by back
translation; or [0012] c) functional equivalents of the nucleic
acid sequence SEQ ID NO:7 with at least 886 identity to the SEQ ID
NO:7.
[0013] The term "comprising" or "to comprise", when referring to
nucleic acid or amino acid sequences, is understood as meaning that
the nucleic acid sequence according to the invention may comprise,
at the 3' or at the 5' end, additional nucleic acid sequences,
where the length of the additional nucleic acid sequences does not
exceed 2000 by at the 5' and 3' end of the nucleic acid sequences
according to the invention, preferably 1500 by at the 5' end and
100 by at the 3' end.
[0014] Further terms used in the description are now defined at
this point.
[0015] "Affinity tag": this refers to a peptide or polypeptide
whose coding nucleic acid sequence can be fused to the nucleic acid
sequence according to the invention either directly or by means of
a linker, using customary cloning techniques. The affinity tag
serves for the isolation, concentration and/or specific
purification of the recombinant target protein by means of affinity
chromatography from total cell extracts. The abovementioned linker
can advantageously comprise a protease cleavage site (for example
for thrombin or factor Xa), whereby the affinity tag can be cleaved
from the target protein when required. The examples of usual
affinity tags are the "His tag" for example from quiagen, hilden,
"Strep tag", the "Myc tag" (Invitrogen, Carlsberg), the tag from
New England Biolabs which consists of a chitin-binding domain and
an inteine, the maltose-binding protein (pMal) from New England
Biolabs, and what is known as the CBD tag from Novagen. It this
context, the affinity tag can be attached to the 5' or the 3' end
of the coding nucleic acid sequence with the sequence encoding the
target protein.
[0016] "Antisense or cosuppression technique" describes
technologies for the suppression (reduction) of gene expression,
where a gene encoding a portion (to be defined in the experiment in
question) of a natural gene to be suppressed is transformed into a
model plant in "sense" or "antisense" orientation under the control
of a suitable promoter. As a rule, the suppression of the
transcription of the natural gene, which can be detected using
suitable methods, is pronounced to a different degree in the
transgenic plants generated in this manner. Thus, this technique
allows the study of the effects, on an organism, of a gene whose
expression has been reduced (for a review, see Trends in Plant
Science, 2000, 5(9), 394-396).
[0017] "Enzymatic activity/activity assay": the term enzymatic
activity describes the ability of an enzyme to convert a substrate
into a product. The enzymatic activity can be determined in what is
known as an activity assay while the increase in the product, the
decrease in the substrate (or starting material) or the decrease in
a specific cofactor, or via a combination of at least two of the
abovementioned parameters, as a function of a defined period of
time.
[0018] "Biological activity of a serine hydroxymethyltransferase":
For the purposes of the present invention, this term describes that
the ability to grow and survive is conferred by the presence of a
serine hydroxymethyltransferase, preferably a glyoxysomal serine
hydroxymethyltransferase. If the activity of a protein with the
biological activity of a glyoxysomal serine
hydroxymethyltransferase is inhibited, this leads to reduced
growth, cessation of growth or death of the plant.
[0019] "Expression cassette": an expression cassette comprises a
nucleic acid sequence according to the invention linked operably to
at least one genetic control element, such as a promoter, and,
advantageously, a further control element, such as a
terminator.
[0020] The nucleic acid sequence of the expression cassette can be
for example a genomic or complementary DNA sequence or an RNA
sequence, and their semi- or fully synthetic analogs. These
sequences can exist in linear or circular form, extrachromosomally
or integrated into the genome. The nucleic acid sequences in
question can be synthesized or obtained naturally or comprise a
mixture of synthetic and natural DNA components, or else consist of
various heterologous gene segments of various organisms.
[0021] Artificial nucleic acid sequences are also suitable in this
context as long as they make possible the expression, in a cell or
an organism, of a polypeptide with the biological activity of an
SHMT, which polypeptide is encoded by a nucleic acid sequence
according to the invention. For example, synthetic nucleotide
sequences can be generated which have been optimized with regard to
the codon usage of the organisms to be transformed.
[0022] All of the abovementioned nucleotide sequences can be
generated from the nucleotide units by chemical synthesis in the
manner known per se, for example by fragment condensation of
individual overlapping complementary nucleotide units of the double
helix. Oligonucleotides can be synthesized chemically for example
in the manner known per se using the phosphoamidite method (Voet,
Voet, 2.sup.nd. Edition, Wiley Press New York, pp. 896-897). When
preparing an expression cassette, various DNA fragments can be
manipulated in such a way that a nucleotide sequence with the
correct direction of reading and the correct reading frame is
obtained. The nucleic acid fragments are linked with each other via
general cloning techniques as are described, for example, in T.
Maniatis, E. F. Fritsch and J. Sambrook, "Molecular Cloning: A
Laboratory Manual", Cold Spring Harbor Laboratory, Cold Spring
Harbor, N.Y. (1989), in T. J. Silhavy, M. L. Berman and L. W.
Enquist, Experiments with Gene Fusions, Cold Spring Harbor
Laboratory, Cold Spring Harbor, N.Y. (1984) and in Ausubel, F. M.
et al., "Current Protocols in Molecular Biology", Greene Publishing
Assoc. and Wiley-Interscience (1994).
[0023] "Operable linkage": an operable, or functional, linkage is
understood as meaning the sequential arrangement of regulatory
sequences or genetic control elements in such a way that each of
the regulatory sequences, or each of the genetic control elements,
can fulfill its intended function when the coding sequence is
expressed.
[0024] "Functional equivalents" describe, in the present context,
nucleic acid sequences which hybridize under standard conditions
with the nucleic acid sequence SEQ ID NO:3 or parts of the SEQ ID
NO:3 and which are capable of bringing about the expression, in a
cell or an organism, of a polypeptide with the biological activity
of an SHMT. The term functional equivalents accordingly also
comprises the nucleic acid sequences SEQ ID NO:7 and also nucleic
acid sequences which hybridize with SEQ ID NO:7 or parts of SEQ ID
NO:7 and are capable of bringing about the expression, in a cell or
an organism, of a polypeptide with the biological activity of an
SHMT.
[0025] To carry out the hybridization, it is advantageous to use
short oligonucleotides with a length of approximately 10-50 bp,
preferably 15-40 bp, for example of the conserved or other regions,
which can be determined in the manner with which the skilled worker
is familiar by comparisons with other related genes. However,
longer fragments of the nucleic acids according to the invention
with a length of 100-500 bp, or the complete sequences, may also be
used for hybridization. Depending on the nucleic
acid/oligonucleotide used, for the length of the fragment or the
complete sequence, or depending on which type of nucleic acid, i.e.
DNA or RNA, is being used for the hybridization, these standard
conditions vary. Thus, for example, the melting temperatures for
DNA:DNA hybrids are approximately 10_C lower than those of DNA:RNA
hybrids of the same length.
[0026] Standard hybridization conditions are to be understood as
meaning, depending on the nucleic acid, for example temperatures of
between 42 and 58_C in an aqueous buffer solution with a
concentration of between 0.1 to 5.times.SSC (1.times.SSC=0.15 M
NaCl, 15 mM sodium citrate, pH 7.2) or additionally in the presence
of 50% formamide, such as, for example, 42_C in 5.times.SSC, 50%
formamide. The hybridization conditions for DNA:DNA hybrids are
advantageously 0.1.times.SSC and temperatures of between
approximately 20_C to 65_C, preferably between approximately 30_C
to 45_C. In the case of DNA:RNA hybrids, the hybridization
conditions are advantageously 0.1.times.SSC and temperatures of
between approximately 30_C to 65_C, preferably between
approximately 45_C to 55_C. These hybridization temperatures which
have been stated are melting temperature values which have been
calculated by way of example for a nucleic acid with a length of
approx. 100 nucleotides and a G+C content of 50% in the absence of
formamide. The experimental conditions for DNA hybridization are
described in specialist textbooks of genetics such as, for example,
in Sambrook et al., "Molecular Cloning", Cold Spring Harbor
Laboratory, 1989, and can be calculated using formulae with which
the skilled worker is familiar, for example as a function of the
length of nucleic acids, the type of the hybrids or the G+C
content. The skilled worker will find further information on
hybridization in the following text books: Ausubel et al. (eds),
1985, "Current Protocols in Molecular Biology", John Wiley &
Sons, New York; Hames and Higgins (eds), 1985, "Nucleic Acids
Hybridization: A Practical Approach", IRL Press at Oxford
University Press, Oxford; Brown (ed), 1991, Essential Molecular
Biology: A Practical Approach, IRL Press at Oxford University
Press, Oxford.
[0027] A functional equivalent of the SEQ ID NO:3 is furthermore
also understood as meaning nucleic acid sequences which comprise a
part-region which has a defined degree of homology with the SEQ ID
NO:3, and furthermore in particular also natural or artificial
mutations of the abovementioned nucleic acid sequences which encode
a polypeptide with the biological activity of a serine
hydroxymethyltransferase. An example of a nucleic acid sequences
which comprise a part-region which has a defined degree of identity
with the SEQ ID NO:3 is SEQ ID NO:7 and the functional equivalents
thereof as defined above.
[0028] Thus, the present invention also comprises, for example,
those nucleotide sequences which are obtained by modification of
the abovementioned nucleic acid sequences. For example, such
modifications can be generated by techniques with which the skilled
worker is familiar, such as "Site Directed Mutagenesis", "Error
Prone PCR", "DNA-shuffling" (Nature 370, 1994, pp. 389-391) or
"Staggered Extension Process" (Nature Biotechnol. 16, 1998, pp.
258-261). The purpose of such a modification can be, for example,
the insertion of further cleavage sites for restriction enzymes,
the removal of DNA in order to truncate the sequence, the
substitution of nucleotides to optimize the codons, or the addition
of further sequences. Proteins which are encoded via modified
nucleic acid sequences must retain the desired functions despite a
deviating nucleic acid sequence.
[0029] The term "functional equivalents" can also relate to the
amino acid sequence encoded by the nucleic acid sequence in
question. In this case, the term "functional equivalent" describes
a protein whose amino acid sequence comprises a part-region which
has a defined percentage of at least 91% identity or homology with
the SEQ ID NO:4.
[0030] Functional equivalents thus comprise naturally occurring
variants of the herein-described sequences and artificial nucleic
acid sequences, for example those which have been obtained by
chemical synthesis and which are adapted to the codon usage, and
also the amino acid sequences derived from them.
[0031] "Genetic control sequence": the term "genetic control
sequence" is considered as equivalent to the term "regulatory
sequence". It describes sequences which have an effect on the
transcription and, if appropriate translation of the nucleic acids
according to the invention in prokaryotic or eukaryotic organisms.
Examples are promoters or what are known as "enhancer" sequences.
In addition to these control sequences, or instead of these
sequences, the natural regulation of these sequences may still be
present before the actual structural genes and may, if appropriate,
have been genetically modified in such a way that the natural
regulation is switched off and the expression of the target gene
has been modified, that is to say increased or reduced. The choice
of the control sequence depends on the host organism or starting
organism. Genetic control sequences furthermore also comprise the
5'-untranslated region, introns or the noncoding 3'-region of
genes. Control sequences are furthermore understood as meaning
those which make possible homologous recombination or insertion
into the genome of a host organism or which permit removal from the
genome. Genetic control sequences also comprise further promoters,
promoter elements or minimal promoters, and sequences which have an
effect on the chromatin structure (for example matrix attachment
regions (MARs)), which can modify the expression-governing
properties. Thus, genetic control sequences may bring about for
example the fact that the tissue-specific expression is
additionally dependent on certain stress factors. Such elements
have been described, for example, for water stress, abscissic acid
(Lam E and Chua N H, J Biol Chem 1991; 266(26): 17131-17135), high-
and low-temperature stress (Plant Cell 1994, (6): 251-264) and heat
stress (Molecular & General Genetics, 1989, 217(2-3):
246-53).
[0032] "Homology" between two nucleic acid sequences or polypeptide
sequences is defined by the identity of the nucleic acid
sequence/polypeptide sequence over in each case the entire sequence
length, which is calculated by alignment with the aid of the
program algorithm BESTFIT (Wisconsin Package Version 10.0,
University of Wisconsin, Genetics Computer Group (GCG), Madison,
USA), setting the following parameters for polypeptides:
TABLE-US-00001 Gap Weight: 8 Length Weight: 2 Average Match: 2,912
Average Mismatch: -2,003
and the following parameters for nucleic acids:
TABLE-US-00002 Gap Weight: 50 Length Weight: 3 Average Match:
10.000 Average Mismatch: -9.000
[0033] In the following text, the term identity is also used
synonymously instead of the term "homologous" or "homology".
[0034] "Mutations" of nucleic or amino acid sequences comprise
substitutions, additions, deletions, inversions or insertions of
one or more nucleotide residues, which may also bring about changes
in the corresponding amino acid sequence of the target protein by
substitution, insertion or deletion of one or more amino acids, and
were the functional properties of the target proteins are, in
total, essentially retained.
[0035] "Natural genetic environment" refers to the natural
chromosomal locus in the organism of origin. In the case of a
genomic library, the natural genetic environment of the nucleic
acid sequence is preferably retained at least in part. The
environment flanks the nucleic acid sequence at least 5'- or 3'-
and has a sequence length of at least 50 bp, preferably at least
100 bp, especially preferably at least 500 bp, very especially
preferably at least 1000 bp, and most preferably at least 5000
bp.
[0036] "Plants" for the purposes of the invention are plant cells,
plant tissues, plant organs, or intact plants, such as seeds,
tubers, flowers, pollen, fruits, seedlings, roots, leaves, stems or
other plant parts. Moreover, the term plants is understood as
meaning propagation material such as seeds, fruits, seedlings,
slips tubers, cuttings or root stocks.
[0037] "Reaction time" refers to the time required for carrying out
an activity assay until a significant finding regarding an activity
is obtained; it depends both on the specific activity of the
protein employed in the assay and on the method used and the
sensitivity of the operators used. The skilled worker is familiar
with the determination of the reaction times. In the case of
methods for identifying herbicidally active compounds which are
based on photometry, the reaction times are, for example, between
>0 to 120 minutes.
[0038] "Recombinant DNA" describes a combination of DNA sequences
which can be generated by recombinant DNA technology.
[0039] "Recombinant DNA technology": generally known techniques for
fusing DNA sequences (for example described in Sambrook et al.,
1989, Cold Spring Harbor, N.Y., Cold Spring Harbor Laboratory
Press).
[0040] "Replication origins" ensure the multiplication of the
expression cassettes or vectors according to the invention in
microorganisms and yeasts, for example the pBR322 on or the P15A on
in E. coli (Sambrook et al.: "Molecular Cloning. A Laboratory
Manual", 2nd ed. Cold Spring Harbor Laboratory Press, Cold Spring
Harbor, N.Y., 1989) and the ARS1 on in yeast (Nucleic Acids
Research, 2000, 28(10): 2060-2068).
[0041] "Reporter genes" encode readily quantifiable proteins. The
transformation efficacy or the transformation site or timing can be
assessed by means of these genes via growth assay, fluorescence
assay, chemoluminescence assay, bioluminescence assay or resistance
assay or via a photometric measurement (intrinsic color) or enzyme
activity. Very especially preferred in this context are reporter
proteins (Schenborn E, Groskreutz D. Mol. Biotechnol. 1999;
13(1):29-44) such as the "green fluorescent protein" (GFP) (Gerdes
H H and Kaether C, FEES Lett. 1996; 389(1):44-47; Chui W L et al.,
Curr Biol 1996, 6:325-330; Leffel S M et al., Biotechniques.
23(5):912-8, 1997), chloramphenicol acetyltransferase, a luciferase
(Giacomin, Plant Sci 1996, 116:59-72; Scikantha, J Bact 1996,
178:121; Millar et al., Plant Mol Biol Rep 1992 10:324-414), and
luciferase genes, in general .beta.-galactosidase or
.beta.-glucuronidase (Jefferson et al., EMBO J. 1987, 6, 3901-3907)
or the Ura3 gene.
[0042] "Selection markers" confer a resistance to antibiotics or
other toxic compounds: examples which may be mentioned in this
context are the neomycin phosphotransferase gene, which confers
resistance to the aminoglycoside antibiotics neomycin (G 418),
kanamycin, paromycin (Deshayes A et al., EMBO J. 4 (1985)
2731-2737), the hygro gene (Marsh J L et al., Gene. 1984;
32(3):481-485), the sul gene (Guerineau F et al., Plant Mol. Biol.
1990; 15(1):127-136), the hygromycin gene (Gen Bank Accession NO: K
01193) and the she-ble gene, which confers resistance to the
bleomycin antibiotic zeocin. Further examples of selection marker
genes are genes which confer resistance to
2-deoxyglucose-6-phosphate (WO 98/45456) or phosphinothricin and
the like, or those which confer a resistance to antimetabolites,
for example the dhfr gene (Reiss, Plant Physiol. (Life Sci. Adv.)
13 (1994) 142-149). Examples of other genes which are suitable are
trpB or hisD (Hartman S C and Mulligan R C, Proc Natl Acad Sci USA.
85 (1988) 8047-8051). Another suitable gene is the mannose
phosphate isomerase gene (WO 94/20627), the ODC (ornithine
decarboxylase) gene (McConlogue, 1987 in: Current Communications in
Molecular Biology, Cold Spring Harbor Laboratory, Ed.) or the
Aspergillus terreus deaminase (Tamura K et al., Biosci Biotechnol
Biochem. 59 (1995) 2336-2338).
[0043] "Transformation" describes a process for introducing
heterologous DNA into a pro- or eukaryotic cell. The term
transformed cell describes not only the product of the
transformation process per se, but also all of the transgenic
progeny of the transgenic organism generated by the
transformation.
[0044] "Target/target protein": a polypeptide encoded via the
nucleic acid sequence according to the invention, which may take
the form of an enzyme in the traditional sense or, for example, of
a structural protein, development protein, regulatory protein such
as transcription factors, kinases, phosphatases, receptors, channel
subunits, transport proteins, regulatory subunits which confer
substrate or activity regulation to an enzyme complex. All of the
targets or sites of action share the characteristic that their
functional presence is essential for the survival or the normal
development and growth.
[0045] "Transgenic": referring to a nucleic acid sequence, an
expression cassette or a vector comprising a nucleic acid sequence
according to the invention or an organism transformed with the
abovementioned nucleic acid sequence, expression cassette or
vector, the term transgenic describes all those constructs which
have been generated by genetic engineering methods in which either
the nucleic acid sequence of the target protein or a genetic
control sequence linked operably to the nucleic acid sequence of
the target protein or a combination of the abovementioned
possibilities are not in their natural genetic environment or have
been modified by recombinant methods. In this context, the
modification can be achieved, for example, by mutating one or more
nucleotide residues of the nucleic acid sequence in question.
[0046] The polypeptides encoded by the nucleic acid sequences
according to the invention display the biological activity of a
pyridoxal-phosphate-dependent serine hydroxymethyltransferase
(SHMT; E.C. 2.1.2.1). SHMTs are found in virtually all types of
cells. The enzyme was first isolated from rabbit liver (Schirch
& Mason, JBC 238, pp. 1032-1037, 1963) and since then from a
large number of organisms such as, for example, plants.
[0047] Inhibitors for plant SHMTs have not been described as yet.
SHMT from Euglena gracilis can be inhibited by millimolar
concentrations of various amino acids (for example glycin, serine,
cystein) (Sakamoto et al., Agricultural and Biological Chemistry,
1991, 55(9), 2243-2249). Micromolar concentrations of the amino
acid analog O-amino-D-serine have an inhibitory effect on ovine
SHMT (Baskaran et al., Biochemistry, 1989, 28(25), 9607-9612). It
is furthermore known that mimosine, a plant amino acid, can be
bound to SHMT from CHO cells by means of photo-linkage, but does
not inhibit it (Lin et al. JBC 271, pp. 2548-2556, 1996).
[0048] A cytosolic and a mitochondrial form of SHMT, which are
involved in different metabolic pathways, can be distinguished in
plants. In addition, the existence of a plastid SHMT has been
postulated (Douce et al. Trends in Plant Science 6, pp. 167-176,
2001). The cytosolic form of SHMT participates in providing Cl
units for the purin and methionin metabolism by catalyzing the
reversible reaction from serine to glycin. An ovine cytosolic SHMT
protein sequence, which has 55.09% identity with the SEQ ID NO:4,
is found under the Gen Bank Acc. No. P35623.
[0049] In Arabidopsis, five SHMT genes (SHM1-5) have been found; of
these, two, SHM1 (Gen Bank Acc. No. AJ271726, Identity to SEQ ID
NO:378.65%; Gen Bank Acc. No. Q490M9, Identity to SEQ ID NO:4
83.71%) and SHM2 (Gen Bank Acc. No. Q04952; Identity to SEQ ID
NO:483.62%), are probably localized in the mitochondria, while
SHM3, SHM4 and SHM5 constitute cytosolic forms (McClung et al.
Plant Physiol. 123, pp 381-391, 2000). A mitochondrial SHMT from
pea mitochondria has furthermore been described (Pisum sativum; Gen
Bank Acc. No. P34899, Identity to SEQ ID NO:483.52%; Turner et al.
JBC 267, pp. 13528-13534, 1992). Sequences encoding mitochondrial
SHMT are also known from Solanum tuberosum (Gen Bank Acc. No.
Z25863 Identity to SEQ ID NO:390.62%, Identity to SEQ ID
NO:490.45%; Identity to SEQ ID NO:786.8%) and from Flayeria
pringlei (Gen Bank Acc. No. P49358, Identity to SEQ ID NO:486.44%).
Moreover, a Lycopersicon esculentum EST nucleic acid sequence,
which probably likewise includes a mitochondrial SHMT, also exists
(Gen Bank Acc. No. AW040079, Identity to SEQ ID NO:390.056%).
[0050] Arabidopsis thaliana mutants in whose mitochondria no SHMT
activity has been detected biochemically (stm plants) are described
in the literature. In these mutants, photosynthesis is inhibited
under ambient CO.sub.2 concentrations, and the plants are not
viable. While the stm plants are only fully viable under increased
CO, concentrations, they become chlorotic after being transferred
to ambient CO, concentrations, and some of them die (Somerville and
Somerville, Plant Physiol. 67, 1981, pp. 666-671; Somerville and
Somerville, J. Exp. Bot. 34, 1983, 415-424). The mitochondrial SHM
gene of the stm plants which carries the mutation is not known.
SHM1 transcript size and quantity are unaltered in stm mutants in
comparison with the wild type. According to Beckmann et al. (Planta
202, pp. 379-386, 1997), a possible loss-of-function mutation of
the SHM1 gene is probably not responsible for the phenotype of the
mutants since this is compensated for by the second SHMT, viz.
SHM2. The fact that the mitochondrial SHMT is essential in plants,
and could therefore constitute a suitable target for herbicides,
has thus not yet been proven unambiguously.
[0051] Surprisingly, it has been found within the scope of the
present invention that the gene products which are encoded via
nucleic acids which comprise the SEQ ID NO:3 are suitable as
targets for herbicides. The proof was provided in each case by a
targeted reduction in the expression of the target protein in
question in Nicotiana tabacum. These plants have phenotypes which
are comparable with phenotypes generated by the application of
herbicides. Among the symptoms observed were growth retardation and
chlorotic leaves, in some cases, the death of entire plants, or of
plant parts.
[0052] The present invention relates to plant SHMTs, hereinbelow
simply referred to as "SHMTs" for the sake of simplicity,
preferably mitochondrial SHMTs, and their use as novel target for
herbicide. The term "SHMT" accordingly preferably describes
mitochondrial SHMT. Claimed within the present scope are nucleic
acid sequences which encode a polypeptide with the biological
activity of an SHMT, the nucleic acids comprising [0053] a) a
nucleic acid sequence with the nucleic acid sequence shown in SEQ
ID NO:3; or [0054] b) a nucleic acid sequence which, on the basis
of the degeneracy of the genetic code, can be derived from the
amino acid sequence shown in SEQ ID NO:4 by back translation; or
[0055] c) functional equivalents of the nucleic acid sequence SEQ
ID NO:3 comprising a part-region with at least 91% identity to the
SEQ ID NO:3.
[0056] Preferred in this context are nucleic acid sequences which
encode a mitochondrial SHMT.
[0057] An example of a nucleic acid sequence according to c) is the
SEQ ID NO:7 which comprises a part-region having 100% identity to
the SEQ ID NO:3. Hence claimed within the scope of the present
invention are also nucleic acid sequences which encode a
polypeptide with the biological activity of an SHMT, comprising
[0058] a) a nucleic acid sequence with the nucleic acid sequence
shown in SEQ ID NO:7; or [0059] b) a nucleic acid sequence which,
on the basis of the degeneracy of the genetic code, can be derived
from the amino acid sequence shown in SEQ ID NO:8 by back
translation; or [0060] c) functional equivalents of the nucleic
acid sequence SEQ ID NO:7 with at least 88% identity to the SEQ ID
NO:7.
[0061] As emerges from the definition of the term SHMT, preferred
in this context are also nucleic acid sequences which encode a
mitochondrial SHMT.
[0062] The abovementioned nucleic acid sequences are hereinbelow
referred to as "nucleic acid sequences according to the
invention".
[0063] Reduced amounts of polypeptides encoded by nucleic acid
sequences according to the invention cause growth retardation and
chlorotic leaves in plants. A reduction in the polypeptide means
that the amount of polypeptide is reduced via recombinant methods.
A plant which has been modified thus is compared with a plant which
has not been genetically modified with regard to this polypeptide,
but which is otherwise identical with the genotype of the
genetically manipulated plant under identical growth
conditions.
[0064] The present invention also relates to the gene products of
the nucleic acids according to the invention, which constitute
novel targets for herbicides which are suitable for controlling
undesired plants.
[0065] Undesired plants are understood as meaning, in the broadest
sense, all those plants which grow at locations where they are
undesired, for example:
Dicotyledonous weeds of the genera: Sinapis, Lepidium, Galium,
Stellaria, Matricaria, Anthemis, Galinsoga, Chenopodium, Urtica,
Senecio, Amaranthus, Portulaca, Xanthium, Convolvulus, Ipomoea,
Polygonum, Sesbania, Ambrosia, Cirsium, Carduus, Sonchus, Solanum,
Rorippa, Rotala, Lindernia, Lamium, Veronica, Abutilon, Emex,
Datura, Viola, Galeopsis, Papaver, Centaurea, Trifolium,
Ranunculus, Taraxacum. Monocotyledonous weeds from the genera:
Echinochloa, Setaria, Panicum, Digitaria, Phleum, Poa, Festuca,
Eleusine, Brachiaria, Lolium, Bromus, Avena, Cyperus, Sorghum,
Agropyron, Cynodon, Monochoria, Fimbristyslis, Sagittaria,
Eleocharis, Scirpus, Paspalum, Ischaemum, Sphenoclea,
Dactyloctenium, Agrostis, Alopecurus, Apera.
[0066] The functional equivalents of the SEQ ID NO:3 comprise a
part-region with at least 91%, preferably at least 92%, 93% and
94%, preferably at least 95% or 96%, especially preferably at least
97% or 98%, very especially preferably at least 99%, identity with
the SEQ ID No:3.
[0067] The functional equivalents of the SEQ ID NO:4 comprise a
part-region with at least 91%, preferably at least 92%, 93% and
94%, preferably at least 95% or 96%, especially preferably at least
97% or 98%, very especially preferably at least 99%, identity with
the SEQ ID No:3.
[0068] The functional equivalents of the SEQ ID NO:7 have at least
88%, 89%, 90%, preferably at least 91%, 92%, 93%, 94%, 95%,
particularly preferably at least 96%, 97%, 98%, 99%, identity with
the SEQ ID NO:7.
[0069] The SEQ ID NO:3 or parts of the SEQ ID NO:3 can be used for
the preparation of hybridization probes, by means of which the
corresponding full-length genes can be isolated. Likewise the SEQ
ID NO:7 or parts of the SEQ ID NO:7 can be used. The preparation of
these probes and the experimental procedure is known. For example,
this can be effected via the tailor-made preparation of radioactive
or nonradioactive probes by PCR and the use of suitably labeled
oligonucleotides, followed by hybridization experiments. The
technologies required for this purpose are given, for example, in
T. Maniatis, E. F. Fritsch and J. Sambrook, "Molecular Cloning: A
Laboratory Manual", Cold Spring Harbor Laboratory, Cold Spring
Harbor, N.Y. (1989). The probes in question can furthermore be
modified by standard technologies (Lit. SDM or random mutagenesis)
that they can be employed for further purposes, for example as
probe which hybridizes specifically with mRNA and the corresponding
coding sequences in order to analyze the corresponding sequences in
other organisms.
[0070] Moreover, the abovementioned probes can be used for the
detection and isolation of functional equivalents of the SEQ ID
NO:3 (or SEQ ID NO:7) from other plant species on the basis of
sequence identities. In this context, part or all of the sequence
of the SEQ ID NO:3 (or SEQ ID NO:7) in question is used as probe
for screening a genomic or cDNA library of the plant species in
question or in a computer search for sequences of functional
equivalents in electronic databases.
[0071] Preferred plant species are the undesired plants which have
already been mentioned at the outset.
[0072] The invention furthermore relates to expression cassettes
comprising [0073] a) genetic control sequences in operable linkage
with a nucleic acid sequence according to the invention; or [0074]
b) additional functional elements; or [0075] c) a combination of a)
and b).
[0076] The invention furthermore relates to the use of the
above-shown expression cassette and to the use of expression
cassettes comprising the abovementioned components a) and b) or c),
wherein the nucleic acid sequence of a) comprises a part-region
with at least 60%, preferably at least 61%, 62%, 63%, 64%, 65%,
66%, 67%, 68%, 69% and 70%, by preference at least 71%, 72%, 73%,
74%, 75%, 76%, 77%, 78%, 79%, 80%, especially preferably at least
81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, very especially
preferably at least 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%
identity with the SEQ ID NO:3, for expressing an SHMT which can be
used in in-vitro assay systems. The abovementioned nucleic acid
sequence of a), which comprise a part-region having at least 60%
identity with the SEQ ID No:3, therefore also comprise functional
equivalents of the SEQ ID NO:7 with an identity of at least 46%,
47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%,
with preference at least 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%,
68%, 69% and 70%, preferably at least 71%, 72%, 73%, 74%, 75%,
especially preferably at least 76%, 77%, 78%, 79%, 80%, 81%, 82%,
83%, 84%, 85%, 86%, 87%, 88%, 89%, very especially preferably at
least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%. Both
embodiments of the above-described expression cassettes are
hereinbelow termed expression cassette according to the
invention.
[0077] In a preferred embodiment, an expression cassette according
to the invention comprises a promoter at the 5' end of the coding
sequence and, at the 3' end, a transcription termination signal
and, if appropriate, further genetic control sequences which are
linked operably with the interposed nucleic acid sequence encoding
an SHMT.
[0078] The expression cassettes according to the invention are also
understood as meaning analogs which can be brought about, for
example, by a combination of the individual nucleic acid sequences
on a polynucleotide (multiple constructs), on a plurality of
polynucleotides in a cell (cotransformation) or by sequential
transformation.
[0079] Advantageous genetic control sequences under item a) for the
expression cassettes according to the invention or for vectors
comprising expression cassettes according to the invention are, for
example, promoters such as the cos, tac, trp, tet, lpp, lac, lacIq,
T7, T5, T3, gal, trc, ara, SP6, .lamda.-PR or the .lamda.-PL
promoter, all of which can be used for expressing SHMT in
Gram-negative bacterial strains.
[0080] Examples of further advantageous genetic control sequences
are present, for example, in the promoters amy and SPO2, both of
which can be used for expressing SHMT in Gram-positive bacterial
strains, and in the yeast or fungal promoters ADC1, MFa, AC, P-60,
CYC1, GAPDH, TEF, rp28, ADH, AOX1 and GAP all of which can be used
for expressing SHMT in yeast strands.
[0081] Examples of genetic control sequences which are suitable for
expression in insect cells are the polyhedrin promoter and the p10
promoter (Luckow, V. A. and Summers, M. D. (1988) Bio/Techn. 6,
47-55).
[0082] Advantageous genetic control sequences for expressing SHMT
in cell culture are, in addition to polyadenylation sequences such
as, for example, from Simian Virus 40 eukaryotic promoters of viral
origin such as, for example, promoters of the polyoma virus,
adenovirus 2, cytomegalovirus or simian virus 40.
[0083] Further advantageous genetic control sequences for
expressing SHMT in plants are present in the plant promoters
CaMV/35S [Franck et al., Cell 21 (1980) 285-294], PRP1 [Ward et
al., Plant. Mol. Biol. 22 (1993)], SSU, OCS, LEB4, USP, STLS1, B33,
NOS; FBPaseP (WO 98/18940) or in the ubiquitin or phaseolin
promoter; a promoter which is preferably used being, in particular,
a plant promoter or a promoter derived from a plant virus.
Especially preferred are promoters of viral origin such as the
promoter of the cauliflower mosaic virus 35S transcript (Franck et
al., Cell 21 (1980), 285-294; Odell et al., Nature 313 (1985),
810-812). Further preferred constitutive promoters are, for
example, the Agrobacterium nopalinsynthase promoter, the TR double
promoter, the agrobacterium OCS (octopine synthase) promoter, the
ubiquitin promoter, (Holtorf S et al., Plant Mol Biol 1995,
29:637-649), the promoters of the vacuola ATPase subunits, or the
promoter of a wheat proline-rich protein (WO 91/13991).
[0084] The expression cassettes may also comprise, as genetic
control sequence, a chemically inducible promoter, by which the
expression of the exogenous gene in the plant can be controlled at
a specific point in time. Such promoters, such as, for example, the
PRP1 promoter (Ward et al., Plant. Mol. Biol. 22 (1993), 361-366),
a salicylic-acid-inducible promoter (WO 95/19443), a
benzenesulfonamide-inducible promoter (EP-A-0388186), a
tetracyclin-inducible promoter (Gatz et al., (1992) Plant J. 2,
397404), an abscissic-acid-inducible promoter (EP-A 335528) or an
ethanol- or cyclohexanone-inducible promoter (WO 93/21334) may also
be used.
[0085] Furthermore, suitable promoters are those which confer
tissue- or organ-specific expression in, for example, anthers,
ovaries, inflorescences and floral organs, leaves, stomata,
trichomes, stems, vascular tissues, roots and seeds. Others which
are suitable in addition to the abovementioned constitutive
promoters are, in particular, those promoters which ensure
leaf-specific expression. Promoters which must be mentioned are the
potato cytosolic FBPase promoter (WO 97/05900), the rubisco
(ribulose-1,5-bisphosphate carboxylase) SSU (small subunit)
promoter or the ST-LSI promoter from potato (Stockhaus et al., EMBO
J. 8 (1989), 2445-245). Promoters which are furthermore preferred
are those which control expression in seeds and plant embryos.
Examples of seed-specific promoters are the phaseolin promoter
(U.S. Pat. No. 5,504,200, Bustos M M et al., Plant Cell. 1989;
1(9):839-53), the promoter of the 2S albumin gene (Joseffson L G et
al., J Biol Chem 1987, 262:12196-12201), the legumin promoter
(Shirsat A et al., Mol Gen Genet. 1989; 215(2):326-331), the USP
(unknown seed protein) promoter (Baumlein H et al., Molecular &
General Genetics 1991, 225(3):459-67), the napin gene promoter
(Stalberg K, et al., L. Planta 1996, 199:515-519), the sucrose
binding protein promoter (WO 00/26388) or the LeB4 promoter
(Baumlein H et al., Mol Gen Genet. 1991, 225: 121-128; Fiedler, U.
et al., Biotechnology (NY) (1995), 13 (10) 1090).
[0086] Further promoters which are suitable as genetic control
sequences are, for example, specific promoters for tubers, storage
roots or roots, such as, for example, the class I patatin promoter
(B33), the potato cathepsin D inhibitor promoter, the starch
synthase (GBSS1) promoter or the sporamin promoter, fruit-specific
promoters such as, for example, the fruit-specific promoter from
tomato (EP-A 409625), fruit-maturation-specific promoters such as,
for example, the fruit-maturation-specific promoter from tomato (WO
94/21794), inflorescence-specific promoters such as, for example,
the phytoene synthase promoter (WO 92/16635) or the promoter of the
P-rr gene (WO 98/22593), or specific plastid chromoplast promoters
such as, for example, the RNA polymerase promoter (WO 97/06250), or
else the Glycine max phosphoribosyl-pyrophosphate amidotransferase
promoter (see also Genbank Accession No. U87999), or another
node-specific promoter as described in EP-A 249676.
[0087] Additional functional elements b) are understood as meaning
by way of example but not by limitation reporter genes, replication
origins, selection markers and what are known as affinity tags, in
fusion with SHMT direct or by means of a linker optionally
comprising a protease cleavage site. Further suitable additional
functional elements are sequences which ensure that the product is
targeted into the apoplasts, into plastids, the vacuole, the
mitochondrion, the peroxisome, the endoplasmatic reticulum (ER) or,
owing to the absence of such operative sequences, remains in the
compartment where it is formed, the zytosol, (Kermode, Crit. Rev.
Plant Sci. 15, 4 (1996), 285-423).
[0088] Also in accordance with the invention are vectors comprising
at least one copy of the nucleic acid sequences according to the
invention and/or the expression cassettes according to the
invention.
[0089] In addition to plasmids, vectors are furthermore also
understood as meaning all of the other known vectors with which the
skilled worker is familiar, such as, for example, phages, viruses
such as SV40, CMV, baculovirus, adenovirus, transposons, IS
elements, phasmids, phagemids, cosmids or linear or circular DNA.
These vectors can be replicated autonomously in the host organism
or replicated chromosomally; chromosomal replication is
preferred.
[0090] In a further embodiment of the vector, the nucleic acid
construct according to the invention can advantageously also be
introduced into the organisms in the form of a linear DNA and
integrated into the genome of the host organism via heterologous or
homologous recombination. This linear DNA may consist of a
linearized plasmid or only of the nucleic acid construct as vector,
or the nucleic acid sequences used.
[0091] Further prokaryotic or eukaryotic expression systems are
mentioned in Chapters 16 and 17 in Sambrook et al., "Molecular
Cloning: A Laboratory Manual." 2nd, ed., Cold Spring Harbor
Laboratory, Cold Spring Harbor Laboratory Press, Cold Spring
Harbor, N.Y., 1989. Further advantageous vectors are described in
Hellens et al. (Trends in plant science, 5, 2000).
[0092] The expression cassette according to the invention and
vectors derived therefrom can be used for transforming bacteria,
cyanobacteria, yeasts, filamentos fungi and algae and eukaryotic
nonhuman cells (for example insect cells) with the aim of producing
SHMT recombinantly, the generation of a suitable expression
cassette depending on the organism in which the gene is to be
expressed.
[0093] In a further advantageous embodiment, the nucleic acid
sequences used in the method according to the invention may also be
introduced into an organism by themselves.
[0094] If, in addition to the nucleic acid sequences, further genes
are to be introduced into the organism, they can all be introduced
into the organism together in a single vector, or each individual
gene can be introduced into the organism in each case one vector,
it being possible to introduce the different vectors simultaneously
or in succession.
[0095] In this context, the introduction, into the organisms in
question (transformation), of the nucleic acid(s) according to the
invention, of the expression cassette or of the vector can be
effected in principle by all methods with which the skilled worker
is familiar.
[0096] In the case of microorganisms, the skilled worker will find
suitable methods in the textbooks by Sambrook, J. et al. (1989)
"Molecular cloning: A laboratory manual", Cold Spring Harbor
Laboratory Press, von F. M. Ausubel et al. (1994) "Current
protocols in molecular biology", John Wiley and Sons, by D. M.
Glover et al., DNA Cloning Vol. 1, (1995), IRL Press (ISBN
019-963476-9), by Kaiser et al. (1994) Methods in Yeast Genetics,
Cold Spring Harbor Laboratory Press or Guthrie et al. "Guide to
Yeast Genetics and Molecular Biology", Methods in Enzymology, 1994,
Academic Press.
[0097] In the case of dicots, the methods which have been described
for the transformation and regeneration of plants from plant
tissues or plant cells can be exploited for transient or stable
transformation. Suitable methods are the biolistic method or the
transformation of protoplasts (cf., for example, Willmitzer, L.,
1993 Transgenic plants. In: Biotechnology, A Multi-Volume
Comprehensive Treatise (H. J. Rehm, G. Reed, A. Pithier, P.
Stadler, eds.), Vol. 2, 627-659, VCH Weinheim-New
York-Basel-Cambridge), electroporation, the incubation of dry
embryos in DNA-comprising solution, microinjection and the
agrobacterium-radiated gene transfer. The abovementioned methods
are described, for example, in B. Jenes et al., Techniques for Gene
Transfer, in: Transgenic Plants, Vol. 1, Engineering and
Utilization, edited by S. D. Kung and R. Wu, Academic Press (1993)
128-143 and in Potrykus, Annu. Rev. Plant Physiol. Plant Molec.
Biol. 42 (1991) 205-225).
[0098] The transformation by means of agrobacteria, and the vectors
to be used for the transformation, are known to the skilled worker
and described extensively in the literature (Bevan et al., Nucl.
Acids Res. 12 (1984) 8711. The intermediary vectors can be
integrated into the agrobacterial Ti or Ri plasmid by means of
homologous recombination owing to sequences which are homologous to
sequences in the T-DNA. This plasmid additionally comprises the vir
region, which is required for the transfer of the T-DNA.
Intermediary vectors are not capable of replication in
agrobacteria. The intermediary vector can be transferred to
Agrobacterium tumefaciens by means of a helper plasmid
(conjugation). Binary vectors are capable of replication both in E.
coli and in agrobacteria. They comprise a selection of marker gene
and a linker or polylinker which are framed by the right and left
T-DNA border region. They can be transformed directly into the
agrobacteria (Holsters et al. Mol. Gen. Genet. 163 (1978),
181-187), EP A 0 120 516; Hoekema, In: The Binary Plant Vector
System Offsetdrukkerij Kanters B. V., Alblasserdam (1985), Chapter
V; Fraley et al., Crit. Rev. Plant. Sci., 4: 1-46 and An et al.
EMBO J. 4 (1985), 277-287).
[0099] The transformation of monocots by means of vectors based on
Agrobacterium has also been described (Chan et al, Plant Mol. Biol.
22 (1993), 491-506; Hiei et al, Plant J. 6 (1994) 271-282; Deng et
al; Science in China 33 (1990), 28-34; Wilmink et al, Plant Cell
Reports 11, (1992) 76-80; May et al; Biotechnology 13 (1995)
486-492; Conner and Domisse; Int. J. Plant Sci. 153 (1992) 550-555;
Ritchie et al; Transgenic Res. (1993) 252-265). Alternative systems
for the transformation of monocots are the transformation by means
of biolistic approach (Wan and Lemaux; Plant Physiol. 104 (1994),
37-48; Vasil et al; Biotechnology 11 (1992), 667-674; Ritala et al,
Plant Mol. Biol. 24, (1994) 317-325; Spencer et al, Theor. Appl.
Genet. 79 (1990), 625-631), protoplast transformation, the
electroporation of partially permeabilized cells, and the
introduction of DNA by means of glass fibers. In particular the
transformation of maize has been described repeatedly in the
literature (WO 95/06128; EP 0513849 A1; EP 0465875 A1; EP 0292435
A1; Fromm et al, Biotechnology 8 (1990), 833-844; Gordon-Kamm et
al, Plant Cell 2 (1990), 603-618; Koziel et al, Biotechnology 11
(1993) 194-200; Moroc et al, Theor Applied Genetics 80 (190)
721-726).
[0100] The successful transformation of other cereal species has
also already been described for example in the case of barley (Wan
and Lemaux, see above; Ritala et al, see above; wheat (Nehra et al,
Plant J. 5 (1994) 285-297).
[0101] Agrobacteria which have been transformed with a vector
according to the invention can likewise be used in a known manner
for the transformation of plants, such as test plants like
Arabidopsis or crop plants like cereals, maize, oats, rye, barley,
wheat, soya, rice, cotton, sugarbeet, canola, sunflower, flax,
hemp, potato, tobacco, tomato, carrot, capsicum, oilseed rape,
tapioca, cassaya, arrowroot, Tagetes, alfalfa, lettuce and the
various tree, nut and grapevine species, for example by bathing
scarified leaves or leaf segments in an agrobacterial solution and
subsequently growing them in suitable media.
[0102] The genetically modified plant cells can be regenerated via
all methods with which the skilled worker is familiar. Such methods
can be found in the abovementioned publications by S. D. Kung and
R. Wu, Potrykus or Hofgen and Willmitzer.
[0103] The transgenic organisms generated by transformation with
one of the above-described embodiments of an expression cassette
comprising a nucleic acid sequence according to the invention or a
vector comprising the abovementioned expression cassette, and the
recombinant SHMT which can be obtained from the transgenic organism
by means of expression, are subject matter of the present
invention. The use of transgenic organisms comprising an expression
cassette according to the invention, for example for providing
recombinant protein, and/or the use of these organisms in in-vivo
assay systems are likewise subject matter of the present
invention.
[0104] Preferred organisms for the recombinant expression are not
only bacteria, yeasts, mosses, algae and fungi, but also eukaryotic
cell lines.
[0105] Preferred mosses are Physcomitrella patens or other mosses
described in Kryptogamen [Cryptogamia], Vol. 2, Moose, Farne
[Mosses, Ferns], 1991, Springer Verlag (ISBN 3540536515).
[0106] Preferred within the bacteria are, for example, bacteria
from the genus Escherichia, Erwinia, Flavobacterium, Alcaligenes or
cyanobacteria, for example from the genus Synechocystis or
Anabena.
[0107] Preferred yeasts are Candida, Saccharomyces,
Schizosaccheromyces, Hansenula or Pichia.
[0108] Preferred fungi are Aspergillus, Trichoderma, Ashbya,
Neurospora, Fusarium, Beauveria, Mortierella, Saprolegnia, Pythium,
or other fungi described in Indian Chem. Engr. Section B. Vol 37,
No 1,2 (1995).
[0109] Preferred plants are selected in particular among
monocotyledonous crop plants such as, for example, cereal species
such as wheat, barley, sorghum or millet, rye, triticale, maize,
rice or oats, and sugarcane. The transgenic plants according to the
invention are, furthermore, in particular selected from among
dicotyledonous crop plants such as, for example, Brassicaceae such
as oilseed rape, cress, Arabidopsis, cabbages or canola;
Leguminosae such as soyabean, alfalfa, pea, beans or peanut,
Solanaceae such as potato, tobacco, tomato, egg plant or capsicum;
Asteraceae such as sunflower, Tagetes, lettuce or Calendula;
Cucurbitaceae such as melon, pumpkin/squash or zucchini, or
linseed, cotton, hemp, flax, red pepper, carrot, carrot, sugar
beet, or various tree, nut and grapevine species.
[0110] In principle, transgenic animals such as, for example, C.
elegans, are also suitable as host organisms.
[0111] Also preferred is the use of expression systems and vectors
which are available to the public or commercially available.
[0112] Those which must be mentioned for use in E. coli bacteria
are the typical advantageous commercially available fusion and
expression vectors pGEX [Pharmacia Biotech Inc; Smith, D. B. and
Johnson, K. S. (1988) Gene 67:31-40], pMAL (New England Biolabs,
Beverly, Mass.) and pRIT5 (Pharmacia, Piscataway, N.J.), which
comprises glutathion S transferase (GST), maltose binding protein
or protein A, the pTrc vectors (Amann et al., (1988) Gene
69:301-315), "pKK233-2" by CLONTECH, Palo Alto, Calif. and the
"pET"-, and the "pBAD" vector series from Stratagene, La Jolla.
[0113] Further advantageous vectors for use in yeast are pYepSec1
(Baldari, et al., (1987) Embo J. 6:229-234), pMFa (Kurjan and
Herskowitz, (1982) Cell 30:933-943), pJRY88 (Schultz et al., (1987)
Gene 54:113-123), and pYES derivatives, pGAPZ derivatives, pPICZ
derivatives, and the vectors of the "Pichia Expression Kit"
(Invitrogen Corporation, San Diego, Calif.). Vectors for use in
filamentous fungi are described in: van den Hondel, C. A. M. J. J.
& Punt, P. J. (1991) "Gene transfer systems and vector
development for filamentous fungi, in: Applied Molecular Genetics
of Fungi, J. F. Peberdy, et al., eds., p. 1-28, Cambridge
University Press: Cambridge.
[0114] As an alternative, insect cell expression vectors may also
be used advantageously, for example for expression in Sf9, Sf21 or
Hi5 cells, which are infected via recombinant Baculoviruses.
Examples of these are the vectors of the pAc series (Smith et al.
(1983) Mol. Cell. Biol. 3:2156-2165) and the pVL series (Lucklow
and Summers (1989) Virology 170:31-39). Others which may be
mentioned are the Baculovirus expression systems "MaxBac 2.0 Kit"
and "Insect Select System" by Invitrogen, Carlsbad or "BacPAK
Baculovirus Expression System" by CLONTECH, Palo Alto, Calif.
Insect cells are particularly suitable for overexpressing
eukaryotic proteins since they effect posttranslational
modifications of the proteins which are not possible in bacteria
and yeasts. The skilled worker is familiar with the handling of
cultured insect cells and with their infection for expressing
proteins, which can be carried out analogously to known methods
(Luckow and Summers, Bio/Tech. 6, 1988, pp. 47-55; Glover and Hames
(eds) in DNA Cloning 2, A practical Approach, Expression Systems,
Second Edition, Oxford University Press, 1995, 205-244).
[0115] Plant cells or algal cells are others which can be used
advantageously for expressing genes. Examples of plant expression
vectors can be found as mentioned above in Becker, D., et al.
(1992) "New plant binary vectors with selectable markers located
proximal to the left border", Plant Mol. Biol. 20: 1195-1197 or in
Bevan, M. W. (1984) "Binary Agrobacterium vectors for plant
transformation", Nucl. Acid. Res. 12: 8711-8721.
[0116] Moreover, the nucleic acid sequences according to the
invention can be expressed in mammalian cells. Examples of suitable
expression vectors are pCDM8 and pMT2PC, which are mentioned in:
Seed, B. (1987) Nature 329:840 or Kaufman et al. (1987) EMBO J.
6:187-195). Promoters preferably to be used in this context are of
viral origin such as, for example, promoters of polyoma virus,
adenovirus 2, cytomegalovirus or simian virus 40. Further
prokaryotic and eukaryotic expression systems are mentioned in
Chapter 16 and 17 in Sambrook et al., Molecular Cloning: A
Laboratory Manual. 2nd, ed., Cold Spring Harbor Laboratory, Cold
Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1989.
Further advantageous vectors are described in Hellens et al.
(Trends in plant science, 5, 2000).
[0117] All of the above-described embodiments of the transgenic
organisms come under the term "transgenic organism according to the
invention".
[0118] The present invention furthermore relates to the use of
nucleic or amino acid sequences of SHMTs in a method for
identifying herbicidally active test compounds. As already
mentioned further above, the term "SHMT" preferably comprises
mitochondrial SHMT. All methods for identifying herbicidally active
inhibitors are hereinbelow referred to as methods according to the
invention.
[0119] The use forms, of methods according to the invention, which
are now described in the following text are preferably based on the
use of SHMTs which are encoded via a nucleic acid sequence
comprising [0120] a) a nucleic acid sequence according to the
invention; or [0121] b) a functional equivalent of the nucleic acid
sequence SEQ ID NO:3 which comprises a part-region which has at
least 60%, preferably at least 61%, 62%, 63%, 64%, 65%, 66%, 67%,
68%, 69% and 70%, preferably at least 71%, 72%, 73%, 74%, 75%, 76%,
77%, 78%, 79%, 80%, especially preferably at least 81%, 82%, 83%,
84%, 85%, 86%, 87%, 88%, 89%, 90%, very especially preferably at
least 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% identity with the
SEQ ID NO:3.
[0122] The abovementioned nucleic acid sequence of b), which
comprise a part-region with at least 60% identity with the SEQ ID
NO:3, accordingly also comprise functional equivalents of the SEQ
ID NO:7 with at least 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%,
55%, 56%, 57%, 58%, 59%, with preference at least 60%, 61%, 62%,
63%, 64%, 65%, 66%, 67%, 68%, 69% and 70%, preferably at least 71%,
72%, 73%, 74%, 75%, especially preferably at least 76%, 77%, 78%,
79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, very
especially preferably at least 90%, 91%, 92%, 93%, 94%, 95%, 96%,
97%, 98%, 99% identity. The nucleic acid sequence of b) a
polypeptide with the enzymatic, preferably biological, activity of
an SHMT.
[0123] The method according to the invention for identifying
herbicidally active substances comprising the following steps:
[0124] i. bringing a nucleic acid molecule encoding a polypeptide
with the enzymatic, preferably biological, activity of a serine
hydroxymethyltransferase, preferably of a mitochondrial serine
hydroxymethyltransferase, or of the polypeptide encoded by the
nucleic acid molecule into contact with one or more test compounds
under conditions which permit the test compound(s) to bind to the
nucleic acid molecule or the polypeptide which is encoded via the
nucleic acid; and [0125] ii. detecting whether the test compound
binds to the polypeptide of i); or [0126] iii. detecting whether
the test compound reduces or blocks the activity of the polypeptide
or of i); [0127] iv. detecting whether the test compound reduces or
blocks the transcription, translation or expression of the nucleic
acid of i).
[0128] Preferred methods according to the invention for identifying
herbicidally active compounds comprise the following steps: [0129]
i. bringing the nucleic acid molecule as defined above, or the
polypeptide encoded by the nucleic acid molecule, into contact with
one or more test compounds under conditions which permit binding of
the test compound(s) to the nucleic acid molecule or the
polypeptide encoded via the nucleic acid; and [0130] ii. detecting
whether the test compound binds to the polypeptide of i); or [0131]
iii. detecting whether the test compound reduces or blocks the
activity of the polypeptide of i); or [0132] iv. detecting whether
the test compound reduces or blocks the transcription, translation
or expression of the nucleic acid of i).
[0133] The detection in accordance with step (ii) of the above
method can be effected using techniques which identify the
interaction between protein and ligand. In this context, either the
test compound or the enzyme can comprise the detectable label such
as, for example, a fluorescent label, a radioisotrope, a
chemiluminescent label or an enzyme label. Examples of enzyme
labels are horseradish peroxidase, alkaline phosphatase or
luciferase. The subsequent detection depends on the label and is
known to the skilled worker.
[0134] In this context, five preferred embodiments which are also
suitable for high-throughput methods (HTS) in connection with the
present invention, must be mentioned in particular: [0135] 1. The
average diffusion rate of a fluorescent molecule as a function of
the mass can be determined in a small sample volume via
fluorescence correlation spectroscopy (FCS) (Proc. Natl. Acad. Sci.
USA (1994) 11753-11575). FCS can be employed for determining
protein/ligand interaction by measuring the changes in the mass, or
the changed diffusion rate which this entails, of a test compound
when binding to SHMT. A method according to the invention can be
designed directly for measuring the binding of a test compound
labeled by a fluorescent molecule. As an alternative, the method
according to the invention can be designed in such a way that a
chemical reference compound which is labeled by a fluorescent
molecule is displaced by further test compounds ("displacement
assay"). The compounds which are identified in this manner may be
suitable as inhibitors. [0136] 2. Fluorescence polarization
exploits the characteristic of a quiescent fluorophore excited with
polarized light to likewise emit polarized light. If, however, the
fluorophore is allowed to rotate during the excited state, the
polarization of the fluorescent light which is emitted is more or
less lost. Under otherwise identical conditions (for example
temperature, viscosity, solvent), the rotation is a function of
molecule size, whereby findings regarding the size of the
fluorophore-bound residue can be obtained via the reading (Methods
in Enzymology 246 (1995), pp. 283-300). A method according to the
invention can be designed directly for measuring the binding of a
fluorescently labeled test compound to the SHMT. As an alternative,
the method according to the invention may also take the form of the
"displacement assay" described under 1. The compounds identified in
this manner may be suitable as inhibitors. [0137] 3. Fluorescent
resonance energy transfer (FRET) is based on the irradiation-free
energy transfer between two spatially adjacent fluorescent
molecules under suitable conditions. A prerequisite is that the
emission spectrum of the donor molecule overlaps with the
excitation spectrum of the acceptor molecule. Using the fluorescent
label of SHMT and the test compound, the binding can be measured by
means of FRET (Cytometry 34, 1998, pp. 159-179). As an alternative,
the method according to the invention may also take the form of the
"displacement assay" described under 1. An especially suitable
embodiment of FRET technology is "Homogeneous Time Resolved
Fluorescence" (HTRF) as can be obtained from Packard BioScience.
The compounds which are identified in this manner may be suitable
as inhibitors. [0138] 4. Surface-enhanced laser
desorption/ionization (SELDI) in combination with a time-of-flight
mass spectrometer (MALDI-TOF) makes possible the rapid analysis of
molecules on a support and can be used for analyzing protein/ligand
interactions (Worral et al., (1998) Anal. Biochem. 70:750-756). In
a preferred embodiment, SHMT is immobilized on a suitable support
and incubated with the test compound. After one or more suitable
wash steps, the test compound molecules which are additionally
bound to SHMT can be detected by means of the above-mentioned
methodology and inhibitors can thus be selected. The compounds
which are identified in this manner may be suitable as inhibitors.
[0139] 5. The measurement of surface plasmon resonance is based on
the change in the refractive index at a surface when a test
compound binds to a protein which is immobilized to said surface.
Since the change in the refractive index is identical for virtually
all proteins and polypeptides for a defined change in the mass
concentration at the surface, this method can be applied to any
protein in principle (Lindberg et al. Sensor Actuators 4 (1983)
299-304; Malmquist Nature 361 (1993) 186-187). The measurement can
be carried out for example with the automatic analyzer based on
surface plasmon resonance which is available from Biacore
(Freiburg) at a throughput of, currently, up to 384 samples per
day. A method according to the invention can be designed directly
for measuring the binding of a test compound to SHMT. As an
alternative, the method according to the invention may also take
the form of the "displacement assay" described under 1. The
compounds identified in this manner may be suitable as
inhibitors.
[0140] All of the substances identified via the abovementioned
methods can subsequently be checked for their herbicidal action in
another embodiment of the method according to the invention.
[0141] Furthermore, there exists the possibility of detecting
further candidates for herbicidal active ingredients by molecular
modeling via elucidation of the three-dimensional structure of SHMT
by x-ray structure analysis. The preparation of protein crystals
required for x-ray structure analysis, and the relevant
measurements and subsequent evaluations of these measurements, the
detection of a binding site in the protein, and the prediction of
potential inhibitor structures are known to the skilled worker. In
principle, an optimization of the compound identified by the
abovementioned methods is also possible via molecular modeling.
[0142] A preferred embodiment of the method according to the
invention, which is based on steps i) and ii), consists in [0143]
a) expressing an SHMT in a transgenic organism according to the
invention, or growing an organism which naturally comprises an
SHMT; [0144] b) bringing the SHMT of step a) in the cell digest of
the transgenic or nontransgenic organism, in partially purified
form or in homogeneously purified form, into contact with a test
compound; and [0145] c) selecting a compound which reduces or
blocks the SHMT activity, the activity of the SHMT incubated with
the test compound being compared with the activity of an SHMT not
incubated with a test compound.
[0146] Based on the abovementioned nucleic acid sequences, the
method can, accordingly, comprise [0147] a) either expressing, in a
transgenic organism, a mitochondrial plant serine
hydroxymethyltransferase which is encoded by a nucleic acid
sequence comprising a nucleic acid sequence with the nucleic acid
sequence shown in SEQ ID NO:3; or a nucleic acid sequence which, on
the basis of the degeneracy of the genetic code, can be derived
from the amino acid sequence shown in SEQ ID NO:4 by back
translation; or functional equivalents of the nucleic acid sequence
SEQ ID NO:3, comprising a part-region with at least 91% identity to
the SEQ ID NO:3, or a nucleic acid sequence comprising a
part-region with at least 60% identity to the SEQ ID NO:3, or
culturing an organism which naturally comprises a plant serine
hydroxymethyltransferase which is encoded by a nucleic acid
sequence comprising a nucleic acid sequence with the nucleic acid
sequence shown in SEQ ID NO:3; or a nucleic acid sequence which, on
the basis of the degeneracy of the genetic code, can be derived
from the amino acid sequence shown in SEQ ID NO:4; or functional
equivalents of the nucleic acid sequence SEQ ID NO:3 by back
translation, comprising a part-region with at least 91% identity to
the SEQ ID NO:3, or a nucleic acid sequence comprising a
part-region with at least 60% identity to the SEQ ID NO:3; [0148]
b) bringing the serine hydroxymethyltransferase of step a) in the
cell digest of the transgenic or nontransgenic organism, in
partially purified form or in homogeneously purified form, into
contact with a test compound, and [0149] c) selecting a test
compound which reduces or blocks the activity of the serine
hydroxymethyltransferase of step a), the activity of the serine
hydroxymethyltransferase incubated with the test compound being
compared with the activity of a serine hydroxymethyltransferase
which is not incubated with a test compound.
[0150] Again, it is evident that the abovementioned nucleic acid
sequences of a) which comprise a part-region with at least 60%
identity to the SEQ ID No:3, also comprise functional equivalents
of the SEQ ID NO:7 with an identity of at least 46%. As regards the
functional equivalents, the abovementioned preferences apply.
[0151] The solution comprising the SHMT can consist of the lysate
of the original organism or of the transgenic organism which has
been transformed with an expression cassette according to the
invention. If appropriate, the SHMT can be purified partially or
fully via customary methods. A general overview over current
protein purification techniques is described, for example, in
Ausubel, F. M. et al., Current Protocols in Molecular Biology,
Greene Publishing Assoc. and Wiley-Interscience (1994); ISBN
0-87969-309-6. If SHMT is obtained recombinantly, the protein which
takes the form of a fusion with an affinity tag can be purified via
affinity chromatography as is known to the skilled worker. In the
in-vitro methods according to the invention, care must be taken
that the essential cofactor of SHMT, namely pyridoxal phosphate, is
present in a sufficient amount, i.e., as a rule, in the range from
50-600 mm, preferably 80-500 mm, per mol of enzyme.
[0152] The SHMT which is required for in-vitro methods can thus be
isolated either by means of heterologous expression from a
transgenic organism according to the invention or from an organism
comprising a polypeptide with SHMT activity, preferably from an
undesired plant, the term "undesired plant" being understood as
meaning the species mentioned at the outset.
[0153] To identify herbicidal compounds, the SHMT is incubated with
a test compound. After a reaction time, the SHMT activity is
determined by one of the abovementioned methods in comparison with
the activity of the uninhibited SHMT. If the polypeptide according
to the invention is inhibited, a significant decrease in activity
in comparison with the activity of the noninhibited polypeptide
according to the invention is observed, the result being a
reduction of at least 10%, advantageously at least 20%, preferably
at least 30%, especially preferably by at least 50%, up to 100%
reduction (blocking). Preferred is an inhibition of at least 50% at
test compound concentrations of 10.sup.-4 M, preferably at
10.sup.-5 M, especially preferably of 10.sup.-6 M, based on enzyme
concentration in the micromolar range.
[0154] The SHMT enzyme activity can be determined for example by an
activity assay, i.e. by incubating the SHMT with a suitable
substrate and cofactors, with monitoring the conversion of the
substrate or of the cofactor.
[0155] Examples of suitable substrates are serine or glycin, and
examples of suitable cofactors tetrahydrofolate or
Cl-tetrahydrofolate. If appropriate, derivatives of the
abovementioned compounds which comprise a detectable label such as,
for example, a fluorescent label, a radioisotope label or a
chemiluminescent label, may also be used.
[0156] For example, the SHMT activity can be measured using a
radioactive method according to the invention (Bourguignon et al.
Biochem. J. 255, pp. 169-178, 1988).
[0157] However, the SHMT enzyme activity can also be determined by
means of a chromatographic separation method based on the
separation of tetrahydrofolate from Cl-tetrahydrofolate, followed
by quantitative analysis of the amount of tetrahydrofolate and
Cl-tetrahydrofolate via integration of the peaks obtained in the
chromatography via UV-spectroscopy. The chromatographic separation
is preferably effected by reversed-phase chromatography (RPC), for
example using an HPLC or FPLC system. The principle of this
chromatography and the buffers and apparatuses used for it are
known to the skilled worker and are described, for example, in
"Introduction to Modern Liquid Chromatography" by L. R. Snyder and
J. J. Kirkland, 2nd Edition. John Wiley & Sons, 1979.
[0158] As a rule, the mobile phases which are conventionally used
in RPC and which are known to the skilled worker are used.
[0159] The amounts of substrate (for example serine) to be employed
in the activity assay range from 1-50 mM, and the amounts of
tetrahydrofolate range from 1-10 mM, based on 1-100 .varies.g/ml
enzyme.
[0160] In an especially preferred embodiment, the conversion of the
substrate is monitored photometrically, using a modification of a
method described by Stover and Schirch (Anal. Biochem. 202, pp.
82-88) which is based on coupling the SHMT reaction with the
reaction catalyzed by NAD-dependent methylenetetrahydrofolate
dehydrogenase (MTD) and photometric measurement at 340 nm.
[0161] A preferred embodiment of the method according to the
invention which is based on steps i) and iii) consists of the
following steps: [0162] a) generating a transgenic organism
according to the invention; [0163] b) applying a test substance to
the transgenic organism of a) and to a nontransgenic organism of
the same type; [0164] c) determining the growth or the viability of
the transgenic and the nontransgenic organisms after application of
the test substance; and [0165] d) selecting test substances which
bring about a reduced growth or a reduced viability of the
nontransgenic organism in comparison with the growth of the
transgenic organism.
[0166] In this context, the difference in growth in step c) for the
selection of a herbicidally active inhibitor amounts to at least
100, preferably 20%, by preference 30%, especially preferably 40%
and very especially preferably 50%.
[0167] The transgenic organism in this context is a bacterium, a
yeast, a fungus, a plant or a eukaryotic cell line, preferably
plants, bacteria or yeasts, which can readily be transformed by
means of customary techniques, such as Arabidopsis thaliana,
Solanum tuberosum, Nicotiana tabacum, Saccharomyces cerevisiae or
E. coli, into which the sequence encoding a polypeptide according
to the invention has been incorporated by transformation. These
transgenic organisms thus show increased tolerance to compounds
which inhibit the polypeptide according to the invention. E. coli
and Saccharomyces cerevisiae are in particular the organisms of
choice since their genomes have been sequenced in their entirety
and they can readily be used for the generation of "knock-out"
mutants (for example Methods in Yeast Genetics, Kaiser, Michaelis,
Mitchell (eds.) CSHL Press, Cold Spring Harbor Laboratory Press,
1994: 73-85).
[0168] However, the abovementioned method can also be used for
identifying substances with a growth-regulatory action. In this
context, the transgenic organism employed is a plant. Moreover,
step d) involves the selection of test compounds which bring about
a modified growth of the nontransgenic organism in comparison with
the growth of the transgenic organism. Modified growth is
understood as meaning, in this context, inhibition of the
vegetative growth of the plants, which can manifest itself in
particular in reduced longitudinal growth. Accordingly, the treated
plants show stunted growth; moreover, their leaves are darker. In
addition, modified growth is also understood as meaning a change of
the course of maturation over time, the inhibition of promotion of
lateral branched growth of the plants, shortened or extended
developmental stages, increased standing ability, the growth of
larger amounts of buds, flowers, leaves, fruits, seed kernels,
roots and tubers, an increased sugar content in plants such as
sugarbeet, sugar cane and citrus fruit, an increased protein
content in plants such as cereals or soybean, or stimulation of the
latex flow in rubber trees. The skilled worker is familiar with the
detection of such modified growth.
[0169] It is also possible, in the method according to the
invention, to employ a plurality of test compounds in a method
according to the invention. If a group of test compounds affect the
target, then it is either possible directly to isolate the
individual test compounds or to divide the group of test compounds
into a variety of subgroups, for example when it consists of a
multiplicity of different components, in order to reduce the number
of the different test compounds in the method according to the
invention. The method according to the invention is then repeated
with the individual test compound or the relevant subgroup of test
compounds. Depending on the complexity of the sample, the
above-described steps can be carried out repeatedly, preferably
until the subgroup identified in accordance with the method
according to the invention only comprises a small number of test
compounds, or indeed just one test compound.
[0170] All of the compounds which have been identified via the
methods according to the invention can subsequently be tested in
vivo for their herbicidal action. One possibility of testing the
compounds for herbicidal action is to use duck weed, Lemna minor in
microtiter plates. Parameters which can be measured are
modifications in the chlorophyll content and the photosynthesis
rate. It is also possible to apply the compound directly to
undesired plants, it being possible to identify the herbicidal
action for example via restricted growth.
[0171] The method according to the invention can advantageously
also be carried out in high-throughput methods, or high-throughput
screening methods (HTS).
[0172] HTS makes possible the simultaneous testing of a
multiplicity of different compounds.
[0173] The use of supports which comprise one or more of the
nucleic acid molecules according to the invention, one or more of
the vectors comprising the nucleic acid sequence according to the
invention, one or more transgenic organisms comprising at least one
of the nucleic acid sequences according to the invention or one or
more (poly)peptides encoded via the nucleic acid sequences
according to the invention lends itself to carrying out an HTS in
practice. The support used can be solid or liquid, it is preferably
solid and especially preferably a microtiter plate. The
abovementioned supports are also the subject matter of the present
invention. In accordance with the most widely used technique,
96-well, 384-well and 1536-well microtiter plates which, as a rule,
can comprise volumes of 200 .varies.l, are used. Besides the
microtiter plates, the further components of an HTS system which
match the corresponding microtiter plates, such as a large number
of instruments, materials, automatic pipetting devices, robots,
automated plate readers and plate washers, are commercially
available.
[0174] In addition to the HTS systems based on microtiter plates,
what are known as "free-format assays" or assay systems where no
physical barriers exist between the samples such as, for example,
in Jayaickreme et al., Proc. Natl. Acad. Sci. U.S.A. 19 (1994)
161418; Chelsky, "Strategies for Screening Combinatorial Libraries,
First Annual Conference of The Society for Biomolecular Screening
in Philadelphia, Pa. (Nov. 710, 1995); Salmon et al., Molecular
Diversity 2 (1996), 5763 and U.S. Pat. No. 5,976,813, may also be
used.
[0175] The invention furthermore relates to compounds identified by
the methods according to the invention. These compounds are
hereinbelow referred to as "selective compounds". They have a
molecular weight of less than 1000 g/mol, advantageously less than
500 g/mol, preferably less than 400 g/mol, especially preferably
less than 300 g/mol. Herbicidally active compounds have a Ki value
of less than 1 mM, preferably less than 1 .varies.M, especially
preferably less than 0.1 .varies.M, very especially preferably less
than 0.01 .varies.M.
[0176] Naturally, the compounds identified by the methods according
to the invention can also be present in the form of their
agriculturally useful salts. Agriculturally useful salts which are
suitable are mainly the salts of those cations, or the acid
addition salts of those acids, whose cations, or anions, do not
adversely affect the herbicidal action of the herbicidally active
compounds identified via the methods according to the
invention.
[0177] If the selected compounds comprise asymmetrically
substituted .alpha.-carbon atoms, they may furthermore also be
present in the form of racemates, enantiomer mixtures, pure
enantiomers or, if they have chiral substituents, also in the form
of diastereomer mixtures.
[0178] The selected compounds can be chemically synthesized
substances or substances produced by microbes and can be found, for
example, in cell extracts or, for example, plants, animals or
microorganisms. The reaction mixture can be a cell-free extract or
comprise a cell or cell culture. Suitable methods are known to the
skilled worker and are described generally for example in Alberts,
Molecular Biology the cell, 3.sup.rd Edition (1994), for example
chapter 17.
[0179] Candidate test compounds can be expression libraries such
as, for example, cDNA expression libraries, peptides, proteins,
nucleic acids, antibodies, small organic substances, hormones, PNAs
or the like (Milner, Nature Medicin 1 (1995), 879-880; Hupp, Cell.
83 (1995), 237-245; Gibbs, Cell. 79 (1994), 193-198 and references
cited therein).
[0180] The selected compounds can be used for controlling undesired
vegetation, if appropriate also for the defoliation of, for
example, potatoes or the desiccation of, for example, cotton, and
as growth regulators. Herbicidal compositions comprising the
selected compounds afford very good control of vegetation on
noncrop areas. In crops such as wheat, rice, maize, soybean and
cotton, they act against broad-leaved weeds and grass weeds without
inflicting any significant damage on the crop plants. This effect
is observed in particular at low application rates. The selected
compounds can be used for controlling the harmful plants which have
already been mentioned above.
[0181] Depending on the application method in question, selected
compounds, or herbicidal compositions comprising them, can
advantageously also be employed in a further number of crop plants
for eliminating undesired plants. Examples of suitable crops
are:
Allium cepa, Ananas comosus, Arachis hypogaea, Asparagus
officinalis, Beta vulgaris spec. altissima, Beta vulgaris spec.
rapa, Brassica napus var. napus, Brassica napus var. napobrassica,
Brassica rapa var. silvestris, Camellia sinensis, Carthamus
tinctorius, Carya illinoinensis, Citrus limon, Citrus sinensis,
Coffea arabica (Coffea canephora, Coffea liberica), Cucumis
sativus, Cynodon dactylon, Daucus carota, Elaeis guineensis,
Fragaria vesca, Glycine max, Gossypium hirsutum, (Gossypium
arboreum, Gossypium herbaceum, Gossypium vitifolium), Helianthus
annuus, Hevea brasiliensis, Hordeum vulgare, Humulus lupulus,
Ipomoea batatas, Juglans regia, Lens culinaris, Linum
usitatissimum, Lycopersicon lycopersicum, Malus spec., Manihot
esculenta, Medicago sativa, Musa spec., Nicotiana tabacum (N.
rustica), Olea europaea, Oryza sativa, Phaseolus lunatus, Phaseolus
vulgaris, Picea abies, Pinus spec., Pisum sativum, Prunus avium,
Prunus persica, Pyrus communis, Ribes sylestre, Ricinus communis,
Saccharum officinarum, Secale cereale, Solanum tuberosum, Sorghum
bicolor (s. vulgare), Theobroma cacao, Trifolium pratense, Triticum
aestivum, Triticum durum, Vicia faba, Vitis vinifera, Zea mays.
[0182] In addition, the selected compounds can also be used in
crops which tolerate the action of herbicides owing to breeding,
including recombinant methods. The generation of such crops is
described hereinbelow.
[0183] The invention furthermore relates to a method of preparing a
herbicidal composition, which comprises formulating selected
compounds with suitable adjuvants to give crop protection
products.
[0184] The present invention likewise relates to a method of
preparing a growth-regulating composition, which comprises
formulating selected compounds with suitable adjuvants to give crop
protection products.
[0185] In this case the selected compounds can be formulated for
example in the form of directly sprayable aqueous solutions,
powders, suspensions, also highly concentrated aqueous, oily or
other suspensions or dispersions, emulsions, oil dispersions,
pastes, dusts, materials for spreading or granules by means of
spraying, atomizing, dusting, spreading or pouring. The use forms
depend on the intended use and the nature of the selected
compounds; in any case, they should guarantee the finest possible
distribution of the selected compounds. The herbicidal compositions
comprise a herbicidally active amount of at least one selected
compound and auxiliaries conventionally used in the formulation of
herbicidal compositions.
[0186] For the preparation of emulsions, pastes or aqueous or oily
formulations and dispersible concentrates (DC), the selected
compounds can be dissolved or dispersed in an oil or solvent, it
being possible to add further formulation auxiliaries for
homogenization purposes. However, it is also possible to prepare
liquid or solid concentrates from selected compound, if appropriate
solvents or oil and, optionally, further auxiliaries comprising
liquid or solid concentrates, and these concentrates are suitable
for dilution with water. The following can be mentioned:
emulsifiable concentrates (EC, EW), suspensions (SC), soluble
concentrates (SL), dispersible concentrates (DC), pastes, pills,
wettable powders or granules, it being possible for the solid
formulations either to be soluble or dispersible (wettable) in
water. In addition, suitable powders or granules or tablets can
additionally be provided with a solid coating which prevents
abrasion or premature release of the active ingredient.
[0187] In principle, the term "auxiliaries" is understood as
meaning the following classes of compounds: antifoam agents,
thickeners, wetters, stickers, dispersants, emulsifiers,
bactericides and/or thixotropic agents. The skilled worker is
familiar with the meaning of the abovementioned agents.
[0188] SLs, EWs and ECs can be prepared by simply mixing the
constituents in question; powders can be prepared by mixing or
grinding in specific types of mills (for example hammer mills).
DCs, SCs and SEs are usually prepared by wet milling, it being
possible to prepare an SE from an SC by addition of an organic
phase which may comprise further auxiliaries or selected compounds.
The preparation is known. Powders, materials for spreading and
dusts can advantageously be prepared by mixing or concomitantly
grinding the active substances together with a solid carrier.
Granules, for example coated granules, impregnated granules and
homogeneous granules, can be prepared by binding the selected
compounds to solid carriers. The skilled worker is familiar with
further details regarding their preparation, which are mentioned
for example in the following publications: U.S. Pat. No. 3,060,084,
EP-A 707445 (for liquid concentrates), Browning, "Agglomeration",
Chemical Engineering, Dec. 4, 1967, 147-48, Perry's Chemical
Engineer's Handbook, 4th Ed., McGraw-Hill, New York, 1963, pages
8-57 and et seq. WO 91/13546, U.S. Pat. No. 4,172,714, U.S. Pat.
No. 4,144,050, U.S. Pat. No. 3,920,442, U.S. Pat. No. 5,180,587,
U.S. Pat. No. 5,232,701, U.S. Pat. No. 5,208,030, GB 2,095,558,
U.S. Pat. No. 3,299,566, Klingman, Weed Control as a Science, John
Wiley and Sons, Inc., New York, 1961, Hance et al., Weed Control
Handbook, 8th Ed., Blackwell Scientific Publications, Oxford, 1989
and Mollet, H., Grubemann, A., Formulation technology, Wiley VCH
Verlag GmbH, Weinheim (Federal Republic of Germany), 2001.
[0189] The skilled worker is familiar with a multiplicity of inert
liquid and/or solid carriers which are suitable for the
formulations according to the invention, such as, for example,
liquid additives such as mineral oil fractions of medium to high
boiling point such as kerosene or diesel oil, furthermore coal tar
oils and oils of vegetable or animal origin, aliphatic, cyclic and
aromatic hydrocarbons, for example paraffin, tetrahydrophthalene,
alkylated naphthalenes or their derivatives, alkylated benzenes or
their derivatives, alcohols such as methanol, ethanol, propanol,
butanol and cyclohexanol, ketones such as cyclohexanone, or
strongly polar solvents, for example amines such as
N-methylpyrrolidone or water.
[0190] Examples of solid carriers are mineral earths such as
silicas, silica gels, silicates, talc, kaolin, limestone, lime,
chalk, bole, loess, clay, dolomite, diatomaceous earth, calcium
sulfate, magnesium sulfate, magnesium oxide, ground synthetic
materials, fertilizers such as ammonium sulfate, ammonium
phosphate, ammonium nitrate, ureas and products of vegetable origin
such as cereal meal, tree bark meal, wood meal and nutshell meal,
cellulose powders or other solid carriers.
[0191] The skilled worker is familiar with the multiplicity of
surface-active substances (surfactants) which are suitable for the
formulations according to the invention such as, for example,
alkali metal salts, alkaline earth metal salts or ammonium salts of
aromatic sulfonic acids for example lignosulfonic acid, phenol
sulfonic acid, naphthalenesulfonic acid, and
dibutylnaphthalenesulfonic acid, and of fatty acids, of alkyl- and
alkylarylsulfonates, of alkyl sulfates, lauryl ether sulfates and
fatty alcohol sulfates, and salts of sulfated hexa-, hepta- and
octadecanols and of fatty alcohol glycol ethers, condensates of
sulfonated naphthalene and its derivatives with formaldehyde,
condensates of naphthalene or of the naphthalenesulfonic acids with
phenol and formaldehyde, polyoxyethylene octylphenol ether,
ethoxylated isooctyl-, octyl- or nonylphenol, alkylphenyl
polyglycol ethers, tributylphenyl polyglycol ether, alkylaryl
polyether alcohols, isotridecyl alcohol, fatty alcohol/ethylene
oxide condensates, ethoxylated caster oil, polyoxyethylene alkyl
ethers or polyoxypropylene alkyl ethers, lauryl alcohol polyglycol
ether acetate, sorbitol esters, lignin-sulfite waste liquors or
methylcellulose.
[0192] The herbicidal compositions, or the selected compounds, can
be applied pre- or post-emergence. If the selected compounds are
less well tolerated by certain crop plants, application techniques
may be used in which the selected compounds are spread, with the
aid of the spraying apparatus, in such a way that they come into as
little contact, if any, with the leaves of the sensitive crop
plants while the selected compounds reach the leaves of undesired
plants which grow underneath, or the bare soil surface
(post-directed, lay-by).
[0193] Depending on the intended aim, the season, the target plants
and the growth stage, the application rates of selected compounds
amount to 0.001 to 3.0, preferably 0.01 to 1.0 kg/ha.
[0194] The invention is illustrated in greater detail by the
examples which follow, which are not to be considered as
limiting.
[0195] Providing the herbicidal target furthermore enables a method
for identifying a protein with the biological activity of an SHMT
which is not inhibited, or inhibited to a limited extent only, by a
herbicide which has SHMT as its site of action, for example the
herbicidally active selected compounds. In the following text, such
a protein which differs in this way from SHMT is referred to as
SHMT variant. Analogously to what has been said above, the term
SHMT again preferably refers to mitochondrial SHMT.
[0196] In a preferred embodiment, the abovementioned method for
generating variants of nucleic acid sequences comprising [0197] i.
a nucleic acid sequence with the nucleic acid sequence shown in SEQ
ID NO:7; or [0198] ii. a nucleic acid sequence which, on the basis
of the degeneracy of the genetic code, can be derived from the
amino acid sequence shown in SEQ ID NO:8 by back translation; or
[0199] iii. functional equivalents of the nucleic acid sequence SEQ
ID NO:7 with at least 460, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%,
55%, 56%, 57%, 58%, 59%, with preference at least 60%, 61%, 62%,
63%, 64%, 65%, 66%, 67%, 68%, 69% and 70%, preferably at least 71%,
72%, 73%, 74%, 75%, especially preferably at least 76%, 77%, 78%,
79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, very
especially preferably at least 90%, 91%, 92%, 93%, 94%, 95%, 96%,
97%, 98%, 99% identity to the SEQ ID NO:7 comprises the following
steps: [0200] a) expressing the proteins encoded by the
abovementioned nucleic acids in a heterologous system or in a
cell-free system; [0201] b) randomized or directed mutagenesis of
the protein by modification of the nucleic acid; [0202] c)
measuring the interaction of the modified gene product with the
herbicide; [0203] d) identifying derivatives of the protein which
show less interaction; [0204] e) assaying the biological activity
of the protein after application of the herbicide; and [0205] f)
selecting the nucleic acid sequences which have a modified
biological activity against the herbicide.
[0206] The sequences selected by the above-described methods are
advantageously introduced into an organism. The invention therefore
furthermore relates to an organism prepared by this method. The
organism is preferably a plant, especially preferably one of the
above-defined crop plants, very especially preferably potato,
tobacco, linseed, oilseed rape, soya, barley, maize, cotton, wheat,
pineapple, pawpaw or pea.
[0207] Thereafter, intact plants are regenerated and the resistance
to the selected compound is checked in intact plants.
[0208] Modified proteins and/or nucleic acids which are capable of
conferring, in plants, resistance to the selected compounds can
also be prepared from the abovementioned nucleic acid sequences via
what is known as site-directed mutagenesis; by means of this
mutagenesis, for example the stability and/or activity of the
target protein or the characteristics such as binding of the
abovementioned inhibitors according to the invention can be
improved or modified in a highly specific manner.
[0209] For example, Zhu et al. (Nature Biotech., Vol. 18, May 2000:
555-558) have described a site-directed mutagenesis method in
plants which can be used advantageously.
[0210] Moreover, modifications can be achieved via the PCR method
described by Spee et al. (Nucleic Acids Research, Vol. 21, No. 3,
1993: 777-78) using dITP for the random mutagenesis, or by the
further-improved method of Rellos et al. (Protein Expr. Purif., 5,
1994: 270-277).
[0211] A further possibility of producing these modified proteins
and/or nucleic acids is an in-vitro recombination technique for
molecular evolution which has been described by Stemmer et al.
(Proc. Natl. Acad. Sci. USA, Vol. 91, 1994: 10747-10751), or the
combination of the PCR and recombination method described by Moore
et al. (Nature Biotechnology Vol. 14, 1996: 458-467).
[0212] A further way for the mutagenesis of proteins is described
by Greener et al. in Methods in Molecular Biology (Vol. 57, 1996:
375-385). A method for modifying proteins using the microorganism
E. coli XL-1 Red is described in EP-A-0 909 821. During its
replication, this microorganism generates mutations in the nucleic
acids which have been introduced and thus leads to a modification
of the genetic information. Advantageous nucleic acids and the
proteins encoded by them can be identified readily by isolating the
modified nucleic acids or the modified proteins and carrying out
resistance tests. The former can then be introduced into plants,
where they are capable of manifesting the resistance and thus lead
to resistance to the herbicides.
[0213] Further methods of mutagenesis and selection are, for
example, methods such as the in-vivo mutagenesis of seeds or pollen
and the selection of resistant alleles in the presence of the
inhibitors according to the invention, followed by genetic and
molecular identification of the modified, resistant allele; so are
the mutagenesis and selection of resistances in cell culture by
propagating the culture in the presence of successively increasing
concentrations of the inhibitors according to the invention. In
this context, the increase of the spontaneous mutation rate by
chemical/physical mutagenic treatment may be exploited. As
described above, modified genes can also be isolated using
microorganisms which have an endogenous or recombinant activity of
the proteins encoded by the nucleic acids used in the method
according to the invention, and which are sensitive to the
inhibitors identified in accordance with the invention. Growing the
microorganisms on media with increasing concentrations of
inhibitors according to the invention permits the selection and
evolution of resistant variants of the targets according to the
invention. The mutation frequency, in turn, can be increased by
mutagenic treatments.
[0214] Methods for the specific modification of nucleic acids are
furthermore available (Zhu et al. Proc. Natl. Acad. Sci. USA, Vol.
96, 8768-8773 and Beethem et al., Proc. Natl. Acad. Sci. USA, Vol.
96, 8774-8778). These methods make possible the replacement, in the
proteins, of those amino acids which are important for the binding
of inhibitors by functionally analogous amino acids which, however,
prevent the inhibitor from binding.
[0215] The invention furthermore therefore relates to a method for
establishing nucleotide sequences which encode gene products which
have a modified biological activity, the biological activity having
been modified in such a way that an increased activity is present.
An increased activity is understood as meaning an activity which is
increased by at least 100, preferably by at least 30%, especially
preferably by at least 50%, very especially preferably by at least
100% in comparison with the starting organism, or the starting gene
product. Moreover, the biological activity can have been modified
in such a way that the substances and/or compositions according to
the invention no longer bind, or no longer properly bind, to the
nucleic acid sequences and/or the gene products encoded by them.
For the purposes of the invention, no longer, or no longer
properly, is to be understood as meaning that the substances bind
by at least 300 less, preferably at least 50% less, especially
preferably by at least 70%, very especially preferably by at least
800, or indeed no longer, to the modified nucleic acids and/or gene
products in comparison with the starting gene product or the
starting nucleic acids.
[0216] Yet a further aspect of the invention therefore relates to a
transgenic plant which has been modified by the above-described
method according to the invention.
[0217] Genetically modified transgenic plants which are resistant
to substances found in accordance with the methods according to the
invention and/or to compositions comprising these substances can
also be generated by overexpressing the nucleic acid sequences used
in the abovementioned methods according to the invention for
identifying herbicides. The invention therefore furthermore relates
to a method for the generation of transgenic plants which are
resistant to substances found by a method according to the
invention, which comprises overexpressing, in these plants, nucleic
acids comprising [0218] a) a nucleic acid sequence with the nucleic
acid sequence shown in SEQ ID NO:7; or [0219] b) a nucleic acid
sequence which, on the basis of the degeneracy of the genetic code,
can be derived from the amino acid sequence shown in SEQ ID NO:8 by
back translation; or [0220] c) functional equivalents of the
nucleic acid sequence SEQ ID NO:7 with at least 46%, 47%, 48%, 49%,
50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, with preference
at least 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69% and 70%,
preferably at least 71%, 72%, 73%, 74%, 75%, especially preferably
at least 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%,
87%, 88%, 89%, very especially preferably at least 90%, 91%, 92%,
93%, 94%, 95%, 96%, 97%, 98%, 99% identity to the SEQ ID NO:7.
[0221] A similar method is described by way of example in
Lermantova et al., Plant Physiol., 122, 2000: 75-83.
[0222] The above-described methods according to the invention for
generating resistant plants make possible the development of novel
herbicides which have as complete as possible an action which is
independent of the plant species (what are known as nonselective
herbicides), in combination with the development of useful plants
which are resistant to the nonselective herbicide. Useful plants
which are resistant to nonselective herbicides have already been
described on several occasions. In this context, one can
distinguish between several principles for achieving a resistance:
[0223] a) Generation of resistance in a plant via mutation methods
or recombinant methods by markedly overproducing the protein which
acts as target for the herbicide and by the fact that, owing to the
large excess of the protein which acts as target for the herbicide,
the function exerted by this protein in the cell is even retained
after application of the herbicide. [0224] b) Modification of the
plant such that a modified version of the protein which acts as
target of the herbicide is introduced and that the function of the
newly introduced modified protein is not adversely affected by the
herbicide. [0225] c) Modification of the plant such that a novel
protein/a novel RNA is introduced wherein the chemical structure of
the protein or of the nucleic acid, such as of the RNA or the DNA,
which structure is responsible for the herbicidal action of the
low-molecular-weight substance, is modified so that, owing to the
modified structure, a herbicidal action can no longer be developed,
that is to say that the interaction of the herbicide with the
target can no longer take place. [0226] d) The function of the
target is replaced by a novel gene introduced into the plant,
creating what is known as an alternative pathway. [0227] e) The
function of the target is taken over by another gene which is
present in the plant, or by its gene product.
[0228] The present invention therefore furthermore comprises the
use of plants, genes affected by T-DNA insertion which have the
abovementioned nucleic acid sequences SEQ ID NO:7 and their
functional equivalents for the development of novel herbicides. The
skilled worker is familiar with alternative methods of identifying
homologous nucleic acids, for example in other plants with similar
sequences, such as, for example, using transposons. The present
invention therefore also relates to the use of alternative
insertion mutagenesis methods for inserting foreign nucleic acid
into the nucleic acid sequences SEQ ID NO:7, into sequences derived
from these sequences on the basis of the genetic code and/or their
derivatives in other plants.
[0229] The transgenic plants are generated using one of the
above-described use forms of the expression cassettes according to
the invention by customary transformation methods which are
likewise described above.
[0230] The expression efficacy of the recombinantly expressed SHMT
can be determined for example in vitro by shoot-meristem
propagation or by a germination test. Moreover, an expression of
the SHMT gene, which has been modified in terms of nature and
level, and its effect on the resistance to SHMT inhibitors in test
plants can be tested in greenhouse experiments.
General DNA Manipulation and Cloning Methods
[0231] Cloning methods such as, for example, restriction cleavages,
agarose gel electrophoreses, purification of DNA fragments,
transfer of nucleic acids to nitrocellulose and nylon membranes,
linking DNA fragments, transformation of Escherichia coli cells,
growing bacterium and sequence analyses of recombinant DNA were
carried out as described by Sambrook et al. (1989) (Cold Spring
Harbor Laboratory Press: ISBN 0-87969-309-6) and Ausubel, F. M. et
al., Current Protocols in Molecular Biology, Greene Publishing
Assoc. and Wiley-Interscience (1994); ISBN 0-87969-309-6.
[0232] Molecular-biological standard methods for plants and plant
transformation methods are described in Schultz et al., Plant
Molecular Biology Manual, Kluwer Academic Publishers (1998),
Reither et al., Methods in Arabidopsis Research, World scientific
press (1992) and Arabidopsis: A Laboratory Manual (2001), ISBN
0-87969-573-0.
[0233] The bacterial strains used hereinbelow (E. coli DH5.alpha.,
XL-1 blue, BL21DE(3)) were obtained from Stratagene, BRL Gibco or
Invitrogen, Carlsberg, Calif. The vectors used for cloning were pCR
T7CT TOPO, pCR T7/NT TOPO and pCR 2.1 TOPO from Invitrogen and
pUC19 from Amersham Pharmacia (Freiburg) and the vector pBinAR
(Hofgen and Willmitzer, Plant Science 66, 1990, 221-230).
EXAMPLE 1
Generation of a cDNA Library in the Plant Transformation Vector
[0234] To generate a cDNA library (hereinbelow termed "binary cDNA
library") in a vector which can be used directly for transforming
plants, mRNA was isolated from a variety of plant tissues and
transcribed into double-stranded cDNA using the cDNA Synthese Kit
(Amersham Pharmacia Biotech, Freiburg). The cDNA first-strand
synthesis was carried out using T.sub.12-18 oligonucleotides
following the manufacturer's instructions. After size fractionation
and the ligation of EcoRI-NotI adapters following the
manufacturer's instructions and filling up the overhangs with Pfu
DNA polymerase (Stratagene), the cDNA population was normalized.
The method of Kohci et al, 1995, Plant Journal 8, 771-776 was
followed, the cDNA being amplified by PCR with the oligonucleotide
N1 under the conditions given in Table 1.
TABLE-US-00003 TABLE 1 Temperature [.degree. C.] Time [sec] Number
of cycles 94 300 1 94 8 10 52 60 72 180 94 8 10 50 60 72 180 94 8
10 48 60 72 180 72 420 1
[0235] The resulting PCR product was bound to the column matrix of
the PCR purification kit (Qiagen, Hilden) and eluted with 300 mM
NaP buffer, pH 7.0, 0.5 mM EDTA, 0.046 SDS. The DNA was denatured
for 5 minutes in a boiling water bath and subsequently renatured
for 24 hours at 60.degree. C. 50 .varies.l of the DNA were applied
to a hydroxylapatite column and the column was washed 3 times with
1 ml of 10 mM NaP buffer, pH 6.8. The bound single-stranded DNA was
eluted with 130 mM NaP buffer, pH 6.8, precipitated with ethanol
and dissolved in 40 .varies.l of water. 20 .varies.l of growth were
used for a further PCR amplification as described above. After
further ssDNA concentration, a third PCR amplification was carried
out as described above.
[0236] The plant transformation vector for taking up the cDNA
population which had been generated as described above was
generated via restriction enzyme cleavage of the vector pUC18 with
SbfI and BamHI, purification of the vector fragment followed by
filling up the overhangs with Pfu DNA polymerase and relegation
with T4 DNA ligase (Stratagene). The resulting construct is
hereinbelow termed pUC18SbfI-.
[0237] The vector pBinAR was first cleaved with NotI, the ends were
filled up and the vector was relegated, cleaved with SbfI, the ends
were filled up and the vector was relegated and subsequently
cleaved with EcoRI and HindIII. The resulting fragment was ligated
into a derivative of the binary plant transformation vector pPZP
(Hajdukiewicz, P, Svab, Z, Maliga, P., (1994) Plant Mol Biol
25:989-994) which makes possible the transformation of plants by
means of agrobacterium and mediates kanamycin resistance in
transgenic plants. The construct generated thus is hereinbelow
termed pSun12/35S.
[0238] pUC18SbfI- was used as template in a polymerase chain
reaction (PCR) with the oligonucleotides V1 and V2 (see Table 2)
and Pfu DNA polymerase. The resulting fragment was ligated into the
SmaI-cut Sun12/35S, giving rise to pSunblues2. Following cleavage
with NotI, dephosphorylation with shrimp alkaline phosphatase
(Roche Diagnostics, Mannheim) and purification of the vector
fragment, pSunblues2 was ligated with the normalized, likewise
NotI-cut cDNA population. Following transformation into E. coli
Xl-lblue (Stratagene), the resulting clones were deposited into
microtiter plates. The binary cDNA library comprises cDNAs in
"sense"--and in "antisense" orientation under the control of the
cauliflower mosaic virus 35S promoter, and, after transformation
into tobacco plants, these cDNAs can, accordingly, lead to
"cosuppression" and "antisense" effects.
TABLE-US-00004 TABLE 2 Oligonucleotides used Oligonucleotide
Nucleic acid sequence N1 5'-AGAATTCGCGGCCGCT-3' V1(PWL93not)
5'-CTCATGCGGCCGCGCGCA ACGCAATTAATGTG-3' V2(pWL92)
5'-TCATGCGGCCGCGAGATCC AGTTCGATGTAAC-3' G1(35S)
5'-GTGGATTGATGTGATATCTCC-3' G2(OCS) 5'-GTAAGGATCTGAGCTACACAT-3'
EXAMPLE 2
Transformation and Analysis of Tobacco Plants
[0239] Selected clones of the binary cDNA library were transformed
into Agrobacterium tumefaciens C58Cl:pGV2260 and (Deblaere et al.,
Nucl. Acids. Res. 13 (1984), 4777-4788) and incubated with
Streptomycin/Spectinomycin selection. The material used for the
transformation of tobacco plants (Nicotiana tabacum cv. Samsun NN)
with the binary clones nt002001035r and nt002001036r was an
overnight culture of a positively transformed agrobacterial colony
diluted with YEB medium to OD600=0.8-1.6. Leaf discs of sterile
plants (approx. 1 cm.sup.2 each) were incubated for 5-10 minutes
with a 1:50 agrobacterial dilution in a Petri dish. This was
followed by incubation in the dark for 2 days at 25.degree. C. on
Murashige-Skoog medium (Physiol. Plant. 15 (1962), 473)
supplemented with 2% sucrose (2MS medium) and 0.8% Bacto agar. The
cultivation was continued after 2 days at a
16-hour-light/8-hour-darkness photoperiod and continued in a weekly
rhythm on MS medium supplemented with 500 mg/l Claforan (cefotaxime
sodium), 50 mg/l kanamycin, 1 mg/l benzylaminopurin (BAP), 0.2 mg/l
naphthylacetic acid and 1.6 g/l glucose. Regenerated shoots were
transferred onto an MS medium supplemented with kanamycin and
Claforan. Transgenic plants of line P.sub.--0000000315 were
generated in this manner.
[0240] The integration of the clone cDNA into the genome of the
transgenic lines was detected via PCR with the oligonucleotides G1
and G2 (see Table 2) and genomic DNA prepared from the transgenic
lines in question. To this end, TAKARA Taq DNA polymerase was
preferably employed for this purpose, following the manufacturer's
instructions (MoBiTec, Gottingen). The cDNA clone of the binary
cDNA library, which clone had been used for the transformation,
acted as template for a PCR reaction as the positive control. PCR
products with an identical size or, if appropriate, identical
cleavage patterns which were obtained after cleavage with a variety
of restriction enzymes acted as proof that the corresponding cDNA
had been integrated. In this manner, the insert of clone
nt002001035r was detected in the transgenic plants with the
abovementioned phenotypes. Furthermore, the repression of an
approx. 1.7 kb mRNA hybridized under stringent conditions with the
cDNA of clone nt002001035r was detected in leaf tissues of the
transgenic plants in comparison with control plants (Nicotiana
tabaccum, Varietat Samsun NN). To this end, a probe of the
nt002001035r insert was labeled with the aid of the High-prime DNA
labeling kit (Roche, Mannheim). The probe was used for the
hybridization of total RNA or mRNA from tissues of the relevant
transgenic plant and control plants, which RNA had been separated
by standard methods and transferred to nitrocellulose membranes
(Schleicher and Schull, Dassel, Germany).
[0241] After the shoots had been transferred into soil, the plants
were observed for 2-20 weeks in the greenhouse for the
manifestation of phenotypes. It emerged that transgenic plants of
line P.sub.--0000000315 were similar in phenotype. Four plants of
line P.sub.--0000000315 (18/8, 18/32, 18/75 and 18/77), which had
the nt002001035r insert, showed pronounced growth retardation after
2 weeks and also chlorotic leaves and, in some cases, necroses.
Moreover, line 18/75 produced virtually no roots and was eventually
damaged to such a degree that it died after approximately 6
weeks.
EXAMPLE 3
Sequence Analysis of the Clones
[0242] Part of the chimeric cDNA of clone nt002001035r (SEQ ID
NO:1) of cDNA (Nucleotide 506-652) encodes a peptide fragment (SEQ
ID NO:2) with a high degree of identity to plant SHMTs. Sequence
alignments with the aid of the BLAST algorithm (Altschul et al.
1990, J. Mol. Biol. 215, pp. 403-410) with a tobacco EST database
revealed further clones with >99% identity to the part-region of
the SEQ ID NO:1 and with a high degree of identity to mitochondrial
SHMTs. One of these clones (clone nt006100023, SEQ ID NO:3) was
sequenced and is chimeric. The part-region of SEQ ID NO:3 which
encodes a mitochondrial SHMT peptide of 180 amino acids (SEQ ID
NO:2) comprises the 378 by region of SEQ ID NO:1 which encodes a
mitochondrial SHMT peptide fragment. A further nonchimeric clone
(clone nt 006043063, SEQ ID NO:5), which is identical with the
SHMT-encoding part-region of SEQ ID:01 with the exception of
nucleotide positions 11, 262 and 333 was also transformed in
tobacco plants. The phenotypes of the resulting transgenic plants
were identical to those of the plants of line
P.sub.--0000000315.
[0243] Thus, it was shown for the first time and in a surprising
manner that the natural expression of SHMT-encoding sequences is
essential for plants and that reduced expression leads to damage as
can be seen on the phenotypes mentioned in Example 2. The
suitability of SHMT as target for herbicides was thus
demonstrated.
[0244] Based on the sequence of nt006043063r, a 5'-RACE was carried
out with tobacco cDNA, following the manufacturer's instructions
(SMART-Kit, Clontech). The sequence of the full-length SHMT cDNA
obtained in this manner was determined (SEQ ID NO: 7). With the
exception of one nucleotide (position 81), the sequence is
identical to SEQ ID NO:5 in the overlap region (from nucleotide
1288 to 1760). SEQ ID NO: 7 is 1835 nt in length and comprises an
open reading frame of 1554 by which encodes a polypeptide 518 amino
acids in length (from nucleotide 56 to 1609, SEQ ID NO: 8). The
highest degree of identity is found between SEQ ID NO: 7 and a
potato mitochondrial SHMT (86.8% identity with Genbank No.
Z25863).
EXAMPLE 4
Expression in E. coli
[0245] An Arabidopsis cDNA encoding a mitochondrial SHMT (SHM1,
Genbank Accession Number: AJ271726) was overexpressed in E. coli
bacteria in order to generate active protein with a plant SHMT
activity.
[0246] To this end, the coding region of AJ271726 was amplified
from cDNA libraries by PCR and ligated into the vector pCR 2.1 TOPO
by standard techniques (constructs SHMT1 and SHMT2, Table 8). The
resulting constructs were subsequently amplified by PCR by means of
specific oligonucleotides, and resulting fragments were ligated
into the expression vectors pCR T7/CT TOPO and pCR T7/NT-TOPO
(Invitrogen) (constructs SHMT 3-6, Table 7). In this manner, fusion
proteins with C-terminal or N-terminal hexahistidine tags were
generated. The use of the oligonucleotides shown in Table 8 in the
cloning step gave N-terminally truncated versions of SHMT in order
to exclude the mitochondrial transit sequence which might
counteract functional expression. Since the mitochondrial transit
sequence of SHMT is not definitely known, a variety of N-terminally
truncated versions were generated. In order to delimit the region
to be deleted, it was possible to refer to the literature (Turner
et al. JBC 19, pp. 13528-13534, 1992).
[0247] The PCR was carried out in 36 cycles following standard
conditions (for example as described by Sambrook, J. et al. (1989)
"Molecular cloning: A laboratory manual", Cold Spring Harbor
Laboratory Press), the annealing temperatures being between 45 and
55_C and the polymerization time being in each case 60 seconds per
1000 bp. The templates and the primers used for the template in
question are shown in Table 7 together with the annealing
temperatures.
TABLE-US-00005 TABLE 7 Annealing Primer temperature (Nucleic acid
Construct [.degree. C.] sequence) SHMT1 * 1 60 5'-AAATGGCGATGGCC
ATGGC-3' 5'-TGGGGTGAAACAGT TTAGTTC-3' SHMT2 * 1 58
5'-AAACCAGAGATAGA GAGAGG-3' 5'-ACATGTATCATCTA TACATTCC-3' SHMT3 **
2 60 5'-ATGGCGATGGCCAT GGCT-3' 5'-TGGGGTGAAACAGT TTAGTTC-3' SHMT4
** 2 60 5'-ATGAAGGAAAGATC TCGTGTC-3' 5'-TGGGGTGAAACAGT TTAGTTC-3'
SHMT5 ** 2 55 5'-ATGTCTTTGCCCAG TGAAG-3' 5'-TGGGGTGAAACAGT
TTAGTTC-3' SHMT6 *** 2 60 5'-ATGAAGGAAAGATC TCGTGTC-3'
5'-TGGGGTGAAACAGT TTAGTTC-3' SHMT7 *** 2 55 5'-ATGGCGATGGCCAT
GGCT-3' 5'-TGGGGTGAAACAGT TTAGTTC-3' *) Vector used: pCR 2.1 TOPO
**) Vector used: pCR T7/CT-TOPO ***) Vector used: pCR T7/NT-TOPO 1)
Template: Arabidopsis thaliana cDNA library 2) Template: SHMT1
[0248] The PCR products were ligated into the vectors shown in
Table 7 and transformed into E. coli. Expression was performed in
E. coli BL21(DE3) strains such as BL21(DE3)pLysS or BL21(DE3)pLysE
(Invitrogen), BL21-CodonPlus(DE3) or BL21-CodonPlus(DE3)RIL
(Stratagene) following induction with IPTG. Standard protocols
(Invitrogen) were followed.
[0249] The expression products of SHMT6 and SHMT7 were purified by
affinity chromatography on Ni-agarose. The manufacturer's
instructions were followed (Qiagen).
EXAMPLE 5
In Vitro Assay Systems
[0250] SHMT can be isolated from plant mitochondria as described
and determined by means of a radioactive method according to the
invention (Bourguignon et al. Biochem. J. 255, pp. 169-178, 1988).
The activity of the SHMT protein which had been expressed
recombinantly in Example 4 and, if appropriate, purified was also
determined using this method according to the invention.
[0251] As an alternative, the SHMT reaction was assayed by means of
an HPLC-aided separation method which is based on the separation of
tetrahydrofolate and Cl-tetrahydrofolate. In this method, the
enzyme-comprising aqueous assay solution (0.4 5 mM
2-mercaptoethanol, 2 mM tetrahydrofolate, 20 mM serine, 56 mM
KH.sub.2PO.sub.4 pH 7.4), which comprised 1-100 .varies.g of
mitochondrial SHMT, was incubated for 30 minutes with shaking,
denatured with 0.1 ml of 0.36M HCl per 100 ml or assay solution and
freed from precipitates by spinning for 5 minutes at a high g
number (10000 g).
[0252] The HPLC runs were carried out with a Symmetry C18 column
(3.5 am 4.6.times.10 mm; sample temperature 10.degree. C., column
temperature 25.degree. C.; flow rate: 1 ml/min; .lamda.=288 nm),
the column being washed for 0.5 minute with 95% buffer A (5% by
volume acetonitrile in water) after application of the sample. The
analytical separation was carried out by applying a gradient of
0-100% buffer B (water) over a period of 6 minutes.
[0253] Moreover, the enzymatic activity was determined analogously
to the method described by Stover and Schirch (Anal. Biochem. 202,
pp. 82-88). This method according to the invention is based on
coupling the SHMT reaction with the reaction catalyzed by
NAD-dependent methylenetetrahydrofolate dehydrogenase (MTD) and
photometric measurement at 340 nm. The amounts of the auxiliary
enzyme MTD which are required for this purpose were obtained by a
recombinant expression of Saccharomyces cerevisiae MTD in E. coli
as follows: following isolation of the MTD-encoding nucleic acid
frayment from genomic DNA as described by Appling and West (Methods
in Enzymology 281, pp. 178-188), it was cloned into the vector pCR
2.1 TOPO. The resulting construct was amplified via PCR using the
oligonucleotides 5'-TTTTTCTTTAGACAGTTCTACGTTC-3' and
5'-ATGTCGAAGCCTGGTCGTA-3'. The PCR was carried out in 36 cycles
under standard conditions (for example those described by Sambrook,
J. et al. (1989) "Molecular cloning: A laboratory manual", Cold
Spring Harbor Laboratory Press), the annealing temperature being
55.degree. C. and the polymerization time being in each case 60
seconds per 1000 bp. The PCR products were ligated into the
expression vector pCR T7/CT-TOPO (construct MTD) and expressed in
E. coli BL21(DE3) strains such as BL21(DE3)pLysS or BL21(DE3)pLysE
(Invitrogen), BL21-CodonPlus(DE3) or BL21-CodonPlus(DE3)RIL
(Stratagene). Standard protocols (Invitrogen) were followed. The
expression product of the construct MTD was purified by affinity
chromatography on Ni-agarose as specified by the manufacturer
(Qiagen).
Sequence CWU 1
1
291884DNANicotiana tabacumCDS(506)..(652) 1gcggccgctc tcaagcgttg
catgactgta catgtacaca ggtggcattg ctctcaggca 60aatgccaaga agttggagtc
gaagatactg catgaccttg caattagaac agttccaaac 120ccaaattggt
cagcctgcag catctggcat gtctatcttg ggtcaacgag ccaaactcaa
180gaataaaatt ggctgggaaa accttctgat ggtttactgt agatatattc
acttcctatg 240caaacattgc cctaggcctg agaagtgaca gacagactag
caggaccgct tgtcagggcc 300tttcagactt ggagctgcgc gcttgttcat
ggtagatata catggacatt tgtcaaacac 360agcatgacat cactttactt
gctagcattt ccatcttctc tagcaaagca cagaagtcgg 420atggagccat
ctgacacccc ctgcagacag ccaccttttg gcaggctgca ctggcgcatg
480ccagcagaaa ctgctagcgg ccgct gga aca aag ttg aaa gac ttt gtg aca
532 Gly Thr Lys Leu Lys Asp Phe Val Thr 1 5aca cta cag tct agc gct
tca atc cag tcg gag att gca aaa ctc cgc 580Thr Leu Gln Ser Ser Ala
Ser Ile Gln Ser Glu Ile Ala Lys Leu Arg10 15 20 25cat ggt gtg gag
gag tat gca aag cag ttc cct aca att gga ttt gag 628His Gly Val Glu
Glu Tyr Ala Lys Gln Phe Pro Thr Ile Gly Phe Glu 30 35 40aag gaa acc
atg aag tac aaa aac tgagagctcg actgagtata tacacaaggg 682Lys Glu Thr
Met Lys Tyr Lys Asn 45accaatatcc aacatcctca aggtgaatgg gatagacatc
caaactgcag ttcgctccca 742aggattggat tgtcatcttt tactaatact
atgtaaaatc cagcagtgtt tggttcctaa 802gtttgccact ttgtatatta
acgattgtaa ttctactgag gtccttgaaa gcaataaact 862cctgttgtct
cggagcggcc gc 884249PRTNicotiana tabacum 2Gly Thr Lys Leu Lys Asp
Phe Val Thr Thr Leu Gln Ser Ser Ala Ser1 5 10 15Ile Gln Ser Glu Ile
Ala Lys Leu Arg His Gly Val Glu Glu Tyr Ala 20 25 30Lys Gln Phe Pro
Thr Ile Gly Phe Glu Lys Glu Thr Met Lys Tyr Lys 35 40
45Asn3772DNANicotiana tabacumCDS(2)..(541) 3g cgg ccg ctg gca gtt
gct ttg aaa cag gca atg act cca gaa tac aga 49 Arg Pro Leu Ala Val
Ala Leu Lys Gln Ala Met Thr Pro Glu Tyr Arg 1 5 10 15gct tac caa
gag caa tgc ctt agc aac tgc tca aaa ttt gcc cag gct 97Ala Tyr Gln
Glu Gln Cys Leu Ser Asn Cys Ser Lys Phe Ala Gln Ala 20 25 30tta gcg
gga atg ggt tat gaa ctt gtt tct ggt gga aca gag aat cac 145Leu Ala
Gly Met Gly Tyr Glu Leu Val Ser Gly Gly Thr Glu Asn His 35 40 45ttg
gtt ttg gtg aac ttg aaa aac aag ggt att gat ggt tct agg gtt 193Leu
Val Leu Val Asn Leu Lys Asn Lys Gly Ile Asp Gly Ser Arg Val 50 55
60gaa aaa gtt ttg gaa gcg gta cat att gca gcg aat aag aac act gtt
241Glu Lys Val Leu Glu Ala Val His Ile Ala Ala Asn Lys Asn Thr
Val65 70 75 80cct gga gat gta tcc gcc atg gtc cct ggt ggc atc aga
atg ggg act 289Pro Gly Asp Val Ser Ala Met Val Pro Gly Gly Ile Arg
Met Gly Thr 85 90 95cct gca ctc aca tca agg gga ttt att gag gaa gat
ttt gtg aaa gtt 337Pro Ala Leu Thr Ser Arg Gly Phe Ile Glu Glu Asp
Phe Val Lys Val 100 105 110gct gaa ttc ttt gat gct gct gtg aag ata
gca gtg aaa ata aag act 385Ala Glu Phe Phe Asp Ala Ala Val Lys Ile
Ala Val Lys Ile Lys Thr 115 120 125gaa gct caa gga aca aag ttg aaa
gac ttt gtg aca aca cta cag tct 433Glu Ala Gln Gly Thr Lys Leu Lys
Asp Phe Val Thr Thr Leu Gln Ser 130 135 140agc gct cca atc cag tcg
gag att gca aaa ctc cgc cat ggt gtg gag 481Ser Ala Pro Ile Gln Ser
Glu Ile Ala Lys Leu Arg His Gly Val Glu145 150 155 160gag tat gca
aag cag ttc cct aca att ggg ttt gag aag gaa acc atg 529Glu Tyr Ala
Lys Gln Phe Pro Thr Ile Gly Phe Glu Lys Glu Thr Met 165 170 175aag
tac aaa aac tgagagctcg actgagtata tacacaaggg accaatatcc 581Lys Tyr
Lys Asn 180aacatcctca aggtgaatgg gatagacatc caaactgcag ttcgctccca
aggattggat 641tgtcatcttt tactaatact atgtaaaatc cagcagtgtt
tggttcctaa gtttgccact 701ttgtatatta acgattgtaa ttctactgag
gtccttgaaa gcaataaact cctgttgtct 761cgagcggccg c
7724180PRTNicotiana tabacum 4Arg Pro Leu Ala Val Ala Leu Lys Gln
Ala Met Thr Pro Glu Tyr Arg1 5 10 15Ala Tyr Gln Glu Gln Cys Leu Ser
Asn Cys Ser Lys Phe Ala Gln Ala 20 25 30Leu Ala Gly Met Gly Tyr Glu
Leu Val Ser Gly Gly Thr Glu Asn His 35 40 45Leu Val Leu Val Asn Leu
Lys Asn Lys Gly Ile Asp Gly Ser Arg Val 50 55 60Glu Lys Val Leu Glu
Ala Val His Ile Ala Ala Asn Lys Asn Thr Val65 70 75 80Pro Gly Asp
Val Ser Ala Met Val Pro Gly Gly Ile Arg Met Gly Thr 85 90 95Pro Ala
Leu Thr Ser Arg Gly Phe Ile Glu Glu Asp Phe Val Lys Val 100 105
110Ala Glu Phe Phe Asp Ala Ala Val Lys Ile Ala Val Lys Ile Lys Thr
115 120 125Glu Ala Gln Gly Thr Lys Leu Lys Asp Phe Val Thr Thr Leu
Gln Ser 130 135 140Ser Ala Pro Ile Gln Ser Glu Ile Ala Lys Leu Arg
His Gly Val Glu145 150 155 160Glu Tyr Ala Lys Gln Phe Pro Thr Ile
Gly Phe Glu Lys Glu Thr Met 165 170 175Lys Tyr Lys Asn
1805564DNANicotiana tabacumCDS(10)..(330) 5gcggccgct gca gcg aat
aag aac act gtt cct gga gat gta tct gcc atg 51 Ala Ala Asn Lys Asn
Thr Val Pro Gly Asp Val Ser Ala Met 1 5 10gtc cct ggt ggc atc aga
atg ggg act ctt gca ctc aca tca agg gga 99Val Pro Gly Gly Ile Arg
Met Gly Thr Leu Ala Leu Thr Ser Arg Gly15 20 25 30ttt att gag gaa
gat ttt gtg aaa gtt gct gaa ttc ttt gat gct gct 147Phe Ile Glu Glu
Asp Phe Val Lys Val Ala Glu Phe Phe Asp Ala Ala 35 40 45gtg aag ata
gca gtg aaa ata aag act gaa gct caa gga aca aag ttg 195Val Lys Ile
Ala Val Lys Ile Lys Thr Glu Ala Gln Gly Thr Lys Leu 50 55 60aaa gac
ttt gtg aca aca cta cag tct agc gct tca atc cag tcg gag 243Lys Asp
Phe Val Thr Thr Leu Gln Ser Ser Ala Ser Ile Gln Ser Glu 65 70 75att
gca aaa ctc cgc cat ggt gtg gag gag tat gca aag cag ttc cct 291Ile
Ala Lys Leu Arg His Gly Val Glu Glu Tyr Ala Lys Gln Phe Pro 80 85
90aca att ggg ttt gag aag gaa acc atg aag tac aaa aac tgagagctcg
340Thr Ile Gly Phe Glu Lys Glu Thr Met Lys Tyr Lys Asn95 100
105actgagtata tacacaaggg accaatatcc aacatcctca aggtgaatgg
gatagacatc 400caaactgcag ttcgctccca aggattggat tgtcatcttt
tactaatact atgtaaaatc 460cagcagtgtt tggttcccaa gtttgccact
ttgtatatta acgattgtaa ttcttctgag 520gtccttgaaa gcaataaact
cctgttgtca cggtaagcgg ccgc 5646107PRTNicotiana tabacum 6Ala Ala Asn
Lys Asn Thr Val Pro Gly Asp Val Ser Ala Met Val Pro1 5 10 15Gly Gly
Ile Arg Met Gly Thr Leu Ala Leu Thr Ser Arg Gly Phe Ile 20 25 30Glu
Glu Asp Phe Val Lys Val Ala Glu Phe Phe Asp Ala Ala Val Lys 35 40
45Ile Ala Val Lys Ile Lys Thr Glu Ala Gln Gly Thr Lys Leu Lys Asp
50 55 60Phe Val Thr Thr Leu Gln Ser Ser Ala Ser Ile Gln Ser Glu Ile
Ala65 70 75 80Lys Leu Arg His Gly Val Glu Glu Tyr Ala Lys Gln Phe
Pro Thr Ile 85 90 95Gly Phe Glu Lys Glu Thr Met Lys Tyr Lys Asn 100
10571835DNANicotiana tabacumCDS(56)..(1609) 7gcacccaaaa cacaagtcat
ttgggtgtgt gtaacagggg gagaagctca caatt atg 58 Met 1gcc atg gca acg
gct ctt cga aga ctt tcc tct tct gtt gac aaa cca 106Ala Met Ala Thr
Ala Leu Arg Arg Leu Ser Ser Ser Val Asp Lys Pro 5 10 15att aag cgt
ctc tat aat ggc ggc tct ctc tat tac atg tca tcg ttg 154Ile Lys Arg
Leu Tyr Asn Gly Gly Ser Leu Tyr Tyr Met Ser Ser Leu 20 25 30cct aat
gaa gct gtt tac gag aag gaa aaa aat ggt gtc acg tgg cca 202Pro Asn
Glu Ala Val Tyr Glu Lys Glu Lys Asn Gly Val Thr Trp Pro 35 40 45aag
caa ctt aat gct cct cta gag gag gtt gat cca gaa att gct gac 250Lys
Gln Leu Asn Ala Pro Leu Glu Glu Val Asp Pro Glu Ile Ala Asp50 55 60
65att att gag ctt gag aaa gca cgc cag tgg aag gga ctt gaa ctc att
298Ile Ile Glu Leu Glu Lys Ala Arg Gln Trp Lys Gly Leu Glu Leu Ile
70 75 80cct tca gaa aat ttc act tct gtg tct gta atg caa gct gtt gga
tct 346Pro Ser Glu Asn Phe Thr Ser Val Ser Val Met Gln Ala Val Gly
Ser 85 90 95gtt atg aca aac aag tac agt gaa gga tac cct ggg gct aga
tac tat 394Val Met Thr Asn Lys Tyr Ser Glu Gly Tyr Pro Gly Ala Arg
Tyr Tyr 100 105 110gga gga aat gag tat att gac atg gcg gaa acc tta
tgc cag aaa cgt 442Gly Gly Asn Glu Tyr Ile Asp Met Ala Glu Thr Leu
Cys Gln Lys Arg 115 120 125gct tta gaa gcc ttc agg ttg gat cct gca
aaa tgg gga gtg aat gtg 490Ala Leu Glu Ala Phe Arg Leu Asp Pro Ala
Lys Trp Gly Val Asn Val130 135 140 145cag cct ctg tca gga tca cct
gct aat ttt cat gtt tac act gca ctt 538Gln Pro Leu Ser Gly Ser Pro
Ala Asn Phe His Val Tyr Thr Ala Leu 150 155 160tta aaa cct cat gaa
aga atc atg gcc ctt gat ctt ccc cac ggt gga 586Leu Lys Pro His Glu
Arg Ile Met Ala Leu Asp Leu Pro His Gly Gly 165 170 175cat ctt tct
cat gga tat cag act gat aca aag aag ata tct gcc gtc 634His Leu Ser
His Gly Tyr Gln Thr Asp Thr Lys Lys Ile Ser Ala Val 180 185 190tct
ata ttt ttt gag acc atg cca tat aga ctg aat gag agc act ggc 682Ser
Ile Phe Phe Glu Thr Met Pro Tyr Arg Leu Asn Glu Ser Thr Gly 195 200
205tac att gac tat gac cag ctt gag aaa agt gcc aca ctc ttt agg cca
730Tyr Ile Asp Tyr Asp Gln Leu Glu Lys Ser Ala Thr Leu Phe Arg
Pro210 215 220 225aag tta att gtc gct ggt gct agt gct tat gca cgt
ctt tat gac tat 778Lys Leu Ile Val Ala Gly Ala Ser Ala Tyr Ala Arg
Leu Tyr Asp Tyr 230 235 240gca cgt atc cga aag gtt tgt gac aaa cag
aag gct atc atg ttg gca 826Ala Arg Ile Arg Lys Val Cys Asp Lys Gln
Lys Ala Ile Met Leu Ala 245 250 255gat atg gct cat att agt ggg tta
gtt gca gct gga gtc atc cca tca 874Asp Met Ala His Ile Ser Gly Leu
Val Ala Ala Gly Val Ile Pro Ser 260 265 270cca ttt gat tat gca gat
gtt gtg acc acc aca acc cac aaa tcc ctt 922Pro Phe Asp Tyr Ala Asp
Val Val Thr Thr Thr Thr His Lys Ser Leu 275 280 285cgc ggg cct cgt
ggt gcc atg att ttc ttc cgg aag ggt gtg aag gag 970Arg Gly Pro Arg
Gly Ala Met Ile Phe Phe Arg Lys Gly Val Lys Glu290 295 300 305gtt
aac aag caa ggc aag gag gtg ttg tac gac tat gaa gat aaa att 1018Val
Asn Lys Gln Gly Lys Glu Val Leu Tyr Asp Tyr Glu Asp Lys Ile 310 315
320aac cag gca gtc ttt ccc gga ctt caa ggt ggt cct cac aac cat aca
1066Asn Gln Ala Val Phe Pro Gly Leu Gln Gly Gly Pro His Asn His Thr
325 330 335att act ggc ttg gca gtt gct ttg aaa cag gca atg act cca
gaa tac 1114Ile Thr Gly Leu Ala Val Ala Leu Lys Gln Ala Met Thr Pro
Glu Tyr 340 345 350aga gct tac caa gag caa tgc ctt agc aac tgc tca
aaa ttt gcc cag 1162Arg Ala Tyr Gln Glu Gln Cys Leu Ser Asn Cys Ser
Lys Phe Ala Gln 355 360 365gct tta gcg gga atg ggt tat gaa ctt gtt
tct ggt gga aca gag aat 1210Ala Leu Ala Gly Met Gly Tyr Glu Leu Val
Ser Gly Gly Thr Glu Asn370 375 380 385cac ttg gtt ttg gtg aac ttg
aaa aac aag ggt att gat ggt tct agg 1258His Leu Val Leu Val Asn Leu
Lys Asn Lys Gly Ile Asp Gly Ser Arg 390 395 400gtt gaa aaa gtt ttg
gaa gcg gta cat att gca gcg aat aag aac act 1306Val Glu Lys Val Leu
Glu Ala Val His Ile Ala Ala Asn Lys Asn Thr 405 410 415gtt cct gga
gat gta tct gcc atg gtc cct ggt ggc atc aga atg ggg 1354Val Pro Gly
Asp Val Ser Ala Met Val Pro Gly Gly Ile Arg Met Gly 420 425 430act
cct gca ctc aca tca agg gga ttt att gag gaa gat ttt gtg aaa 1402Thr
Pro Ala Leu Thr Ser Arg Gly Phe Ile Glu Glu Asp Phe Val Lys 435 440
445gtt gct gaa ttc ttt gat gct gct gtg aag ata gca gtg aaa ata aag
1450Val Ala Glu Phe Phe Asp Ala Ala Val Lys Ile Ala Val Lys Ile
Lys450 455 460 465act gaa gct caa gga aca aag ttg aaa gac ttt gtg
aca aca cta cag 1498Thr Glu Ala Gln Gly Thr Lys Leu Lys Asp Phe Val
Thr Thr Leu Gln 470 475 480tct agc gct tca atc cag tcg gag att gca
aaa ctc cgc cat ggt gtg 1546Ser Ser Ala Ser Ile Gln Ser Glu Ile Ala
Lys Leu Arg His Gly Val 485 490 495gag gag tat gca aag cag ttc cct
aca att ggg ttt gag aag gaa acc 1594Glu Glu Tyr Ala Lys Gln Phe Pro
Thr Ile Gly Phe Glu Lys Glu Thr 500 505 510atg aag tac aaa aac
tgagagctcg actgagtata tacacaaggg accaatatcc 1649Met Lys Tyr Lys Asn
515aacatcctca aggtgaatgg gatagacatc caaactgcag ttcgctccca
aggattggat 1709tgtcatcttt tactaatact atgtaaaatc cagcagtgtt
tggttcccaa gtttgccact 1769ttgtatatta acgattgtaa ttcttctgag
gtccttgaaa gcaataaact cctgttgtca 1829cggtaa 18358518PRTNicotiana
tabacum 8Met Ala Met Ala Thr Ala Leu Arg Arg Leu Ser Ser Ser Val
Asp Lys1 5 10 15Pro Ile Lys Arg Leu Tyr Asn Gly Gly Ser Leu Tyr Tyr
Met Ser Ser 20 25 30Leu Pro Asn Glu Ala Val Tyr Glu Lys Glu Lys Asn
Gly Val Thr Trp 35 40 45Pro Lys Gln Leu Asn Ala Pro Leu Glu Glu Val
Asp Pro Glu Ile Ala 50 55 60Asp Ile Ile Glu Leu Glu Lys Ala Arg Gln
Trp Lys Gly Leu Glu Leu65 70 75 80Ile Pro Ser Glu Asn Phe Thr Ser
Val Ser Val Met Gln Ala Val Gly 85 90 95Ser Val Met Thr Asn Lys Tyr
Ser Glu Gly Tyr Pro Gly Ala Arg Tyr 100 105 110Tyr Gly Gly Asn Glu
Tyr Ile Asp Met Ala Glu Thr Leu Cys Gln Lys 115 120 125Arg Ala Leu
Glu Ala Phe Arg Leu Asp Pro Ala Lys Trp Gly Val Asn 130 135 140Val
Gln Pro Leu Ser Gly Ser Pro Ala Asn Phe His Val Tyr Thr Ala145 150
155 160Leu Leu Lys Pro His Glu Arg Ile Met Ala Leu Asp Leu Pro His
Gly 165 170 175Gly His Leu Ser His Gly Tyr Gln Thr Asp Thr Lys Lys
Ile Ser Ala 180 185 190Val Ser Ile Phe Phe Glu Thr Met Pro Tyr Arg
Leu Asn Glu Ser Thr 195 200 205Gly Tyr Ile Asp Tyr Asp Gln Leu Glu
Lys Ser Ala Thr Leu Phe Arg 210 215 220Pro Lys Leu Ile Val Ala Gly
Ala Ser Ala Tyr Ala Arg Leu Tyr Asp225 230 235 240Tyr Ala Arg Ile
Arg Lys Val Cys Asp Lys Gln Lys Ala Ile Met Leu 245 250 255Ala Asp
Met Ala His Ile Ser Gly Leu Val Ala Ala Gly Val Ile Pro 260 265
270Ser Pro Phe Asp Tyr Ala Asp Val Val Thr Thr Thr Thr His Lys Ser
275 280 285Leu Arg Gly Pro Arg Gly Ala Met Ile Phe Phe Arg Lys Gly
Val Lys 290 295 300Glu Val Asn Lys Gln Gly Lys Glu Val Leu Tyr Asp
Tyr Glu Asp Lys305 310 315 320Ile Asn Gln Ala Val Phe Pro Gly Leu
Gln Gly Gly Pro His Asn His 325 330 335Thr Ile Thr Gly Leu Ala Val
Ala Leu Lys Gln Ala Met Thr Pro Glu 340 345 350Tyr Arg Ala Tyr Gln
Glu Gln Cys Leu Ser Asn Cys Ser Lys Phe Ala 355 360 365Gln Ala Leu
Ala Gly Met Gly Tyr Glu Leu Val Ser Gly Gly Thr Glu 370 375 380Asn
His Leu Val Leu Val Asn Leu Lys Asn Lys Gly Ile Asp Gly Ser385 390
395 400Arg Val Glu Lys Val Leu Glu Ala Val His Ile Ala Ala Asn Lys
Asn 405 410 415Thr Val Pro Gly Asp Val Ser Ala Met Val Pro Gly Gly
Ile Arg Met 420 425 430Gly Thr Pro Ala Leu Thr Ser Arg Gly Phe Ile
Glu
Glu Asp Phe Val 435 440 445Lys Val Ala Glu Phe Phe Asp Ala Ala Val
Lys Ile Ala Val Lys Ile 450 455 460Lys Thr Glu Ala Gln Gly Thr Lys
Leu Lys Asp Phe Val Thr Thr Leu465 470 475 480Gln Ser Ser Ala Ser
Ile Gln Ser Glu Ile Ala Lys Leu Arg His Gly 485 490 495Val Glu Glu
Tyr Ala Lys Gln Phe Pro Thr Ile Gly Phe Glu Lys Glu 500 505 510Thr
Met Lys Tyr Lys Asn 515916DNANicotiana tabacum 9agaattcgcg gccgct
161032DNAArtificial Sequenceoligonucleotide primer with homology to
pUC18SbfI vector 10ctcatgcggc cgcgcgcaac gcaattaatg tg
321132DNAArtificial Sequenceoligonucleotide primer with homology to
pUC18SbfI vector 11tcatgcggcc gcgagatcca gttcgatgta ac
321221DNANicotiana tabacum 12gtggattgat gtgatatctc c
211321DNANicotiana tabacum 13gtaaggatct gagctacaca t
211419DNAArabidopsis thaliana 14aaatggcgat ggccatggc
191521DNAArabidopsis thaliana 15tggggtgaaa cagtttagtt c
211620DNAArabidopsis thaliana 16aaaccagaga tagagagagg
201722DNAArabidopsis thaliana 17acatgtatca tctatacatt cc
221818DNAArabidopsis thaliana 18atggcgatgg ccatggct
181921DNAArabidopsis thaliana 19tggggtgaaa cagtttagtt c
212021DNAArabidopsis thaliana 20atgaaggaaa gatctcgtgt c
212121DNAArabidopsis thaliana 21tggggtgaaa cagtttagtt c
212219DNAArabidopsis thaliana 22atgtctttgc ccagtgaag
192321DNAArabidopsis thaliana 23tggggtgaaa cagtttagtt c
212421DNAArabidopsis thaliana 24atgaaggaaa gatctcgtgt c
212521DNAArabidopsis thaliana 25tggggtgaaa cagtttagtt c
212618DNAArabidopsis thaliana 26atggcgatgg ccatggct
182721DNAArabidopsis thaliana 27tggggtgaaa cagtttagtt c
212825DNAArtificial Sequenceoligonucleotide primer with homology to
pCR 2.1 TOPO vector with NAD-dependent methylenetetrahydrofolate
dehyrdrogenase (MTD) insert 28tttttcttta gacagttcta cgttc
252919DNAArtificial Sequenceoligonucleotide primer with homology to
pCR 2.1 TOPO vector with NAD-dependent methylenetetrahydrofolate
dehyrdrogenase (MTD) insert 29atgtcgaagc ctggtcgta 19
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