Cotton transcription factors and their uses

Details Cotton transcription factors and their uses Cotton transcription factors and their uses

1999-12-02

2004-12-07

McElwain, Elizabeth F. (Department: 1638)

Multicellular living organisms and unmodified parts thereof and

Method of introducing a polynucleotide molecule into or...

The polynucleotide alters plant part growth

C800S287000, C800S298000, C800S278000, C800S314000, C536S023100, C536S023600, C435S468000, C435S320100

Reexamination Certificate

active

06828476

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to plant genetic engineering. In particular, it relates to methods of modulating transcription in plant cells.
BACKGROUND OF THE INVENTION
An array of eukaryotic functions are regulated at the transcriptional level by a type of DNA-binding proteins encoded by the MYB-domain genes (Martin, C. et al.,
Trends in Genet
13:67-73 (1997); Thompson, M. A. et al.,
Bioessays
17:341-350 (1995)). MYB proteins are characterized by a modular design, comprising discrete functional domains that permit transcription activities to be highly regulated. The amino-terminal DNA-binding domain, or DBD, consists of two or three helix-tum-helix motifs of 51-52 amino acids (R1, R2 and R3) that are highly conserved across phyla. Yet, the precise structure of each of the DBDs determines the specificity of MYB-DNA interactions, and in turn, dictates the level of MYB-mediated transcription (Ramsay, R. G. et al.,
J. Biol Chem
267:5656-5662 (1992); Tanikawa, J. et al.,
Proc Natl Acad Sci USA
90:9320-9324 (1993)). The transactivation domain, or TAD, varies in composition and in its relative position within the protein from MYB-to-MYB (Paz-Ares, J. et al.,
EMBO J
9:315-321 (1990); Sainz, M. B. et al.,
Mol Cell Biol
17:115-122 (1997); Urao, T. et al.,
Plant J
10:1145-1148 (1996)), and serves to regulate transcription efficiency in trans. A leucine-zipperlike structure that presumably mediates MYB-MYB interactions, as well as protein interactions with other transcription factors (Kanei-Ishii, C. et al.,
Proc Natl Acad Sci USA
89:3088-3092 (1992); Nomura, T. et al.,
J Biol Chem
268:21914-21923 (1993)) is referred to as the negative regulatory domain (NRD). However, NRDs have thus far only been identified in animal systems. MYB-mediated transcription is also subject to modulation by the transcription and translation rates inherent to the MYB genes themselves (Nicolaides, N. C. et al.,
J Biol Chem
267:19665-19672 (1992); Wissenbach, M. et al.,
Plant J
4:411-422 (1993)).
In contrast to other eukaryotes which contain only a few copies per haploid genome (Thompson, M. A. et al.,
Bioessays
17:341-350 (1995)), the number of genes in the R2R3-MYB family in plant genomes is considerably higher (Avila, J. et al.,
Plant J
3:553-562 (1993); Jackson, D. et al.,
Plant Cell
3:115-125 (1991); Lin, Q. et al.,
Plant Mol Biol
30:1009-1020 (1996); Lipsick, J. S.
Oncogene
13:223-235 (1996); Romero, L. et al.,
Plant J
14:273-284 (1998); Solano, R. et al.,
Plant J
8:673-682 (1995b)). At least 85 R2R3-MYB genes have been identified in
Arabidopsis thaliana
thus far (Romero, L. et al.,
Plant J
14:273-284 (1998); Meissner et al.,
Plant Cell.
10:1827-40 (1999)). The expansion of the plant R2R3-MYB gene family during the course of evolution is believed by many to provide a mechanism for the regulation of plant-specific processes and functions (Martin, C. et al.,
Trends in Genet
13:67-73 (1997)). Most of the relatively few plant MYBs that have been assigned functions are involved in regulation of phenylpropanoid biosynthesis (Cone, K. C. et al.,
Plant Cell
5:1795-1805 (1993); Franken, P. et al.,
Plant J
6:21-30 (1994); Grotewold, E. et al.,
Cell
76:543-553 (1994); Moyano, E. et al.,
Plant Cell
8:1519-1532 (1996); Quattrocchio et al.,
Plant J
13:475-488 (1993); Solano et al.,
EMBO J.
14:1773-1784 (1995)). In two known instances, MYB genes control the differentiation of epidermal cells. Glabrous1 (AtMYBG/1) governs leaf trichome formation in
Arabidopsis thaliana
(Oppenheimer, D.G. et al.,
Cell
67:483-493 (1991)), while MIXTA (AmMYBMx) of
Antirrhinum majus
controls the development of conical cells or multicellular trichomes, depending on the timing of MIXTA gene expression (Glover, B. J. et al.,
Development
125:3497-3508 (1998)).
The economically important “fibers” of cotton used in textile manufacturing are, in actuality, single-celled seed trichomes that develop from the epidernis of the ovule (Wilkins, T. A. et al.,
In Basra AS (ed) Cotton Fibers. Food Products Press New York
(1999)). There is a need to improve the quality of cotton fibers for use in a variety of textile products, In particular, means for improving fiber, such as fiber strength, fiber length and the like. The present invention addresses these and other needs.
SUMMARY OF THE INVENTION
The present invention provides methods of modulating transcription in a plants. The methods comprise introducing into a plant a recombinant expression cassette comprising a promoter sequence operably linked to a heterologous polynucleotide sequence encoding a MYB polypeptide. A MYB polypeptide of the invention can be, for example, a polypeptide that is at least substantially identical to MYB poylypeptides exemplified here (e.g. SEQ ID NOS:2, 4, 6 or 8). The polynucleotide can be, for example, SEQ ID NOS:1, 3, 5, or 7.
The particular plant used in the methods of the invention is not critical. In some embodiments, the plant is a cotton plant. In these embodiments, it is particularly useful to use a promoter that directs expression of the polynucleotide sequence in cotton fibers.
A explained below, a number of valuable phenotypes are conferred on plants produced by the methods of the invention. They include, for examnple, increased fiber quality, alteration of root architecture, enhanced growth and the like. A recombinant expression cassette comprising a promoter sequence operably linked to a heterologous polynucleotide sequence encoding a MYB polypeptide.
The invention further provides recombinant expression cassettes useful in the methods of the invention. Plants made by the claimed methods are also provided.
DEFINITIONS
The phrase “nucleic acid sequence” refers to a single or double-stranded polymer of deoxyribonucleotide or ribonucleotide bases read from the 5′ to the 3′ end. It includes chromosomal DNA, self-replicating plasmids, infectious polymers of DNA or RNA and DNA or RNA that performs a primarily structural role.
A “promoter” is defined as an array of nucleic acid control sequences that direct transcription of an operably linked nucleic acid. As used herein, a “plant promoter” is a promoter that functions in plants, even though obtained from other organisms, such as plant viruses. Promoters include necessary nucleic acid sequences near the start site of transcription, such as, in the case of a polymerase II type promoter, a TATA element. A promoter also optionally includes distal enhancer or repressor elements, which can be located as much as several thousand base pairs from the start site of transcription. The term “operably linked” refers to a functional linkage between a nucleic acid expression control sequence (such as a promoter, or array of transcription factor binding sites) and a second nucleic acid sequence, wherein the expression control sequence directs transcription of the nucleic acid corresponding to the second sequence.
The term “plant” includes whole plants, plant organs (e.g., leaves, stems, flowers, roots, etc.), seeds and plant cells and progeny of same. The class of plants that can be used in the method of the invention is generally as broad as the class of higher plants amenable to transformation techniques, including angiosperms (monocotyledonous and dicotyledonous plants), as well as gymnosperms. It includes plants of a variety of ploidy levels, including polyploid, diploid, haploid and hemizygous.
A polynucleotide sequence is “heterologous to” an organism or a second polynucleotide sequence if it originates from a foreign species, or, if from the same species, is modified from its original form. For example, a promoter operably linked to a heterologous coding sequence refers to a coding sequence from a species different from that from which the promoter was derived, or, if from the same species, a coding sequence which is different from any naturally occurring allelic variants.
A polynucleotide “exogenous to” an individual plant is a polynucleotide which is introduced into the plant by any means other than by a sexual cross. Examples of mean

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