Multicellular living organisms and unmodified parts thereof and – Method of introducing a polynucleotide molecule into or... – The polynucleotide alters plant part growth
Reexamination Certificate
2000-03-01
2004-07-13
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
C800S278000, C800S298000, C800S295000, C435S419000, C435S468000, C435S320100, C435S430000, C536S023600, C536S024100
Reexamination Certificate
active
06762348
ABSTRACT:
This invention relates to the genetic control of growth and/or development of plants and the cloning and expression of genes involved therein. More particularly, the invention relates to the cloning and expression of the Rht gene of
Triticum Aestivum
, and homologues from other species, and use of the genes in plants.
An understanding of the genetic mechanisms which influence growth and development of plants, including flowering, provides a means for altering the characteristics of a target plant. Species for which manipulation of growth and/or development characteristics may be advantageous includes all crops, with important examples being the cereals, rice and maize, probably the most agronomically important in warmer climatic zones, and wheat, barley, oats and rye in more temperate climates. Important crops for seed products are oil seed rape and canola, maize, sunflower, soyabean and sorghum. Many crops which are harvested for their roots are, of course, grown annually from seed and the production of seed of any kind is very dependent upon the ability of the plant to flower, to be pollinated and to set seed. In horticulture, control of the timing of growth and development, including flowering, is important. Horticultural plants whose flowering may be controlled include lettuce, endive and vegetable brassicas including cabbage, broccoli and cauliflower, and carnations and geraniums. Dwarf plants on the one hand and over-size, taller plants on the other may be advantageous and/or desirable in various horticultural and agricultural contexts, further including trees, plantation crops and grasses.
Recent decades have seen huge increases in wheat grain yields due to the incorporation of semi-dwarfing Rht homeoalleles into breeding programmes. These increases have enabled wheat productivity to keep pace with the demands of the rising world population. Previously, we described the cloning of the
Arabidopsis gai
alleles (International patent application PCT/GB97/00390 filed Feb. 12, 1997 and published as WO97/29123 on Aug. 14, 1998, John Innes Centre Innovations Limited, the full contents of which are incorporated herein by reference) which, like Rht mutant alleles in wheat (a monocot), confers a semi-dominant dwarf phenotype in Arabidopsis (a dicot) and a reduction in responsiveness to the plant growth hormone gibberellin (GA). gai encodes a mutant protein (gai) which lacks a 17 amino acid residue segment found near the N-terminus of the wild-type (GAI) protein. The sequence of this segment is highly conserved in a rice cDNA sequence (EST). Here we show that this cDNA maps to a short section of the overlapping cereal genome maps known to contain the Rht loci, and that we have used the cDNA to isolate the Rht genes of wheat. That genomes as widely diverged as those of Arabidopsis and Triticum should carry a conserved sequence which, when mutated, affects GA responsiveness, indicates a role for that sequence in GA signalling that is conserved throughout the plant kingdom. Furthermore, cloning of Rht permits its transfer to many different crop species, with the aim of yield enhancement as great as that obtained previously with wheat.
The introduction of semi-dwarfing Rht homeoalleles (originally known as Norin 10 genes, derived from a Japanese variety, Norin 10) into elite bread-wheat breeding lines was one of the most significant contributors to the so-called “green revolution” (Gale et al, 1985. Dwarfing genes in wheat. In: Progress in Plant Breeding, G.E. Russell (ed) Butterworths, London pp 1-35). Wheat containing these homeoalleles consistently out-yield wheats lacking them, and now comprise around 80% of the world's wheat crop. The biological basis of this yield-enhancement appears to be two-fold. Firstly, the semi-dwarf phenotype conferred by the Rht alleles causes an increased resistance to lodging (flattening of plants by wind/rain with consequent loss of yield). Secondly, these alleles cause a reallocation of photoassimilate, with more being directed towards the grain, and less towards the stem (Gale et al, 1985). These properties have major effects on wheat yields, as demonstrated by the fact that UK wheat yields increased by over 20% during the years that Rht-containing lines were taken up by farmers.
The rht mutants are dwarfed because they contain a genetically dominant, mutant rht allele which compromises their responses to gibberellin (GA, an endogenous plant growth regulator) (Gale et al, 1976. Heredity 37; 283-289). Thus the coleoptiles of rht mutants, unlike those of wild-type wheat plants, do not respond to GA applications. In addition, rht mutants accumulate biologically active GAs to higher levels than found in wild-type controls (Lenton et al, 1987. Gibberellin insensitivity and depletion in wheat—consequences for development. In: Hormone action in Plant Development—a critical appraisal. G V Haod, J R Lenton, M E Jackson and R K Atkin (eds) Butterworths, London pp 145-160). These properties (genetic dominance, reduced GA-responses, and high endogenous GA levels) are common to the phenotypes conferred by mutations in other species (D8/D9 in maize; gai in Arabidopsis), indicating that these mutant alleles define orthologous genes in these different species, supported further by the observation that D8/D9 and Rht are syntenous loci in the genomes of maize and wheat.
According to a first aspect of the present invention there is provided a nucleic acid molecule comprising a nucleotide sequence encoding a polypeptide with Rht function. The term “Rht function” indicates ability to influence the phenotype of a plant like the Rht gene of Triticum. “Rht function” may be observed phenotypically in a plant as inhibition, suppression, repression or reduction of plant growth which inhibition, suppression, repression or reduction is antagonised by GA. Rht expression tends to confer a dwarf phenotype on a plant which is antagonised by GA.
Overexpression in a plant from a nucleotide sequence encoding a polypeptide with Rht function may be used to confer a dwarf phenotype on a plant which is correctable by treatment with GA.
Also according to an aspect of the present invention there is provided a nucleic acid molecule comprising a nucleotide sequence encoding a polypeptide with ability to confer a rht mutant phenotype upon expression. rht mutant plants are dwarfed compared with wild-type, the dwarfing being GA-insensitive. Herein, “Rht” (capitalised) is used to refer to the wild-type function, while “rht” (uncapitalised) is used to refer to mutant function.
Many plant growth and developmental processes are regulated by specific members of a family of tetracyclic diterpenoid growth factors known as gibberellins (GA) (Hooley,
Plant Mol. Biol.
26, 1529-1555 (1994)). By gibberellin or GA is meant a diterpenoid molecule with the basic carbon-ring structure shown in FIG.
5
and possessing biological activity, i.e. we refer to biologically active gibberellins.
Biological activity may be defined by one or more of stimulation of cell elongation, leaf senescence or elicitation of the cereal aleurone &agr;-amylase response. There are many standard assays available in the art, a positive result in any one or more of which signals a test gibberellin as biologically active (Hoad et al.,
Phytochemistry
20, 703-713 (1981); Serebryakov et al.,
Phytochemistry
23, 1847-1854 (1984); Smith et al.,
Phytochemistry
33, 17-20 (1993)).
Assays available in the art include the lettuce hypocotyl assay, cucumber hypocotyl assay, and oat first leaf assay, all of which determine biological activity on the basis of ability of an applied gibberellin to cause elongation of the respective tissue. Preferred assays are those in which the test composition is applied to a gibberellin-deficient plant. Such preferred assays include treatment of dwarf GA-deficient Arabidopsis to determine growth, the dwarf pea assay, in which internode elongation is determined, the Tan-ginbozu dwarf rice assay, in which elongation of leaf sheath is determined, and the d5-maize assay, also in which elongation of leaf she
Harberd Nicholas P.
Peng Jinrong
Richards Donald E.
Ibrahim Medina A.
McElwain Elizabeth F.
Nixon & Vanderhye PC
Pioneer Hi-Bred International , Inc.
LandOfFree
Genetic control of plant growth and development does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Genetic control of plant growth and development, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Genetic control of plant growth and development will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3234613