The role of gibberellin in the regulation of wheat grain development

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The project investigates the processes regulated by gibberellins (GAs) in cereal grain development, using wheat as the experimental system. The results will indicate whether GAs play a role in determining grain yield and quality and may identify target genes for breeding for these characteristics. Existing transgenic lines with altered GA metabolism in the endosperm will be analysed for effects of transgene expression on grain morphology and in their propensity for preharvest sprouting and pre-maturity alpha- amylase production, both factors which are potentially under GA regulation and which reduce flour quality. Rht dwarfing genes, which confer insensitivity to GA, will be introgressed into the GA-overproducing lines to confirm that a functional GA-signal transduction pathway is necessary for any phenotypic changes identified. Sites of expression within the developing grain of genes of GA biosynthesis and signal transduction will be determined using reporter genes, in situ hybridisation and laser capture microdissection coupled with real time RT-PCR. The major objectives are to: Characterise in detail the morphological, biochemical and molecular phenotypes of wheat grains with altered GA levels; Identify the target tissues for GA action in grain development through identification of the sites of expression of GA-biosynthetic genes and the use of rht dwarfing genes to modify GA responses in the grain; Determine the roles of specific GA- biosynthetic genes in grain development through the isolation of mutants in diploid wheat (Triticum monococcum); Test alternative promoters for expression of GA 20-oxidase genes early in endosperm development to affect grain,development without compromising grain quality.

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