Action of Hormones in Plant Development: Hormonal Regulationof Gene Expression in Barley Aleurone Layers

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Gibberellic acid (GA), a plant hormone, regulates several important physiological and developmental processes such as seed germination, post-germination growth, stem elongation and flower induction. Together with another hormone, abscisic acid (ABA), GA is known to regulate the synthesis and secretion of several enzymes which are responsible for the utilization of nutrients stored in the seed. The enzymes are essential for post-germination growth of many cereal grains. The most abundant of these enzymes is alpha-amylase, which degrades starch. As part of a long term effort to elucidate the mode of action of GA and ABA this research will focus on gene expression in the aleurone layers of germinating barley seeds. Previous research has revealed that hormone-mediated regulation of enzyme expression in the barley-aleurone system is mainly at the level of gene transcription. The proposed research will investigate specific interactions between specific protein factors with regulatory regions (promoters) of hormone-regulated genes in the barley-aleurone system. Goal for this research include: (1) determination of specific DNA sequences in the alpha-amylase promoters that interact with protein factors, (2) investigation of the effect of hormonal treatments on the activity of the protein factors, (3) determination of the importance of promoter sequences inside the aleurone cells and (4) investigation of the activity of these factors in genetic mutants with altered sensitivities to GA and ABA. Results from this research should improve our understanding of the primary action of GA and ABA, thus revealing new insights into the signal transduction pathway governing hormonal regulation of gene expression in plants.