The role of abscisic acid and its catabolic genes in the regulation of wheat seed dormancy and germination
Frontiers in Plant Science, Planta, Plos one
Common wheat is the one of the most important cereal crop in the world. Pre-harvest sprouting (PHS) is one of the major problems affecting wheat yield and quality in Canada and globally. The occurrence of PHS is closely associated with the level of seed dormancy, and abscisic acid (ABA) plays a pivotal role in the regulation of seed dormancy. The catabolism of ABA plays a crucial role for maintaining its homeostasis in plant tissues, including seeds, and this reaction is mediated primarily by ABA 8' hydroxylase, an enzyme encoded by genes designated as CYP707A. This study identified the three homeologues of TaCYP707A1 from Canadian wheat genotypes with contrasting PHS phenotype, and comparison of their genomic sequences indicated the presence of allelic and other variations. Analysis of the total expression of TaCYP707A1 in different wheat tissues revealed that it is predominantly expressed in seeds during maturation, and genomic contribution of transcripts to the total expression of TaCYP707A1 are shown to vary with tissues and genotypes. Ectopic expression of TaCYP707A1 in Arabidopsis demonstrated its function in regulating seed ABA level and dormancy. Furthermore, the spatiotemporal expression patterns of TaCYP707A1 along with TaCYP707A2 in the seeds of the wheat genotypes studied suggest that both genes are involved in the regulation of seed ABA and dormancy levels, however, TaCYP707A1 appears to play a major role. The findings of this thesis also show that the role of ABA in inhibiting the germination of wheat seed is partly mediated by transcriptional regulation of genes involved in the metabolic and signaling pathways of brassinosteroids, ethylene and cytokinin, which in turn suggests changes in the contents and responses of seeds to these particular phytohormones.
Seed dormancy, Pre-harvest sprouting, Abscisic acid, CYP707A1, Wheat, ABA 8' hydroxylase, Brassinosteroids, Ethylene, Cytokinin, Gene expression
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