Molecular mechanism of seed maturation, dormancy and germination using viviparous mutants

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Abscisic acid(ABA) is an important phytohormone regulating various physiological processes including seed maturation, dormancy and germination. SRK2D, SRK2E and SRK2I are redundant ABA-activated SNF1-related protein kinases 2(SnRK2s) in Arabidopsis thaliana. The triple mutant of the SnRK2 protein kinases(srk2d srk2e srk2i) showed viviparous germination. It was sensitive to desiccation and showed severe growth defects during seed development. It exhibited a loss of dormancy, strong ABA-insensitivity, and elevated seed ABA content relative to wild-type seeds. The triple mutant had greatly reduced phosphorylation activity in in-gel kinase experiments using bZIP transcription factors including ABI5.Microarray experiments indicate that SRK2D, SRK2E and SRK2I protein kinases involved in ABA signaling are essential for the control of seed development, dormancy and germination through the extensive control of gene expression.