Abstract
ABA is an important phytohormone regulating various plant processes, including stress tolerance, seed development and germination. SRK2D/SnRK2.2, SRK2E/SnRK2.6/OST1 and SRK2I/SnRK2.3 are redundant ABA-activated SNF1-related protein kinases 2 (SnRK2s) in Arabidopsis thaliana. We examined the role of SRK2D, SRK2E and SRK2I in seeds. The triple mutant (srk2d srk2e srk2i) was sensitive to desiccation, showed severe growth defects during seed development, exhibited a loss of dormancy and vivipary, and showed highly enhanced insensitivity to ABA (Nakashima et al., 2009, Fujita et al., 2009). It also showed insensitivity to sugars and paclobutrazol (PAC), a gibberellin biosynthesis inhibitor. Disruption of the three protein kinases induced global changes in the expression of ABA/stress-related genes including genes encoding LEA proteins and HSPs in seeds. Stress tolerant assay revealed that the triple mutant seeds were sensitive to cold and heat stresses. These results indicate that these protein kinases are essential for the control of seed development, dormancy and abiotic stress tolerance through the extensive regulation of global gene expression.
