Involved in gene regulation and confers tolerance to drought and osmotic stress. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with I-2 and TOPP1. Expressed in seedlings. By abscisic acid (ABA), cold, H(2)O(2), salt, and osmotic stress (at protein level). Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.