May play a role in signal transduction of hyperosmotic response. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Activated by hyperosmotic stress. Weakly expressed in roots. Expressed in roots of young seedlings. By hyperosmotic stress in roots. Weakly induced by hyperosmotic stress and abscisic acid (ABA) in leaf blades (PubMed:15084714). Accumulates upon incompatible interaction with Xanthomonas oryzae pv. oryzicola (Ref.2). May be phosphorylated. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.