May play a role in signal transduction of hyperosmotic response (Probable). Can phosphorylate BZIP46 in vitro (PubMed:22301130). 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 and abscisic acid (ABA). Interacts with BZIP46. Expressed in leaf sheaths and roots. Expressed in shoots of young seedlings. Down-regulated by ABA in roots (PubMed:15084714). Induced during incompatible interaction with the bacterial pathogen Xanthomonas oryzae pv. oryzicola (Ref.2). May be phosphorylated. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.