May play a role in signal transduction of hyperosmotic response (Probable). Together with PYL10, PP2C53 and SAPK10, may form an abscisic acid (ABA) signaling module involved in stress response (PubMed:26491145). 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 PP2C53. Expressed in leaf blades, leaf sheaths and roots. Expressed in shoots and roots of young seedlings. Neither induced by hyperosmotic stress nor by ABA. The C-terminal region is necessary for the kinase activation in response to ABA treatment. May be phosphorylated. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.