May play a role in signal transduction of hyperosmotic response. Together with PYL10, PP2C53 and SAPK8, may form an abscisic acid (ABA) signaling module involved in stress response (PubMed:26491145). Together with PYL3 and PP2C50, may form an ABA signaling module involved in stress response (PubMed:28827170). 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 (PubMed:26491145). Interacts with PP2C50 (PubMed:28827170). Expressed in leaf blades, leaf sheaths and roots. Expressed in shoots and roots of young seedlings. Down-regulated by ABA in roots. May be phosphorylated. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.