Receptor-like cytoplasmic kinase (RLCK) that triggers abscisic acid (ABA) signaling by phosphorylating and activating ABA receptors (e.g. PYL8/RCAR3 and PYR1/RCAR11), which in turn repress ABI1, a negative regulator of ABA responses (PubMed:29928509). Promotes drought tolerance (PubMed:29970817). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with PYL8/RCAR3 and PYR1/RCAR11 in the cytosol. Autophosphorylated at threonine residues and to a lesser extent at serine residues. Impaired kinase activity and reduced plant sensitivity to abscisic acid (ABA). Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.