Dual specificity protein kinase that phosphorylates ANN1, ANN2 and CP29B at serine and threonine residues, and ANN1, ANN2 and ANN4 at tyrosine residues. May regulate the phosphorylation status of annexin proteins (PubMed:26452715). Acts as positive regulator in abscisic acid (ABA)-mediated regulation of postgermination growth and drought response. May regulate the expression of ABA-responsive genes such as RD22, RD29A, LTI65/RD29B and RAB18 (PubMed:27264339). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Induced by drought stress. Autophosphorylated at Ser-222. No visible phenotype under normal growth conditions, but mutant seedlings exhibit decreased sensitivity to abscisic acid (ABA) inhibition of seed germination, cotyledon greening, seedling growth, and stomatal movement. Decreased tolerance to drought stress. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.