Involved in defense response to geminivirus infection. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Inhibited by the viral nuclear shuttle protein (NSP) that binds to the region required for oligomerization. Oligomer. Interacts with geminivirus nuclear shuttle protein (NSP). Expressed in seedlings, leaves and flowers. Autophosphorylated. Enhanced susceptibility to geminivirus infection. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.