A serine-threonine kinase involved in the hypersensitive response (HR)-mediated signaling cascade. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with PTO. Autophosphorylated at threonine residues and to a lesser extent at serine residues. Phosphorylated in vitro by PTO at threonine residues and to a lesser extent at serine residues. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.