ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Expressed in the whole plant, but preferentially in young seedlings and rosette leaves. By salicylic acid (SA). Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. CRK subfamily. Truncated N-terminus.