Plays an essential role in proper timing of early development events. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] May be regulated by calcium or a calmodulin-like protein. Developmentally regulated to start immediately before spore formation. Autophosphorylated. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.