ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Expressed in tail neurons (PVQ and PHAL/PQR). RNAi-mediated knockdown causes no obvious phenotype. Belongs to the protein kinase superfamily. RIO-type Ser/Thr kinase family.