Required for larval development. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Expressed in pharynx (metacorpus and posterior bulbus). Expression is restricted to adult stage. RNAi-mediated knockdown causes early larval arrest. In adults, results in no obvious phenotype. Belongs to the protein kinase superfamily. RIO-type Ser/Thr kinase family.