Phosphorylates oma-1, a regulator of the oocyte-to-embryo transition, enabling its degradation (PubMed:16343905, PubMed:16289132). Phosphorylates skn-1, preventing it from accumulating in nuclei and thus inhibiting phase II gene expression in the oxidative stress defense (PubMed:16251270). Involved in mesendoderm specification and mitotic spindle orientation in EMS blastomeres (PubMed:11463373). Thought to be a branch point in these processes as proteins downstream are not required (PubMed:10444600). Negatively regulates Wnt signaling in vulval precursor cells and acts as a Wnt-independent repressor of med-1 and med-2 in the C lineage inhibiting mesoderm development (PubMed:10444600, PubMed:11463373, PubMed:15572126). Required for normal lifespan and LiCl-induced lifespan extension (PubMed:17959600). ATP + L-seryl-[tau protein] = ADP + H(+) + O-phospho-L-seryl-[tau protein] ATP + L-threonyl-[tau protein] = ADP + H(+) + O-phospho-L-threonyl-[tau protein] Monomer (By similarity). Interacts with axl-1. Worms exhibit defects in endoderm specification and mitotic spindle alignment (PubMed:10444600). RNAi-mediated knockdown results in stability and delayed degradation of the maternal oocyte protein oma-1 in embryos beyond the 2-cell stage (PubMed:16289132). Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. GSK-3 subfamily.