Plays a role in spindle positioning during asymmetric division of one-cell stage embryos. Affects spindle position by promoting microtubule assembly during anaphase. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with tac-1. Enriched at microtubule asters throughout the cell cycle and is present on the spindle during mitosis. Maternal-effect embryonic lethal resulting in dramatic spindle positioning defects in one-cell stage embryos. Belongs to the protein kinase superfamily. CAMK Ser/Thr protein kinase family. CaMK subfamily.