May have a role in germline establishment. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Speckled subnuclear compartment. In stage 3 embryos, both isoforms are expressed in both somatic and pole cell nuclei. Expression in pole cell nuclei is sustained until stage 9 and weakly expressed after pole cell invagination into the abdominal cavity. Expressed both maternally and zygotically in adult females. Levels of the long isoform remain fairly constant from ovaries to embryos, the levels of short isoform decrease dramatically. Does not affect male germline stem cells maintenance (PubMed:34644293). In the germline, RNAi-mediated knockdown of Rtel1 in lok mutant background results in partial rescue of single Rtel1 knockdown phenotype which includes loss of germline stem cell and reduced levels of Stat92E expression (PubMed:34644293). Belongs to the protein kinase superfamily. CAMK Ser/Thr protein kinase family. CDS1 subfamily.