Serine/threonine-protein kinase which is required for normal oogenesis and suppression of germline cell apoptosis. Inhibits phosphorylation and thus probably activation of mpk-1 during pachytene stage (PubMed:19826475). Involved in excretory canal elongation during postembryonic development, probably acting downstream of ccm-3 (PubMed:25743393). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts (via N-terminus) with mpk-1 (isoform a) (PubMed:19826475). Interacts with ccm-3 (PubMed:25743393). Co-localizes with ccm-3 in the apical membrane of the excretory canals. RNAi-mediated knockdown causes sterility resulting from several defects in oogenesis. Proximal ends of the gonads are filled with small germ cells and have a decrease in the number of nuclei in all stages of oogenesis especially at the pachytene stage where there is 60 percent less nuclei. In addition, animals lack a discernible rachis which is a tube-like formation of anucleate cytoplasm between pachytene nuclei, no clear transition into progression from pachytene to diplotene stage and a failure to progress from diplotene into diakinesis. Increased germline cell apoptosis (PubMed:19826475). RNAi-mediated knockdown causes truncated excretory canals associated with the formation of cysts, a reduced distribution of Golgi and ER components along the excretory canals and a decrease in cdc-42 activation (PubMed:25743393). Belongs to the protein kinase superfamily. STE Ser/Thr protein kinase family. STE20 subfamily.