Dual specificity protein kinase which acts as an essential component of the p38 signal transduction pathway which is also composed of upstream effector nsy-1 and downstream effector pmk-1 (PubMed:11751572). May phosphorylate pmk-1 (PubMed:12142542, PubMed:16166371). Downstream of CaMKII unc-43 and adapter protein tir-1, plays a role in determining asymmetric cell fates in olfactory AWC neurons during neuronal development. Activation results in the repression of odorant receptor str-2 expression in one of the 2 AWC neurons (PubMed:11751572, PubMed:12142542). Involved in resistance to pathogenic Gram-positive and Gram-negative bacterial and fungal infection (PubMed:12142542, PubMed:18394898, PubMed:22216003). Involved in resistance to the nematotoxic C.cinerea galectin Cgl2 (PubMed:20062796). Probably by promoting pmk-1-mediated activation of skn-1, involved in the up-regulation of gcs-1 and glutathione-S-transferase gst-4 expression upon bacterial infection (PubMed:22216003). Probably downstream of tir-1, required for the expression of antimicrobial peptide nlp-29 in the epidermis in response to fungal infection or physical injury (PubMed:18394898, PubMed:22308034). Regulates susceptibility of B.thuringiensis pore-forming toxin Cry5B and Cry21A (PubMed:15256590). Involved in the response to oxidative stress (PubMed:15888317, PubMed:22308034). May regulate transcription factor daf-16 localization during oxidative stress (PubMed:15888317). By phosphorylating pmk-1, regulates skn-1 localization during oxidative stress (PubMed:16166371). By phosphorylating and activating pmk-1, plays a role in the stabilization of transcription factor rnt-1 in the intestine during oxidative stress (PubMed:22308034). Up-regulates expression of gcs-1 in intestine upon arsenite treatment (PubMed:16166371). Regulates germline proliferation in response to osmotic stress, starvation and germline apoptosis induced by heavy metals, such as Cu(2+) (PubMed:16729024, PubMed:19497412). In association with mek-1, regulates germline cell apoptosis in response to oxidative, osmotic and heat shock stresses (PubMed:16729024). Plays a role downstream of tir-1/nsy-1 in regulating susceptibility to anoxia (PubMed:21212236). In males, by regulating pqn-41 expression, involved in non-apoptotic death of the linker cell which guides gonad elongation during larval development (PubMed:22363008). Involved in egg laying (PubMed:12142542). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Activated by nsy-1-mediated phosphorylation. Interacts with nsy-1 (PubMed:11751572). Interacts with unc-16 (PubMed:11738026). Expressed in linker cell in males. By B.thuringiensis pore-forming toxin Cry5B. Upon infection by P.aeruginosa and E.faecalis, RNAi-mediated knockdown results in a reduced up-regulation of gst-4 and gcs-1 expression (PubMed:22216003). Causes a severe reduction in rnt-1 accumulation in the intestine during oxidative stress mediated by paraquat (PubMed:22308034). RNAi-mediated knockdown in a ced-1 mutant background causes a moderate reduction in germline cell apoptosis during oogenesis in response to oxidative and heat shock stresses. The phenotype is more severe and also affects the response to osmotic stress in a mek-1 and ced-1 mutant background (PubMed:16729024). Belongs to the protein kinase superfamily. STE Ser/Thr protein kinase family. MAP kinase kinase subfamily.