Serine/threonine-protein kinase which, by phosphorylating and activating sek-1, plays an important role in the activation of the p38 pathway also composed of the downstream effectors sek-1 and pmk-1 (PubMed:11751572, PubMed:12142542, PubMed:21212236, PubMed:24448648). 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:11336672, PubMed:11751572, PubMed:15625192). Involved in resistance to pathogenic Gram-positive and Gram-negative bacterial and fungal infection (PubMed:12142542, PubMed:18394898, PubMed:24448648). Involved in resistance to the nematotoxic C.cinerea galectin Cgl2 (PubMed:20062796). Probably by activating the sek1/pmk-1/skn-1 pathway, 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 and nipi-3, required for the expression of antimicrobial peptide nlp-29 in the epidermis in response to fungal infection or physical injury (PubMed:18394898). Plays a role in resistance to several environmental stresses including oxidative, protein misfolding (ER) and osmotic stresses, and DNA-damaging reagents (PubMed:21212236, PubMed:15888317). Plays a role in the stabilization of transcription factor rnt-1 in the intestine during oxidative stress (PubMed:22308034). Involved in germline apoptosis induced by heavy metals, such as Cu(2+) (PubMed:19497412). In addition, plays a role in the up-regulation of gcs-1 upon arsenite treatment, most likely through activation of pmk-1, to confer protection against toxicity induced by heavy metals (PubMed:25204677). Plays a role downstream of tir-1 in regulating susceptibility to anoxia (PubMed:21212236). 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] Interacts with unc-43 (PubMed:11336672). Interacts with sek-1 (PubMed:11751572). Localizes to post-synaptic regions and is enriched in punctate structures in AWC neuron axon where co-localizes with tir-1. Localization is regulated by tir-1. Expressed in intestine, hypodermis, rectal gland cell and neurons including sensory AWC neurons. May be phosphorylated upon pathogenic bacterial infection. May be regulated by proteosomal degradation mediated by the E3-ubiquitin ligase rle-1. RNAi-mediated knockdown results in an increase in survival rate in anoxic conditions (PubMed:21212236). Upon infection by P.aeruginosa and E.faecalis, RNAi-mediated knockdown results in a moderate reduction in the 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). Belongs to the protein kinase superfamily. STE Ser/Thr protein kinase family. MAP kinase kinase kinase subfamily.