Serine/threonine-protein kinase required in the somatic gonadal cells to regulate germline proliferation during larval development and in adulthood (PubMed:23904186). Plays a role in the development/differentiation of gonadal distal tip cells (PubMed:23904186). Required for normal lifespan in a pha-4 and mxl-2-dependent manner (PubMed:26791749, PubMed:29036198). Also contributes to survival following heat or oxidative stress (PubMed:26791749). Prevents sumoylation and inactivation of heat shock transcription factor hsf-1 which enhances hsf-1-dependent transcriptional induction of chaperones in response to heat shock (PubMed:29036198). Also required for hormetic extension of longevity in response to heat stress (PubMed:29036198). Provides protection against polyglutamine aggregate formation and associated locomotory toxicity (PubMed:29036198). Also contributes to longevity by promoting autophagy under nutrient stress conditions through induction of autophagosome formation and autophagy gene expression (PubMed:29036198). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Localizes to nuclear moving puncta. Puncta number and intensity decrease in the adult (PubMed:12618396). In some large cells, a nuclear speckle pattern can be detected (PubMed:23904186). Broadly expressed during embryogenesis (PubMed:12618396, PubMed:29036198). Expression becomes more restricted during larval development (PubMed:29036198). L3 larvae display robust expression in many head and motor neurons, and lower levels of expression in the intestine and the seam cells of the hypodermis (PubMed:29036198). By late L4 stage, expression is largely restricted to neurons and is maintained in nerve cells of the head and nerve cord during adulthood (PubMed:29036198). Expressed in adult pharyngeal cells, hypodermal cells, gonadal sheath cells and distal tip cells but not in germline cells (PubMed:23904186). Induced by heat stress (PubMed:23904186, PubMed:26791749, PubMed:29036198). Transcription from the hpk-1 promoter is not altered by heat shock treatment, suggesting that heat shock affects hpk-1 levels through a post-transcriptional mechanism (PubMed:26791749). Induction is greatest in hypodermal seam cells and neurons with much lower levels of induction in intestinal cells (PubMed:29036198). Enhanced sensitivity to heat and oxidative stress with reduced survival under both conditions (PubMed:26791749, PubMed:29036198). Following exposure to gamma irradiation, no effect on DNA damage response in the germline but significantly reduced embryonic survival (PubMed:26791749). Significantly reduced lifespan with a more rapid decline in body movement and pharyngeal pumping, indicative of accelerated aging (PubMed:26791749, PubMed:29036198). Premature accumulation of polyglutamine aggregates and increased polyglutamine-associated paralysis at day 8 of adulthood (PubMed:29036198). RNAi-mediated knockdown results in small and underdeveloped germlines with a reduction in the number of cells in G2/M stages (PubMed:23904186). RNAi-mediated knockdown from the L1 larval stage onwards results in shortened lifespan while RNAi-mediated knockdown initiated at the L4 larval stage decreases lifespan to a smaller but significant extent (PubMed:29036198). RNAi-mediated knockdown in the intestine, hypodermis or neurons reduces lifespan while RNAi-mediated knockdown in muscle cells does not (PubMed:29036198). Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. HIPK subfamily.