Serine/threonine-protein kinase which is required for ciliogenesis. Regulates the length and the morphology of sensory neuron cilia. In addition, plays a role in the anterograde intraflagellar transport (IFT) in the cilia by regulating the undocking of kinesin-II motor complex (composed of klp-11, klp-20 and kap-1) before reaching the distal segment and the docking of kinesin motor osm-3 onto IFT cargos. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Enriched at the transition zone between the base of the cilia and the dendrites and to a lesser extent in the cilia. Expressed in head neurons including amphid and labial sensory neurons and 3 pairs of neurons in the tail including phasmid sensory neurons. In male, expressed in the tail including the sensory rays and the spicule. Sensory neuron cilia are longer, not correctly aligned in the amphid channel, more dispersed, misdirected and sometimes turned back towards the transition zone. Abnormal localization of kap-1 along the full cilia length. Abnormal accumulation in the middle of cilia and in the distal segment and reduced speed along the cilium axoneme of components of the IFT machinery kap-1, osm-3, xbx-1, che-11 and osm-5. In a kap-1 mutant background, 30 percent of mutants have branched cilia. In a kap-1 and osm-3 double mutant background, loss of cilia formation. Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. RCK subfamily.