Plays an essential role in spindle orientation and organizing cellular and embryonic polarity by controlling the localization and activity of PAR (partitioning-defective) proteins. Required for maintaining the asymmetric cortical localization of the anterior complex proteins par-3 and par-6, the posterior cortical protein par-2, and pkc-3 (PubMed:11412996, PubMed:11412997). Involved in hypodermal cell fusion, together with pak-1 and ced-10, leading to embryonic body elongation, which involves dramatic cytoskeletal reorganization (PubMed:8824291). During gonad morphogenesis, plays a role in distal tip cell (DTC)-mediated guidance of gonad elongation, probably by activating max-2 (PubMed:19797046, PubMed:19023419). May play a role in controlling canal length and in maintaining Golgi and ER stability during excretory canal elongation, probably downstream of ccm-3, which may regulate its activity and expression levels (PubMed:25743393). May play a role in yolk protein clatherin-mediated endocytosis by oocytes during oogenesis (PubMed:19798448). Involved in toca-1 and toca-2-mediated protein trafficking controlling the recycling of endocytic cargo protein mig-14 to the Golgi apparatus (PubMed:25775511). Plays a role in male tail tip morphogenesis (PubMed:21408209). Together with kpc-1 and chin-1, plays a role in guiding axons from neurons, including AIY interneurons, into the nerve ring (PubMed:28846083). The GTP-bound, but not the GDP-bound, form binds to the p21-activated kinase (pak-1) (PubMed:8824291). Interaction with par-6 required for activation of the par-3/par-6/pkc-3 complex (PubMed:11412997). Interacts with toca-1 and toca-2 (PubMed:25775511). May interact with unc-89 (via DH and PH domains); the interaction does not stimulate GTPase activity in vitro (PubMed:18801371). Co-localizes with ced-10/rac-1 and pak-1 at hypodermal cell boundaries during embryo elongation (PubMed:8824291). Localizes in punctate cytoplasmic structures along the length of excretory canals (PubMed:25743393). Co-localizes with rme-1 and toca-1 on recycling endosomes (PubMed:25775511). Diffusely localizes in the cytoplasm of tail tip cells, but then localizes to the apical surfaces of the tail tip cells before male tail tip retraction during the L4 larval stage (PubMed:21408209). During male tail tip retraction localizes to the cytoplasm (PubMed:21408209). Expressed in the intestine and seam cells. Highest levels at the embryonic stage, decreasing progressively during development, except for an increase at the L3 stage (PubMed:8514766). Expressed in hypodermal cells during elongation throughout the second phase of embryogenesis (PubMed:8824291). RNAi-mediated knockdown disrupts tail tip morphogenesis resulting in retention of the pointed larval tail tip in adult males (also known as the Lep phenotype) (PubMed:21408209). RNAi-mediated knockdown in distal tip cells (DTC) causes additional turns during their migration (PubMed:19023419). RNAi-mediated knockdown in addition, causes a truncation of excretory canals associated with the formation of cysts and a reduced distribution of Golgi and ER components along the excretory canal length (PubMed:25743393). RNAi-mediated knockdown results in defective endocytosis by oocytes characterized by an accumulation of aggregated yolk protein in the pseudocoelomatic space, and accumulation of endocytic cargo protein mig-14 in late endosomes and expansion of recycling endosomes that express toca-1 and toca-2 (PubMed:19798448, PubMed:25775511). RNAi-mediated knockdown enhances the axon guidance defects in glia and sublateral neurons of the kpc-1 gk mutant, in which non-commissural interneurons AIY fail to extend dorsally and enter the nerve ring (PubMed:28846083). Belongs to the small GTPase superfamily. Rho family. CDC42 subfamily.