Interneuron Control of C. elegans Developmental Decision-making
Animals integrate external stimuli to shape their physiological responses throughout development. In adverse environments, Caenorhabditis elegans larvae can enter a stress-resistant diapause state with arrested metabolism and reproductive physiology. Amphid sensory neurons feed into both rapid chemotactic and short-term foraging mode decisions, mediated by amphid and premotor interneurons, as well as the long-term diapause decision. We identify amphid interneurons that integrate pheromone cues and propagate this information via a neuropeptidergic pathways to influence larval developmental fate, bypassing the pre-motor system. AIA interneuron-derived FLP-2 neuropeptide signaling promotes reproductive growth and AIA activity is suppressed by pheromone. FLP-2 acts antagonistically to the insulin-like INS-1. FLP-2s growth promoting effects are inhibited by upstream metabotropic glutamatergic signaling and mediated by the broadly-expressed neuropeptide receptor NPR-30. Conversely, the AIB interneurons and their neuropeptide receptor NPR-9/GALR2 promote diapause entry. These neuropeptidergic outputs allow reuse of parts of a sensory system for a decision with a distinct timescale.