Insulin signaling activity in the somatic gonad controls dauer entry via the germ line in C. elegans.

C. elegans displays remarkable developmental plasticity in response to environmental conditions. Under favorable conditions-for example, when food is abundant-larvae develop rapidly and continuously through four larval stages (L1-L4) separated by molts to reproductive adulthood. In adverse conditions, L1 larvae enter an alternative developmental pathway comprising a prolonged second larval stage ("L2d") and a prolonged molt into dauer diapause. Dauer larvae survive in a state of suspended development, with precursor cells maintained in a quiescent state, for many times the normal lifespan of a worm. If conditions improve, dauer larvae recover and resume reproductive development. A canonical insulin/insulin growth factor (IGF) signaling (IIS) pathway, comprising DAF-2/insulin receptor, the signal transducer AKT, and the transcription factor DAF-16/FoxO, is a major input into the global decision between reproductive development and dauer entry. Previous studies have suggested that IIS has a diffuse cellular focus for regulating dauer entry, but here we have identified a specific cellular focus by showing that low IIS activity in the somatic gonad is sufficient to promote entry into dauer diapause. Furthermore, we show that laser ablation of the germline precursors suppresses dauer entry when DAF-2 is depleted in the somatic gonad, demonstrating that the germ line acts with the somatic gonad as a signaling nexus. Our analysis implicates the somatic gonad as an endocrine organ for regulating a critical life history decision and identifies an unexpected role for the germ line in orchestrating the global somatic development of an individual.