Pre-dauer starvation rapidly and reversibly reduces niche proliferative signaling to the Caenorhabditis elegans germ line

Early life stresses impact reproductive outcomes in many organisms. In response to crowding and starvation, Caenorhabditis elegans nematodes diapause as dauer larvae, in which development arrests until conditions improve. We discovered dramatic differences in gonad size and germ cell number among dauers that form under different conditions. We used live cell imaging of fluorescent proteins in otherwise wild-type and mutant animals combined with food-removal, recovery, and brood-size assays to investigate the causes and consequences of germline differences. Pre-dauer feeding, but not nutrient sensing via the DAF-2/insulin-like signaling receptor or DAF-7/TGFβ, is required for plasticity in gonad size. Gonad differences in dauer have lifelong reproductive consequences; severely starved worms make small dauer gonads and have small broods. Pre-dauer starvation induces germline quiescence and near-instantaneous reduction of the Notch ligand LAG-2 on the germline stem cell niche. A rapid return to germline Notch dependence and an increase in presentation by the germline stem cell niche of LAG-2 - independent of lag-2 transcriptional upregulation - are among the earliest events of dauer recovery.