Parasitoid cues modulate Drosophila germline development and stem cell proliferation.

Environmental factors influence an organism's reproductive ability by regulating germline development and physiology. While the reproductive adaptations in response to extrinsic stress cues offer fitness and survival advantages to individuals, the mechanistic understanding of these modifications remains unclear. Here, we find that parasitoid wasps' stress signaling regulates Drosophila melanogaster oogenesis. We show that fruit flies dwelling in the wasp-infested area elevate their fecundity, and the observed reproductive response is specific to Pachycrepoideus sp., a pupal parasitoid wasp. Pachycrepoideus-specific olfactory and visual cues recruit the signaling pathways that promote germline stem cell proliferation and accelerate follicle development, increasing egg production in Drosophila females. Downregulation of signaling engaged in oocyte development by shifting flies to a non-wasp-infested environment increases apoptosis of the developing follicles. Thus, this study establishes host germline responsiveness to parasitoid-specific signals and supports a predator strategy to increase hosts for infection.