Gametogenesis and mating are two essential components of animal reproduction. Gametogenesis must be modulated by the need for gametes, yet little is known of how mating, a process that consumes gametes, may modulate the process of gametogenesis at the cellular level.
Here we report that mating stimulates female germline stem cell (GSC) proliferation via neuronal and endocrine systems in Drosophila. Mating-induced GSC proliferation is not simply owing to the indirect effect of emission of stored eggs, but rather is caused by a sex peptide (SP) and its receptor SPR, the canonical pathway to transduce the signal from male seminal fluid to female flies. We also identify ecdysteroid, the principal insect steroid hormone, as a key mediator of GSC proliferation after mating. Importantly, ovarian ecdysteroid biosynthesis is induced by neuronal SP signaling, suggesting that GSC proliferation is under the control of the characterized neuroendocrine system in response to an external stimulus, mating.
Previous studies and our own analysis, however, suggest that SPR gene is not expressed in GSC cells or GSC niche cells. Therefore, neuroendocrine mechanisms transmitting SP signals to GSCs still remain to be elucidated. To address this question, we carried out a transgenic RNAi screen to search genes that are required for transmits SP signals to GSCs. We examined GSC phenotypes in females in which a wide variety of membrane receptor genes in neurons as well as GSC niche cells have been knocked down. We identify 50 candidate genes, including 13 neuropeptide receptors, which are potentially involved in controlling mating-induced GSC proliferation. We also show that genes encoding ligands for some of the neuropeptide receptors are expressed in the midgut and are required for mating-induced GSC proliferation. Moreover, overexpression of the ligand genes are sufficient to induce GSC proliferation. These results suggest that neuropeptide signaling mediates mating-induced GSC proliferation via the hormonal interactions among different tissues. Our work reveals a novel role of neuropeptide signaling in regulating GSC proliferation that coordinates gametogenesis in response to the stimulus of mating.
In this presentation, the relationship between SP, ecdysteroid and neuropeptide in regulating GSC will be discussed.