| Summary: | Summary: Although typically upregulated upon cellular stress, autophagy can also be utilized under homeostatic conditions as a quality control mechanism or in response to developmental cues. Here, we report that autophagy is required for the maintenance of somatic cyst stem cells (CySCs) in the Drosophila testis. Disruption of autophagy in CySCs and early cyst cells (CCs) by the depletion of autophagy-related (Atg) genes reduced early CC numbers and affected CC function, resembling decreased epidermal growth factor receptor (EGFR) signaling. Indeed, our data indicate that EGFR acts to stimulate autophagy to preserve early CC function, whereas target of rapamycin (TOR) negatively regulates autophagy in the differentiating CCs. Finally, we show that the EGFR-mediated stimulation of autophagy regulates lipid levels in CySCs and CCs. These results demonstrate a key role for autophagy in regulating somatic stem cell behavior and tissue homeostasis by integrating cues from both the EGFR and TOR signaling pathways to control lipid metabolism. : Sênos Demarco et al. demonstrate that Drosophila somatic cyst stem cells (CySCs) rely on basal levels of autophagy, which is regulated by EGFR signaling, for maintenance under homeostatic conditions. Blocking autophagy results in the accumulation of lipid droplets; therefore, one role of autophagy is to regulate lipid homeostasis in the soma. Keywords: autophagy, EGFR, TOR, Drosophila, lipids, somatic stem cells, testis
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