An RNAi screen of Rab GTPase genes in reveals that somatic cells of the reproductive system depend on for morphogenesis but not stem cell niche maintenance.

Membrane trafficking is a crucial function of all cells and is regulated at multiple levels from vesicle formation, packaging, and localization to fusion, exocytosis, and endocytosis. Rab GTPase proteins are core regulators of eukaryotic membrane trafficking, but developmental roles of specific Rab GTPases are less well characterized, potentially because of their essentiality for basic cellular function. gonad development entails the coordination of cell growth, proliferation, and migration-processes in which membrane trafficking is known to be required. Here we take an organ-focused approach to Rab GTPase function to assess the roles of Rab genes in reproductive system development. We performed a whole-body RNAi screen of the entire Rab family in to uncover Rabs essential for gonad development. Notable gonad defects resulted from RNAi knockdown of the key regulator of ER-Golgi trafficking. We then examined the effects of tissue-specific RNAi knockdown of in somatic reproductive system and germline cells. We interrogated the dual functions of the distal tip cell (DTC) as both a leader cell of gonad organogenesis and the germline stem cell niche. We find that functions cell-autonomously and non-cell-autonomously to regulate both somatic gonad and germline development. Gonad migration, elongation, and gamete differentiation-but surprisingly not germline stem niche function-are highly sensitive to RNAi.