An RNAi screen of Rab GTPase genes inC. elegansreveals that somatic cells of the reproductive system depend onrab-1for morphogenesis but not stem cell niche maintenance

Abstract

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.C. elegansgonad development entails the coordination of cell growth, proliferation, and migrationprocesses in which membrane trafficking is known to be required. Here we take an organ-focused approach to Rab GTPase functionin vivoto assess the roles of Rab genes in reproductive system development. We performed a whole-body RNAi screen of the entire Rab family inC. elegansto uncover Rabs essential for gonad development. Notable gonad defects resulted from RNAi knockdown ofrab-1, the key regulator of ER-Golgi trafficking. We then examined the effects of tissue-specific RNAi knockdown ofrab-1in 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 thatrab-1functions cell-autonomously and non-cell-autonomously to regulate both somatic gonad and germline development. Gonad migration, elongation, and gamete differentiationbut surprisingly not germline stem niche functionare highly sensitive torab-1RNAi.