The Drosophila Dead end Arf-like3 GTPase controls vesicle trafficking during tracheal fusion cell morphogenesis

The Drosophila larval tracheal system consists of a highly branched tubular organ that becomes interconnected by migration-fusion events during embryonic development. Fusion cells at the tip of each branch guide migration, adhere, and then undergo extensive remodeling as the tracheal lumen extends between the two branches. The Drosophila dead end gene is expressed in fusion cells, and encodes an Arf-like3 GTPase. Analyses of dead end RNAi and mutant embryos reveal that the lumen fails to connect between the two branches. Expression of a constitutively active form of Dead end in S2 cells reveals that it influences the state of actin polymerization, and is present on particles that traffic along actin/microtubule-containing processes. Imaging experiments in vivo reveal that Dead end-containing vesicles are associated with recycling endosomes and the exocyst, and control exocyst localization in fusion cells. These results indicate that the Dead end GTPase plays an important role in trafficking membrane components involved in tracheal fusion cell morphogenesis and lumenal development.