Endogenously tagged rab proteins: a resource to study membrane trafficking in Drosophila.

Membrane trafficking is key to the cell biological mechanisms underlying development. Rab GTPases control specific membrane compartments, from core secretory and endocytic machinery to less-well-understood compartments. We tagged all 27 Drosophila Rabs with YFP(MYC) at their endogenous chromosomal loci, determined their expression and subcellular localization in six tissues comprising 23 cell types, and provide this data in an annotated, searchable image database. We demonstrate the utility of these lines for controlled knockdown and show that similar subcellular localization can predict redundant functions. We exploit this comprehensive resource to ask whether a common Rab compartment architecture underlies epithelial polarity. Strikingly, no single arrangement of Rabs characterizes the five epithelia we examine. Rather, epithelia flexibly polarize Rab distribution, producing membrane trafficking architectures that are tissue- and stage-specific. Thus, the core machinery responsible for epithelial polarization is unlikely to rely on polarized positioning of specific Rab compartments.