Sculpting the endomembrane system in deep time: High resolution phylogenetics of Rab GTPases

• DOI: 10.1242/jcs.101378
• Publication Date: 2012-02-25T01:55:20Z
• Authors: Marek Elias; Andrew Brighouse; Carme Gabernet Ca...; Mark C. Field; Joel B. Dacks
• Keywords: Rab; Endomembrane system

The presence of a nucleus and other membrane-bounded intracellular compartments is the defining feature eukaryotic cells. Endosymbiosis accounts for origins mitochondria plastids, but evolutionary ancestry remaining cellular incompletely documented. Resolving history organelle-identity encoding proteins within endomembrane system necessity unraveling diversification endogenously-derived organelles. Comparative genomics reveals events after last common ancestor (LECA), resolution prior to LECA, full account present in has proved elusive. We have devised exploited novel phylogenetic strategy reconstruct Rab GTPases, key family endomembrane-specificity proteins. Strikingly, we infer remarkably sophisticated organellar composition which predict possessed as many 23 GTPases. This repertoire significantly greater than that modern organisms unexpectedly indicates major role secondary loss system. Two paralogs unknown function wide distribution, thus presumably ancient nature, are identified; RabTitan RTW. Further, show emerged relatively suddenly during early metazoan evolution, stark contrast lack significant expansions at onset most groups. Finally, higher-order ancestral clades Rabs primarily linked with endocytic exocytic process, suggesting primordial associated establishment those pathways giving deepest glimpse date into pre-LECA