title: Rab-A2 and Rab-A3 GTPases define a trans-golgi endosomal membrane domain in Arabidopsis that contributes substantially to the cell plate.
abstract: The Ypt3/Rab11/Rab25 subfamily of Rab GTPases has expanded greatly in Arabidopsis thaliana, comprising 26 members in six provisional subclasses, Rab-A1 to Rab-A6. We show that the Rab-A2 and Rab-A3 subclasses define a novel post-Golgi membrane domain in Arabidopsis root tips. The Rab-A2/A3 compartment was distinct from but often close to Golgi stacks and prevacuolar compartments and partly overlapped the VHA-a1 trans-Golgi compartment. It was also sensitive to brefeldin A and accumulated FM4-64 before prevacuolar compartments did. Mutations in RAB-A2a that were predicted to stabilize the GDP- or GTP-bound state shifted the location of the protein to the Golgi or plasma membrane, respectively. In mitosis, KNOLLE accumulated principally in the Rab-A2/A3 compartment. During cytokinesis, Rab-A2 and Rab-A3 proteins localized precisely to the growing margins of the cell plate, but VHA-a1, GNOM, and prevacuolar markers were excluded. Inducible expression of dominant-inhibitory mutants of RAB-A2a resulted in enlarged, polynucleate, meristematic cells with cell wall stubs. The Rab-A2/A3 compartment, therefore, is a trans-Golgi compartment that communicates with the plasma membrane and early endosomal system and contributes substantially to the cell plate. Despite the unique features of plant cytokinesis, membrane traffic to the division plane exhibits surprising molecular similarity across eukaryotic kingdoms in its reliance on Ypt3/Rab11/Rab-A GTPases.
authors.affiliation: Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom.
authors.forename: Cheung-Ming
authors.initials: CM
authors.lastname: Chow
authors.forename: Hélia
authors.initials: H
authors.lastname: Neto
authors.forename: Camille
authors.initials: C
authors.lastname: Foucart
authors.forename: Ian
authors.initials: I
authors.lastname: Moore
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000378:metabolism; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000201:enzymology*; D048749:Cytokinesis; D011992:Endosomes / Q000201:enzymology*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D021381:Protein Transport; D011726:Pyridinium Compounds / Q000378:metabolism; D050765:Qa-SNARE Proteins / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014617:Vacuoles / Q000201:enzymology; D020691:rab GTP-Binding Proteins / Q000378:metabolism*; D021601:trans-Golgi Network / Q000201:enzymology*
chemical_list: D029681:Arabidopsis Proteins; C092350:FM 4-64; C097724:KNOLLE protein, Arabidopsis; D011726:Pyridinium Compounds; D050765:Qa-SNARE Proteins; D000644:Quaternary Ammonium Compounds; D011993:Recombinant Fusion Proteins; D006160:Guanosine Triphosphate; D020691:rab GTP-Binding Proteins