title: A membrane trafficking pathway regulated by the plant-specific RAB GTPase ARA6.
abstract: Endosomal trafficking plays an integral role in various eukaryotic cell activities and serves as a basis for higher-order functions in multicellular organisms. An understanding of the importance of endosomal trafficking in plants is rapidly developing, but its molecular mechanism is mostly unknown. Several key regulators of endosomal trafficking, including RAB5, which regulates diverse endocytic events in animal cells, are highly conserved. However, the identification of lineage-specific regulators in eukaryotes indicates that endosomal trafficking is diversified according to distinct body plans and lifestyles. In addition to orthologues of metazoan RAB5, land plants possess a unique RAB5 molecule, which is one of the most prominent features of plant RAB GTPase organization. Plants have also evolved a unique repertoire of SNAREs, the most distinctive of which are diverse VAMP7-related longins, including plant-unique VAMP72 derivatives. Here, we demonstrate that a plant-unique RAB5 protein, ARA6, acts in an endosomal trafficking pathway in Arabidopsis thaliana. ARA6 modulates the assembly of a distinct SNARE complex from conventional RAB5, and has a functional role in the salinity stress response. Our results indicate that plants possess a unique endosomal trafficking network and provide the first indication of a functional link between a specific RAB and a specific SNARE complex in plants.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Ebine
authors.forename: Masaru
authors.initials: M
authors.lastname: Fujimoto
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Okatani
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Nishiyama
authors.forename: Tatsuaki
authors.initials: T
authors.lastname: Goh
authors.forename: Emi
authors.initials: E
authors.lastname: Ito
authors.forename: Tomoko
authors.initials: T
authors.lastname: Dainobu
authors.forename: Aiko
authors.initials: A
authors.lastname: Nishitani
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Uemura
authors.forename: Masa H
authors.initials: MH
authors.lastname: Sato
authors.forename: Hans
authors.initials: H
authors.lastname: Thordal-Christensen
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Tsutsumi
authors.forename: Akihiko
authors.initials: A
authors.lastname: Nakano
authors.forename: Takashi
authors.initials: T
authors.lastname: Ueda
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology*; D011992:Endosomes / Q000201:enzymology*; D005838:Genotype; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D009154:Mutation; D010641:Phenotype; D030821:Plants, Genetically Modified; D021381:Protein Transport; D050765:Qa-SNARE Proteins / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D050600:SNARE Proteins / Q000378:metabolism; D012965:Sodium Chloride / Q000378:metabolism; D013312:Stress, Physiological; D013997:Time Factors; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C479425:PEN1 protein, Arabidopsis; D050765:Qa-SNARE Proteins; D011993:Recombinant Fusion Proteins; D050600:SNARE Proteins; C108430:Vam3 protein, Arabidopsis; D012965:Sodium Chloride; C436706:Ara6 protein, Arabidopsis; D020691:rab GTP-Binding Proteins