title: ARF GEF-dependent transcytosis and polar delivery of PIN auxin carriers in Arabidopsis.
abstract: Cell polarity manifested by the polar cargo delivery to different plasma-membrane domains is a fundamental feature of multicellular organisms. Pathways for polar delivery have been identified in animals; prominent among them is transcytosis, which involves cargo movement between different sides of the cell [1]. PIN transporters are prominent polar cargoes in plants, whose polar subcellular localization determines the directional flow of the signaling molecule auxin [2, 3]. In this study, we address the cellular mechanisms of PIN polar targeting and dynamic polarity changes. We show that apical and basal PIN targeting pathways are interconnected but molecularly distinct by means of ARF GEF vesicle-trafficking regulators. Pharmacological or genetic interference with the Arabidopsis ARF GEF GNOM leads specifically to apicalization of basal cargoes such as PIN1. We visualize the translocation of PIN proteins between the opposite sides of polarized cells in vivo and show that this PIN transcytosis occurs by endocytic recycling and alternative recruitment of the same cargo molecules by apical and basal targeting machineries. Our data suggest that an ARF GEF-dependent transcytosis-like mechanism is operational in plants and provides a plausible mechanism to trigger changes in PIN polarity and hence auxin fluxes during embryogenesis and organogenesis.
authors.affiliation: Department of Plant Systems Biology, Flanders Institute for Biotechnology VIB, Ghent University, 9052 Gent, Belgium.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kleine-Vehn
authors.forename: Pankaj
authors.initials: P
authors.lastname: Dhonukshe
authors.forename: Michael
authors.initials: M
authors.lastname: Sauer
authors.forename: Philip B
authors.initials: PB
authors.lastname: Brewer
authors.forename: Justyna
authors.initials: J
authors.lastname: Wiśniewska
authors.forename: Tomasz
authors.initials: T
authors.lastname: Paciorek
authors.forename: Eva
authors.initials: E
authors.lastname: Benková
authors.forename: Jirí
authors.initials: J
authors.lastname: Friml
mesh_terms: D017360:Arabidopsis / Q000196:embryology / Q000378:metabolism* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000378:metabolism*; D020126:Brefeldin A; D016764:Cell Polarity / Q000502:physiology*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism*; D009024:Morphogenesis / Q000502:physiology; D022161:Transport Vesicles / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; C088087:GNOM protein, Arabidopsis; D020662:Guanine Nucleotide Exchange Factors; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; C116363:PIN1 protein, Arabidopsis; D020126:Brefeldin A