title: Cellular and molecular requirements for polar PIN targeting and transcytosis in plants.
abstract: The polar, sub-cellular localization of PIN auxin efflux carriers determines the direction of intercellular auxin flow, thus defining the spatial aspect of auxin signalling. Dynamic, transcytosis-like relocalizations of PIN proteins occur in response to external and internal signals, integrating these signals into changes in auxin distribution. Here, we examine the cellular and molecular mechanisms of polar PIN delivery and transcytosis. The mechanisms of the ARF-GEF-dependent polar targeting and transcytosis are well conserved and show little variations among diverse Arabidopsis ecotypes consistent with their fundamental importance in regulating plant development. At the cellular level, we refine previous findings on the role of the actin cytoskeleton in apical and basal PIN targeting, and identify a previously unknown role for microtubules, specifically in basal targeting. PIN protein delivery to different sides of the cell is mediated by ARF-dependent trafficking with a previously unknown complex level of distinct ARF-GEF vesicle trafficking regulators. Our data suggest that alternative recruitment of PIN proteins by these distinct pathways can account for cell type- and cargo-specific aspects of polar targeting, as well as for polarity changes in response to different signals. The resulting dynamic PIN positioning to different sides of cells defines a three-dimensional pattern of auxin fluxes within plant tissues.
authors.affiliation: Department of Plant Systems Biology, Ghent University, 9052 Gent, Belgium.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kleine-Vehn
authors.forename: Lukasz
authors.initials: L
authors.lastname: Langowski
authors.forename: Justyna
authors.initials: J
authors.lastname: Wisniewska
authors.forename: Pankaj
authors.initials: P
authors.lastname: Dhonukshe
authors.forename: Philip B
authors.initials: PB
authors.lastname: Brewer
authors.forename: Jirí
authors.initials: J
authors.lastname: Friml
mesh_terms: D020727:ADP-Ribosylation Factors / Q000378:metabolism; D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D020126:Brefeldin A / Q000494:pharmacology; D016764:Cell Polarity / Q000187:drug effects; D004705:Endocytosis / Q000187:drug effects; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D009928:Organ Specificity / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects
chemical_list: D020727:ADP-Ribosylation Factors; D000199:Actins; D029681:Arabidopsis Proteins; D020126:Brefeldin A; D020662:Guanine Nucleotide Exchange Factors; D026901:Membrane Transport Proteins; C116363:PIN1 protein, Arabidopsis; C117013:AT5G57090 protein, Arabidopsis