title: Subcellular trafficking of the Arabidopsis auxin influx carrier AUX1 uses a novel pathway distinct from PIN1.
abstract: The directional flow of the plant hormone auxin mediates multiple developmental processes, including patterning and tropisms. Apical and basal plasma membrane localization of AUXIN-RESISTANT1 (AUX1) and PIN-FORMED1 (PIN1) auxin transport components underpins the directionality of intercellular auxin flow in Arabidopsis thaliana roots. Here, we examined the mechanism of polar trafficking of AUX1. Real-time live cell analysis along with subcellular markers revealed that AUX1 resides at the apical plasma membrane of protophloem cells and at highly dynamic subpopulations of Golgi apparatus and endosomes in all cell types. Plasma membrane and intracellular pools of AUX1 are interconnected by actin-dependent constitutive trafficking, which is not sensitive to the vesicle trafficking inhibitor brefeldin A. AUX1 subcellular dynamics are not influenced by the auxin influx inhibitor NOA but are blocked by the auxin efflux inhibitors TIBA and PBA. Furthermore, auxin transport inhibitors and interference with the sterol composition of membranes disrupt polar AUX1 distribution at the plasma membrane. Compared with PIN1 trafficking, AUX1 dynamics display different sensitivities to trafficking inhibitors and are independent of the endosomal trafficking regulator ARF GEF GNOM. Hence, AUX1 uses a novel trafficking pathway in plants that is distinct from PIN trafficking, providing an additional mechanism for the fine regulation of auxin transport.
authors.affiliation: Center for Molecular Biology of Plants, University of Tübingen, D-72076 Tübingen, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kleine-Vehn
authors.forename: Pankaj
authors.initials: P
authors.lastname: Dhonukshe
authors.forename: Ranjan
authors.initials: R
authors.lastname: Swarup
authors.forename: Malcolm
authors.initials: M
authors.lastname: Bennett
authors.forename: Jirí
authors.initials: J
authors.lastname: Friml
mesh_terms: D000199:Actins / Q000378:metabolism; D017360:Arabidopsis / Q000187:drug effects / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D020126:Brefeldin A / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism; D036681:Fluorescence Recovery After Photobleaching; D006056:Golgi Apparatus / Q000187:drug effects / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008954:Models, Biological; D052585:Phloem / Q000166:cytology / Q000187:drug effects; D019441:Plant Epidermis / Q000166:cytology / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D013261:Sterols / Q000378:metabolism
chemical_list: C100794:AUX1 protein, Arabidopsis; D000199:Actins; D029681:Arabidopsis Proteins; C088087:GNOM protein, Arabidopsis; D020662:Guanine Nucleotide Exchange Factors; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; C116363:PIN1 protein, Arabidopsis; D013261:Sterols; D020126:Brefeldin A