title: Sterol-dependent endocytosis mediates post-cytokinetic acquisition of PIN2 auxin efflux carrier polarity.
abstract: The polarization of yeast and animal cells relies on membrane sterols for polar targeting of proteins to the plasma membrane, their polar endocytic recycling and restricted lateral diffusion. However, little is known about sterol function in plant-cell polarity. Directional root growth along the gravity vector requires polar transport of the plant hormone auxin. In Arabidopsis, asymmetric plasma membrane localization of the PIN-FORMED2 (PIN2) auxin transporter directs root gravitropism. Although the composition of membrane sterols influences gravitropism and localization of two other PIN proteins, it remains unknown how sterols contribute mechanistically to PIN polarity. Here, we show that correct membrane sterol composition is essential for the acquisition of PIN2 polarity. Polar PIN2 localization is defective in the sterol-biosynthesis mutant cyclopropylsterol isomerase1-1 (cpi1-1) which displays altered sterol composition, PIN2 endocytosis, and root gravitropism. At the end of cytokinesis, PIN2 localizes initially to both newly formed membranes but subsequently disappears from one. By contrast, PIN2 frequently remains at both daughter membranes in endocytosis-defective cpi1-1 cells. Hence, sterol composition affects post-cytokinetic acquisition of PIN2 polarity by endocytosis, suggesting a mechanism for sterol action on establishment of asymmetric protein localization.
authors.affiliation: Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-90183 Umeå, Sweden.
authors.forename: Shuzhen
authors.initials: S
authors.lastname: Men
authors.forename: Yohann
authors.initials: Y
authors.lastname: Boutté
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Ikeda
authors.forename: Xugang
authors.initials: X
authors.lastname: Li
authors.forename: Klaus
authors.initials: K
authors.lastname: Palme
authors.forename: York-Dieter
authors.initials: YD
authors.lastname: Stierhof
authors.forename: Marie-Andrée
authors.initials: MA
authors.lastname: Hartmann
authors.forename: Thomas
authors.initials: T
authors.lastname: Moritz
authors.forename: Markus
authors.initials: M
authors.lastname: Grebe
mesh_terms: D017360:Arabidopsis / Q000378:metabolism / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D004705:Endocytosis / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D019753:Intramolecular Lyases / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D010937:Plant Growth Regulators / Q000378:metabolism / Q000494:pharmacology; D018517:Plant Roots / Q000502:physiology; D013261:Sterols / Q000378:metabolism* / Q000494:pharmacology; D018523:Tropism
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D019753:Intramolecular Lyases; D010937:Plant Growth Regulators; D013261:Sterols; C117013:AT5G57090 protein, Arabidopsis; C408484:cycloeucalenol cycloisomerase