title: GTPase ROP2 binds and promotes activation of target of rapamycin, TOR, in response to auxin.
abstract: Target of rapamycin (TOR) promotes reinitiation at upstream ORFs (uORFs) in genes that play important roles in stem cell regulation and organogenesis in plants. Here, we report that the small GTPase ROP2, if activated by the phytohormone auxin, promotes activation of TOR, and thus translation reinitiation of uORF-containing mRNAs. Plants with high levels of active ROP2, including those expressing constitutively active ROP2 (CA-ROP2), contain high levels of active TOR ROP2 physically interacts with and, when GTP-bound, activates TORin vitroTOR activation in response to auxin is abolished in ROP-deficientrop2 rop6 ROP4 RNAiplants. GFP-TOR can associate with endosome-like structures in ROP2-overexpressing plants, indicating that endosomes mediate ROP2 effects on TOR activation. CA-ROP2 is efficient in loading uORF-containing mRNAs onto polysomes and stimulates translation in protoplasts, and both processes are sensitive to TOR inhibitor AZD-8055. TOR inactivation abolishes ROP2 regulation of translation reinitiation, but not its effects on cytoskeleton or intracellular trafficking. These findings imply a mode of translation control whereby, as an upstream effector of TOR, ROP2 coordinates TOR function in translation reinitiation pathways in response to auxin.
authors.affiliation: Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, UPR 2357, Université de Strasbourg, Strasbourg, France.
authors.forename: Mikhail
authors.initials: M
authors.lastname: Schepetilnikov
authors.affiliation: Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, UPR 2357, Université de Strasbourg, Strasbourg, France.
authors.forename: Joelle
authors.initials: J
authors.lastname: Makarian
authors.affiliation: Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, UPR 2357, Université de Strasbourg, Strasbourg, France.
authors.forename: Ola
authors.initials: O
authors.lastname: Srour
authors.affiliation: Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, UPR 2357, Université de Strasbourg, Strasbourg, France.
authors.forename: Angèle
authors.initials: A
authors.lastname: Geldreich
authors.affiliation: Department of Botany and Plant Sciences, Center for Plant Cell Biology, University of California, Riverside, CA, USA.
authors.forename: Zhenbiao
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Plateforme Proteómique Strasbourg-Esplanade, Centre National de la Recherche Scientifique, FRC 1589, Université de Strasbourg, Strasbourg, France.
authors.forename: Johana
authors.initials: J
authors.lastname: Chicher
authors.affiliation: Plateforme Proteómique Strasbourg-Esplanade, Centre National de la Recherche Scientifique, FRC 1589, Université de Strasbourg, Strasbourg, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Hammann
authors.affiliation: Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, UPR 2357, Université de Strasbourg, Strasbourg, France lyuba.ryabova@ibmp-cnrs.unistra.fr.
authors.forename: Lyubov A
authors.identifier: 0000-0003-1989-203X
authors.initials: LA
authors.lastname: Ryabova
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D029681:Arabidopsis Proteins; D019204:GTP-Binding Proteins; D007210:Indoleacetic Acids; D019869:Phosphatidylinositol 3-Kinases; D010937:Plant Growth Regulators; C512171:TOR protein, Arabidopsis; C499714:AT1G20090 protein, Arabidopsis
keywords: S6K1; endosomes; phosphorylation; phytohormone auxin; signal transduction