title: The TIR1 protein of Arabidopsis functions in auxin response and is related to human SKP2 and yeast grr1p.
abstract: Genetic analysis in Arabidopsis has led to the identification of several genes that are required for auxin response. One of these genes, AXR1, encodes a protein related to yeast Aos1p, a protein that functions to activate the ubiquitin-related protein Smt3p. Here we report the identification of a new gene called TRANSPORT INHIBITOR RESPONSE 1 (TIR1). The tir1 mutants are deficient in a variety of auxin-regulated growth processes including hypocotyl elongation and lateral root formation. These results indicate that TIR1 is also required for normal response to auxin. Further, mutations in TIR1 display a synergistic interaction with mutations in AXR1, suggesting that the two genes function in overlapping pathways. The TIR1 protein contains a series of leucine-rich repeats and a recently identified motif called an F box. Sequence comparisons indicate that TIR1 is related to the yeast protein Grr1p and the human protein SKP2. Because Grr1p and other F-box proteins have been implicated in ubiquitin-mediated processes, we speculate that auxin response depends on the modification of a key regulatory protein(s) by ubiquitin or a ubiquitin-related protein.
authors.affiliation: Department of Biology, Indiana University, Bloomington, Indiana 47405 USA.
authors.forename: M
authors.initials: M
authors.lastname: Ruegger
authors.forename: E
authors.initials: E
authors.lastname: Dewey
authors.forename: W M
authors.initials: WM
authors.lastname: Gray
authors.forename: L
authors.initials: L
authors.lastname: Hobbie
authors.forename: J
authors.initials: J
authors.lastname: Turner
authors.forename: M
authors.initials: M
authors.lastname: Estelle
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000494:pharmacology; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins; D002455:Cell Division / Q000502:physiology; D017343:Genes, Plant; D005808:Genes, Recessive; D005838:Genotype; D006133:Growth Substances; D007210:Indoleacetic Acids / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D010797:Phthalimides / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology; D018517:Plant Roots / Q000187:drug effects; D028901:alpha Karyopherins
chemical_list: C081977:AXR1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D006133:Growth Substances; D007210:Indoleacetic Acids; D009687:Nuclear Proteins; D010797:Phthalimides; D010940:Plant Proteins; D028901:alpha Karyopherins; D015084:2,4-Dichlorophenoxyacetic Acid; C002687:alpha-naphthylphthalamic acid