title: Arabidopsis SGT1b is required for SCF(TIR1)-mediated auxin response.
abstract: The SCF(TIR1) complex is a central regulator of the auxin response pathway in Arabidopsis. This complex functions as a ubiquitin protein ligase that targets members of the auxin/indoleacetic acid (Aux/IAA) family of transcriptional regulators for ubiquitin-mediated degradation in response to auxin. In an attempt to identify additional factors required for SCF(TIR1) activity, we conducted a genetic screen to isolate enhancers of the auxin response defect conferred by the tir1-1 mutation. Here, we report the identification and characterization of the eta3 mutant. The eta3 mutation interacts synergistically with tir1-1 to strongly enhance all aspects of the tir1 mutant phenotype, including auxin inhibition of root growth, lateral root development, hypocotyl elongation at high temperature, and apical dominance. We isolated the ETA3 gene using a map-based cloning strategy and determined that ETA3 encodes SGT1b. SGT1b was identified recently as a factor involved in plant disease resistance signaling, and SGT1 from barley and tobacco extracts was shown to interact with SCF ubiquitin ligases. We conclude that ETA3/SGT1b is required for the SCF(TIR1)-mediated degradation of Aux/IAA proteins.
authors.affiliation: Department of Plant Biology, University of Minnesota--Twin Cities, St. Paul, Minnesota 55108, USA. grayx051@tc.umn.edu
authors.forename: William M
authors.initials: WM
authors.lastname: Gray
authors.forename: Paul R
authors.initials: PR
authors.lastname: Muskett
authors.forename: Huey-wen
authors.initials: HW
authors.lastname: Chuang
authors.forename: Jane E
authors.initials: JE
authors.lastname: Parker
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D003517:Cyclopentanes / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D018546:Hypocotyl / Q000254:growth & development; D007113:Immunity, Innate / Q000235:genetics; D007210:Indoleacetic Acids / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009154:Mutation; D054883:Oxylipins; D010453:Peptide Synthases / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D018517:Plant Roots / Q000254:growth & development; D044843:SKP Cullin F-Box Protein Ligases; D015398:Signal Transduction / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; D003517:Cyclopentanes; D007210:Indoleacetic Acids; D054883:Oxylipins; C452192:SGT1b protein, Arabidopsis; C011006:jasmonic acid; C030737:indoleacetic acid; D044843:SKP Cullin F-Box Protein Ligases; D010453:Peptide Synthases