title: Arabidopsis iba response5 suppressors separate responses to various hormones.
abstract: Auxin controls numerous plant growth processes by directing cell division and expansion. Auxin-response mutants, including iba response5 (ibr5), exhibit a long root and decreased lateral root production in response to exogenous auxins. ibr5 also displays resistance to the phytohormone abscisic acid (ABA). We found that the sar3 suppressor of auxin resistant1 (axr1) mutant does not suppress ibr5 auxin-response defects, suggesting that screening for ibr5 suppressors might reveal new components important for phytohormone responsiveness. We identified two classes of Arabidopsis thaliana mutants that suppressed ibr5 resistance to indole-3-butyric acid (IBA): those with restored responses to both the auxin precursor IBA and the active auxin indole-3-acetic acid (IAA) and those with restored response to IBA but not IAA. Restored IAA sensitivity was accompanied by restored ABA responsiveness, whereas suppressors that remained IAA resistant also remained ABA resistant. Some suppressors restored sensitivity to both natural and synthetic auxins; others restored responsiveness only to auxin precursors. We used positional information to determine that one ibr5 suppressor carried a mutation in PLEIOTROPIC DRUG RESISTANCE9 (PDR9/ABCG37/At3g53480), which encodes an ATP-binding cassette transporter previously implicated in cellular efflux of the synthetic auxin 2,4-dichlorophenoxyacetic acid.
authors.affiliation: Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005, USA.
authors.forename: Lucia C
authors.initials: LC
authors.lastname: Strader
authors.forename: Melanie
authors.initials: M
authors.lastname: Monroe-Augustus
authors.forename: Kristen C
authors.initials: KC
authors.lastname: Rogers
authors.forename: Grace L
authors.initials: GL
authors.lastname: Lin
authors.forename: Bonnie
authors.initials: B
authors.lastname: Bartel
mesh_terms: D000070996:ATP Binding Cassette Transporter, Subfamily G; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000040:Abscisic Acid / Q000378:metabolism; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D054637:Dual-Specificity Phosphatases / Q000235:genetics* / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism / Q000494:pharmacology*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D010937:Plant Growth Regulators / Q000378:metabolism / Q000494:pharmacology*; D013489:Suppression, Genetic
chemical_list: D000070996:ATP Binding Cassette Transporter, Subfamily G; D018528:ATP-Binding Cassette Transporters; C081977:AXR1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; C515019:PDR9 protein, Arabidopsis; D010937:Plant Growth Regulators; C030737:indoleacetic acid; D000040:Abscisic Acid; D054637:Dual-Specificity Phosphatases; C483728:IBR5 protein, Arabidopsis