title: Arabidopsis SMALL AUXIN UP RNA63 promotes hypocotyl and stamen filament elongation.
abstract: Auxin regulates plant growth and development in part by activating gene expression. Arabidopsis thaliana SMALL AUXIN UP RNAs (SAURs) are a family of early auxin-responsive genes with unknown functionality. Here, we show that transgenic plant lines expressing artificial microRNA constructs (aMIR-SAUR-A or -B) that target a SAUR subfamily (SAUR61-SAUR68 and SAUR75) had slightly reduced hypocotyl and stamen filament elongation. In contrast, transgenic plants expressing SAUR63:GFP or SAUR63:GUS fusions had long hypocotyls, petals and stamen filaments, suggesting that these protein fusions caused a gain of function. SAUR63:GFP and SAUR63:GUS seedlings also accumulated a higher level of basipetally transported auxin in the hypocotyl than did wild-type seedlings, and had wavy hypocotyls and twisted inflorescence stems. Mutations in auxin efflux carriers could partially suppress some SAUR63:GUS phenotypes. In contrast, SAUR63:HA plants had wild-type elongation and auxin transport. SAUR63:GFP protein had a longer half-life than SAUR63:HA. Fluorescence imaging and microsomal fractionation studies revealed that SAUR63:GFP was localized mainly in the plasma membrane, whereas SAUR63:HA was present in both soluble and membrane fractions. Low light conditions increased SAUR63:HA protein turnover rate. These results indicate that membrane-associated Arabidopsis SAUR63 promotes auxin-stimulated organ elongation.
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, NC 27599-3280, USA.
authors.forename: Keun
authors.initials: K
authors.lastname: Chae
authors.forename: Cameron G
authors.initials: CG
authors.lastname: Isaacs
authors.forename: Paul H
authors.initials: PH
authors.lastname: Reeves
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Maloney
authors.forename: Gloria K
authors.initials: GK
authors.lastname: Muday
authors.forename: Punita
authors.initials: P
authors.lastname: Nagpal
authors.forename: Jason W
authors.initials: JW
authors.lastname: Reed
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001692:Biological Transport / Q000235:genetics; D002462:Cell Membrane / Q000378:metabolism; D035264:Flowers / Q000235:genetics* / Q000254:growth & development*; D018506:Gene Expression Regulation, Plant; D006207:Half-Life; D018546:Hypocotyl / Q000235:genetics* / Q000254:growth & development*; D007210:Indoleacetic Acids / Q000378:metabolism; D008027:Light; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D035683:MicroRNAs; D018520:Plant Shoots / Q000235:genetics; D030821:Plants, Genetically Modified; D018749:RNA, Plant; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D008565:Membrane Proteins; D035683:MicroRNAs; D018749:RNA, Plant; D011993:Recombinant Fusion Proteins; C580620:SAUR-63 protein, Arabidopsis