Arabidopsis SMALL AUXIN UP RNA63 promotes hypocotyl and stamen filament elongation

Plant J. 2012 Aug;71(4):684-97. doi: 10.1111/j.1365-313X.2012.05024.x. Epub 2012 Jun 14.


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.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Arabidopsis / genetics*
  • Arabidopsis / growth & development
  • Arabidopsis Proteins / genetics*
  • Arabidopsis Proteins / metabolism
  • Biological Transport / genetics
  • Cell Membrane / metabolism
  • Flowers / genetics*
  • Flowers / growth & development*
  • Gene Expression Regulation, Plant
  • Half-Life
  • Hypocotyl / genetics*
  • Hypocotyl / growth & development*
  • Indoleacetic Acids / metabolism
  • Light
  • Membrane Proteins / genetics*
  • Membrane Proteins / metabolism
  • MicroRNAs
  • Plant Shoots / genetics
  • Plants, Genetically Modified
  • RNA, Plant
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism


  • Arabidopsis Proteins
  • Indoleacetic Acids
  • Membrane Proteins
  • MicroRNAs
  • RNA, Plant
  • Recombinant Fusion Proteins
  • SAUR-63 protein, Arabidopsis