Regulation of Arabidopsis SHY2/IAA3 protein turnover

Plant J. 2003 Dec;36(5):643-51. doi: 10.1046/j.1365-313x.2003.01909.x.


Auxin/indole acetic acid (Aux/IAA) proteins regulate transcriptional responses to the plant hormone auxin. Gain-of-function mutations in the Arabidopsis SHORT HYPOCOTYL 2 (SHY2/IAA3) gene encoding an Aux/IAA protein increase steady-state levels of SHY2/IAA3 protein and decrease auxin responses, indicating that SHY2/IAA3 negatively regulates auxin signaling. These shy2 mutations also cause ectopic light responses, suggesting that SHY2/IAA3 may promote light signaling. Auxin regulates turnover of the related Auxin-resistant (AXR)2/IAA7 and AXR3/IAA17 proteins by increasing their interaction with the Skp1-Cdc53/cullin-F-box (SCFTIR1) E3 ubiquitin ligase complex. To investigate whether SHY2/IAA3 is regulated similarly, we have used a turnover assay to reveal that axr1 and transport inhibitor resistant (tir)1 mutations affecting SCFTIR1 decrease SHY2/IAA3 turnover. In pull-down assays, SHY2/IAA3 protein interacted with TIR1, the F-box component of SCFTIR1 and with the photoreceptor phytochrome B. Auxin stimulated SHY2/IAA3 interaction with TIR1, whereas the shy2-2 gain-of-function mutation decreased this interaction. Light did not affect the interaction, suggesting that light regulates some other aspect of Aux/IAA gene or protein function. The chemical juglone (5-hydroxy-1,4-naphthoquinone) inhibited the interaction, suggesting that peptidyl-prolyl isomerization may mediate auxin-induced SHY2/IAA3 protein turnover.

Publication types

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

MeSH terms

  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Base Sequence
  • Cloning, Molecular
  • DNA Primers
  • Escherichia coli / genetics
  • Gene Expression Regulation, Plant / genetics
  • Kinetics
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Polymerase Chain Reaction
  • Recombinant Proteins / metabolism


  • Arabidopsis Proteins
  • DNA Primers
  • Nuclear Proteins
  • Recombinant Proteins
  • SHY2 protein, Arabidopsis