Regulation of Arabidopsis SHY2/IAA3 protein turnover.
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.
Tian
Qing
Q
Department of Biology, University of North Carolina at Chapel Hill, CB #3280, Coker Hall, Chapel Hill, NC 27599-3280, USA.
Nagpal
Punita
P
Reed
Jason W
JW
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D004926:Escherichia coli / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D007700:Kinetics; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000378:metabolism
D029681:Arabidopsis Proteins; D017931:DNA Primers; D009687:Nuclear Proteins; D011994:Recombinant Proteins; C117994:SHY2 protein, Arabidopsis