Auxin-induced, SCFTIR1-mediated poly-ubiquitination marks AUX/IAA proteins for degradation

被引:166
作者
Maraschin, Felipe dos Santos [1 ]
Memelink, Johan [1 ]
Offringa, Remko [1 ]
机构
[1] Leiden Univ, Inst Biol, Clusius Lab, NL-2333 AL Leiden, Netherlands
关键词
auxin response; transcriptional repressor; F-box protein; E3 ubiquitin ligase; 26S proteasome; protoplast; F-BOX PROTEIN; ARABIDOPSIS-THALIANA; MESOPHYLL PROTOPLASTS; TRANSCRIPTION FACTOR; SIGNAL-TRANSDUCTION; GENE-EXPRESSION; RECEPTOR; LIGASE; IDENTIFICATION; SYSTEM;
D O I
10.1111/j.1365-313X.2009.03854.x
中图分类号
Q94 [植物学];
学科分类号
071001 ;
摘要
P>The plant hormone auxin (indole-3-acetic acid or IAA) regulates plant development by inducing rapid cellular responses and changes in gene expression. Auxin promotes the degradation of Aux/IAA transcriptional repressors, thereby allowing auxin response factors (ARFs) to activate the transcription of auxin-responsive genes. Auxin enhances the binding of Aux/IAA proteins to the receptor TIR1, which is an F-box protein that is part of the E3 ubiquitin ligase complex SCFTIR1. Binding of Aux/IAA proteins leads to degradation via the 26S proteasome, but evidence for SCFTIR1-mediated poly-ubiquitination of Aux/IAA proteins is lacking. Here we used an Arabidopsis cell suspension-based protoplast system to find evidence for SCFTIR1-mediated ubiquitination of the Aux/IAA proteins SHY2/IAA3 and BDL/IAA12. Each of these proteins showed a distinct abundance and repressor activity when expressed in this cell system. Moreover, the amount of endogenous TIR1 protein appeared to be rate-limiting for a proper auxin response measured by the co-transfected DR5::GUS reporter construct. Co-transfection with 35S::TIR1 led to auxin-dependent degradation, and excess of 35S::TIR1 even led to degradation of Aux/IAAs in the absence of auxin treatment. Expression of the mutant tir1-1 protein or the related F-box protein COI1, which is involved in jasmonate signaling, had no effect on Aux/IAA degradation. Our results show that SHY2/IAA3 and BDL/IAA12 are poly-ubiquitinated and degraded in response to increased auxin or TIR1 levels. In conclusion, our data provide experimental support for the model that SCFTIR1-dependent poly-ubiquitination of Aux/IAA proteins marks these proteins for degradation by the 26S proteasome, leading to activation of auxin-responsive gene expression.
引用
收藏
页码:100 / 109
页数:10
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