Identical Amino Acid Substitutions in the Repression Domain of Auxin/Indole-3-Acetic Acid Proteins Have Contrasting Effects on Auxin Signaling
Identical Amino Acid Substitutions in the Repression Domain of Auxin/Indole-3-Acetic Acid Proteins Have Contrasting Effects on Auxin Signaling
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DOI：
10.1104/pp.110.171322
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发表时间：
2011-03-01
期刊：
影响因子：
7.4
通讯作者：
Guilfoyle, Tom J.
中科院分区：
文献类型：
--
作者：
Li, Hanbing;Tiwari, Shiv B.;Guilfoyle, Tom J.
生长素/吲哚-3-乙酸（Aux/IAA）蛋白在细胞中生长素浓度低时作为生长素反应基因表达的阻遏物起作用。在生长素浓度升高时，这些阻遏物通过泛素-蛋白酶体途径被破坏，导致生长素反应基因的去阻遏/激活。大多数Aux/IAA阻遏物含有四个保守的结构域，其中一个是活性的、可携带的阻遏结构域（结构域I），第二个是生长素依赖的不稳定结构域（结构域II）。在这里，我们分析了氨基酸取代的抑制结构域中的选择Aux/IAA蛋白的影响。我们表明，当在转化的拟南芥（Arabidopsis thaliana）植物中表达时，在结构域I中具有氨基酸取代的稳定版本的Aux/IAA蛋白显示出截然不同的表型。当在转化的拟南芥植物中从35 S或IAA 19启动子表达时（如用IAA 19测试的），IAA 3、IAA 6或IAA 19的LxLxL（其中L是亮氨酸，x是另一种氨基酸）阻遏结构域中的丙氨酸取代亮氨酸赋予增强的生长素应答基因表达和“高生长素”表型。与此形成鲜明对比的是，IAA 12或IAA 17的结构域I中的单个丙氨酸取代亮氨酸赋予生长素反应基因和“低生长素”表型的阻遏。这些结果表明IAA蛋白的阻遏结构域存在内在差异，并表明某些IAA蛋白具有比其他蛋白更强或更复杂的阻遏结构域。
Auxin/indole-3-acetic acid (Aux/IAA) proteins function as repressors of auxin response gene expression when auxin concentrations in a cell are low. At elevated auxin concentrations, these repressors are destroyed via the ubiquitin-proteasome pathway, resulting in derepression/activation of auxin response genes. Most Aux/IAA repressors contain four conserved domains, with one of these being an active, portable repression domain (domain I) and a second being an auxin-dependent instability domain (domain II). Here, we have analyzed the effects of amino acid substitutions in the repression domain of selected Aux/IAA proteins. We show that stabilized versions of Aux/IAA proteins with amino acid substitutions in domain I display contrasting phenotypes when expressed in transformed Arabidopsis (Arabidopsis thaliana) plants. An alanine-for-leucine substitution in the LxLxL (where L is leucine and x is another amino acid) repression domain of IAA3, IAA6, or IAA19 confers enhanced auxin response gene expression and "high-auxin" phenotypes when expressed from the 35S or IAA19 promoter (as tested with IAA19) in transformed Arabidopsis plants. In marked contrast, a single alanine-for-leucine substitution in domain I of IAA12 or IAA17 confers repression of auxin response genes and "low-auxin" phenotypes. These results point to intrinsic differences in the repression domain(s) of IAA proteins and suggest that some IAA proteins have stronger or more complex repression domains than others.