Aux/IAA proteins are phosphorylated by phytochrome in vitro
Aux/IAA proteins are phosphorylated by phytochrome in vitro
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DOI：
10.1104/pp.124.4.1728
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发表时间：
2000-12-01
期刊：
影响因子：
7.4
通讯作者：
Abel, S
中科院分区：
文献类型：
--
作者：
Colón-Carmona, A;Chen, DL;Abel, S
生长素/吲哚-3-乙酸(AUX/IAA)基因编码短暂的转录因子，这些转录因子是对植物生长激素IAA或生长素的初级反应。拟南芥基因SHY2/IAA3、AXR3/IAA17和AXR2/IAA7的功能获得突变导致与生长素反应增强一致的多效性表型，这可能是通过增加AUX/IAA蛋白的稳定性来实现的。半显性突变shy2-1D、shy2-2、axr3-1和axr2-1在暗生长的幼苗中诱导异位光反应。由于遗传学研究表明shy2-1D和shy2-2突变绕过了光形态发生的某些方面对光敏色素的要求，我们测试了SHY2/IAA3和相关的AUX/IAA蛋白是否直接与光敏色素相互作用，以及它们是否是其蛋白激酶活性的底物。在这里，我们发现来自拟南芥和豌豆的重组AUX/IAA蛋白在体外与来自燕麦的重组光敏色素A相互作用。我们进一步证明，重组燕麦光敏色素A在体外可使重组的SHY2/IAA3、AXR3/IAA17、IAA1、IAA9和Ps-IAA4磷酸化。对Ps-IAA4的缺失分析表明，光敏色素A的磷酸化发生在蛋白质的N-末端。用亲和纯化的IAA3抗体进行的代谢标记和免疫沉淀研究表明，在体内，突变的IAA3在shy2-2植物中的稳定水平增加，并且SHY2-2蛋白在体内被磷酸化。AUX/IAA蛋白的光敏色素依赖的磷酸化为植物发育中生长素和光信号的整合提供了一种分子机制。
Auxin/indole-3-acetic acid (Aux/IAA) genes encode short-lived transcription factors that are induced as a primary response to the plant growth hormone IAA or auxin. Gain-of-function mutations in Arabidopsis genes, SHY2/IAA3, AXR3/IAA17, and AXR2/IAA7 cause pleiotropic phenotypes consistent with enhanced auxin responses, possibly by increasing Aux/IAA protein stability. Semidominant mutations shy2-1D, shy2-2, axr3-1, and axr2-1 induce ectopic light responses in dark-grown seedlings. Because genetic studies suggest that the shy2-1D and shy2-2 mutations bypass phytochrome requirement for certain aspects of photomorphogenesis, we tested whether SHY2/IAA3 and related Aux/IAA proteins interact directly with phytochrome and whether they are substrates for its protein kinase activity. Here we show that recombinant Aux/IAA proteins from Arabidopsis and pea (Pisum sativum) interact in vitro with recombinant phytochrome A from oat (Avena sativa). We further show that recombinant SHY2/IAA3, AXR3/IAA17, IAA1, IAA9, and Ps-IAA4 are phosphorylated by recombinant oat phytochrome A in vitro. Deletion analysis of Ps-IAA4 indicates that phytochrome A phosphorylation occurs on the N-terminal half of the protein. Metabolic labeling and immunoprecipitation studies with affinity-purified antibodies to IAA3 demonstrate increased in vivo steady-state levels of mutant IAA3 in shy2-2 plants and phosphorylation of the SHY2-2 protein in vivo. Phytochrome-dependent phosphorylation of Aux/IAA proteins is proposed to provide one molecular mechanism for integrating auxin and light signaling in plant development.