Regulation of the anthocyanin biosynthetic pathway by the TTG1/bHLH/Myb transcriptional complex in Arabidopsis seedlings
Regulation of the anthocyanin biosynthetic pathway by the TTG1/bHLH/Myb transcriptional complex in Arabidopsis seedlings
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DOI：
10.1111/j.1365-313x.2007.03373.x
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发表时间：
2008-03-01
期刊：
影响因子：
7.2
通讯作者：
Lloyd, Alan M.
中科院分区：
文献类型：
--
作者：
Gonzalez, Antonio;Zhao, Mingzhe;Lloyd, Alan M.
在迄今为止研究的所有高等植物中，花青素色素途径由一系列转录因子调控，包括Myb， bHLH和WD-repeat蛋白。然而，在拟南芥中，Myb调控因子仍未被最终确定，而ttg1依赖性转录复合物对花青素通路的调控知之甚少。先前PAP1 Myb的过表达表明，与其他植物不同，拟南芥中来自整个苯丙素途径的基因是Myb/bHLH/WD-repeat复合物调控的靶标。在这里，我们证明了Myb113或Myb114的过表达导致色素产生的大幅增加，这与之前看到的PAP1过表达的结果相似，并且这些过表达者的色素产生仍然依赖于TTG1-和bhhl。此外，含有针对PAP1和3种Myb候选物（PAP2、Myb113和Myb114）的RNAi构建体的植物显示Myb基因表达下调和明显的花青素缺乏。与这些花青素缺乏相关的是ttg1和bHLH花青素突变体中相同的晚期花青素结构基因的下调。GL3:GR和TTG1:GR融合的表达研究显示，只有晚期生物合成基因可以直接调控。GL3:GR在单株和双株bHLH突变苗上的研究揭示了GL3和EGL3在基因靶标激活方面的功能多样化。Myb和bHLH调节因子的表达谱也在幼苗色素生产的背景下提出。
In all higher plants studied to date, the anthocyanin pigment pathway is regulated by a suite of transcription factors that include Myb, bHLH and WD-repeat proteins. However, in Arabidopsis thaliana, the Myb regulators remain to be conclusively identified, and little is known about anthocyanin pathway regulation by TTG1-dependent transcriptional complexes. Previous overexpression of the PAP1 Myb suggested that genes from the entire phenylpropanoid pathway are targets of regulation by Myb/bHLH/WD-repeat complexes in Arabidopsis, in contrast to other plants. Here we demonstrate that overexpression of Myb113 or Myb114 results in substantial increases in pigment production similar to those previously seen as a result of over-expression of PAP1, and pigment production in these overexpressors remains TTG1- and bHLH-dependent. Also, plants harboring an RNAi construct targeting PAP1 and three Myb candidates (PAP2, Myb113 and Myb114) showed downregulated Myb gene expression and obvious anthocyanin deficiencies. Correlated with these anthocyanin deficiencies is downregulation of the same late anthocyanin structural genes that are downregulated in ttg1 and bHLH anthocyanin mutants. Expression studies using GL3:GR and TTG1:GR fusions revealed direct regulation of the late biosynthetic genes only. Functional diversification between GL3 and EGL3 with regard to activation of gene targets was revealed by GL3:GR studies in single and double bHLH mutant seedlings. Expression profiles for Myb and bHLH regulators are also presented in the context of pigment production in young seedlings.