Department of Plant Breeding and Genetics, Cornell University, Ithaca, NY 14853, USA.
Planta. 2012 Oct;236(4):1153-64. doi: 10.1007/s00425-012-1665-3. Epub 2012 May 29.
Purple cauliflower (Brassica oleracea L. var. botrytis) Graffiti represents a unique mutant in conferring ectopic anthocyanin biosynthesis, which is caused by the tissue-specific activation of BoMYB2, an ortholog of Arabidopsis PAP2 or MYB113. To gain a better understanding of the regulatory network of anthocyanin biosynthesis, we investigated the interaction among cauliflower MYB-bHLH-WD40 network proteins and examined the interplay of BoMYB2 with various bHLH transcription factors in planta. Yeast two-hybrid studies revealed that cauliflower BoMYBs along with the other regulators formed the MYB-bHLH-WD40 complexes and BobHLH1 acted as a bridge between BoMYB and BoWD40-1 proteins. Different BoMYBs exhibited different binding activity to BobHLH1. Examination of the BoMYB2 transgenic lines in Arabidopsis bHLH mutant backgrounds demonstrated that TT8, EGL3, and GL3 were all involved in the BoMYB2-mediated anthocyanin biosynthesis. Expression of BoMYB2 in Arabidopsis caused up-regulation of AtTT8 and AtEGL3 as well as a subset of anthocyanin structural genes encoding flavonoid 3'-hydroxylase, dihydroflavonol 4-reductase, and leucoanthocyanidin dioxygenase. Taken together, our results show that MYB-bHLH-WD40 network transcription factors regulated the bHLH gene expression, which may represent a critical feature in the control of anthocyanin biosynthesis. BoMYB2 together with various BobHLHs specifically regulated the late anthocyanin biosynthetic pathway genes for anthocyanin biosynthesis. Our findings provide additional information for the complicated regulatory network of anthocyanin biosynthesis and the transcriptional regulation of transcription factors in vegetable crops.
紫色花椰菜（ Brassica oleracea L. var. botrytis ）涂鸦代表了一种独特的突变体，它通过组织特异性激活 BoMYB2 赋予异位类黄酮生物合成，BoMYB2 是拟南芥 PAP2 或 MYB113 的同源物。为了更好地理解类黄酮生物合成的调控网络，我们研究了花椰菜 MYB-bHLH-WD40 网络蛋白之间的相互作用，并检查了 BoMYB2 与各种 bHLH 转录因子在体内的相互作用。酵母双杂交研究表明，花椰菜 BoMYBs 与其他调节剂一起形成 MYB-bHLH-WD40 复合物，而 BobHLH1 充当 BoMYB 和 BoWD40-1 蛋白之间的桥梁。不同的 BoMYBs 对 BobHLH1 表现出不同的结合活性。在拟南芥 bHLH 突变体背景下对 BoMYB2 转基因系的检查表明，TT8、EGL3 和 GL3 均参与了 BoMYB2 介导的类黄酮生物合成。BoMYB2 在拟南芥中的表达导致 AtTT8 和 AtEGL3 的上调以及黄酮 3'-羟化酶、二氢黄酮醇 4-还原酶和无色花青素双加氧酶等一系列类黄酮结构基因的表达。总之，我们的结果表明，MYB-bHLH-WD40 网络转录因子调节 bHLH 基因的表达，这可能是控制类黄酮生物合成的一个关键特征。BoMYB2 与各种 BobHLHs 一起特异性调节晚期类黄酮生物合成途径基因，用于类黄酮生物合成。我们的发现为蔬菜作物中类黄酮生物合成的复杂调控网络和转录因子的转录调控提供了更多信息。
