MYB-bHLH-WDR (MBW) transcription factor (TF) complexes regulate Arabidopsis seed coat development including mucilage and tannin biosynthesis. The R2R3 MYBs MYB5, MYB23 and TRANSPARENT TESTA2 (TT2) participate in the MBW complexes with the WD-repeat protein TRANSPARENT TESTA GLABRA1 (TTG1). These complexes regulate GLABRA2 (GL2) and TTG2 expression in developing seeds. Microarray transcriptome analysis of ttg1-1- and wild-type (Ler) developing seeds identified 246 TTG1-regulated genes, which include all known metabolic genes of the tannin biosynthetic pathway. The first detailed TTG1-dependent metabolic pathways could be proposed for the biosynthesis of mucilage, jasmonic acid (JA) and cuticle including wax ester in developing seeds. We also assigned many known and previously uncharacterized genes to the activation/inactivation of hormones, plant immunity and nutrient transport. The promoters of six cuticle pathway genes were active in developing seeds. Expression of 11 genes was determined in the developing seeds of the combinatorial mutants of MYB5, MYB23 and TT2, and in the combinatorial mutants of GL2, HOMEODOMAIN GLABROUS2 (HDG2) and TTG2. These six TFs positively co-regulated the expression of four repressor genes while three of the six TFs repressed the wax biosynthesis genes examined, suggesting that the three TFs upregulate the expression of these repressor genes, which, in turn, repress the wax biosynthesis genes. Chromatin immunoprecipitation analysis identified 21 genes directly regulated by MYB5 including GL2, HDG2, TTG2, four repressor genes and various metabolic genes. We propose a multi-tiered regulatory mechanism by which MBWs regulate tannin, mucilage, JA and cuticle biosynthetic pathways.

中文翻译：

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MYB-bHLH-TTG1通过多层转录因子直接和间接调节拟南芥种子皮生物合成途径。

MYB-bHLH-WDR（MBW）转录因子（TF）复合物调节拟南芥种皮的发育，包括粘液和单宁的生物合成。R2R3 MYB MYB5，MYB23和TRANSPARENT TESTA2（TT2）与WD重复蛋白TRANSPARENT TESTA GLABRA1（TTG1）一起参与MBW复合体。这些复合物调节发育中种子中的GLABRA2（GL2）和TTG2表达。ttg1-1和野生型（Ler）发育中的种子的微阵列转录组分析确定了246个TTG1调控的基因，其中包括单宁生物合成途径的所有已知代谢基因。可以提出第一个详细的TTG1依赖性代谢途径，用于发育中的种子中粘液，茉莉酸（JA）和表皮（包括蜡酯）的生物合成。我们还为激素的激活/失活分配了许多已知的和以前未知的基因，植物免疫力和养分转运。六个表皮途径基因的启动子在发育中的种子中活跃。在MYB5，MYB23和TT2组合突变体的发育种子中以及在GL2，HOMEODOMAIN GLABROUS2（HDG2）和TTG2的组合突变体中确定了11个基因的表达。这六个TF积极地共同调节了四个阻抑基因的表达，而六个TF中的三个则抑制了所检测的蜡生物合成基因，这表明三个TF上调了这些阻抑基因的表达，从而反过来又抑制了蜡生物合成基因。染色质免疫沉淀分析鉴定了21种受MYB5直接调控的基因，包括GL2，HDG2，TTG2，四个阻抑基因和各种代谢基因。我们提出了一种多层监管机制，MBW通过该机制来监管单宁，粘液，