Polyphenols are the main active components of the anti-inflammatory compounds in dandelion, and chlorogenic acid (CGA) is one of the primary polyphenols. However, the molecular mechanism underlying the transcriptional regulation of CGA biosynthesis remains unclear. Hydroxycinnamoyl-CoA:quinate hydroxycinnamoyl transferase (HQT2) is the last rate-limiting enzyme in chlorogenic acid biosynthesis in Taraxacum antungense. Therefore, using the TaHQT2 gene promoter as a probe, a yeast one-hybrid library was performed, and a basic helix-loop-helix (bHLH) transcription factor, TabHLH1, was identified that shared substantial homology with Gynura bicolor DC bHLH1. The TabHLH1 transcript was highly induced by salt stress, and the TabHLH1 protein was localized in the nucleus. CGA and luteolin concentrations in TabHLH1-overexpression transgenic lines were significantly higher than those in the wild type, while CGA and luteolin concentrations in TabHLH1-RNA interference (RNAi) transgenic lines were significantly lower. Quantitative real-time polymerase chain reaction demonstrated that overexpression and RNAi of TabHLH1 in T. antungense significantly affected CGA and luteolin concentrations by upregulating or downregulating CGA and luteolin biosynthesis pathway genes, especially TaHQT2, 4-coumarate-CoA ligase (Ta4CL), chalcone isomerase (TaCHI), and flavonoid-3′-hydroxylase (TaF3′H). Dual-luciferase, yeast one-hybrid, and electrophoretic mobility shift assays indicated that TabHLH1 directly bound to the bHLH-binding motifs of proTaHQT2 and proTa4CL. This study suggests that TabHLH1 participates in the regulatory network of CGA and luteolin biosynthesis in T. antungense and might be useful for metabolic engineering to promote plant polyphenol biosynthesis.

中文翻译：

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碱性螺旋-环-螺旋转录因子 TabHLH1 增加了蒲公英中绿原酸和木犀草素的生物合成

多酚是蒲公英中抗炎化合物的主要活性成分，绿原酸（CGA）是主要多酚之一。然而，CGA 生物合成转录调控的分子机制仍不清楚。羟基肉桂酰辅酶A:奎宁酸羟基肉桂酰转移酶(HQT2)是绿原酸生物合成的最后一个限速酶蒲公英. 因此，使用TaHQT2基因启动子作为探针，进行酵母单杂交文库，以及碱性螺旋-环-螺旋（bHLH）转录因子，标签HLH1, 已确定与Gynura 双色直流bHLH1. 这标签HLH1转录本受到盐胁迫的高度诱导，并且 TabHLH1 蛋白定位于细胞核中。CGA 和木犀草素浓度标签HLH1-过表达转基因株系显着高于野生型，而TabHLH1-RNA干扰（RNAi）转基因株系中CGA和木犀草素浓度显着降低。定量实时聚合酶链反应表明，过表达和 RNAi标签HLH1在T.antungense通过上调或下调 CGA 和木犀草素生物合成途径基因显着影响 CGA 和木犀草素浓度，尤其是TaHQT2, 4-香豆酸-CoA 连接酶 (Ta4CL), 查尔酮异构酶 (太极) 和类黄酮 3'-羟化酶 (TaF3'H）。双荧光素酶、酵母单杂交体和电泳迁移率变动分析表明，TabHLH1 直接与 BHLH 结合基序结合proTaHQT2和proTa4CL. 本研究表明 TabHLH1 参与了 CGA 和木犀草素生物合成的调控网络T.antungense并且可能有助于代谢工程促进植物多酚的生物合成。