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Article|01 Sep 2021|OPEN
The basic helix-loop-helix transcription factor TabHLH1 increases chlorogenic acid and luteolin biosynthesis in Taraxacum antungense Kitag
Qun Liu1,2,3, Li Li2, Haitao Cheng4, Lixiang Yao5, Jie Wu6, Hui Huang1, Wei Ning2, & Guoyin Kai 1,
1Laboratory for Core Technology of TCM Quality Improvement and Transformation, College of Pharmacy, School of Pharmaceutical Sciences, The Third Affiliated Hospital, Zhejiang Chinese Medical University, Hangzhou, Zhejiang 310053, PR China
2College of Horticulture, Shenyang Agricultural University, Shenyang 110866, China
3Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem.Sun Yat-Sen), Nanjing 210014, China
4College of Traditional Chinese Materia Medica, Shenyang Pharmaceutical University, Shenyang 110016, PR China
5Guangxi Botanical Garden of Medicinal Plants, Nanning 530023, PR China
6College of Life Sciences and Engineering, Shenyang University, Shenyang 110044, PR China

Horticulture Research 8,
Article number: 195 (2021)
doi: 10.1038/hortres.2021.195
Views: 93

Received: 09 Dec 2020
Revised: 30 Apr 2021
Accepted: 07 Jun 2021
Published online: 01 Sep 2021

Abstract

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 (TaF3H). 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.