The basic helix-loop-helix transcription factor TabHLH1 increases chlorogenic acid and luteolin biosynthesis in Taraxacum antungense Kitag

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 (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.

The Effect of Light Intensity on the Chlorogenic Acid Biosynthesis Pathway in Marsdenia tenacissima

“…In addition, some negative regulatory factors were also identified, such as the transcription factor genes AmMYB308 and AmMYB330, which encode the goldfish grass transcription factor, and were transferred into tobacco to inhibit the synthesis of polyphenols, such as chlorogenic acid [36]. In addition, transcription factors such as WRKY [10], ERF [37], and bHLH [38] are also involved in the regulation of chlorogenic acid biosynthesis. In this study, four transcription factors related to the change in chlorogenic acid content under light induction were identified by the WGCNA method, including MYB, SBP, and MIKC.…”

Full‐length transcriptome sequencing and transgenic tobacco revealed the key genes in the chlorogenic acid synthesis pathway of Sambucus chinensis L.

“…TaWRKY14 positively regulates resistance to powdery mildew by up‐regulation of CGA biosynthesis in T. antungense (Liu et al, 2020). Overexpression of bHLH1 increased the content of CGA in Taraxacum antungense Kitag (Liu et al, 2021).…”

Integrative analysis of the metabolome and transcriptome reveals the molecular mechanism of chlorogenic acid synthesis in peach fruit

“…Transcription factors, such as MYB, WRKY, and ERF, can activate or inhibit the expression of structural genes, thereby regulating CGA biosynthesis ( 17 , 21 , 22 ). In this study, we identified 571 TFs, including 172 MYB, 58 WRKY, 120 AP2/ERF, 46 ZIP, 98 bHLH, and 77 WD40.…”

“…Moreover, in L. japonica , the TF LjbZIP8 binds specifically to the G-box element of the LjPAL2 5′-UTR and regulates the synthesis of CGA by inhibiting the expression of PALs ( 21 ). In T. antungense , TabHLH1 binds directly to the bHLH-binding motifs of proTaHQT2 and proTa4CL, and the concentrations of CGA and luteolin are significantly higher in the OE-TabHLH1 transgenic line ( 22 ). In Salvia miltiorrhiza , the overexpression of ERF115 increases phenolic acid content, but silencing it reduces the level of this acid ( 23 ).…”