Fig. 7: Proposed model of the role of TabHLH1 in regulating polyphenol biosynthesis.

Using the HQT2 promoter E-box region as a probe, a bHLH transcription factor (named TabHLH1) was obtained by yeast one-hybrid screening. TabHLH1 significantly promoted the expression levels of key enzyme genes in the polyphenol biosynthesis pathway, including 4CL, HQT, CHI, and F3′H, thus increasing CGA and luteolin accumulation