Molecular Cloning and Characterization of PnbHLH1 Transcription Factor in Panax notoginseng

Abstract

<i>Panax notoginseng</i> has been extensively used as a traditional Chinese medicine. In the current study, molecular cloning and characterization of PnbHLH1 transcription factor were explored in <i>Panax notoginseng</i>. The full length of the <i>PnbHLH1</i> gene obtained by splicing was 1430 bp, encoding 321 amino acids. Prokaryotic expression vector <i>pET-28a-PnbHLH1</i> was constructed and transferred into the <i>BL21</i> prokaryotic expression strain. An electrophoretic mobility shift assay of PnbHLH1 protein binding to E-box cis-acting elements verified that PnbHLH1 belonged to the bHLH class transcription factor which could interact with the promoter region of the E-box core sequence. The expression levels of key genes involved in the biosynthesis of triterpenoid saponins in <i>PnbHLH1</i> transgenic cells were higher than those in the wild cells. Similarly, the total saponin contents were increased in the <i>PnbHLH1</i> transgenic cell lines compared with the wild cell lines. Such results suggest that the <i>PnbHLH1</i> transcription factor is a positive regulator in the biosynthesis of triterpenoid saponins in <i>Panax notoginseng</i>.