An AP2/ERF Family Transcription Factor PnERF1 Raised the Biosynthesis of Saponins in Panax notoginseng

Transcription factors (TFs) are important regulative factors that mediate many life processes. The ERF family of TFs harbors a conserved AP2 domain, which plays vital roles in secondary metabolism in plants. However, few ERF genes in Panax notoginseng have been reported to date. In this study, a P. notoginseng ERF gene was cloned and designated as PnERF1. The cDNA of PnERF1 is 1113 bp long and encodes a protein consisting of 266 amino acids. Electrophoretic mobility shift assay (EMSA) demonstrated that the protein could bind to cis-element GCC-box, indicating that PnERF1 might bind to the promoter regions which contained GCC-box. The expression levels of some genes involved in triterpenoid saponin biosynthesis in PnERF1-transgenic cells were relatively higher than those in the wild cells. Correspondingly, the contents of total saponins were raised in the PnERF1-transgenic cell lines compared to the wild cell lines. Additionally, the contents of six major monomer saponins (Rg3, Rh1, Rd, Rg1, F1 and Re) were also increased in the transgenic cells. Such results suggest that the transcription factor PnERF1 is a positive regulator related to triterpenoid saponin biosynthesis in P. notoginseng.