The transcription factor PjERF1 enhances the biosynthesis of triterpenoid saponins in Panax japonicus

The ERF-type transcription factors (TFs) play vital roles in plant secondary metabolism. ERF TFs simultaneously regulate the expression levels of key enzyme genes involved in the biosynthesis of secondary metabolites due to its “multi-point control” function. In this study, one gene of ERF TFs from Panax japonicus (PjERF1) was cloned. The open reading frame of PjERF1 was 801 bp and encoded 266 amino acids. Phylogenetic analysis showed that PjERF1 belonged to ERF subfamily with a typical conserved domain. Subcellular localization found that PjERF1 protein might be located in eukaryotic cell nucleus. Yeast one-hybrid assay demonstrated that PjERF1 could bind to the promoters of PjβAS, PjCAS, and PjSE specifically and regulate the expression levels of such key enzyme genes involved in the triterpene saponins biosynthesis. Therefore, in the PjERF1 overexpression cell lines, the expression levels of some key enzyme genes involved in the triterpenoid saponins biosynthesis were significantly increased compared with those in non-transgenic cell line. As a result of it, the biosynthesis of chikusetsusaponin IV and IVa, and other ginsenosides (Rd, Rb1, Re, and R0) were also promoted in the PjERF1 overexpression cell lines. This study indicated that PjERF1 could regulate the biosynthesis of saponins in P. japonicus through controlling the expression levels of key enzyme genes related to the biosynthesis of triterpenoid saponins.