The bZIP Transcription Factor PgbZIP48-3 Gene Regulates Ginsenoside Biosynthesis in Panax ginseng

Panax ginseng is a traditional Chinese herbal medicine. Ginsenosides, the main bioactive components responsible for the medicinal value of ginseng, are regulated by transcription factors. Among these regulatory factors, basic leucine zipper (bZIP) transcription factors play crucial roles in plant development and secondary metabolism. To verify that members of the bZIP gene family are involved in regulating ginsenoside biosynthesis and explore their potential mechanisms of action, a correlation analysis was first conducted in this study between the expression levels of PgbZIP genes and ginsenoside content. Additionally, the effects of single-nucleotide polymorphisms (SNPs) and Insertions/Deletions (InDels) on ginsenoside content were analyzed in this study. Through these analyses, PgbZIP48-3, a gene highly associated with ginsenoside biosynthesis, was identified. Subsequently, we systematically analyzed PgbZIP48-3, including its gene structure, protein properties, and phylogenetic relationships. To further verify the function of PgbZIP48-3, an overexpression vector was constructed. Positive ginseng hairy roots were obtained via Agrobacterium-mediated transformation of explants, and the ginsenoside content in these positive hairy roots was determined. The results showed that in the PgbZIP48-3 overexpression positive lines, the contents of ginsenosides Re, Rb2, Rb3, Rc, and Rd were significantly higher than those in the control group, whereas the contents of ginsenosides Rg1, Rf, and Rb1 were lower than those in the control group. Finally, by investigating the SNP/InDel data of PgbZIP48-3 in 346 accessions of a natural P. ginseng population and constructing a predicted interaction map between PgbZIP48-3 and key enzyme genes involved in ginsenoside synthesis, this study preliminarily revealed the potential molecular mechanism by which PgbZIP48-3 regulates ginsenoside biosynthesis from two dimensions: gene mutation and gene expression correlation. Meanwhile, this study provides genetic resources for the breeding of ginseng cultivars with high ginsenoside content.