Screening of AP2/ERF transcription factors regulating the squalene synthase gene of Panax japonicusand their functional analysis in triterpenoid saponin biosynthesis

AP2/ERF is one of the largest transcription factor families in plants and has become a promising candidate gene for studying plant stress responses and the biosynthesis of bioactive compounds. An increasing number of plant AP2/ERF families and their members have been reported. Based on transcriptome data, three AP2/ERF CDS sequences were obtained and named PjERF-I, PjERF-II, and PjERF-III, respectively. Using the squalene synthase gene of Panax japonicus as the key structural gene, yeast two-hybrid technology identified that PjERF-I and PjERF-II can specifically bind to PjSS. The PjERF-I open reading frame was obtained through gene cloning, spanning 666 bp and encoding 221 amino acids. PjERF-I exhibits high homology with other ERF transcription factors, suggesting its classification within the ERF family. A three-dimensional structure for PjERF-I was constructed using the tertiary structure of Panax notoginseng ERF (PnERF: A0A3Q8D532.1.A) as a template, achieving 97.74% sequence identity.