Objective To systematically define the composition and structural features of the AP2/ERF family in Oplopanax elatus and to characterize its transcriptional responses to methyl jasmonate (MeJA). Methods Using bioinformatics tools such as HMM, TBtools, and MAFFT to conduct genome-wide identification of AP2/ERF family members, phylogenetic inference, and analyses of protein physicochemical properties, gene structures, and promoter cis-acting elements. In vitro–cultured adventitious roots were treated with 75 μmol/L MeJA for 0–12 h, followed by RNA-seq to profile time-resolved expression patterns of AP2/ERF genes. Results We identified 167 AP2/ERF genes, classified into five subfamilies—ERF, DREB, AP2, RAV, and B3—distributed across 12 chromosomes. Members exhibited broad variation in protein properties (amino acid length, 100—699 aa; molecular mass, 11 410—76 697; isoelectric point, 4.45—11.22; instability index, 23.47—78.46; aliphatic index, 45.52—83.15; grand average of hydropathicity [GRAVY], -1.245 to -0.240). Promoter analysis revealed enrichment of cis-elements associated with light responsiveness, hormone signaling, and stress regulation. RNA-seq showed that MeJA treatment markedly upregulated root-expressed genes encoding enzymes in the triterpenoid saponin pathway. Thirty-two OeAP2/ERF members were MeJA-inducible, among which OeAP2/ERF4, OeAP2/ERF48, OeAP2/ERF131, and OeAP2/ERF143 maintained high expression levels in roots. Conclusion This work delineates the composition and structural characteristics of the AP2/ERF family in O. elatus and defines its time-resolved transcriptional responses to MeJA. Four root-preferential, positively MeJA-responsive transcription factors (OeAP2/ERF4, OeAP2/ERF48, OeAP2/ERF131, and OeAP2/ERF143) are prioritized as key candidates, providing a foundation for functional dissection of AP2/ERF-mediated regulation of triterpenoid saponin biosynthesis and for subsequent metabolic engineering.

Oplopanax elatus Nakai  /  AP2/ERF transcription factors  /  methyl jasmonate  /  triterpenoid saponins  /  expression profiling