Transcriptome-wide analysis of the AP2/ERF transcription factor gene family involved in the regulation of gypenoside biosynthesis in Gynostemma pentaphyllum

Gynostemma pentaphyllum is a traditional Chinese medicinal herb, serving as natural source of gypenosides (triterpene saponins). The APETALA2/ethylene response factor (AP2/ERF) transcription factors, playing essential regulation roles in plant biotic and abiotic stress responses and secondary metabolism biosynthesis. However, the regulation roles of AP2/ERF transcription factors in gypenosides biosynthesis in G. pentaphyllum remains little understood. In the present study, 125 AP2/ERF genes were identified from G. pentaphyllum transcriptome datasets. Phylogenetic, conserved motifs and expression pattern were employed to comprehensively analyze the 125 GpAP2/ERF genes. Based on the sequence similarity and phylogeny tree, the 125 GpAP2/ERF genes can be classified into 10 groups. Moreover, the distribution of conserved motifs among GpAP2/ERF proteins in phylogenetic trees was consistent with previous studies, thus supporting the classification. Expression profiling indicated that the 125 GpAP2/ERF genes exhibited distinct tissue-specific expression patterns. As confirmed by qRT-PCR, the four candidate GpAP2/ERF genes and gypenoside biosynthetic genes were highly expressed in leaves and/or flowers, and show similar expression patterns in response to MeJA. Base on the expression patterns and phylogenetic relationships, two GpAP2/ERF genes were considered as potential regulatory genes for gypenoside biosynthesis. Our study enhances understanding roles of GpAP2/ERF genes in regulation of gypenosides biosynthesis.