Genome-wide comprehensive characterization and transcriptomic analysis of AP2/ERF gene family revealed its role in seed oil and ALA formation in perilla (Perilla frutescens)

Perilla (Perilla frutescens) is a potential specific oilseed crop with an extremely high alpha-linolenic acid (ALA) content in its seeds. AP2/ERF transcription factors (TFs) play important roles in multiple biological processes. However, limited information is known about the regulatory mechanism of the AP2/ERF family in perilla's oil accumulation. In this research, we identified 212 AP2/ERF family members in the genome of perilla, and their domain characteristics, collinearity, and sub-genome differentiation were comprehensively analyzed. Transcriptome sequencing revealed that genes encoding key enzymes involved in oil biosynthesis (e.g., ACCs, KASII, GPAT, PDAT and LPAAT) were up-regulated in the high-oil variety. Moreover, the endoplasmic reticulum-localized FAD2 and FAD3 were significantly up-regulated in the high-ALA variety. To investigate the roles of AP2/ERFs in lipid biosynthesis, we conducted a correlation analysis between non-redundant AP2/ERFs and key lipid metabolism genes using WGCNA. A significant correlation was found between 36 AP2/ERFs and 90 lipid metabolism genes. Among them, 12 AP2/ERFs were identified as hub genes and showed significant correlation with lipid synthase genes (e.g., FADs, GPAT and ACSL) and key regulatory TFs (e.g., LEC2, IAA, MYB, UPL3). Furthermore, gene expression analysis identified three AP2/ERFs (WRI, ABI4, and RAVI) potentially playing an important role in the regulation of oil accumulation in perilla. Our study suggests that PfAP2/ERFs are important regulatory TFs in the lipid biosynthesis pathway, providing a foundation for the molecular understanding of oil accumulation in perilla and other oilseed crops.