Two APETALA2/ETHYLENE RESPONSE FACTORS coordinately with CaMYC2 positively regulate capsaicinoid biosynthesis in pepper (Capsicum annuum)

The transcriptional cascade and regulatory loop play crucial roles in regulating plant-specialized metabolite biosynthesis. Capsaicinoids are unique to the genus Capsicum and confer a pungent flavor to its fruits. However, the transcriptional regulation of capsaicinoid biosynthesis remains largely unknown. In this study, two AP2/ERF transcription factors (TFs), CaERF102 and CaERF111, were characterized for their role in the capsaicinoid biosynthesis process. Expression analysis of two ERFs and capsaicinoid biosynthetic genes (CBGs) suggested that they were associated with capsaicinoid biosynthesis. Both ERFs encode nuclear-localized proteins and function as transcriptional activators through their C-terminal activation motifs. The two ERF TFs participated in capsaicinoid biosynthesis by directly activating the promoters of key CBGs, and this activation was significantly enhanced when CaMYC2 was co-expressed. Moreover, CaERF102 and CaERF111 were found to interact with CaMYC2. This study helps elucidate the AP2/ERF TF regulatory network that governs capsaicinoid biosynthesis in Capsicum species.