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.

To improve the understanding of molecular mechanisms of anther and/or pollen development in Chili pepper, in the present study, full-length cDNA and DNA sequences of the pollen development-related gene CaMF5 were obtained from the anthers of a Capsicum annuum nuclear male-fertile line. Sequence analysis indicated that the full length of CaMF5 was 747 bp, containing a maximum opening reading frame of 447 bp. Amino acid sequence alignment and phylogenetic analysis revealed that CaMF5 shared approximately 37%–77% homology with a series of uncharacterized or hypothetical proteins and late embryogenesis abundant (LEA) proteins from other plants. However, no LEA structural domain was detected in CaMF5, which indicated that it might be a new type of LEA gene. CaMF5 was only expressed in flower buds at stages 7 and 8 and in open flowers of the male-fertile line, whereas it exhibited no expression in any examined organs of the male-sterile line. In addition, CaMF5 showed the highest transcript abundance in the anthers of the male-fertile line, with no expression being detected in any other examined organs, such as the sepals, petals, pistils, roots, stems, or leaves. Taken together, our results suggest that CaMF5 is an anther-specific gene that might encode a new type of LEA protein related to anther and/or pollen development in C. annuum.