Identification and characterization of DFR gene family and cloning of candidate genes for anthocyanin biosynthesis in pepper (Capsicum annuum L.).

Dihydroflavonol-4 reductase (DFR) is a key enzyme in plant anthocyanin synthesis and can affect the synthesis of anthocyanin. In order to explore the role of DFR in anthocyanin synthesis of capsicum, the sequence of the DFR gene family was downloaded from the Arabidopsis genome database. The study showed the presence of nine members of the DFR gene family in pepper, which are primarily localized in the cytoplasm and chloroplasts. The majority of these proteins exhibit hydrophilic characteristics, with their secondary structure predominantly consisting of α-helices and random coils. Furthermore, these genes can be categorized into four distinct subfamilies, with the gene structure and conserved motifs of CaDFR members within the same subfamily providing robust support for this classification. The promoter regions of CaDFRs are enriched with numerous light-responsive elements, phytohormone-responsive elements, stress-responsive elements, and elements associated with plant growth and development, in addition to binding sites for 35 different transcription factors. According to the results of qRT-PCR analysis, the expression level of CaDFR5 was consistent with the change of anthocyanin content, and the full length of the CaDFR5 gene was further cloned. This study provides an important reference for improving fruit colour and lays a foundation for further exploring the function of the DFR gene family.