Genome-wide identification of putative dihydroflavonol 4-reductase (DFR) gene family in eight Solanaceae species and expression analysis in Solanum lycopersicum

Dihydroflavonol 4-reductase (DFR; EC1.1.1.219) is an important rate-limiting enzyme in the plant flavonoid pathway toward both anthocyanins and proanthocyanidins. Although DFR genes have been isolated from multiple plants and their functions have been well characterized in some plants, little is known about DFRs in Solanaceae species. Therefore, in this study, we performed genome-wide analysis and identified 6, 5, 4, 5, 5, 6, 6 and 5 DFR gene family members in eight Solanaceae species ( S. lycopersicum , S. pennellii , S. tuberosum , S. melongena , C. annuum , N. tabacum, P. inflata , and P. axillaris ) respectively. The putative DFR genes were systematically identified using bioinformatics to predict their protein properties, cellular location, phylogenetic relationships, gene structure, conserved motifs, and cis -acting elements in the promoters. Furthermore, quantitative real-time PCR (qRT-PCR) was used to identify the expression pattern of DFRs in tomato. We classified all DFRs into five groups based on their phylogenetic features. Sequence analysis showed that all encoded DFR protein sequences possess a highly conserved NAD-dependent epimerase/dehydratase. In addition, almost all the members of each group displayed similar gene structures and motif distributions, which might be related to their identical executive functions. All 42 DFRs possess a series of light-responsive, phytohormone-responsive, MYB-responsive, stress-responsive, and tissue-specific expression-related cis -elements in the promoter sequences. qRT-PCR analysis showed that tomato DFRs were expressed in many different organs. This study will provide a theoretical basis for further investigation of the function of DFRs in Solanaceae.