Objective   The dihydroflavonol-4-reductase (DFR) gene in bracts of Bougainvillea spectabilis was cloned and characterized to study the role it plays in color formation.

  Method  BsDFRwas cloned based on the transcriptome data on the ornamental plant to study the related bioinformatics. Molecular docking technology was employed to predict the substrate specificity, and qRT-PCR applied to examine the relative transcription levels of the genes in B. spectabilis of different colors.

  Result   The full-length coding sequence of BsDFR (GenBank ID: ON417750) was 987 bp encoding 328 amino acids. The protein had a calculated molecular weight of 36.49 kDa and an isoelectric point of 6.33. It had the NADPH and substrate specific binding sites unique to DFR of Asn type without a transmembrane structure or signal peptide. The subcellular localization of the protein indicated it to be cytoplasmic. Alpha helices were the most abundant secondary structure of the protein, while the tertiary structure was a dimer. A substrate docking simulation, consistent with the structural analysis, predicted BsDFR to possess a catalytic activity on dihydrokaempferol, dihydroquercetin, and dihydromyricetin. The phylogenetic tree analysis grouped it along with caryophyllales plants. High expression of the gene was found in the orange B. spectabilis by qRT-PCR. It was speculated that the main substrate to be DHK, which was catalyzed by BsDFR into leucopelargonidin, a precursor of orange-colored anthocyanidin——pelargonidin.

  Conclusion   BsDFR in B. spectabilis had typical molecular characteristics of the plant dihydroflavonol-4-reductase, which is associated with the pigment synthesis in the bracts of orange B. spectabilis.