Cloning, expression analysis and enzyme activity verification of dihydroflavonol 4-reductase from Cistanche tubulosa (Schenk) Wight flower / 药学学报

ABSTRACT

Dihydroflavonol 4-reductase (DFR) plays an essential role in the biosynthesis of anthocyanin and regulation of plant flower color. Based on the transcriptome data of Cistanche tubulosa (Schenk) Wight, a full-length cDNA sequence of CtDFR gene was cloned by reverse transcription-polymerase chain reaction (RT-PCR). CtDFR contains an open reading frame (ORF) of 1 263 bp which encodes 420 amino acids with a predicted molecular weight of 47.5 kDa. The sequence analysis showed that CtDFR contains a nicotinamide adenine dinucleotide phosphate (NADPH) binding domain and a specific substrate binding domain. The expression analysis indicated that CtDFR was highly expressed in red and purple flowers, and the relative expression levels were 4.04 and 19.37 times higher than those of white flowers, respectively. The recombinant CtDFR protein was expressed in E.coli BL21 (DE3) using vector pET-28a-CtDFR and was purified. In vitro enzyme activity analysis, CtDFR could reduce three types of dihydroflavonols including dihydrokaempferol, dihydroquercetin, and dihydromyricetin to leucopelargonidin, leucocyanidin and leucodelphinidin. Subcellular localization analysis showed that CtDFR was mainly localized in the cytoplasm. These results demonstrate that CtDFR plays an important role in regulation of flower color in C. tubulosa and make a valuable contribution for the further investigation on the regulation mechanism of C. tubulosa (Schenk) Wight flower color.