Abstract: Dihydroflavonol 4-Reductase (DFR) plays a key role in the formation of different floral color.By using RT-PCR method, a dfr gene was cloned from Dendrobium and designated as Dendfr. The Dendfr gene was 1 164 bp in length and encoded 352 amino acid residues. Amino acid sequence analysis revealed that Den DFR sequence share homologies of 81% - 86% with three species of orchid, and share homologies of 56% - 72% with the other species. Den DFR protein contains a reserved NADP domain at the N-terminal and a specific 26 amino acid region of substrate specificity with an asparagine ( position 134 ) . The encoding region of Dendfr was constructed into pQE30 vector and effectively expressed the protein in E.coli. These will be helpful for studying molecular mechanism of floral color formation and genetic improvement of the Dendrobium.

Key words: Dendrobium, flower color, dfr gene, cloning, sequence analysis, prokaryotic expression