Isolation and location of three homoeologous dihydroflavonol-4-reductase (DFR) genes of wheat and their tissue-dependent expression.

DFR is involved in an important step in the flavonoid biosynthesis pathway upstream of anthocyanin, proanthocyanidin, and phlobaphene production, which contributes to the pigmentation of various plant tissues. Full genomic sequences of three DFRs were isolated in hexaploid wheat. Loci of TaDFRs were found in a more proximal region of the long arm of chromosomes of homoeologous group 3 than the R gene for red grain colour of wheat. These DFRs were designated TaDFR-A, TaDFR-B, and TaDFR-D on chromosome 3A, 3B, and 3D, respectively. In the 5' upstream region of DFR genes, two or three combinations of a G box core element and a putative binding site for a Myb-type transcription factor, P, of maize were found. Expression of DFR reached a maximal level in red grain of wheat cv. Chinese Spring (CS) at 5 d post-anthesis (DPA) and decreased gradually in the grain coat tissue from 10 to 20 DPA, in contrast to a very low expression level of DFR in white wheat grain during the same period. These DFRs differed in their expression. TaDFR-B and -D were expressed predominantly in grains. In developing leaves, DFR expression was light-responsive, and TaDFR-B was more up-regulated in leaves and roots than the other two.