Red grain colour gene (R) of wheat is a Myb-type transcription factor

Red pigment of wheat grain was reported to be polyphenol compounds, phlobaphene or proanthocyanidin, which were synthesized through the flavonoid biosynthesis pathway. We examined the expression of four genes in the flavonoid pathway in developing wheat grains: chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), and dihydroflavonol 4-reductase (DFR). The expression of these genes in the white-grained wheat lines was reduced, compared with that in the red-grained wheats. These results suggest that the R genes for grain colour, located on the long arms of chromosomes 3A, 3B and 3D, are transcriptional activators of the flavonoid synthesis genes. We identified three Myb-type transcription factors (Tamyb10-A1 on 3A, Tamyb10-B1 on 3B and Tamyb10-D1 on 3D), which were also located in the same region as the R loci, and were expressed predominantly in developing grains. In wheat lines with the recessive allele r3 (3B) Tamyb10-B1 had a deletion which caused a frame-shift in its open reading frame. Tamyb10-A1, and -D1 were not expressed in wheats with r2 (3A) and r1 (3D).