Ant28 gene for proanthocyanidin synthesis encoding the R2R3 MYB domain protein (Hvmyb10) highly affects grain dormancy in barley
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A number of anthocyanin- and proanthocyanidin-free mutants (ant mutants) in barley were induced and selected because of breeding interest to reduce proanthocyanidins, which could cause haze and degrade the quality of beer. Ant loci, known as anthocyanin or proanthocyanidin synthesis genes, are classified into Ant1 to Ant30 through allelism tests. However, only the Ant18 gene has been molecularly shown to encode dihydroflavonol 4-reductase (DFR), which is involved in both anthocyanin and proanthocyanidin synthesis. In this study, an R2R3 MYB gene of barley was isolated by PCR and named Hvmyb10 due to its similarity to Tamyb10 of wheat, which is a candidate for the R-1 gene grain color regulator. The predicted amino acid sequences of Hvmyb10 showed high similarity not only to Tamyb10 but also to TT2, the proanthocyanidin regulator of Arabidopsis. Non-synonymous nucleotide substitutions in the Hvmyb10 gene were found in all six ant28 mutants tested. Mapping showed that a polymorphism in Hvmyb10 perfectly cosegregated with the ant 28 phenotype on the distal region of the long arm of chromosome 3H. These results demonstrate that ant28 encodes Hvmyb10, the R2R3 MYB domain protein that regulates proanthocyanidin accumulation in developing grains. The reduced grain dormancy of ant28 mutants compared with those of the respective wild types indicates that Hvmyb10 is a key factor in grain dormancy in barley.
KeywordsBarley Proanthocyanidin Grain dormancy Ant mutants
Days after pollination
We thank Dr. Udda Lundqvist, Nordic Genetic Resource Center, and Dr. Fredric Ottosson, Department of Crop Science, Swedish University of Agricultural Sciences, Alnarp, Sweden, for kindly providing the grains of the ant28 mutants. This work was supported by Ofu-Kai for the Promotion of Education and Culture at Japan Women’s University, the Elizabeth Arnold Fuji Foundation, and a grant from the Ministry of Agriculture, Forestry, and Fisheries of Japan. (Development of crop production technology for all year round multi-utilization of paddy fields).
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