Development of a visible marker trait based on leaf sheath–specific anthocyanin pigmentation applicable to various genotypes in rice

To overcome a limitation to the breeding of autogamous crops, recurrent selection using transgenic male sterility (RSUTMS) has been proposed. In this system, negatively or positively selectable marker traits are required along with dominant transgenic male sterility. Anthocyanin pigmentation is an excellent marker trait. Two regulatory genes for MYB and bHLH and a structural gene for DFR are required for anthocyanin pigmentation in rice. Therefore, to apply anthocyanin pigmentation as a marker trait in various rice genotypes, coordinated expression of the three genes is required. In this study, we developed a leaf sheath–specific promoter and introduced three genes—DFR and C1/Myb, driven by the 35S promoter, and OsB2/bHLH, driven by the leaf sheath–specific promoter—into the rice genome. Leaf sheath–specific pigmentation was confirmed in all seven genotypes tested, which included japonica and indica cultivars. Analysis of genome sequence data from 25 cultivars showed that the strategy of conferring leaf sheath–specific anthocyanin pigmentation by introduction of these three genes would be effective for a wide range of genotypes and will be applicable to RSUTMS.