Black rice contains substantial levels of anthocyanins, a class of bioactive compounds recognized for their health-promoting properties, constituting a crucial determinant of rice nutritional and functional quality. In this study, we cloned OsTT2, a regulatory gene for anthocyanin biosynthesis in rice, located on chromosome 3, with a 331 bp segmental duplication in its promoter region. OsTT2 encodes an R2R3-MYB transcription factor that localizes to the nucleus. Interestingly, OsTT2 significantly influences plant height, panicle length, total grain number per plant, grain length, and grain width in rice. Although no significant differences were detected in the number of panicles per plant or thousand-grain weight, the presence of a functional OsTT2 gene substantially increases overall rice yield. Further research has found that OsTT2 binds to the promoter region of OsMED15a, which activates the OsMED15a-OsNAC024 pathway, thereby modulating rice grain length and width. Our findings provide new genetics resources and novel approaches for the genetic improvement of rice anthocyanin biosynthesis, quality and yield.
Yang et al. (Thu,) studied this question.