Beijing, March 9 (Reporter Yang Shu) - Polycaryotic rice, a unique rice germplasm resource, differs from regular rice in that its seeds can grow in clusters of three, earning it the nickname "Triple Grain Wonder." The mechanism behind this "triple-grain cluster" trait has remained a mystery until now. Recently, a team led by Hongning Tong from the Institute of Crop Science at the Chinese Academy of Agricultural Sciences, in collaboration with the Rice Research Institute of Fujian Academy of Agricultural Sciences and the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences, has unveiled the genetic mechanism behind the "triple-grain cluster" of polycaryotic rice. This breakthrough provides a theoretical basis and new approaches for breeding high-yield rice varieties. The findings were published in the international journal Science on March 8, Beijing time.
Hongning Tong, a researcher at the Institute of Crop Science, Chinese Academy of Agricultural Sciences, explained that rice is China's main food crop and feeds more than half of the global population. With the world's population increasing and per capita arable land decreasing, boosting rice yield per unit area is crucial for global food security. The key to breaking yield barriers largely depends on the discovery and utilization of significant genes within rice germplasm resources. Increasing the number of panicles per mu, the number of grains per panicle, and grain weight are essential. Therefore, since the 1930s, the international genetics community has been fascinated by the "triple-grain cluster" phenomenon in polycaryotic rice but has been unable to crack its genetic basis.
The team led by Hongning Tong has been engaged in research on the regulation of rice growth and development by plant hormones. In this study, by creating a large number of derivative mutants of polycaryotic rice, they eventually identified and cloned the key gene BRD3 that controls the "triple-grain cluster" phenomenon. The protein encoded by this gene degrades a hormone known as "brassinosteroids." Experiments have shown that it is the action of BRD3 that reduces the level of "brassinosteroids," leading to an increase in the secondary branches of the rice panicle, which results in the "triple-grain cluster" phenomenon. Further research clarified the mechanism of action of "brassinosteroids" and found that due to precise hormonal regulation in polycaryotic rice, the number of grains per panicle could be increased without the negative effects commonly associated with other hormones, such as a reduction in grain weight.
Academician Jia Yang Li commented that generally, the more grains per panicle in rice, the smaller the grain weight, often showing a negative correlation. This research achievement has to some extent unraveled the negative balance between the two, presenting a highly potential molecular design breeding strategy.
(Original Title: Scientists at Our Institute Unravel the Mystery of Clustered Grains in Rice)
