Source: School of Life Sciences
Written by: School of Life Sciences
Edited by: Wang Dongmei

Recently, Prof. Yue-Qin Chen’s group from School of Life Sciences in Sun Yat-sen University discovered an microRNA positively regulating rice grain yield through increasing grain size and promoting panicle branching. This is the first report of miRNAs in the control of plant seed size and grain yield. Prof. Chen and her group has made their findings online published in the July 21st issue of the journal Nature Biotechnology, and the paper entitled "Overexpression of microRNA OsmiR397 improves rice yield by increasing grain size and promoting panicle branching". As increasing grain yields is a major focus of crop breeders around the world, this finding is of great importance for both theoretical research and potential applications.

MicroRNA is a kind of small non-coding RNA, which is about 22nt in length, playing an important role in the processes of development and metabolism, and becoming the research hotspot and frontier in recent years. Prof. Chen’s group discovered that a microRNA, miR397, which is highly expressed in the panicles and grains of rice, could substantially increase the grain size and the panicle branches and positively regulates grain yield about 25%. As miR397 is conserved in various crops including wheat, maize, sorghum, etc., the finding provides a new gene resource for increasing grain yield in crops.

Most importantly, the paper reported a novel regulation pathway the miRNA mediated. That is, miR397 increases grain yield though down-regulating the expression of OsLAC, a laccase-like protein. Laccase is broadly accepted to participant in the metabolism of lignin, and there is no report about the relationship between laccase and grain yield. Prof. Chen’s group unraveled that miR397 directly down-regulated OsLAC, which could affect the brassinosteroid sensitivity of rice plant, and in turn regulate the yield related characters. This finding revealed a new and important function of laccase family.

Dr. Yu-Chan Zhang, who is a Ph.D. student of Prof. Chen, is the first author of this paper. This study was supported by the National Natural Science Foundation of China, funds from Ph.D. Programs Foundation of Ministry of Education of China, and from the Natural Science and Technology Department of Guangdong Province.

Figure legends: In the OXmiR397 (miR397 over-expression) plants, miR397 down-regulates the expression level of LAC, a laccase-like protein, through cleave the mRNA of LAC gene, which then promotes the brassinosteroid (BR) signaling, leading to an increased number of panicle branches and the enlarged grain sizes, promotes the grain yield of rice plants.