水稻籽粒大小关键microRNA的功能及其调控机制

Crop grain size is one of the key factors determining crop yields and thus exploring new genes that modulate the traits would help us better understand the relevant molecular mechanisms and would also facilitate the breeding of new varieties with increased yields. We previously found that miR397, an microRNA (miRNA) expressed in rice meristem and embryo, associated with the rice grain size and the spikelet branches. Over-expression of miR397 in rice results in a phenotype of enlarged grain sizes and increased the number of spikelet branches. In addition to miR397, two other miRNAs, miR408 and miR528 showed the same expression patterns with miR397. More interestingly, bioinformatics analysis indicated that the three miRNAs all target to different members of the blue copper oxidase family, suggesting that they might have same functions in determining rice agronomic traits. Based on these findings, in this project, we propose to further study on the following aspects. (1) Cloning and functional studies of miRNAs (miR397, miR408 and miR528), and demonstrating their effects on rice grain size and yield production; (2) Demonstrating the mechanisms and regulatory networks of the miRNAs-mediated pathway on grain size. The implementation and completion of this project would not only provide a new approach for rice breeding, but also provide theoretical basis for higher yield breeding of crops.

作物籽粒大小是构成产量的三大要素之一，挖掘籽粒大小新的基因资源，对提高作物产量有重要意义。我们前期研究发现，水稻分生组织特异性表达的miRNA，如miR397等与水稻籽粒发育及小穗分枝数量有关，miR397过表达突变株籽粒有明显增大的特点。除了miR397外，其它2个miRNA分子(miR408和miR528)与miR397具有相同时空表达，重要的是，这3个miRNA下游靶基因都是同一家族不同成员，提示它们可能具有相同的功能。因此，本项目拟在这些前期发现基础上开展以下研究：一是进一步开展miR397、miR408和miR528的功能研究，明确其对水稻籽粒大小的影响；二是研究这3个miRNA分子介导的靶基因沉默在籽粒发育中的作用机制及调控网络, 阐明其介导的蓝铜蛋白家族如何调控下游因子从而影响籽粒的大小。该项目的实施和完成可为水稻籽粒大小的选育、提高水稻产量提供新的遗传资源和理论支撑。

作物籽粒大小是构成产量的三大要素之一，挖掘籽粒大小新的基因资源，对提高作物产量有重要意义。本项目重点围绕水稻籽粒大小和发育相关miRNA的功能及调控网络这一关键科学问题，从两个不同方向和层次展开研究：一是探索和解析了miRNA对作物籽粒大小的影响；二是研究了miRNA（miR397和miR408）介导的蓝铜蛋白沉默在籽粒发育中的作用机制及调控网络。获得如下重要结果：（1）发现了miR397对水稻籽粒大小、水稻产量的正调控作用，阐明了miR397对下游靶基因漆酶蛋白的影响以及对油菜素内酯的作用，从而影响了水稻产量；（2）进一步研究还发现，miR397介导的靶基因沉默不仅调控籽粒大小，而且影响了水稻育性和结实率 ；（3）除了miR397, 我们通过高通量分析及功能验证，还获得另一个正调控水稻产量的miRNA分子---miR408,证明了miR408是通过对其下游靶基因UCL(uclacyanin)来行使其功能的。项目的实施和完成可为水稻籽粒大小的选育、提高水稻产量提供新的遗传资源和理论支撑。