Anti-OsPDCD5/Cas9-OsPDCD5提高水稻生物量、增加产量的分子机制

Biomass is the most obvious heterosis in hybrid rice, the breakthrough of hybrid rice yield was based on increasing biomass. Molecular Design Breeding，which mainly counts on the understanding of key genes functions, has become an effective way for genetic improvement right now, the success or not for Molecular Design Breeding lies on the breakthrough or not of biomass, so the studies on the molecular basis of enhancing biomass is vital in rice. OsPDCD5, an ortholog to mammalian programmed cell death 5 gene has been identified and characterized from rice in our study previously. Our research show that constitutive overexpression of OsPDCD5 proved to induce plant death in rice, but the antisense-OsPDCD5 transgenic or knockout-OsPDCD5 plants demonstrate a enhance of biomass and plant type improvement, leading to a great increase on grain yield. In this project, more detail of OsPDCD5 and anti-OsPDCD5 function will be identified. By yeast two-hybrid system, the interacting genes downstream OsPDCD5 will be detected, and the molecular mechanism of anti-OsPDCD5 or knockout-OsPDCD5 on controlling biomass will be revealed; In addition, by analyzing gene expression variation, we will clarify the regulatory network of anti-OsPDCD5 or knockout-OsPDCD5 for improving yield; and by genetic methods, we will evaluate the effects of Cas9-OsPDCD5 on Yield in different genetic backgrounds. This study will supply gene resources and theoretical basis to the super rice breeding in China.

杂交稻最明显的杂种优势体现在生物产量上，其产量的突破建立在生物量大幅提升的基础上。当前分子设计育种的目标是培育“颠覆性品种”，生物量的突破是其成功的关键，因此水稻提高生物产量的分子基础研究至关重要。我们在水稻中克隆了一个与哺乳动物同源的程序性死亡基因OsPDCD5，该基因过表达引起水稻死亡，但下调表达水平或阻断其功能，则促进水稻生物量提升，并改良株型和粒型，显著提高产量。本研究将进一步分析OsPDCD5的功能，利用酵母双杂等方法找出其下游互作基因，并通过生化及生物学等方法揭示下调OsPDCD5表达或阻断OsPDCD5功能调控穗和籽粒发育以及提高生物量的分子机制；通过表达谱分析，解析anti-OsPDCD5/Cas9-OsPDCD5改良株型及粒型的调控网络；应用遗传学方法评估Cas9-OsPDCD5在不同遗传背景中对产量的影响。为我国“颠覆性育种”提供基因资源和理论依据。

株型是影响农作物产量的重要农艺性状。我们利用差显法从珍汕97B中同源克隆了一个程序性细胞死亡基因OsPDCD5。功能研究发现OsPDCD5负调控水稻的株型和产量。我们使用CRISPR / Cas9系统定点编辑一批不同遗传背景的水稻品种，发现OsPDCD5的突变可通过增加株高并优化穗型和粒型来改善株型并提高水稻产量，增产最大幅度超过20%。机制研究发现OsPDCD5蛋白与OsAGAP结合并负向调控其转录水平，而OsAGAP参与生长素运输，并正向调控株型。进一步研究发现，OsPDCD5会影响赤霉素的生物合成活性和细胞分裂素的生物合成及信号传导活性，突变OsPDCD5基因会促进赤霉素与细胞分裂素的合成与活性，上调能量与代谢相关基因的表达，增加细胞数目，提高生物量及产量。该研究为水稻超高产育种提供了基因资源及新的育种途径。