SOD与DEP1互作调控水稻穗粒数的分子机制研究

Increasing the grain number per panicle is one of the effective ways to improve rice yield. Grain number is a complex quantitative trait controlled by multiple genes and collaborative environment and in recent years a small number of QTLs for grain number per panicle have been identified, however, ony a few genes can be used in rice production, and DEP1 (Dense and Erect Panicle 1) is one of them. The dominant allele dep1 enhances grain yield by increasing grain number and has been widely used in rice production. Recently, a sod (suppressor of dep1) mutant which shows reduced panicle branching and grain number is identified by genetic screenings, furthermore, the SOD gene is isolated by map-based cloning. In addition, DEP1 and LAX1 are identified as SOD interacting proteins by yeast two-hybrid screening and BiFC showes that SOD protein can directly interact with LAX1 protein in protoplast. In this proposal, the molecular characterization of SOD gene will be analyzed, and more importantly, the molecular mechanism of action of DEP1-SOD regulatory module will be the focus of analysis through analyzing the relationship among DEP1, SOD and LAX1, and identifing the target genes of DEP1-SOD-LAX1 regulatory module by RNA-seq transcriptome analysis. The purpose of this research is to help us further understand the molecular mechanism of rice panicle development and to provide important gene resources for molecular design breeding of rice.

增加每穗穗粒数是水稻高产育种的有效途径之一。由于穗粒数是受多个基因和环境共同控制的复杂数量性状，目前已克隆的调控水稻穗粒数的基因还很少，而能够在生产中应用的关键基因则少之又少，DEP1基因是其中之一，其显性突变的dep1能够显著增加穗粒数和产量。迄今，关于DEP1调控水稻穗粒数的分子机制和遗传网络还不清晰。本项目通过遗传筛选获得了一个能够使dep1的穗粒数减少的突变体sod (suppressor of dep1)，利用图位克隆方法克隆了SOD候选基因并进行了遗传互补验证。酵母双杂交筛库获知，SOD能够与DEP1和LAX1发生蛋白互作。在此基础上，本项目将进一步研究SOD基因的功能，解析SOD、DEP1和LAX1基因之间的互作关系及其调控穗粒数的遗传网络。这些研究结果将为揭示水稻穗粒数的调控机制提供新的生长点，并为水稻高产分子设计育种提供理论基础和基因资源。

水稻的每穗粒数与产量直接相关，一直是水稻高产育种研究的热点之一。虽然到目前为止，已克隆了多个调控水稻穗粒数的主效QTL/基因，但是可以直接育种应用的关键基因还很少。DEP1基因是被我国水稻高产育种广泛应用的重要基因，该基因的显性突变dep1能够提高茎顶端分生组织的活性，促进细胞分裂，增加枝梗数和每穗粒数，进而提高产量。目前，我们对于DEP1调控水稻穗粒数的分子机制还不清楚。基于这种情况，本项目围绕“DEP1调控水稻穗粒数的分子机制和遗传网络解析”这一重要科学问题，综合运用生物信息学、生物化学、遗传学等手段开展了系统研究，获得了以下重要研究结果：在dep1突变体背景下进行遗传筛选，获得了一个穗粒数和枝梗数减少的突变体，即抑制dep1表型的突变体sod (suppressor of dep1)；利用图位克隆的方法分离了SOD候选基因，突变的sod缺失一个外显子；遗传互补实验和转基因研究均证明SOD基因具有调控水稻穗粒数的功能；通过酵母双杂交筛库以及体内、体外的蛋白互作实验确定SOD与DEP1、LAX1之间存在蛋白-蛋白相互作用；利用生物信息学、生物化学、CRISPR/Cas9基因编辑等方法获得了SOD、DEP1和LAX1共同调控的下游基因OsCKX2和TGL2，并证明了TGL2具有调控水稻穗粒数的功能。这些研究结果表明SOD通过与DEP1和LAX1蛋白互作并通过共同调控OsCKX2、TGL2基因的表达来实现对穗粒数的调控。该研究为揭示水稻穗发育和穗粒数调控的分子机制提供了重要信息和线索。