玉米种子发育关键PPR基因的功能和作用机理研究

Seed development is essential to cereal yield, whereas CMS is a major means used in hybrid production. However, the fundamental mechanisms governing these processes are obscure. Recent studies revealed that PPR genes play critical roles in both processes; hence identifying these genes and elucidating their functions is the key to a better understanding of the underlying mechanisms. Unfortunately,.mutants in many of these genes are embryo lethality or pollen sterile, obstructing further study. We uncovered the maize seed mutant system that allows functional study of these genes. Taking advantage of our mutant collection and Mu flanking sequence data, we have identified more than 20 PPR gene mutants which showed seed development and/or CMS phenotype. Here we propose a comprehensive and through study to reveal the molecular functions of these genes, to decipher their binding sites, to elucidate their roles in intron splicing. All these results will facilitate the elucidation of the underlying mechanism of embryogenesis, endosperm development and pollen development. This project will also explore the application potential of these genes as they affect seed development and CMS. This comprehensive study will substantially broaden our understanding of PPR gene functions and provide insights to the molecular mechanism by which PPR proteins.function.

种子发育是影响作物产量的关键步骤，细胞质雄性不育是杂交育种的重要手段，因此揭示其分子机理不仅是植物学的基本问题，也是高产育种的关键。最近研究表明，PPR基因在植物胚胎发育和CMS过程中起重要作用，但由于其家族庞大、突变致死等原因，多数PPR基因的功能和调节胚胎发育和CMS的分子机制还不清楚。玉米籽粒体积大且发育同步，是研究致死基因的适宜材料，课题组从前期建立的玉米突变体库中筛选PPR突变体，获得了20多个与胚胎胚乳发育和CMS相关的突变体。在此基础上，本课题将对这些基因进行功能和机理研究，这包括 1）系统解析这些PPR基因的分子功能，确定底物和活性； 2）确定PPR与RNA的结合位点，协助解析P类型PPR识别RNA的分子机制；3）揭示特殊类型PPR的功能；4）了解PPR在内含子剪接中的作用机制；5）探索PPR在农业生产上的潜力。以上研究将显著增进对PPR的认识，也为作物育种提供理论支持。

种子发育既是植物学的基本理论问题，也是作物产量和品质改良的应用基础。聚焦 “玉米种子发育关键PPR基因的功能和作用机理研究” 的课题目标，利用转座子标签和Mu-Seq高通量测序技术，结合反向遗传学和分子生物学方法，本课题取得了以下成果：1）克隆并解析了30余个调控玉米籽粒发育的PPR基因的功能，这些基因皆为功能未知的新基因，这包括10个线粒体或叶绿体RNA编辑因子，17个线粒体RNA剪接因子，1个参与RNA稳定性的PPR蛋白。2）解析了与PPR基因互作共同参与RNA编辑和内含子剪接的非PPR蛋白的功能，并构建了个别PPR基因的互作关系。3）揭示了线粒体RNA的C-U编辑机理并初步解析了编辑体构成组分；4）初步揭示了PPR介导内含子剪接的机制；5）明确了以上基因调控籽粒大小和发育的生物学功能并探索了在应用中的潜力。以上成果在主流期刊发表论文20篇。这些成果加深了对PPR功能的理解，揭示了线粒体RNA后加工的机制，明确了PPR基因在玉米籽粒发育过程中的重要作用。这些成果回答了关于PPR基因功能和作用机理这一重要科学问题，也为作物分子育种提供了理论支撑。