大豆Rj4基因调节共生固氮的分子机理以及在分子育种中的应用

Legume-rhizobial symbiosis plays a critical role in sustainable agriculture. One striking feature of the legume-rhizobial symbiosis is its high level of specificity. Understanding the molecular mechanisms underlying symbiotic specificity is not only able to genetically improve the biological nitrogen fixation of leguminous crops to broaden the host range, but also help us to optimize the plant-rhizobia symbiosis system and provide the theoretical basis for maximizing nitrogen fixation efficiency. However, the genetic regulation mechanism symbiotic specificity is very complex, and few related researches were made. Rj4 is a gene controlling nodulation specificity in soybean. Studying the molecular mechanism of Rj4 in this project will reveal the regulation mechanism underlying the symbiotic specificity, and add a new dimension to our knowledge about the genetic control of nodulation specificity in the legume-rhizobial symbiosis. Based on the successful cloning of Rj4 gene, our present study will use molecular, cellular and biochemical approaches to elucidate the biological function of Rj4, and identify the interacting proteins of Rj4 through yeast-two hybrid system. Combined with the RNA-seq results, the genomic signatures of Rj4-mediated nodulation restriction will be explored and the molecular mechanism of Rj4 in regulating symbiotic specificity will be revealed. In addition, this project will develop a number of cleaved amplified polymorphic sequences (CAPS) markers associated with nodulation traits for marker-assisted breeding as well as germplasm identification in soybean.

豆科植物与根瘤菌的共生固氮在实现生态农业提质增效中具有重要的作用。豆科植物-根瘤菌共生有着高度的特异性，系统解析共生特异性调控的分子机理，不仅能对豆科作物的生物固氮进行遗传改良，扩大寄主范围，也有助于优化植物-根瘤菌共生体系，为固氮效率最大化提供理论依据。但是调控共生特异性的遗传机制非常复杂，其相关研究鲜有报道。本项目以调控大豆结瘤特异性的Rj4基因为切入点，通过研究Rj4基因作用的分子机理，揭示豆科植物共生特异性的调控机制, 为遗传调控共生特异性开发一个全新的研究领域。在前期 Rj4基因成功克隆的基础上，拟从分子水平、细胞水平和蛋白质水平对Rj4的生物学功能进行鉴定，并利用酵母双杂交鉴定Rj4的互作蛋白，结合转录组测序解析Rj4调控共生特异性的下游基因网络，阐明Rj4调控共生特异性的分子机理。除此以外，本项目还将开发多个与结瘤性状相关的CAPS分子标记，用于大豆育种和种质资源的鉴定。

豆科植物与根瘤菌的共生固氮在实现生态农业提质增效中具有重要的作用。豆科植物-根瘤菌共生有着高度的特异性，系统解析共生特异性调控的分子机理，不仅能对豆科作物的生物固氮进行遗传改良，扩大寄主范围，也有助于优化植物-根瘤菌共生体系，为固氮效率最大化提供理论依据。但是调控共生特异性的遗传机制非常复杂，其相关研究鲜有报道。本项目以调控大豆结瘤特异性的Rj4基因为切入点，通过研究Rj4基因作用的分子机理，揭示豆科植物共生特异性的调控机制, 为遗传调控共生特异性开发一个全新的研究领域。通过对Rj4的进行亚细胞定位，确定了Rj4定位于细胞质中，与其基因家族其他成员定位均有不同，暗示其作用机制的独特性。利用转录组测序解析了Rj4调控共生特异性的下游基因网络，阐明了Rj4调控共生特异性的分子机理是通过激活植物免疫防御反应，抑制共生信号通路而实现的。以外，本项目还开发了三个稳定高效的与根瘤菌B. elkanii USDA61共生结瘤性状相关的分子标记，可用于大豆育种和种质资源的鉴定。