群体感应在菌-植共生中起重要作用。目前对典型的LuxR/LuxI类群体感应在共生中的功能进行了相关研究，而对无同源LuxI类蛋白的LuxR solo的调控功能鲜有报道。茎瘤固氮根瘤菌ORS571共存在4个LuxR solos蛋白，它们在自生和共生过程中的调控机制还不清楚。本项目拟对其中一个在自生及共生状态下都具有重要功能的LuxR solo蛋白Sla1进行深入研究。一方面通过构建基因缺失突变株，分析在自生状态下生物膜形成能力、胞外多糖分泌能力、运动行为和固氮酶活性；在共生状态下形成根、茎瘤的数目、固氮酶活性以及与野生型的竞争性结瘤等表型。另一方面，通过对自生菌和共生茎瘤类菌体进行转录组测序，试图找出LuxR solo转录因子Sla1的调控网络。通过对以上内容的研究旨在为揭示Sla1调控细菌之间的信号交流、感应植物信号、调节菌-植共生结瘤固氮机理等科学问题提供新知识。

LuxR/LuxI-type quorum-sensing systems have been shown to play a critical role in symbiotic process. However, the mechanisms of LuxR solos in symbiotic process remain rarely explored. Our previously results show that ORS571 genome has four unknown functions LuxR solo proteins. In this study, the function of the solo LuxR Sla1 protein will be determined by the construction gene deletion mutant, and detection of phenotypic differences of these strains. In free-living condition, we will detect biofilm-formation ability, exopolysaccharides secretion, motility behavior, and nitrogen-fixing ability of wild-type and mutant strains; in symbiotic nitrogen fixation condition, nodulation capacity, nitrogen-fixing ability and competitive nodulation capacity in stem and root will be analyzed. Furthermore, RNA sequencing analysis will performed on free-living cells and in bacteroids isolated from stem nodules. Overall, it is hoped that these study will provide a theoretical framework for quorum sensing in ORS571 involved in free-living and symbiosis.