为了使根瘤菌在贫瘠沙漠地区能有效地为防风固沙豆科植物锦鸡儿提供充足的氮素营养，一个重要的问题就是根瘤菌在长期自然进化过程中如何保持较强的环境适应性与高效的共生固氮能力。本项目以一株锦鸡儿属高效根瘤菌作为出发菌株，借助全基因组重测序、比较基因组学、转录组学等手段，研究胁迫介质下连续转接500代的进化菌株中分别参与耐碱性提高而结瘤、固氮能力丧失的相关基因，并针对重要目的基因在出发菌株、进化菌株两基因组背景下开展遗传学工作，分析目的基因生物学功能及存在的上位效应，进而揭示根瘤菌适应性进化过程中结瘤固氮能力丧失的分子机制。

In order to provide sufficient nitrogen for windproof and sand stabilization legume Caragana in barren desert area, a key question is how to keep the strong environmental adaptation and high effectiveness of nitrogen-fixing symbiosis in the Long-term natural evolution process of rhizobia. The aim of this item is to explore molecular mechanism underlying the loss of nitrogen-fixing symbiosis disability in adaptive evolution of rhizobia. Genome re-sequencing, comparative genomics, transcriptomics will be used to find functional genes involved in alkali-resistant increase and nitrogen-fixing symbiosis disability for the offspring evolved from initial strain in stress condition for 500 generations. Biological function of evolved genes and existed epistasis will be analyzed genetically under genomic background of initial and evolved strains respectively.