Liu Yuan, Lin Ye, Guan Ning, Song Yuting, Li Youguo, Xie Xianan
State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
State Key Laboratory of Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Laboratory for Lingnan Modern Agriculture, Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510642, China.
Microorganisms. 2022 Dec 25;11(1):59. doi: 10.3390/microorganisms11010059.
Rhizobium lipopolysaccharide (LPS) is an important component of the cell wall of gram-negative bacteria and serves as a signal molecule on the surface of rhizobia, participating in the symbiosis during rhizobia-legume interaction. In this study, we constructed a deletion mutant of ADP-L-glycerol-D-mannoheptosyl-6-exoisomerase () of 7653R and a functional complementary strain. The results showed that the deletion of did not affect the free-living growth rate of 7653R, but that it did affect the LPS synthesis and that it increased sensitivity to abiotic stresses. The promoter-GUS reporter assay showed that the gene was mainly expressed in the infection zone of the mature nodules. The root nodules formation of the mutant was delayed during symbiosis with the host plant of . The symbiotic phenotype analyses showed that the nodules of lost symbiotic nitrogen fixation ability, when inoculated with the mutant strain. In conclusion, our results reveal that the 7653R gene plays a crucial role in the LPS synthesis involved in the symbiotic interaction between rhizobia and . This study also provides new insights into the molecular mechanisms by which the rhizobia regulate their own gene expression and cell wall components enabling nodulation in legumes.
根瘤菌脂多糖（LPS）是革兰氏阴性细菌细胞壁的重要组成部分，作为根瘤菌表面的信号分子，参与根瘤菌与豆科植物相互作用过程中的共生作用。在本研究中，我们构建了7653R的ADP-L-甘油-D-甘露庚糖基-6-表异构酶（）缺失突变体和功能互补菌株。结果表明，的缺失不影响7653R的自由生活生长速率，但影响LPS合成，并增加了对非生物胁迫的敏感性。启动子-GUS报告基因检测表明该基因主要在成熟根瘤的感染区表达。与的宿主植物共生期间，突变体的根瘤形成延迟。共生表型分析表明，接种突变菌株时，的根瘤失去共生固氮能力。总之，我们的结果表明7653R基因在根瘤菌与共生相互作用中涉及的LPS合成中起关键作用。本研究还为根瘤菌调节自身基因表达和细胞壁成分以实现豆科植物结瘤的分子机制提供了新的见解。
