Sinorhizobium meliloti lsrB is involved in alfalfa root nodule development and nitrogen-fixing bacteroid differentiation  

作　　者：TANG GuiRong LU DaWei WANG Dong LUO Li 

机构地区：[1]State Key Laboratory of Plant Molecular Genetics,Institute of Plant Physiology and Ecology,Shanghai Institutes for Biological Sciences,Chinese Academy of Sciences [2]University of the Chinese Academy of Sciences [3]School of Life Science,Anhui University

出　　处：《Chinese Science Bulletin》2013年第33期4077-4083,共7页

基　　金：supported by National Basic Research Program of China (2010CB126501, 2011CB100702);the National Natural Science Foundation of China (31070218)

摘　　要：Rhizobia interact with host legumes to induce the formation of nitrogen-fixing nodules,which is very important in agriculture and ecology.The development of nitrogen-fixing nodules is stringently regulated by host plants and rhizobial symbionts.In our previous work,a new Sinorhizobium meliloti LysR regulator gene(lsrB)was identified to be essential for alfalfa nodulation.However,how this gene is involved in alfalfa nodulation was not yet understood.Here,we found that this gene was associated with prevention of premature nodule senescence and abortive bacteroid formation.Heterogeneous deficient alfalfa root nodules were induced by the in-frame deletion mutant of lsrB(lsrB1-2),which was similar to the plasmid-insertion mutant,lsrB1.Irregular senescence zones earlier appeared in these nodules where bacteroid differentiation was blocked at different stages from microscopy observations.Interestingly,oxidative bursts were observed in these nodules by DAB staining.The decreased expression of lipopolysaccharide core genes(lpsCDE)was correspondingly determined in these nodules.S.meliloti lipopolysaccharide is required for suppression of oxidative bursts or host cell defense.These findings demonstrate that the S.meliloti lsrB gene is involved in alfalfa root nodule development and bacteroid differentiation by suppressing oxidative bursts or defense responses in host cells.Rhizobia interact with host legumes to induce the formation of nitrogen-fixing nodules, which is very important in agriculture and ecology. The development of nitrogen-fixing nodules is stringently regulated by host plants and rhizobial symbionts. In our pre- vious work, a new Sinorhizobium meliloti LysR regulator gene （lsrB） was identified to be essential for alfalfa nodulation. Howev- er, how this gene is involved in alfalfa nodulation was not yet understood. Here, we found that this gene was associated with pre- vention of premature nodule senescence and abortive bacteroid formation. Heterogeneous deficient alfalfa root nodules were in- duced by the in-frame deletion mutant of lsrB （lsrB1-2）, which was similar to the plasmid-insertion mutant, lsrB1. Irregular se- nescence zones earlier appeared in these nodules where bacteroid differentiation was blocked at different stages from microscopy observations, Interestingly, oxidative bursts were observed in these nodules by DAB staining. The decreased expression of lipo- polysaccharide core genes （lpsCDE） was correspondingly determined in these nodules. S. meliloti lipopolysaccharide is required for suppression of oxidative bursts or host cell defense. These findings demonstrate that the S. meliloti lsrB gene is involved in alfalfa root nodule development and bacteroid differentiation by suppressing oxidative bursts or defense responses in host cells.

关 键 词：苜蓿根瘤菌 固氮根瘤 分化抑制 类菌体 发育 缺失突变体 调节基因 宿主细胞 

分 类 号：S541.9[农业科学—作物学] S154.381