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Chinese Science Bulletin

, Volume 58, Issue 33, pp 4077–4083 | Cite as

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

  • GuiRong Tang
  • DaWei Lu
  • Dong Wang
  • Li LuoEmail author
Open Access
Article Microbiology

Abstract

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.

Keywords

Sinorhizobium meliloti LsrB root nodule development bacteroid differentiation oxidative burst lipopolysaccharide 

Supplementary material

11434_2013_5960_MOESM1_ESM.pdf (486 kb)
Supplementary material, approximately 486 KB.

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Copyright information

© The Author(s) 2013

Authors and Affiliations

  1. 1.State Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological SciencesChinese Academy of SciencesShanghaiChina
  2. 2.University of the Chinese Academy of SciencesBeijingChina
  3. 3.School of Life ScienceAnhui UniversityHefeiChina

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