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Updated: Aug 22, 2026

Single-plant, Sterile Microcosms for Nodulation and Growth of the Legume Plant Medicago truncatula with the Rhizobial Symbiont Sinorhizobium meliloti
20:01

Single-plant, Sterile Microcosms for Nodulation and Growth of the Legume Plant Medicago truncatula with the Rhizobial Symbiont Sinorhizobium meliloti

Published on: October 1, 2013

Sinorhizobium meliloti ExoR and ExoS proteins regulate both succinoglycan and flagellum production

Shi-Yi Yao1, Li Luo, Katherine J Har

  • 1Biological Sciences Department, Lehman College, The City University of New York, 250 Bedford Park Blvd., West, Bronx, NY 10468, USA.

Journal of Bacteriology
|September 3, 2004
PubMed

Insights

Sinorhizobium meliloti mutations overproducing succinoglycan impaired symbiosis and flagellar biosynthesis. The ExoR and ExoS/ChvI systems regulate both exopolysaccharide and flagella production in this important plant symbiont.

Area of Science:

  • Microbiology
  • Plant-Bacterial Interactions
  • Molecular Biology

Background:

  • Succinylglycan exopolysaccharide production by Sinorhizobium meliloti is essential for alfalfa nodulation.
  • Mutations affecting succinoglycan regulation can impact symbiotic efficiency.

Purpose of the Study:

  • To investigate the symbiotic phenotypes of S. meliloti mutants with altered succinoglycan production.
  • To elucidate the regulatory roles of ExoR and ExoS/ChvI in S. meliloti.

Main Methods:

  • Generating and characterizing Tn5 insertion mutants (exoR95 and exoS96).
  • Assessing symbiotic phenotypes, including root hair colonization and nodulation efficiency.
  • Analyzing flagellar biosynthesis and motility (swimming and swarming).
  • Investigating gene expression related to flagellar biosynthesis.

Main Results:

  • Mutations exoR95 and exoS96 led to succinoglycan overproduction and reduced symbiosis.
  • These mutants exhibited decreased root hair colonization and impaired motility.
  • Flagellar biosynthesis was significantly reduced, suggesting ExoR and ExoS/ChvI regulate flagellar gene expression.

Conclusions:

  • The ExoR protein and the ExoS/ChvI two-component system regulate both succinoglycan and flagellum biosynthesis in S. meliloti.
  • These regulatory systems are crucial for coordinating physiological changes during early symbiosis.
  • Findings offer insights into signal transduction pathways governing S. meliloti-alfalfa interactions.

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