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Compatible and incompatible rhizobia alter membrane potentials of soybean root cells
T Ersek1, A Novacky, S G Pueppke
1Department of Plant Pathology, University of Missouri, Columbia, Missouri 65211.
Plant Physiology
|December 1, 1986
Summary
Soybean root cells inoculated with Rhizobium bacteria showed reduced electrical potential (E(m)) and diffusion potential (E(D)). These changes, linked to bacterial interaction, were dose-dependent and specific to live Rhizobium strains.
Area of Science:
- Plant-microbe interactions
- Plant physiology
- Molecular biology
Background:
- Rhizobium bacteria form symbiotic relationships with legumes, crucial for nitrogen fixation.
- Understanding the early cellular responses of host plants to rhizobial inoculation is vital for agricultural applications.
- Electrical transmembrane potential (E(m)) is a key indicator of cellular activity and membrane integrity.
Purpose of the Study:
- To investigate the immediate effects of Rhizobium inoculation on soybean root cell electrical potential.
- To determine the specificity of the observed electrical response to live Rhizobium bacteria.
- To explore the role of diffusion potential (E(D)) in mediating these cellular changes.
Main Methods:
- Measurement of electrical transmembrane potential (E(m)) and diffusion potential (E(D)) in soybean root cells.
- Inoculation with specific Rhizobium strains (R. japonicum, R. meliloti) and control treatments (heat-killed rhizobia, Pseudomonas fluorescens).
- Varying sodium phosphate concentrations in the perfusion solution to assess dose-dependent effects.
Main Results:
- Inoculation with live Rhizobium japonicum or R. meliloti rapidly reduced E(m) and E(D) in soybean root cells.
- The observed electrical changes were transient, returning to baseline by day two, with a secondary decrease by day seven in R. meliloti-inoculated tissue.
- Increased sodium phosphate concentrations amplified the inoculation-induced reduction in E(m).
- Neither heat-killed rhizobia nor Pseudomonas fluorescens induced similar electrical potential changes.
- Nodule cells exhibited significantly lower E(m) and E(D) compared to adjacent root cortical cells.
Conclusions:
- Live Rhizobium bacteria specifically induce rapid alterations in soybean root cell electrical potential, likely via changes in diffusion potential.
- The host cell's electrical response is influenced by bacterial viability and concentration.
- These findings highlight the dynamic electrophysiological changes occurring during the early stages of legume-rhizobia symbiosis.
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