Evidence for calcium-mediated perception of plant symbiotic signals in aequorin-expressing <it>Mesorhizobium loti</it>
<p>Abstract</p> <p>Background</p> <p>During the interaction between rhizobia and leguminous plants the two partners engage in a molecular conversation that leads to reciprocal recognition and ensures the beginning of a successful symbiotic integration. In host plants, i...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
BMC
2009-09-01
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| Series: | BMC Microbiology |
| Online Access: | http://www.biomedcentral.com/1471-2180/9/206 |
| Summary: | <p>Abstract</p> <p>Background</p> <p>During the interaction between rhizobia and leguminous plants the two partners engage in a molecular conversation that leads to reciprocal recognition and ensures the beginning of a successful symbiotic integration. In host plants, intracellular Ca<sup>2+ </sup>changes are an integral part of the signalling mechanism. In rhizobia it is not yet known whether Ca<sup>2+ </sup>can act as a transducer of symbiotic signals.</p> <p>Results</p> <p>A plasmid encoding the bioluminescent Ca<sup>2+ </sup>probe aequorin was introduced into <it>Mesorhizobium loti </it>USDA 3147<sup>T </sup>strain to investigate whether a Ca<sup>2+ </sup>response is activated in rhizobia upon perception of plant root exudates. We find that <it>M. loti </it>cells respond to environmental and symbiotic cues through transient elevations in intracellular free Ca<sup>2+ </sup>concentration. Only root exudates from the homologous host <it>Lotus japonicus </it>induce Ca<sup>2+ </sup>signalling and downstream activation of nodulation genes. The extracellular Ca<sup>2+ </sup>chelator EGTA inhibits both transient intracellular Ca<sup>2+ </sup>increase and inducible <it>nod </it>gene expression, while not affecting the expression of other genes, either constitutively expressed or inducible.</p> <p>Conclusion</p> <p>These findings indicate a newly described early event in the molecular dialogue between plants and rhizobia and highlight the use of aequorin-expressing bacterial strains as a promising novel approach for research in legume symbiosis.</p> |
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| ISSN: | 1471-2180 |