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  • Open Access

Nitric oxide is required for an optimal establishment of the Medicago truncatula–Sinorhizobium meliloti symbiosis

Authors

  • Jennifer del Giudice,

    1. UMR INRA 1301/CNRS 6243/Université de Nice – Sophia Antipolis, Interactions Biotiques et Santé Végétale, Institut Agrobiotech, 400 route des Chappes, BP 167, F–06903 Sophia-Antipolis Cedex, France
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  • Yvan Cam,

    1. UMR CNRS 2594/INRA 441, Laboratoire des Interactions Plantes Microorganismes, F–31320 Castanet Tolosan, France
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  • Isabelle Damiani,

    1. UMR INRA 1301/CNRS 6243/Université de Nice – Sophia Antipolis, Interactions Biotiques et Santé Végétale, Institut Agrobiotech, 400 route des Chappes, BP 167, F–06903 Sophia-Antipolis Cedex, France
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  • Franck Fung-Chat,

    1. UMR INRA 1301/CNRS 6243/Université de Nice – Sophia Antipolis, Interactions Biotiques et Santé Végétale, Institut Agrobiotech, 400 route des Chappes, BP 167, F–06903 Sophia-Antipolis Cedex, France
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  • Eliane Meilhoc,

    1. UMR CNRS 2594/INRA 441, Laboratoire des Interactions Plantes Microorganismes, F–31320 Castanet Tolosan, France
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  • Claude Bruand,

    1. UMR CNRS 2594/INRA 441, Laboratoire des Interactions Plantes Microorganismes, F–31320 Castanet Tolosan, France
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  • Renaud Brouquisse,

    1. UMR INRA 1301/CNRS 6243/Université de Nice – Sophia Antipolis, Interactions Biotiques et Santé Végétale, Institut Agrobiotech, 400 route des Chappes, BP 167, F–06903 Sophia-Antipolis Cedex, France
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  • Alain Puppo,

    1. UMR INRA 1301/CNRS 6243/Université de Nice – Sophia Antipolis, Interactions Biotiques et Santé Végétale, Institut Agrobiotech, 400 route des Chappes, BP 167, F–06903 Sophia-Antipolis Cedex, France
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  • Alexandre Boscari

    1. UMR INRA 1301/CNRS 6243/Université de Nice – Sophia Antipolis, Interactions Biotiques et Santé Végétale, Institut Agrobiotech, 400 route des Chappes, BP 167, F–06903 Sophia-Antipolis Cedex, France
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Author for correspondence:
Alexandre Boscari
Tel: +33 492 386637
Email: boscari@sophia.inra.fr

Summary

  • Nitric oxide (NO) is a gaseous molecule that participates in numerous plant signalling pathways. It is involved in plant responses to pathogens and development processes such as seed germination, flowering and stomatal closure.
  • Using a permeable NO-specific fluorescent probe and a bacterial reporter strain expressing the lacZ gene under the control of a NO-responsive promoter, we detected NO production in the first steps, during infection threads growth, of the Medicago truncatulaSinorhizobium meliloti symbiotic interaction. Nitric oxide was also detected, by confocal microscopy, in nodule primordia.
  • Depletion of NO caused by cPTIO (2-(4-carboxyphenyl)-4,4,5,5-tetramethyl imidazoline-1-oxyl-3-oxide), an NO scavenger, resulted in a significant delay in nodule appearance. The overexpression of a bacterial hmp gene, encoding a flavohaemoglobin able to scavenge NO, under the control of a nodule-specific promoter (pENOD20) in transgenic roots, led to the same phenotype. The NO scavenging resulting from these approaches provoked the downregulation of plant genes involved in nodule development, such as MtCRE1 and MtCCS52A. Furthermore, an Hmp-overexpressing S. meliloti mutant strain was found to be less competitive than the wild type in the nodulation process.
  • Taken together, these results indicate that NO is required for an optimal establishment of the M. truncatula–S. meliloti symbiotic interaction.

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