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Endosymbiotic Sinorhizobium meliloti modulate Medicago root susceptibility to secondary infection via ethylene

Sorroche, Fernando and Walch, Mathilda and Zou, Lan and Rengel, David and Maillet, Fabienne and Gibelin-Viala, Chrystel and Poinsot, Verena and Chervin, Christian and Masson-Boivin, Catherine and Gough, Clare and Batut, Jacques and Garnerone, Anne-Marie Endosymbiotic Sinorhizobium meliloti modulate Medicago root susceptibility to secondary infection via ethylene. (2019) New Phytologist, 223 (2). ISSN 0028-646X

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Official URL: https://doi.org/10.1111/nph.15883


A complex network of pathways coordinates nodulation and epidermal root hair infection in the symbiotic interaction between rhizobia and legume plants. Whereas nodule formation was known to be autoregulated, it was so far unclear whether a similar control is exerted on the infection process. We assessed the capacity of Medicago plants nodulated by Sinorhizobium meliloti to modulate root susceptibility to secondary bacterial infection or to purified Nod factors in split-root and volatile assays using bacterial and plant mutant combinations. Ethylene implication in this process emerged from gas production measurements, use of a chemical inhibitor of ethylene biosynthesis and of a Medicago mutant affected in ethylene signal transduction. We identified a feedback mechanism that we named AOI (for Autoregulation Of Infection) by which endosymbiotic bacteria control secondary infection thread formation by their rhizospheric peers. AOI involves activation of a cyclic adenosine 30,50-monophosphate (cAMP) cascade in endosymbiotic bacteria, which decreases both root infectiveness and root susceptibility to bacterial Nod factors. These latter two effects are mediated by ethylene. AOI is a novel component of the complex regulatory network controlling the interaction between Sinorhizobium meliloti and its host plants that emphasizes the implication of endosymbiotic bacteria in fine-tuning the interaction.

Item Type:Article
HAL Id:hal-02181509
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
French research institutions > Institut National de la Recherche Agronomique - INRA (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
Laboratory name:
Agence Nationale de la Recherche- ANR
Deposited On:12 Jul 2019 08:45

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