Degradation of the plant defense signal salicylic acid protects Ralstonia solanacearum from toxicity and enhances virulence on tobacco

Lowe-Power Tiffany M., Jacobs Jonathan M., Ailloud Florent, Fochs Brianna, Prior Philippe, Allen Caitilyn. 2016. Degradation of the plant defense signal salicylic acid protects Ralstonia solanacearum from toxicity and enhances virulence on tobacco. Mbio, 7 (3):e00656-16, 12 p.

Quartile : Outlier, Sujet : MICROBIOLOGY

Résumé : Plants use the signaling molecule salicylic acid (SA) to trigger defenses against diverse pathogens, including the bacterial wilt pathogen Ralstonia solanacearum. SA can also inhibit microbial growth. Most sequenced strains of the heterogeneous R. solanacearum species complex can degrade SA via gentisic acid to pyruvate and fumarate. R. solanacearum strain GMI1000 expresses this SA degradation pathway during tomato pathogenesis. Transcriptional analysis revealed that subinhibitory SA levels induced expression of the SA degradation pathway, toxin efflux pumps, and some general stress responses. Interestingly, SA treatment repressed expression of virulence factors, including the type III secretion system, suggesting that this pathogen may suppress virulence functions when stressed. A GMI1000 mutant lacking SA degradation activity was much more susceptible to SA toxicity but retained the wild-type colonization ability and virulence on tomato. This may be because SA is less important than gentisic acid in tomato defense signaling. However, another host, tobacco, responds strongly to SA. To test the hypothesis that SA degradation contributes to virulence on tobacco, we measured the effect of adding this pathway to the tobacco-pathogenic R. solanacearum strain K60, which lacks SA degradation genes. Ectopic addition of the GMI1000 SA degradation locus, including adjacent genes encoding two porins and a LysR-type transcriptional regulator, significantly increased the virulence of strain K60 on tobacco. Together, these results suggest that R. solanacearum degrades plant SA to protect itself from inhibitory levels of this compound and also to enhance its virulence on plant hosts like tobacco that use SA as a defense signal molecule.

Mots-clés Agrovoc : Ralstonia solanacearum, mécanisme de défense cellulaire, acide salicylique, virulence, génie génétique, expression des gènes, Solanum lycopersicum, Nicotiana tabacum

Classification Agris : H20 - Maladies des plantes
F60 - Physiologie et biochimie végétale

Champ stratégique Cirad : Axe 4 (2014-2018) - Santé des animaux et des plantes

Auteurs et affiliations

• Lowe-Power Tiffany M., University of Wisconsin (USA)
• Jacobs Jonathan M., IRD (FRA)
• Ailloud Florent, ANSES-LSV (REU)
• Fochs Brianna, University of Wisconsin (USA)
• Prior Philippe, CIRAD-BIOS-UMR PVBMT (REU)
• Allen Caitilyn, University of Wisconsin (USA)

Source : Cirad-Agritrop (https://agritrop.cirad.fr/582159/)

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