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Mol Plant Pathol. 2017 Dec;18(9):1267-1281. doi: 10.1111/mpp.12489. Epub 2017 Jan 3.

Resistance to citrus canker induced by a variant of Xanthomonas citri ssp. citri is associated with a hypersensitive cell death response involving autophagy-associated vacuolar processes.

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Instituto de Biología Molecular y Celular de Rosario (IBR)-Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Área Virología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Ocampo y Esmeralda s/n, Rosario, S2000FHN, Argentina.
Laboratorio de Fisiología Vegetal, Departamento de Ciencias Naturales, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Ruta 36 Km. 601, Río Cuarto X5804ZAB, Córdoba, Argentina.
Instituto de Ciencia y Tecnología Dr. Cesar Milstein, Fundación Pablo Cassará-CONICET, Saladillo 2468, Ciudad de Buenos Aires, C1440FFX, Argentina.
Instituto de Tecnología Agroindustrial del Noroeste Argentino (ITA-NOA), Estación Experimental Agroindustrial Obispo Colombres (EEAOC)-CONICET, Av. William Cross 3150, Las Talitas, Tucumán, T4101XAC, Argentina.
Citrus Research and Education Center (CREC), University of Florida, 700 Experiment Station Rd., Lake Alfred, FL, 33850, USA.
Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universidad Politécnica de Valencia (UPV)-Consejo Superior de Investigaciones Científicas (CSIC), Ciudad Politécnica de la Innovación (CPI), Ed. 8E, C/Ingeniero Fausto Elio s/n, Valencia, 46022, Spain.


Xanthomonas citri ssp. citri (X. citri) is the causal agent of Asiatic citrus canker, a disease that seriously affects most commercially important Citrus species worldwide. We have identified previously a natural variant, X. citri AT , that triggers a host-specific defence response in Citrus limon. However, the mechanisms involved in this canker disease resistance are unknown. In this work, the defence response induced by X. citri AT was assessed by transcriptomic, physiological and ultrastructural analyses, and the effects on bacterial biofilm formation were monitored in parallel. We show that X. citri AT triggers a hypersensitive response associated with the interference of biofilm development and arrest of bacterial growth in C. limon. This plant response involves an extensive transcriptional reprogramming, setting in motion cell wall reinforcement, the oxidative burst and the accumulation of salicylic acid (SA) and phenolic compounds. Ultrastructural analyses revealed subcellular changes involving the activation of autophagy-associated vacuolar processes. Our findings show the activation of SA-dependent defence in response to X. citri AT and suggest a coordinated regulation between the SA and flavonoid pathways, which is associated with autophagy mechanisms that control pathogen invasion in C. limon. Furthermore, this defence response protects C. limon plants from disease on subsequent challenges by pathogenic X. citri. This knowledge will allow the rational exploitation of the plant immune system as a biotechnological approach for the management of the disease.


autophagy; biofilm formation; biological control; citrus canker resistance; hypersensitive response; salicylic acid; secondary metabolites

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