Colletotrichum acutatum produces a compound that exerts opposite effects on the defense response of strawberry plants depending on the pathogen lifestyle

TOMAS GRAU, RODRIGO H; DIAZ RICCI, J UAN C.

Salta

Congreso; 55º Reunión Anual de la Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular (SAIB) and Panamerican Association of Biochemistry and Molecular Biology (PABMB); 2019

SOCIEDAD ARGENTINA DE INVESTIGACIONES BIOQUIMICAS (SAIB)

The fungal pathogen Colletotrichum acutatum, the causal agent of anthracnose disease causes important economic losses in strawberry farming worldwide. Crop fungal diseases are usually controlled with fungicides that despite the different origins and chemical nature, are contaminants of the environment and dangerous for human and animal health. The use of crude or barely purified microbe-derived extracts containing defense elicitors are interesting alternatives, as they can induce plant defenses with the advantage that they do not require highly demanding and expensive purification procedures. In this context, we have evaluated the effects on the defense response produced in planta of the supernatant obtained from a liquid culture of a virulent isolate (M11) of the hemibiotrophic fungus C. acutatum (M11-CF). Results obtained showed that M11-CF is capable to suppress the accumulation of the reactive oxygen species (ROS), and the defense response induced by the protein AsES against the hemibiotrophic fungus C. acutatum. Since M11-CF exhibits the capacity to suppress the oxidative burst, and taking into account that there is a direct correlation between the occurrence of the oxidative burst and the pathogenicity of necrotrophic fungi, we hypothesized that M11-CF may further confer protection against a necrotrophic pathogen such as B. cinerea. Results indicate that strawberry plants treated with M11-CF induces ethylene accumulation, and up-regulates ethylene-related genes (e.g., FaETR1, FaERS1, FaERF1) causing the induction of a defense response against Botrytis cinerea. The latter was evidenced by the decrease of the lesion diameter in M11-CF-treated plants as compared to control plants. In contrast, salicylic acid-related genes (e.g., FaPR1, FaOGBG, FaCHI2-2) did not show changes after the treatment. This outcome confirms the above-mentioned hypothesis about the capacity of M11, and its extracts, to exert opposite effects depending on the pathogen tested. That include, to activate a defense response against a necrotrophic pathogen by activating the ethylene pathway, and to suppress a defense response against a hemibiotrophic pathogen by the negative regulation exerted by ethylene on the salicylic acid pathway, and the suppression of the oxidative burst. The results presented here highlight the necessity to make an integral study of the microbiome present in soils and plant biosphere before applying any bioproduct that would activate the defense response to control crop diseases.