Overexpression of the carbohydrate-binding module of Solanum lycopersicum expansin 1 (SlEXP1) modifies susceptibility to Botrytis cinerea

PERINI MAURO ALEJANDRO; SIN, IGNACIO NICOLAS; VILLARREAL, NATALIA M.; MARINA, MARÍA; NARDI, CRISTINA; ROSSI, FRANCO; MARTINEZ, GUSTAVO ADOLFO; POWELL, ANN L.T.; CIVELLO, PEDRO MARCOS

Congreso; XVII ​INTERNATIONAL BOTRYTIS SYMPOSIUM; 2016

Fruit firmness depends largely on the mechanical resistance imposed by cell walls and wallintegrity is a major determinant of postharvest quality, shelf life and diseaseresistance. Botrytis cinerea causesgray mold disease and, as a necrotophic opportunistic plant pathogenic fungus,contributes substantially to the postharvest decay of fleshy fruits. Multiplestrategies have been evaluated to control firmness losses during storage and,thereby, reduce susceptibility to pathogen infections. Most of the approacheshave been designed to suppress the expression of key enzymes involved in fruitcell wall metabolism. Expansins (EXPs), modular extracellular plant proteinswith a characteristic putative catalytic domain and a carbohydrate-bindingmodule (CBM) common in many carbohydrate-associated proteins, are involved inthe non-hydrolytic metabolic disassembly of plant cell walls, especially when relaxationof the wall is necessary, such as during fruit development and ripening.Previous work has shown that expansins influence firmness, cell wall metabolismand susceptibility to B. cinerea.Overexpression of the just the CBM module of strawberry expansin 2 in A. thaliana modified cell wall metabolismand increased resistance to B. cinerea.Suppression of tomato fruit SlEXP1expression reduced susceptibility to B.cinerea and A. alternata. Simultaneoussuppression of the tomato ripening-associated polygalacturonase and SlEXP1resulted in tomato fruit less susceptible to B. cinerea. Transgenic tomato lines overproducing the S. lycopersicum expansin 1 CBM (CBM-SlEXP1)peptide in the cell wall were generated to test the hypothesis that theendogenous CBM itself influences wall metabolism and infection susceptibility.CBM-SlEXP1 overexpression increased the mechanical resistance of leaves andfruit firmness, delayed ripening-associated softening and reduced symptoms inripe fruit of B. cinerea infections.Furthermore, the growth of B. cinereawas reduced in solid media containing polysaccharides extracted from CBM-SlEXP1 expressing. These results suggestthat the overexpression of just the CBM from SlEXP1 might influence the courseof a pathogen infection, possibly due to modifications of the overall cell wallstructure and/or by altering the accessibility of fruit?s cell wallpolysaccharides to Botrytis or host cell wall degrading enzymes.