Overexpression of the carbohydrate binding module from Solanum lycopersicum Expansin 1 (Sl-EXP1) modifies Botrytis cinerea susceptibility.

PERINI, MA; SIN, IN; VILLARREAL, NM; NARDI, CF; MARINA, M; ROSSI, F; MARTÍNEZ, GA; POWELL, ALT; CIVELLO, PM

Santiago, Chile

Simposio; XVII International Botrytis Symposium; 2016

Laboratorio de Fitopatología Frutal y Molecular del Departamento de Sanidad Vegetal de la Facultad de Ciencias Agronómicas de la Universidad de Chile, Santiago, Chile.

Firmness, determined largely by the mechanic resistanceimposed by the cell wall, is a major determinant of fruit postharvest quality,shelf life and disease resistance. Botrytiscinerea causes gray mold disease and as a necrotophic opportunisticplant pathogenic fungus, contributes substantially to the postharvest decay of fleshyfruits. Multiple strategieshave been evaluated to control firmness losses during storage and, thereby, reducepathogen infection susceptibility. Most of the approaches have been designed tosuppress the expression of key enzymes involved in fruit cell wall metabolism.Expansins, modular extracellular plant proteins with acharacteristic putative catalytic domain and a carbohydrate-binding module (CBM)common to many carbohydrate-associated proteins, are involved in the non-hydrolyticplant cell wall metabolic disassembly of plant cell walls, especially whererelaxation of the cell wall is necessary, such as fruit development andripening. Previous work has shown that expansins influence tissue firmness,cell wall metabolism and susceptibility to B.cinerea. Overexpression of the just the CBM module ofstrawberry expansin 2 in A. thaliana modifiedcell wall metabolism and increased resistance to B. cinerea. Suppression of tomato fruit Sl-EXP1 expression reduced susceptibility to B. cinerea and A. alternata. The simultaneous suppression of thetomato ripening-associated polygalacturonase and Sl-EXP1 resulted in tomato fruit less susceptible to B. cinerea.Transgenic tomato lines overproducing the S. lycopersicum expansin 1 CBM (CBM-SlExp1) peptide in the cell wallwere generated to test the hypothesis that the endogenous CBM itself influenceswall metabolism and infection susceptibility.CBM-SlExp1overexpression increased leaf mechanical resistance andfruit firmness, delayed ripening-associated softening and reduced symptoms of B. cinerea infections ofripe fruit. Furthermore, the growth of B.cinerea in solid media containing, as carbon sources, polysaccharidesextracted from CBM-SlExp1 expressing fruit was significantly lower, than growthin media containing carbon source polysaccharides from control fruit. Theseresults suggest that the overexpression of just the CBM from SlEXP1 might influence the course of apathogen infection, possibly due to modifications of the overall cell wallstructure and/or by altering accessibility of fruit?s cell wall polysaccharidesto Botrytis or host cell walldegrading enzymes.