Expression of the Carbohydrate binding module from Solanum lycopersicum α-Expansin 1 modifies susceptibility of fruit to Botrytis cinerea

MAURO PERINI; IGNACIO SIN; NATALIA VILLARREAL; MARÍA MARINA; CRISTINA NARDI; FRANCO ROSSI; GUSTAVO MARTINEZ; ANN POWELL; MARCOS CIVELLO

Santa Cruz

Simposio; XVII International Botrytis Symposium; 2016

Firmness, determined largely by the mechanic resistance imposed by the cell wall, is a major determinant of fruit postharvest quality, shelf life and disease resistance. Botrytis cinerea causes gray mold disease and as a necrotophic opportunistic plant pathogenic fungus, contributes substantially to the postharvest decay of fleshy fruits. Multiple strategies have been evaluated to control firmness losses during storage and, thereby, reduce pathogen infection susceptibility. Most of the approaches have been designed to suppress the expression of key enzymes involved in fruit cell wall metabolism. Expansins, modular extracellular plant proteins with a characteristic putative catalytic domain and a carbohydrate-binding module (CBM) common to many carbohydrate-associated proteins, are involved in the non-hydrolytic plant cell wall metabolic disassembly of plant cell walls, especially where relaxation of the cell wall is necessary, such as fruit development and ripening. Previous work has shown that expansins influence tissue firmness, cell wall metabolism and susceptibility to B. cinerea. Overexpression of the just the CBM module of strawberry expansin 2 in A. thaliana modified cell 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 the tomato 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 wall were generated to test the hypothesis that the endogenous CBM itself influences wall metabolism and infection susceptibility. CBM-SlExp1overexpression increased leaf mechanical resistance and fruit firmness, delayed ripening-associated softening and reduced symptoms of B. cinerea infections of ripe fruit. Furthermore, the growth of B. cinerea in solid media containing, as carbon sources, polysaccharides extracted from CBM-SlExp1 expressing fruit was significantly lower, than growth in media containing carbon source polysaccharides from control fruit. These results suggest that the overexpression of just the CBM from SlEXP1 might influence the course of a pathogen infection, possibly due to modifications of the overall cell wall structure and/or by altering accessibility of fruit?s cell wall polysaccharides to Botrytis or host cell wall degrading enzymes.