ALTERATIONS OF CELL WALL STRUCTURE AND INTEGRITY IMPROVE RESISTANCE TO PATHOGENS

Cell wall modifying enzymes (CWMEs) are expressed by microbial pathogens during invasion to penetrate the cell wall barrier. Plants sense loss of cell wall integrity and trigger defenses leading to an improved resistance to pathogens. The expression of CWMEs or their inhibit ors in planta represents a useful tool not only to improve resistance to pathogens but also to investigate therole of the altered cell wall structure and integrity in plant-pathogen interactions. Loss of homogalacturonan integrity in tobacco and Arabidopsis obtained by expressing a fungal endopolygalacturonase induces specific defense responses and enhances plant resistance to Botrytis cinerea and Pseudomonas syringae. Ectopic expression of fungal xylan or pectins acetylesterases in Arabidopsis and Brachipodium triggers specific responses leading to higher resistance to B. cinerea and Bipolaris sorokiniana, respectively. A targeted inhibition of the susceptibility fact or pectin methylesterase (PME) through the overexpression of PME inhibitors (PMEI) or the knockout of a specific PME gene causes an increased esterification of pectin and a concomitant reduced susceptibility toB. cinerea and Pectobacterium carotovorum. Moreover, the spreading of two Tobamovirus is retarded in tobacco and Arabidopsis plants overexpressing PMEIs