THE COMPLEXITY OF PATHOGEN DEFENSE IN PLANTS

Abstract

Summary. Plants defend themselves against pathogen attack by activating a multicomponent defense response. In host defense, pathogen invasion is recognized by proteins encoded by plant disease resistance (R) genes that bind specific pathogen-derived avirulence (Avr) proteins. In nonhost resistance, specific pathogen or plant cell wall derived exogenous or endogenous elicitors are recognized. A complex signalling network, involving cytosolic Ca 2+ and H + ions, reactive oxygen intermediates, jasmonate, salicylic acid, ethylene, triggers the induction of the defense mechanisms. Defense genes encode pathogenesis-related proteins, such as glucanases, chitinases; enzymes involved in the biosynthesis of phytoalexins; the enzymes of oxidative stress protection, tissue repair, lignification, and others.