Plant Disease Resistance Genes: From Perception to Signal Transduction

Abstract

Plants defend themselves against pathogen attack by activating a multicomponent defence response. The pathogen invasion is recognised by proteins encoded by plant disease resistance (R) genes that bind specific pathogen-derived avirulence (Avr) proteins either directly or indirectly via guard to decoy to mechanistic model. As a result, an intracellular signal transduction cascade is initiated, triggering activation of the defence arsenal of the challenged host plant cell and resulting in a localised cell and tissue death at the site of infection and a non-specific systemic acquired resistance (SAR) throughout the plant, which prevents the further spread of the infection termed as hypersensitive response (HR). A large number of plant resistance genes have been grouped into eight basic classes that can be grouped into several superfamilies, based on their protein domains. The vast majority of genes cloned so far belong to the NB–LRR, eLRR or LRR kinase superfamilies and provide a lot of information about the structure and function of R genes that exhibit resistance response against a variety of pathogens such as virus, bacteria, fungi, nematodes and pests. These and other domains like TIR and WRKY have been reported to play a major role in signal transduction. The present chapter focuses on R genes, structure of R proteins and perception of signal at early stages of R–Avr interaction to signal transduction.