Systemic acquired resistance
Systemic acquired resistance is a "whole-plant" resistance response that occurs following an earlier localized exposure to a pathogen. SAR is analogous to the innate immune system found in animals, and although there are many shared aspects between the two systems, it is thought to be a result of convergent evolution.Discovery
The first plant receptors of conserved microbial signatures were identified in rice and in Arabidopsis.Mechanism
Plants use pattern-recognition receptors to recognize conserved microbial signatures. This recognition triggers an immune response. Plants also carry immune receptors that recognize highly variable pathogen effectors, these include the NBS-LRR class of proteins. SAR is associated with the induction of a wide range of genes, and the activation of SAR requires the accumulation of endogenous salicylic acid. The pathogen-induced SA signal activates a molecular signal transduction pathway that is identified by a gene called NIM1, NPR1 or SAI1 in the model genetic system Arabidopsis thaliana.
