Recent Understanding on Structure, Function and Evolution of Plant Disease Resistance Genes

Plant disease resistance ( R) gene triggers defense mechanisms by detecting non-self or modified self-molecules ( elicitors) which results in hypersensitive response. Plant possesses a large number of R-genes with diverse recognition specificities which are activated in response to a variety of microbial pathogens. Many studies have shown that variation in R-genes is the result of gene duplication followed by divergence employing tandem or segmental duplication, recombination, unequal crossing over, transposable element activity, point mutation and diversifying selection. Large scale sequencing of plant species has revealed that most of the resistance genes are found in clusters of tandemly duplicated genes within the genome. Recent advances in genetics and genomics hold promise for better understanding of the mechanisms of R-gene evolution. The recent understanding on structure, function and evolution of disease resistance genes is reviewed with emphasis on the population dynamics of rice blast resistance gene Pi54. Based on evolution studies, novel strategies can be designed for developing durable disease resistance plant varieties.