Plant resistance (R) genes exhibit conserved domains, each of which performs discrete functions in the resistance to pathogens. The most abundant R genes belong to the classes of nucleotide binding site leucine rich repeats (NBS-LRR), receptor-like kinases (RLK), and receptor-like proteins (RLP). The list also includes genes encoding proteins with a unique transmembrane domain, genes encoding toxin reductases, genes encoding CC and transmembrane proteins and genes encoding an intracytoplasmic protein kinase. This chapter sheds light on recent advances in the classification of R genes, based on their conserved structural characteristics. Knowledge about the R proteins cellular localization and advances in the molecular cloning of R genes are also treated.
Keywords: Classes of plant disease resistance (R) genes, Cellular localization, Domain architecture, Nucleotide Binding Site-Leucine Rich Repeat (NBS-LRR), R-gene cloning, Receptor-Like Kinase (RLK), Receptor-Like Protein (RLP).