The leucine-rich repeat domain can determine effective interaction betweenRPS2 and other host factors in Arabidopsis RPS2-mediated disease resistance

Like many other plant disease resistance genes, Arabidopsis thaliana RPS2 e ncodes a product with nucleotide-binding site (NBS) and leucine-rich repeat (LRR) domains. This study explored the hypothesized interaction of RPS2 wi th other host factors that may be required for perception of Pseudomonas sy ringae pathogens that express avrRpt2 and/or for the subsequent induction o f plant defense responses. dresses between Arabidopsis ecotypes Col-0 (resi stant) and Po-1 (susceptible) revealed segregation of more than one gene th at controls resistance to P. syringae that express avrRpt2. Many F? and Fs progeny exhibited intermediate resistance phenotypes. In addition to RPS2, at least one additional genetic interval associated with this defense respo nse was identified and mapped using quantitative genetic methods. Further g enetic and molecular genetic complementation experiments with cloned RPS2 a lleles revealed that the Po-1 allele of RPS2 can Function in a Col-0 geneti c background, but not in a Po-1 background. The other resistance-determinin g genes of Po-1 can function, however, as they successfully conferred resis tance in combination with the Col-0 allele of RPS2. Domain-swap experiments revealed that in RPS2, a polymorphism at six amino acids in the LRR region is responsible for this allele-specific ability to function with other hos t factors.