Functional analysis of plant disease resistance genes and their downstreameffectors

Plant disease resistance (R) genes encode proteins that both determine reco gnition of specific pathogen-derived avirulence (Avr) proteins and initiate signal transduction pathways leading to complex defense responses. Recent developments suggest that recognition specificity of R proteins is determin ed by either a protein kinase domain or by a region consisting of leucine-r ich repeats. R genes conferring resistance to bacterial, viral, and fungal pathogens appear to use multiple signaling pathways, some of which involve distinct proteins and others which converge upon common downstream effector s. Manipulation of R genes and their signaling pathways by transgenic expre ssion is a promising strategy to improve disease resistance in plants.