La Dolce Vita: A Molecular Feast in Plant–Pathogen Interactions

very different extracellular and intracellular lifestyles. Thus, it was astounding that all of these R genes encode United Kingdom a limited set of products with related structural features. The cloning of R genes continues apace and has recently been augmented by isolation of other key signal transPlants are sessile organisms and lack a circulating, so-duction components. Additionally, the last year has pro-matically adaptive immune system to protect them-duced evidence that bacterial plant pathogens probably selves against pathogens. They instead have evolved " inject " virulence and avirulence proteins directly into other mechanisms for defense against a spectrum of eukaryotic host cells. This is consistent with the require-pathogens. Plants are, in fact, resistant to most microor-ment for evolutionarily conserved Type III secretion sys-ganisms by means of constitutive chemical or physical tems in these pathogens and with the finding that bacte-barriers such as cuticular coats of wax armor that a rial pathogens of mammals also use this system to potential pathogen must penetrate or bypass. Disease deliver virulence factors to host cells. is therefore the exception rather than the rule when Current key questions in this research field include: microbes and plants meet. Yet yield loss due to plant what are the structures of plant R proteins? How is disease remains an important component of modern specificity determined, how do new specificities evolve, agriculture, as many pathogens are evolutionarily spe-and how is genetic diversity organized and maintained cialized to overcome preformed defense barriers. Plant in the host species? Do all R proteins directly interact defense is based on recognition of specific pathogen with pathogen avr proteins? What are the molecular molecules and subsequent induction of a broad defense steps required for R-dependent recognition to be trans-response. Recognition evolves germinally, so that an lated into disease resistance as measured by killing or individual plant can only defend itself with the spectrum inhibiting pathogen growth? What are the positive func-genes it inherited from its parents. Genetic diversity tions of avr proteins for pathogens? Recent advances among individuals is therefore essential for survival of to answer these questions were addressed by nearly 80 the host species against rapidly evolving pathogens. participants in a recent sunbathed EMBO Workshop in Specific pathogen recognition is governed genetically Maratea, Italy organized by Jonathan Jones and Giulia by interactions between the product of a disease resis-DeLorenzo. tance (R) gene in the host and molecules encoded in a given pathogen isolate …