Signal transmission in the plant immune response

Genetic and biochemical dissection of signaling pathways regulating plant p athogen defense has revealed remarkable similarities with the innate immune system of mammals and Drosophila. Numerous plant proteins resembling eukar yotic receptors have been implicated in the perception of pathogen-derived signal molecules. Receptor-mediated changes in levels of free calcium in th e cytoplasm and production of reactive oxygen species and nitric oxide cons titute early events generally observed in plant-pathogen interactions. Posi tive and negative regulation of plant pathogen defense responses has been a ttributed to mitogen-activated protein kinase cascades. In addition, salicy lic acid, jasmonic acid and ethylene are components of signaling networks t hat provide the molecular basis for specificity of plant defense responses. This article reviews recent advances in our understanding of early signali ng events involved in the establishment of plant disease resistance.