The Rx gene from potato controls separate virus resistance and cell death responses

Rx-mediated extreme resistance against potato virus X in potato does not in volve a necrotic hypersensitive response at the site of initial infection a nd thereby differs from the more usual type of disease resistance in plants . However, the Rx protein is structurally similar to products of disease re sistance genes conferring the hypersensitive response. We show in both Nico tiana spp and potato that Rx has the potential to initiate a cell death res ponse but that extreme resistance is separate and epistatic to necrosis. Th ese data indicate that cell death and pathogen arrest are separate disease resistance responses in plants.