The <i>Rx</i> Gene from Potato Controls Separate Virus Resistance and Cell Death Responses

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