Elicitation ofRx-Mediated Resistance to PVX in Potato Does Not Require New RNA Synthesis and May Involve a Latent Hypersensitive Response

The Rx gene in potato confers extreme resistance against potato virus X (PVX) that is elicited by the viral coat protein (CP). Using actinomycin D to inhibit transcription of nuclear genes, we have shown that Rx is expressed prior to virus inoculation and that induction of the resistance mechanism does not require novel gene expression or continued transcription of previously expressed genes. We have also shown that transgenic plants could not be produced carrying a CP transgene from an Rx-avirulent PVX in an Rx background. These data indicate that Rx-mediated resistance involves a mechanism that suppresses viability of plant cells.