Development of virus resistance in transgenic tobacco plants that express cucumber mosaic virus satellite RNA

Abstract

The ability to transform plant genomes with alien genetic material by the Agrobacterium tumefaciens Ti plasmid system has made it possible to test whether plant resistance to viruses can be increased by incorporating virus-related nucleotide sequences into the nuclear genome of the host. We have used this approach with a satellite RNA of cucumber mosaic virus (CMV) that is replicated only in CMV-infected cells and attenuates the symptoms induced by CMV. The cDNA copy of CMV satellite RNA was introduced into the tobacco plants by Agrobacterium Ti plasmid-mediated transformation system. From the Southern and Northern blot analyses, it was confirmed that the cDNA of satellite RNA was integrated into the plant genome and was expressed stably in the transgenic tobacco plants. Symptom development was largely suppressed in these transgenic plants upon CMV infection. Western blot analyses also show that symptom suppression in systemic infection is paralleled by decrease of 30-kDa protein, which is regarded as a movement protein. We also show that chitinases, involved in inducible defenses of plants, are induced upon CMV infection. These results indicate that genetically engineered protection by virus nucleic acid is a feasible strategy for enhancing the virus resistance of plants.