STRATEGIES FOR ENGINEERING VIRUS-RESISTANCE IN TRANSGENIC PLANTS

Transgenic virus-resistant plants were first produced in 1986 by genet ically engineering tobacco plants to express the coat protein of tobac co mosaic virus. The introduction of coat protein transgenes has since proved to be an extremely effective and generally applicable approach to engineering virus resistance in crop plants. Extensive field trial s with transgenic, virus-resistant tobacco, tomato, potato and cucumbe r lines have confirmed not only the durability of the resistance under natural conditions but the ease with which virus-resistant lines reta ining the original cultivar traits can be recovered. A number of alter native anti-viral strategies based on transgenes from a surprisingly w ide variety of sources have also been developed. These include the use of viral genes coding for proteins involved in the replication cycle and in systemic transport of viruses within the plant, the use of inte rfering viral RNA sequences, and the use of transgenes derived from pl ant and animal sources. In the latter category, the use of mammalian a ntibodies to confer disease resistance in plants is a particularly exc iting new development. Considerable progress has also been made toward s the molecular cloning of natural anti-viral resistance genes in plan ts.