Genetically Engineer Protection Against Viruses and Fungi

The first examples of plant genetic engineering for disease resistance were for the control of virus diseases. Plants that were transformed with a gene to express the coat protein of tobacco mosaic virus (TMV) were shown to have increased resistance to infection by TMV. This approach, referred to as coat protein-mediated resistance (CP-MR), has been applied to give protection against at least 35 different viruses, belonging to 12 virus groups in at least 13 plant species. Field trials of some of these examples have demonstrated that CP-MR can effectively protect plants under field conditions. Other viral genes have also been demonstrated to confer resistance when expressed in transgenic plants. These resistances appear to have different modes of action and may give high levels of resistance. Additionally, they may confer protection against infection by viruses for which CP-MR has not been demonstrated. A somewhat different approach has been taken to produce transgenic plants with increased resistance to fungal infection. Plant genes encoding proteins with anti-fungal activity have been engineered for expression at higher levels, in different tissues, or in different plant species. With CP-MR, resistance based on other virus-derived genes, plant-derived resistances, and combinations of resistances from several sources, there exists significant potential for the control of agriculturally important diseases. Further research to determine the cellular and molecular mechanisms responsible for each type of resistance is needed to maximise the realisation of that potential