Abstract
Plant virus resistance breeding is difficult as resistance sources are limited and because many resistance factors are monogenic, thus resistance can be broken easily. Therefore, it would be desirable to incorporate a 'horizontal' virus resistance trait into major crops that could provide durable protection against many different viruses. Translational readthrough is required for the gene expression of many plant viruses. Therefore we hypothesize that plants, in which the readthrough is inefficient, could be resistant against all readthrough utilizing viruses. This resistance might be durable as to break it the gene expression strategy of the virus should be completely changed. In yeast, mutant termination factors have been reported that reduced the efficacy of readthrough dramatically in a dominant manner without causing phenotype. Here we aim to elaborate a novel, horizontal virus resistance system based on artificial reduction of readthrough activity in plants. First, a transient readthrough measuring system will be established. We would clone the termination factors of tobacco, and then several mutants (similar mutants that efficiently reduced readthrough in yeast and random mutants) would be generated from these genes. The mutant termination factors would be transiently expressed and their effect on readthrough would be studied in the readthrough measuring system. Mutant termination factors that significantly reduce readthrough efficacy in transient assays will be stable expressed in transgenic tobacco lines, and then the virus resistance of these plants will be tested. Finally, if any of these lines is virus resistant, similar mutant termination factors of other major crops will be created.
Hungary