Project description:White clover mosaic virus (WCMV) is a major pathogen of white clover (Trifolium repens L.), with significant effects on yield and persistence. Due to the absence of natural sources of WCMV resistance a transgenic strategy has been employed to produce plants constitutively expressing WCMV replicase gene derivatives, designed to inhibit the propagation of WCMV through an RNA silencing mechanism. A 12,000 feature oligonucleotide microarray has been used to identify global changes in host plant, in addition to virus genome-encoded gene expression associated with WCMV infection in non-transgenic and transgenic WCMV-resistant white clover. Pairwise comparison between the transcriptome of mock-inoculated non-transgenic and WCMV-inoculated transgenic plants provides clear evidence for substantial equivalence between these two genotype/treatments, and demonstrate the efficacy of the transgenic strategy. WCMV- inoculated non-transgenic plants exhibit elevated abundance of many virus-encoded, and host immune response-specific transcripts compared to the transgenic resistant plants or mock-inoculated non-transgenic plants. By contrast, relative to inoculated sensitive plants, the majority of significantly up-regulated genes in mock-inoculated non-transgenic plants or WCMV-inoculated transgenic plants are markers of healthy cellular function. These results, and the occurrence of levels of WCMV-encoded transcripts in inoculated transgenic plants equivalent to those in virus-free plants, confirm the validity of the transgenic RNA silencing approach.<br>
