A single chimeric transgene derived from two distinct viruses confers multi-virus resistance in transgenic plants through homology-dependent gene silencing

We showed previously that 218 and 110 bp N gene segments of tomato spotted wilt virus (TSWV) that were fused to the non-target green fluorescent prote in (GFP) gene were able to confer resistance to TSWV via post-transcription al gene silencing (PTGS). N gene segments expressed alone did not confer re sistance. Apparently, the GFP DNA induced PTGS that targetted N gene segmen ts and the incoming homologous TSWV for degradation, resulting in a resista nt phenotype, These observations suggested that multiple resistance could b e obtained by replacing the GFP DNA with a viral DNA that induces PTGS. The full-length coat protein (CP) gene of turnip mosaic virus (TuMV) was linke d to 218 or 110 bp N gene segments and transformed into Nicotiana benthamia na. A high proportion (4 of 18) of transgenic lines with the 218 bp N gene segment linked to the TuMV CP gene were resistant to both viruses, and resi stance was transferred to R-2 plants. Nuclear run-on and Northern experimen ts confirmed that resistance was via PTGS. In contrast, only one of 14 tran sgenic lines with the TuMV CP linked to a 110 bp N gene segment yielded pro geny with multiple resistance. Only a few R-1 plants were resistant and res istance was not observed in R-2 plants. These results clearly show the appl icability of multiple virus resistance through the fusion of viral segments to DNAs that induce PTGS.