It has been shown that mixed infections (with two or more viruses) occur frequently in nature, and that when two related viruses replicate simultaneously in the same cells, genetic recombination between them can take place. There is also evidence that recombination can occur between cellular and viral RNAs. Thus, virus-resistant transgenic plants (VRTPs) that express viral sequences could be a source of novel recombinant viral genomes. From a biosafety point of view, it is therefore important to understand if the recombinants that are generated in VRTPs are novel, and if they could contribute to an increased risk of emergence of recombinant viruses. Since it is impossible to test all possible recombinants, the best way to evaluate this risk is to compare the recombinants that appear in infected transgenic plants with those that appear in doubly infected non-transgenic plants under conditions of low selection pressure, i.e. in the presence of wild-type virus that can replicate recombinants in trans. Using this approach, previous results under conditions of low selection pressure showed that the populations of recombinant viral RNAs found in tobacco plants infected with two strains of Cucumber mosaic virus (CMV), a subgroup I strain (I17F-CMV) and subgroup II strain (R-CMV), were comparable to those found in tobacco transgenic for part of the R-CMV genome infected with I17F-CMV (Turturo et al. 2008). This suggests that in this case novel viral recombinants are not expected to appear. However, the recombinant viral RNAs were quite rare, and the populations of recombinants were strongly dominated by a single hot spot, which severely limited the number of recombination sites observed. In addition, when inoculated to plants in the absence of wild-type virus, the predominant recombinant was not viable (Pierrugues et al. 2007). In order to obtain a broader sample of the types of recombinant molecules generated in transgenic plants, the same system was studied under conditions of high selection pressure, using partially disabled viruses that contain a six-nucleotide deletion of in the 3’ untranslated region of RNA3. Under these conditions, additional recombination sites between RNA3 and either the transgene mRNA or CMV genomic RNA1 were observed.
|Titolo:||Analysis of recombination between RNA3 of Cucumber mosaic virus and transgene mRNAs under conditions of high selection pressure|
MORRONI, MARCO (Primo)
|Data di pubblicazione:||ago-2008|
|Citazione:||Analysis of recombination between RNA3 of Cucumber mosaic virus and transgene mRNAs under conditions of high selection pressure / M. Morroni, J.R. Thompson, M. Tepfer. ((Intervento presentato al 14. convegno IUMS : International Congress of Virology tenutosi a Istanbul nel 2008.|
|Appare nelle tipologie:||14 - Intervento a convegno non pubblicato|