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Characterization of the Recombinant Forms Arising from a Potato virus X Chimeric Virus Infection under RNA Silencing Pressure

August 2006 , Volume 19 , Number  8
Pages  904 - 913

D. Barajas , F. Tenllado , and J. R. Díaz-Ruíz

Departamento de Biología de Plantas, Centro de Investigaciones Biológicas, CSIC, Campus de la Ciudad Universitaria, Av. Ramiro de Maeztu 9, 28040 Madrid, Spain


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Accepted 20 March 2006.

Recombination is a frequent phenomenon in RNA viruses whose net result is largely influenced by selective pressures. RNA silencing in plants acts as a defense mechanism against viruses and can be used to engineer virus resistance. Here, we have investigated the influence of RNA silencing as a selective pressure to favor recombinants of PVX-HCT, a chimeric Potato virus X (PVX) vector carrying the helper-component proteinase (HC-Pro) gene from Plum pox virus (PPV). All the plants from two lines expressing a silenced HC-Pro transgene were completely resistant to PPV. However a significant proportion became infected with PVX-HCT. Analysis of viral RNAs accumulating in silenced plants revealed that PVX-HCT escaped silencing-based resistance by removal of the HC-Pro sequences that represented preferential targets for transgene-promoted silencing. The virus vector also tended to lose the HC-Pro insert when infecting transgenic plants containing a nonsilenced HC-Pro transgene or wild-type (wt) Nicotiana benthamiana plants. Nevertheless, loss of HC-Pro sequences was faster in nonsilenced transgenic plants than in wt plants, suggesting the transgene plays a role in promoting a higher selective pressure in favor of recombinant virus versions. These results indicate that the outcome of recombination processes depends on the strength of selection pressures applied to the virus.


Additional keywords: HC-Pro transgenic plants , virus stability , siRNA .

© 2006 The American Phytopathological Society