RESISTANCE TO PLUM POX VIRUS PPV IN NICOTIANA BENTHAMIANA PLANTS TRANSFORMED WITH THE PPV HCPRO SILENCING SUPPRESSOR GENE
D. Barajas, F. Tenllado, P. González-Jara, B. Martínez-García, F.A. Atencio, J.R. Díaz-Ruíz
Resistance to Plum pox virus (PPV) was tested in transgenic Nicotiana benthamiana plants containing a translatable construct derived from the full-length helper-component proteinase (HC-Pro) gene of PPV. Some of the lines tested showed a resistance characterized by a lack of systemic symptoms and viral RNA accumulation in systemic and inoculated leaves. Resistance was also effective against another closely related PPV strain, but not against other potyviruses such as Tobacco etch virus (TEV) and Potato virus Y (PVY). Resistance to PPV correlated with a lower accumulation of HC-Pro transgene mRNA and the accumulation of short-interfering RNAs (siRNAs) derived from the transgene. Resistance to PPV also correlated with the trans-inactivation of a transiently expressed GUS gene, which shares homology with the 3’ portion of the HCPro transgene. These results indicate that the PPV resistance was caused by a post-transcriptional gene silencing (PTGS) process promoted by the HC-Pro transgene, which can induce silencing under certain conditions despite encoding a suppressor of PTGS.