P0 proteins of European beet-infecting poleroviruses display variable RNA silencing suppression activity.

Post-transcriptional gene silencing (PTGS), or RNA silencing, is one of the key mechanisms of antiviral defence used by plants. To counter this defence response, viruses produce suppressor proteins that are able to inhibit the PTGS pathway or to interfere with some of its function. The aim of this study was to evaluate the RNA silencing suppressor (RSS) activity of P0 proteins from selected European isolates of the beet-infecting poleroviruses beet chlorosis virus (BChV) and beet mild yellowing virus (BMYV) using two different experimental systems: (i) agro-infiltration of Nicotiana benthamiana green fluorescent protein-positive plants and (ii) mechanical inoculation of Chenopodium quinoa using a beet necrotic yellow vein virus (BNYVV, genus Benyvirus) RNA3-based replicon.

Use of a Beet necrotic yellow vein virus RNA-5-derived replicon as a new tool for gene expression.

A new gene-expression system based on RNA-5 of Beet necrotic yellow vein virus (BNYVV) was constructed to allow the expression of recombinant proteins in virally infected cells. Replication and expression levels of the RNA-5-based replicon containing the green fluorescence protein (GFP) gene were compared with those obtained with the well-characterized RNA-3-derived replicon (Rep-3). When RNA-3 and/or RNA-4 BNYVV RNAs were added to the inoculum, the expression levels of RNA-5-encoded GFP were considerably reduced.