V2 protein encoded by Tomato yellow leaf curl China virus is an RNA silencing suppressor

The V2 protein of Tomato yellow leaf curl China virus (TYLCCNV) was identified as an RNA silencing suppressor by Agrobacterium-mediated co-infiltration. The V2 protein could inhibit local RNA silencing, systemic RNA silencing of the green fluorescent protein (GFP) gene and the spread of a systemic GFP RNA silencing signal. However, the V2 could not interfere with the cell-to-cell spread of RNA silencing. Subcellular localization assay indicated that the V2 protein was distributed in the cytoplasm of Nicotiana benthamiana cells, and accumulated in irregular cytoplasmic bodies. The V2 bound 21nt and 24nt small interfering RNA (siRNA) duplexes and 24nt single-stranded (ss)-siRNA but not 21nt ss-siRNA in electrophoresis mobility shift assays. Expression of the V2 protein via the Potato virus X (PVX) vectors heterogenous system induced severe symptoms in N. benthamiana. In a yeast two-hybrid system, TYLCCNV V2 could interact with itself, but not with SlSGS3, which is known to been involved in RNA silencing pathway and to interact with a closely related Tomato yellow leaf curl virus (TYLCV) V2. These results indicate that TYLCCNV V2 is an RNA silencing suppressor, possibly through sequestering siRNA molecules.