Suppressor of RNA silencing encoded by the monopartite tomato leaf curl Java']Java begomovirus

We previously isolated the monopartite begomovirus tomato leaf curl Java virus (ToLCJAV) and satellite DNA beta 02 from the same naturally infected tomato source in Indonesia. ToLCJAV induced mild leaf curl symptoms in Nicotiana benthamiana plants; DNA beta 02 encoded the beta C1 gene and produced severe leaf curl symptoms when co-inoculated with ToLCJAV in N. benthamiana. However, DNA beta 02m beta C1, which contains a frame shift mutation, did not induce severe symptoms in N. benthamiana when co-inoculated with ToLCJAV. Expression of the beta C1 gene in N. benthamiana using a potato virus X (PVX) vector induced virus-like symptoms in the absence of ToLCJAV infection. When beta C1 and green fluorescent protein (GFP) genes were co-expressed in the GFP-expressing N. benthamiana line 16c from a PVX vector, beta C1 was able to suppress posttranscriptional gene silencing (PTGS) induced by GFP and eliminated the short interfering RNA (siRNA) associated with GFP expression, with a correlated increase in GFP mRNA accumulation. When C2 or C4 genes of ToLCJAV and the GFP gene were co-expressed in the GFP-expressing N. benthamiana line 16c, C2 showed a weak suppressor activity and C4 was unable to suppress PTGS induced by GFP, and siRNA associated with GFP was detected. The results of the sub-cellular localization of ToLCJAV-beta C1 in the epidermal cells of N. benthamiana and onion tissues showed that this protein is accumulated towards the periphery of the cell.