Silencing suppressor activity of a begomovirus DNA β encoded protein and its effect on heterologous helper virus replication

DNA beta satellites are circular single-stranded molecules associated with some monopartite begomoviruses in the family Geminiviridae. They co-infect with their helper viruses to induce severe disease in economically important crops. The beta C1 protein encoded by DNA beta is a pathogenicity determinant and has been reported to suppress post-transcriptional gene silencing (PTGS). The beta C1 proteins from various DNA beta molecules show low levels of amino acid sequence conservation. We show here that the beta C1 from DNA beta associated with Cotton leaf curl Multan virus (CLCuMV) is a suppressor of systemic PTGS. When this DNA beta satellite co-inoculated with a heterologous helper virus, Tomato leaf curl virus (ToLCV), reduced the level of ToLCV siRNA and this was associated with a higher level of virus accumulation in infected tobacco plants. This may be a mechanism by which beta C1 protects a heterologous virus from host gene silencing (C) 2012 Elsevier B.V. All rights reserved.