It is well-established that plants use cytoplasmic, post-transcriptional gene silencing (PTGS) as a defense against RNA viruses and DNA virus transcripts. More recently, it has become clear that small RNA-directed methylation leading to transcriptional gene silencing (TGS) is also used as a defense against DNA virus chromatin. Here we use the DNA-containing geminiviruses as models to discuss what is currently known about both types of antiviral silencing, and viral suppression of PTGS and TGS as a counterdefense.
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