Viroids and RNA Silencing

In plants, RNA silencing refers to a network of pathways where small RNAs are associated with gene regulation and the defense against foreign nucleic acids including transgenes, viruses, and viroids. Replicating viroids recruit host RNA silencing machinery and trigger the production of abundant viroid-derived small interfering RNAs. Here, the recent advances in viroid–host RNA silencing are summarized. Possible implications of viroid-induced RNA silencing for viroid symptoms, host gene expression, and epigenetics are discussed.