RNA SILENCING AND VIROIDS
M. Barba, A. Hadidi
Viroids are autonomously replicating, small singlestranded circular RNA molecules that do not code for proteins and may cause disease in infected, susceptible plants. Viroids have the ability to induce both RNA-mediated transcriptional gene silencing (TGS) and posttranscriptional gene silencing (PTGS) in infected plants. Viroid PTGS has also been demonstrated in a wheat germ extract system. A possible role of gene silencing in viroid pathogenicity and evolution has been proposed.