title: Viroid-induced DNA methylation in plants.
abstract: In eukaryotes, DNA methylation refers to the addition of a methyl group to the fifth atom in the six-atom ring of cytosine residues. At least in plants, DNA regions that become de novo methylated can be defined by homologous RNA molecules in a process termed RNA-directed DNA methylation (RdDM). RdDM was first discovered in viroid-infected plants. Viroids are pathogenic circular, non-coding, single-stranded RNA molecules. Members of the Pospiviroidae family replicate in the nucleus through double-stranded RNA intermediates, attracting the host RNA silencing machinery. The recruitment of this machinery results in the production of viroid-derived small RNAs (vd-sRNAs) that mediate RNA degradation and DNA methylation of cognate sequences. Here, we provide an overview of the cumulative data on the field of viroid-induced RdDM and discuss three possible scenarios concerning the mechanistic details of its establishment.
authors.forename: Athanasios
authors.initials: A
authors.lastname: Dalakouras
authors.forename: Elena
authors.initials: E
authors.lastname: Dadami
authors.forename: Michael
authors.initials: M
authors.lastname: Wassenegger
mesh_terms: D019175:DNA Methylation; D018744:DNA, Plant / Q000235:genetics; D010935:Plant Diseases / Q000821:virology*; D010944:Plants / Q000235:genetics / Q000821:virology*; D034622:RNA Interference; D012367:RNA, Viral / Q000235:genetics; D014772:Viroids / Q000254:growth & development*
chemical_list: D018744:DNA, Plant; D012367:RNA, Viral