title: Viroids: the minimal non-coding RNAs with autonomous replication.
abstract: Viroids are small (246-401 nucleotides), non-coding, circular RNAs able to replicate autonomously in certain plants. Viroids are classified into the families Pospiviroidae and Avsunviroidae, whose members replicate in the nucleus and chloroplast, respectively. Replication occurs by an RNA-based rolling-circle mechanism in three steps: (1). synthesis of longer-than-unit strands catalyzed by host DNA-dependent RNA polymerases forced to transcribe RNA templates, (2). processing to unit-length, which in family Avsunviroidae is mediated by hammerhead ribozymes, and (3). circularization either through an RNA ligase or autocatalytically. Disease induction might result from the accumulation of viroid-specific small interfering RNAs that, via RNA silencing, could interfere with normal developmental pathways.
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas (UPV-CSIC), Universidad Politécnica de Valencia, 46022 Valencia, Spain. rflores@ibmcp.upv.es
authors.forename: Ricardo
authors.initials: R
authors.lastname: Flores
authors.forename: Sonia
authors.initials: S
authors.lastname: Delgado
authors.forename: María-Eugenia
authors.initials: ME
authors.lastname: Gas
authors.forename: Alberto
authors.initials: A
authors.lastname: Carbonell
authors.forename: Diego
authors.initials: D
authors.lastname: Molina
authors.forename: Selma
authors.initials: S
authors.lastname: Gago
authors.forename: Marcos
authors.initials: M
authors.lastname: De la Peña
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry; D020868:Gene Silencing; D008954:Models, Biological; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010942:Plant Viruses / Q000737:chemistry*; D012313:RNA / Q000737:chemistry*; D034622:RNA Interference; D012323:RNA Processing, Post-Transcriptional; D016337:RNA, Catalytic / Q000737:chemistry; D014772:Viroids / Q000737:chemistry* / Q000502:physiology*; D014779:Virus Replication
chemical_list: D016337:RNA, Catalytic; C427204:hammerhead ribozyme; D012313:RNA; D004247:DNA