title: Extremely high mutation rate of a hammerhead viroid.
abstract: The mutation rates of viroids, plant pathogens with minimal non-protein-coding RNA genomes, are unknown. Their replication is mediated by host RNA polymerases and, in some cases, by hammerhead ribozymes, small self-cleaving motifs embedded in the viroid. By using the principle that the population frequency of nonviable genotypes equals the mutation rate, we screened for changes that inactivated the hammerheads of Chrysanthemum chlorotic mottle viroid. We obtained a mutation rate of 1/400 per site, the highest reported for any biological entity. Such error-prone replication can only be tolerated by extremely simple genomes such as those of viroids and, presumably, the primitive replicons of the RNA world. Our results suggest that the emergence of replication fidelity was critical for the evolution of complexity in the early history of life.
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-Universidad Politécnica de València, 46022 València, Spain.
authors.forename: Selma
authors.initials: S
authors.lastname: Gago
authors.forename: Santiago F
authors.initials: SF
authors.lastname: Elena
authors.forename: Ricardo
authors.initials: R
authors.lastname: Flores
authors.forename: Rafael
authors.initials: R
authors.lastname: Sanjuán
mesh_terms: D016679:Genome, Viral; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D016337:RNA, Catalytic / Q000737:chemistry / Q000235:genetics*; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics*; D012093:Replicon; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012641:Selection, Genetic; D014772:Viroids / Q000235:genetics* / Q000502:physiology; D014779:Virus Replication
chemical_list: D016337:RNA, Catalytic; D012367:RNA, Viral; C427204:hammerhead ribozyme