title: Mutational fitness effects in RNA and single-stranded DNA viruses: common patterns revealed by site-directed mutagenesis studies.
abstract: The fitness effects of mutations are central to evolution, yet have begun to be characterized in detail only recently. Site-directed mutagenesis is a powerful tool for achieving this goal, which is particularly suited for viruses because of their small genomes. Here, I discuss the evolutionary relevance of mutational fitness effects and critically review previous site-directed mutagenesis studies. The effects of single-nucleotide substitutions are standardized and compared for five RNA or single-stranded DNA viruses infecting bacteria, plants or animals. All viruses examined show very low tolerance to mutation when compared with cellular organisms. Moreover, for non-lethal mutations, the mean fitness reduction caused by single mutations is remarkably constant (0.10-0.13), whereas the fraction of lethals varies only modestly (0.20-0.41). Other summary statistics are provided. These generalizations about the distribution of mutational fitness effects can help us to better understand the evolution of RNA and single-stranded DNA viruses.
authors.affiliation: Institut Cavanilles de Biodiversitat i Biologia Evolutiva and Departamento de Genética, Universitat de València, C/Catedrático Agustín Escardino 9, Valencia 46980, Spain. rafael.sanjuan@uv.es
authors.forename: Rafael
authors.initials: R
authors.lastname: Sanjuán
mesh_terms: D004267:DNA Viruses / Q000235:genetics*; D004277:DNA, Single-Stranded / Q000235:genetics*; D019143:Evolution, Molecular; D016297:Mutagenesis, Site-Directed / Q000379:methods*; D012328:RNA Viruses / Q000235:genetics*
chemical_list: D004277:DNA, Single-Stranded