title: Adaptive synonymous mutations in an experimentally evolved Pseudomonas fluorescens population.
abstract: Conventional wisdom holds that synonymous mutations, nucleotide changes that do not alter the encoded amino acid, have no detectable effect on phenotype or fitness. However, a growing body of evidence from both comparative and experimental studies suggests otherwise. Synonymous mutations have been shown to impact gene expression, protein folding and fitness, however, direct evidence that they can be positively selected, and so contribute to adaptation, is lacking. Here we report the recovery of two beneficial synonymous single base pair changes that arose spontaneously and independently in an experimentally evolved population of Pseudomonas fluorescens. We show experimentally that these mutations increase fitness by an amount comparable to non-synonymous mutations and that the fitness increases stem from increased gene expression. These results provide unequivocal evidence that synonymous mutations can drive adaptive evolution and suggest that this class of mutation may be underappreciated as a cause of adaptation and evolutionary dynamics.
authors.affiliation: 1] Department of Biology, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5 [2].
authors.forename: Susan F
authors.initials: SF
authors.lastname: Bailey
authors.affiliation: Department of Biology, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5.
authors.forename: Aaron
authors.initials: A
authors.lastname: Hinz
authors.affiliation: Department of Biology, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5.
authors.forename: Rees
authors.initials: R
authors.lastname: Kassen
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D019143:Evolution, Molecular; D035001:Host Factor 1 Protein / Q000235:genetics; D058619:Maltose-Binding Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D018272:Porins / Q000235:genetics; D011551:Pseudomonas fluorescens / Q000235:genetics*; D012641:Selection, Genetic
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D035001:Host Factor 1 Protein; D058619:Maltose-Binding Proteins; C086247:OprB protein, Pseudomonas; D018272:Porins; C069253:fliJ protein, Bacteria