Experimental evolution and the dynamics of genomic mutation rate modifiers

Raynes, Yevgeniy; Sniegowski, Paul D.

doi:10.1038/hdy.2014.49

Cited by 59 publications

(70 citation statements)

References 84 publications

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“…For example, a high prevalence of mutator strains in pathogens has been attributed to a continued need to evade the host immune system, and pathogen genes mediating host interactions are subject to selection favoring novel variants. 46 In long-term mutualisms, the host immune system may likewise regulate endosymbionts. 47 In principle, symbiont mutations that overcome host control may be favored by symbiont-level selection.…”

Section: Shifts In Evolutionary Processes: a Priori Predictionsmentioning

confidence: 99%

Endosymbiont evolution: predictions from theory and surprises from genomes

Wernegreen

2015

Annals of the New York Academy of Sciences

116

128

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Genome data has created new opportunities to untangle evolutionary processes shaping microbial variation. Among bacteria, long-term mutualists of insects represent the smallest and (typically) most AT-rich genomes. Evolutionary theory provides a context to predict how an endosymbiotic lifestyle may alter fundamental evolutionary processes - mutation, selection, genetic drift, and recombination - and thus contribute to extreme genomic outcomes. These predictions can then be explored by comparing evolutionary rates, genome size and stability, and base compositional biases across endosymbiotic and free-living bacteria. Recent surprises from such comparisons include genome reduction among uncultured, free-living species. Some studies suggest that selection generally drives this streamlining, while drift drives genome reduction in endosymbionts; however, this remains an hypothesis requiring additional data. Unexpected evidence of selection acting on endosymbiont GC content hints that even weak selection may be effective in some long-term mutualists. Moving forward, intraspecific analysis offers a promising approach to distinguish underlying mechanisms, by testing the null hypothesis of neutrality and by quantifying mutational spectra. Such analyses may clarify whether endosymbionts and free-living bacteria occupy distinct evolutionary trajectories or alternatively, represent varied outcomes of similar underlying forces.

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Section: Shifts In Evolutionary Processes: a Priori Predictionsmentioning

confidence: 99%

Endosymbiont evolution: predictions from theory and surprises from genomes

Wernegreen

2015

Annals of the New York Academy of Sciences

116

128

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“…In largely asexually reproducing populations, an allele that causes an increased mutation rate (a 'mutator') can remain linked to any beneficial mutations that it induces, and hence increase in frequency by 'hitchhiking' [100]. Adaptation in microbial populations indeed often leads to evolution of mutator strains whose DNA repair is defective, and which produce beneficial mutations more frequently than non-mutators, resulting (often temporarily) in an increased mutation rate [107]. In sexual populations, however, recombination quickly disassociates mutator alleles from any beneficial mutations, and their increased frequency of deleterious mutations favours alleles conferring lower mutation rates [61,108].…”

Section: Is There An Evolvability Problem? (A) Genetic Variation and mentioning

confidence: 99%

“…(b) The evolution of mutation rates, sex and genetic recombination Selection on variants that alter the mutation rate has been intensively studied, both theoretically and experimentally [61,107,108], with the aim of understanding the outcome of the conflict between the potential advantage of producing beneficial mutations, and the fact that most mutations that affect fitness are deleterious [27,61]. In largely asexually reproducing populations, an allele that causes an increased mutation rate (a 'mutator') can remain linked to any beneficial mutations that it induces, and hence increase in frequency by 'hitchhiking' [100].…”

Section: Is There An Evolvability Problem? (A) Genetic Variation and mentioning

confidence: 99%

The sources of adaptive variation

2017

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The role of natural selection in the evolution of adaptive phenotypes has undergone constant probing by evolutionary biologists, employing both theoretical and empirical approaches. As Darwin noted, natural selection can act together with other processes, including random changes in the frequencies of phenotypic differences that are not under strong selection, and changes in the environment, which may reflect evolutionary changes in the organisms themselves. As understanding of genetics developed after 1900, the new genetic discoveries were incorporated into evolutionary biology. The resulting general principles were summarized by Julian Huxley in his 1942 book Evolution: the modern synthesis . Here, we examine how recent advances in genetics, developmental biology and molecular biology, including epigenetics, relate to today's understanding of the evolution of adaptations. We illustrate how careful genetic studies have repeatedly shown that apparently puzzling results in a wide diversity of organisms involve processes that are consistent with neo-Darwinism. They do not support important roles in adaptation for processes such as directed mutation or the inheritance of acquired characters, and therefore no radical revision of our understanding of the mechanism of adaptive evolution is needed.

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“…Mutators are Evolutionary dynamics of integronscharacterized by an elevated mutation rate, usually caused by mutations in genes responsible for DNA mismatch correction (Denamur and Matic, 2006;Raynes and Sniegowski, 2014). In a well-adapted population, mutators are disfavored because of their increased genetic load.…”

Section: Evolutionary Dynamics Of Integronsmentioning

confidence: 99%

The evolutionary dynamics of integrons in changing environments

2016

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Integrons are genetic elements that are common in bacteria and are hotspots for genome evolution. They facilitate the acquisition and reassembly of gene cassettes encoding a variety of functions, including drug resistance. Despite their importance in clinical settings, the selective forces responsible for the evolution and maintenance of integrons are poorly understood. We present a mathematical model of integron evolution within bacterial populations subject to fluctuating antibiotic exposures. Bacteria carrying a functional integrase that mediates reshuffling of cassette genes and thereby modulates gene expression patterns compete with bacteria without a functional integrase. Our results indicate that for a wide range of parameters, the functional integrase can be stably maintained in the population despite substantial fitness costs. This selective advantage arises because gene-cassette shuffling generates genetic diversity, thus enabling the population to respond rapidly to changing selective pressures. We also show that horizontal gene transfer promotes stable maintenance of the integrase and can also lead to de novo assembly of integrons. Our model generates testable predictions for integron evolution, including loss of functional integrases in stable environments and selection for intermediate gene-shuffling rates in changing environments. Our results highlight the need for experimental studies of integron population biology.

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Experimental evolution and the dynamics of genomic mutation rate modifiers

Cited by 59 publications

References 84 publications

Endosymbiont evolution: predictions from theory and surprises from genomes

Endosymbiont evolution: predictions from theory and surprises from genomes

The sources of adaptive variation

The evolutionary dynamics of integrons in changing environments

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