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Mutation exposed: a neutral explanation for extreme base composition of an endosymbiont genome.

Publication ,  Journal Article
Wernegreen, JJ; Funk, DJ
Published in: Journal of molecular evolution
December 2004

The influence of neutral mutation pressure versus selection on base composition evolution is a subject of considerable controversy. Yet the present study represents the first explicit population genetic analysis of this issue in prokaryotes, the group in which base composition variation is most dramatic. Here, we explore the impact of mutation and selection on the dynamics of synonymous changes in Buchnera aphidicola, the AT-rich bacterial endosymbiont of aphids. Specifically, we evaluated three forms of evidence. (i) We compared the frequencies of directional base changes (AT-->GC vs. GC-->AT) at synonymous sites within and between Buchnera species, to test for selective preference versus effective neutrality of these mutational categories. Reconstructed mutational changes across a robust intraspecific phylogeny showed a nearly 1:1 AT-->GC:GC-->AT ratio. Likewise, stationarity of base composition among Buchnera species indicated equal rates of AT-->GC and GC-->AT substitutions. The similarity of these patterns within and between species supported the neutral model. (ii) We observed an equivalence of relative per-site AT mutation rate and current AT content at synonymous sites, indicating that base composition is at mutational equilibrium. (iii) We demonstrated statistically greater equality in the frequency of mutational categories in Buchnera than in parallel mammalian studies that documented selection on synonymous sites. Our results indicate that effectively neutral mutational pressure, rather than selection, represents the major force driving base composition evolution in Buchnera. Thus they further corroborate recent evidence for the critical role of reduced N(e) in the molecular evolution of bacterial endosymbionts.

Duke Scholars

Published In

Journal of molecular evolution

DOI

EISSN

1432-1432

ISSN

0022-2844

Publication Date

December 2004

Volume

59

Issue

6

Start / End Page

849 / 858

Related Subject Headings

  • Symbiosis
  • Sequence Analysis, DNA
  • Selection, Genetic
  • Mutation
  • Molecular Sequence Data
  • Genome, Bacterial
  • Genetics, Population
  • Evolutionary Biology
  • Evolution, Molecular
  • Databases, Nucleic Acid
 

Citation

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Wernegreen, J. J., & Funk, D. J. (2004). Mutation exposed: a neutral explanation for extreme base composition of an endosymbiont genome. Journal of Molecular Evolution, 59(6), 849–858. https://doi.org/10.1007/s00239-003-0192-z
Wernegreen, Jennifer J., and Daniel J. Funk. “Mutation exposed: a neutral explanation for extreme base composition of an endosymbiont genome.Journal of Molecular Evolution 59, no. 6 (December 2004): 849–58. https://doi.org/10.1007/s00239-003-0192-z.
Wernegreen JJ, Funk DJ. Mutation exposed: a neutral explanation for extreme base composition of an endosymbiont genome. Journal of molecular evolution. 2004 Dec;59(6):849–58.
Wernegreen, Jennifer J., and Daniel J. Funk. “Mutation exposed: a neutral explanation for extreme base composition of an endosymbiont genome.Journal of Molecular Evolution, vol. 59, no. 6, Dec. 2004, pp. 849–58. Epmc, doi:10.1007/s00239-003-0192-z.
Wernegreen JJ, Funk DJ. Mutation exposed: a neutral explanation for extreme base composition of an endosymbiont genome. Journal of molecular evolution. 2004 Dec;59(6):849–858.
Journal cover image

Published In

Journal of molecular evolution

DOI

EISSN

1432-1432

ISSN

0022-2844

Publication Date

December 2004

Volume

59

Issue

6

Start / End Page

849 / 858

Related Subject Headings

  • Symbiosis
  • Sequence Analysis, DNA
  • Selection, Genetic
  • Mutation
  • Molecular Sequence Data
  • Genome, Bacterial
  • Genetics, Population
  • Evolutionary Biology
  • Evolution, Molecular
  • Databases, Nucleic Acid