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Molecular evolution of the Bovini tribe (Bovidae, Bovinae): Is there evidence of rapid evolution or reduced selective constraint in Domestic cattle?

BACKGROUND: If mutation within the coding region of the genome is largely not adaptive, the ratio of nonsynonymous (dN) to synonymous substitutions (dS) per site (dN/dS) should be approximately equal among closely related species. Furthermore, dN/dS in divergence between species should be equivalent...

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Autores principales: MacEachern, Sean, McEwan, John, McCulloch, Alan, Mather, Andrew, Savin, Keith, Goddard, Mike
Formato: Texto
Lenguaje:English
Publicado: BioMed Central 2009
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Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2681479/
https://www.ncbi.nlm.nih.gov/pubmed/19393048
http://dx.doi.org/10.1186/1471-2164-10-179
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author MacEachern, Sean
McEwan, John
McCulloch, Alan
Mather, Andrew
Savin, Keith
Goddard, Mike
author_facet MacEachern, Sean
McEwan, John
McCulloch, Alan
Mather, Andrew
Savin, Keith
Goddard, Mike
author_sort MacEachern, Sean
collection PubMed
description BACKGROUND: If mutation within the coding region of the genome is largely not adaptive, the ratio of nonsynonymous (dN) to synonymous substitutions (dS) per site (dN/dS) should be approximately equal among closely related species. Furthermore, dN/dS in divergence between species should be equivalent to dN/dS in polymorphisms. This hypothesis is of particular interest in closely related members of the Bovini tribe, because domestication has promoted rapid phenotypic divergence through strong artificial selection of some species while others remain undomesticated. We examined a number of genes that may be involved in milk production in Domestic cattle and a number of their wild relatives for evidence that domestication had affected molecular evolution. Elevated rates of dN/dS were further queried to determine if they were the result of positive selection, low effective population size (N(e)) or reduced selective constraint. RESULTS: We have found that the domestication process has contributed to higher dN/dS ratios in cattle, especially in the lineages leading to the Domestic cow (Bos taurus) and Mithan (Bos frontalis) and within some breeds of Domestic cow. However, the high rates of dN/dS polymorphism within B. taurus when compared to species divergence suggest that positive selection has not elevated evolutionary rates in these genes. Likewise, the low rate of dN/dS in Bison, which has undergone a recent population bottleneck, indicates a reduction in population size alone is not responsible for these observations. CONCLUSION: The effect of selection depends on effective population size and the selection coefficient (N(e)s). Typically under domestication both selection pressure for traits important in fitness in the wild and N(e )are reduced. Therefore, reduced selective constraint could be responsible for the observed elevated evolutionary ratios in domesticated species, especially in B. taurus and B. frontalis, which have the highest dN/dS in the Bovini. This may have important implications for tests of selection such as the McDonald-Kreitman test. Surprisingly we have also detected a significant difference in the supposed neutral substitution rate between synonymous and noncoding sites in the Bovine genome, with a 30% higher rate of substitution at synonymous sites. This is due, at least in part, to an excess of the highly mutable CpG dinucleotides at synonymous sites, which will have implications for time of divergence estimates from molecular data.
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spelling pubmed-26814792009-05-14 Molecular evolution of the Bovini tribe (Bovidae, Bovinae): Is there evidence of rapid evolution or reduced selective constraint in Domestic cattle? MacEachern, Sean McEwan, John McCulloch, Alan Mather, Andrew Savin, Keith Goddard, Mike BMC Genomics Research Article BACKGROUND: If mutation within the coding region of the genome is largely not adaptive, the ratio of nonsynonymous (dN) to synonymous substitutions (dS) per site (dN/dS) should be approximately equal among closely related species. Furthermore, dN/dS in divergence between species should be equivalent to dN/dS in polymorphisms. This hypothesis is of particular interest in closely related members of the Bovini tribe, because domestication has promoted rapid phenotypic divergence through strong artificial selection of some species while others remain undomesticated. We examined a number of genes that may be involved in milk production in Domestic cattle and a number of their wild relatives for evidence that domestication had affected molecular evolution. Elevated rates of dN/dS were further queried to determine if they were the result of positive selection, low effective population size (N(e)) or reduced selective constraint. RESULTS: We have found that the domestication process has contributed to higher dN/dS ratios in cattle, especially in the lineages leading to the Domestic cow (Bos taurus) and Mithan (Bos frontalis) and within some breeds of Domestic cow. However, the high rates of dN/dS polymorphism within B. taurus when compared to species divergence suggest that positive selection has not elevated evolutionary rates in these genes. Likewise, the low rate of dN/dS in Bison, which has undergone a recent population bottleneck, indicates a reduction in population size alone is not responsible for these observations. CONCLUSION: The effect of selection depends on effective population size and the selection coefficient (N(e)s). Typically under domestication both selection pressure for traits important in fitness in the wild and N(e )are reduced. Therefore, reduced selective constraint could be responsible for the observed elevated evolutionary ratios in domesticated species, especially in B. taurus and B. frontalis, which have the highest dN/dS in the Bovini. This may have important implications for tests of selection such as the McDonald-Kreitman test. Surprisingly we have also detected a significant difference in the supposed neutral substitution rate between synonymous and noncoding sites in the Bovine genome, with a 30% higher rate of substitution at synonymous sites. This is due, at least in part, to an excess of the highly mutable CpG dinucleotides at synonymous sites, which will have implications for time of divergence estimates from molecular data. BioMed Central 2009-04-24 /pmc/articles/PMC2681479/ /pubmed/19393048 http://dx.doi.org/10.1186/1471-2164-10-179 Text en Copyright © 2009 MacEachern et al; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( (http://creativecommons.org/licenses/by/2.0) ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Article
MacEachern, Sean
McEwan, John
McCulloch, Alan
Mather, Andrew
Savin, Keith
Goddard, Mike
Molecular evolution of the Bovini tribe (Bovidae, Bovinae): Is there evidence of rapid evolution or reduced selective constraint in Domestic cattle?
title Molecular evolution of the Bovini tribe (Bovidae, Bovinae): Is there evidence of rapid evolution or reduced selective constraint in Domestic cattle?
title_full Molecular evolution of the Bovini tribe (Bovidae, Bovinae): Is there evidence of rapid evolution or reduced selective constraint in Domestic cattle?
title_fullStr Molecular evolution of the Bovini tribe (Bovidae, Bovinae): Is there evidence of rapid evolution or reduced selective constraint in Domestic cattle?
title_full_unstemmed Molecular evolution of the Bovini tribe (Bovidae, Bovinae): Is there evidence of rapid evolution or reduced selective constraint in Domestic cattle?
title_short Molecular evolution of the Bovini tribe (Bovidae, Bovinae): Is there evidence of rapid evolution or reduced selective constraint in Domestic cattle?
title_sort molecular evolution of the bovini tribe (bovidae, bovinae): is there evidence of rapid evolution or reduced selective constraint in domestic cattle?
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2681479/
https://www.ncbi.nlm.nih.gov/pubmed/19393048
http://dx.doi.org/10.1186/1471-2164-10-179
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