Positive diversifying selection in avian Mx genes |
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Authors: | Sofia Berlin Lujiang Qu Xianyao Li Ning Yang Hans Ellegren |
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Institution: | (1) Department of Evolutionary Biology, Uppsala University, Norbyvagen 18 D, 752 36 Uppsala, Sweden;(2) College of Animal Science and Technology, State Key Laboratory for Agro Biotechnology, China Agricultural University, Beijing, 100094, China |
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Abstract: | Mx proteins are interferon-induced GTPases that confer antiviral activities against RNA viruses. We analysed the molecular
evolution of the Mx gene in birds using data on interspecific divergence in anseriform and galliform birds, and on intraspecific diversity in
commercial chicken lines, local Chinese chicken breeds as well as in the mallard. The overall ratio of non-synonymous to synonymous
substitution was unusually high, 0.80, indicating relaxed constraint or positive selection. Evidence for the latter was provided
by that a total of 11–18 codons were found to have evolved under positive selection. The great majority of these codons are
located in a region unique to birds at the N-terminal end of the Mx protein. We found an excess of non-synonymous polymorphisms
relative to synonymous variants in all comparisons. This, together with positive Tajima’s D values in the local Chinese chicken breeds and in the mallard suggests that balancing selection is acting in avian Mx genes. As such, Mx mimics the major histocompatibility complex system, indicating that heterozygous individuals are better
off withstanding pathogen attack.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
S.B. and L.Q. contributed equally to this work. |
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Keywords: | Mx gene Birds Positive selection Avian influenza virus Chicken |
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