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- Title
Natural selection in avian protein-coding genes expressed in brain.
- Authors
AXELSSON, ERIK; HULTIN-ROSENBERG, LINA; BRANDSTRÖM, MIKAEL; ZWAHLÉN, MARTIN; CLAYTON, DAVID F.; ELLEGREN, HANS
- Abstract
The evolution of birds from theropod dinosaurs took place approximately 150 million years ago, and was associated with a number of specific adaptations that are still evident among extant birds, including feathers, song and extravagant secondary sexual characteristics. Knowledge about the molecular evolutionary background to such adaptations is lacking. Here, we analyse the evolution of > 5000 protein-coding gene sequences expressed in zebra finch brain by comparison to orthologous sequences in chicken. Mean dN/ dS is 0.085 and genes with their maximal expression in the eye and central nervous system have the lowest mean dN/ dS value, while those expressed in digestive and reproductive tissues exhibit the highest. We find that fast-evolving genes (those which have higher than expected rate of nonsynonymous substitution, indicative of adaptive evolution) are enriched for biological functions such as fertilization, muscle contraction, defence response, response to stress, wounding and endogenous stimulus, and cell death. After alignment to mammalian orthologues, we identify a catalogue of 228 genes that show a significantly higher rate of protein evolution in the two bird lineages than in mammals. These accelerated bird genes, representing candidates for avian-specific adaptations, include genes implicated in vocal learning and other cognitive processes. Moreover, colouration genes evolve faster in birds than in mammals, which may have been driven by sexual selection for extravagant plumage characteristics.
- Subjects
BIRDS; GENES; HEREDITY; ORGANS (Anatomy); PRESERVATION of organs, tissues, etc.; MAMMALS; CENTRAL nervous system; MUSCLE contraction; CELL death
- Publication
Molecular Ecology, 2008, Vol 17, Issue 12, p3008
- ISSN
0962-1083
- Publication type
Article
- DOI
10.1111/j.1365-294X.2008.03795.x