Conflicts of interest: None.
Molecular evolution and expression of archosaurian β-keratins: Diversification and expansion of archosaurian β-keratins and the origin of feather β-keratins
Article first published online: 6 JUN 2013
Copyright © 2013 Wiley Periodicals, Inc.
Journal of Experimental Zoology Part B: Molecular and Developmental Evolution
Volume 320, Issue 6, pages 393–405, September 2013
How to Cite
2013. Molecular evolution and expression of archosaurian β-keratins: Diversification and expansion of archosaurian β-keratins and the origin of feather β-keratins. J. Exp. Zool. (Mol. Dev. Evol.) 320B:393–405., .
- Issue published online: 8 AUG 2013
- Article first published online: 6 JUN 2013
- Manuscript Accepted: 4 MAY 2013
- Manuscript Revised: 25 APR 2013
- Manuscript Received: 21 DEC 2012
The archosauria consist of two living groups, crocodilians, and birds. Here we compare the structure, expression, and phylogeny of the beta (β)-keratins in two crocodilian genomes and two avian genomes to gain a better understanding of the evolutionary origin of the feather β-keratins. Unlike squamates such as the green anole with 40 β-keratins in its genome, the chicken and zebra finch genomes have over 100 β-keratin genes in their genomes, while the American alligator has 20 β-keratin genes, and the saltwater crocodile has 21 β-keratin genes. The crocodilian β-keratins are similar to those of birds and these structural proteins have a central filament domain and N- and C-termini, which contribute to the matrix material between the twisted β-sheets, which form the 2–3 nm filament. Overall the expression of alligator β-keratin genes in the integument increases during development. Phylogenetic analysis demonstrates that a crocodilian β-keratin clade forms a monophyletic group with the avian scale and feather β-keratins, suggesting that avian scale and feather β-keratins along with a subset of crocodilian β-keratins evolved from a common ancestral gene/s. Overall, our analyses support the view that the epidermal appendages of basal archosaurs used a diverse array of β-keratins, which evolved into crocodilian and avian specific clades. In birds, the scale and feather subfamilies appear to have evolved independently in the avian lineage from a subset of archosaurian claw β-keratins. The expansion of the avian specific feather β-keratin genes accompanied the diversification of birds and the evolution of feathers. J. Exp. Zool. (Mol. Dev. Evol.) 320B: 393–405, 2013. © 2013 Wiley Periodicals, Inc.