Defensins: Evolution


The α and β defensins are short, cationic peptides that are used in the antibacterial defences of mammals. The α‐ and β‐defensin gene families have diversified as a result of recent gene duplications in several lineages of mammals, and there is evidence that positive Darwinian selection has had a role in their diversification.

Keywords: defensin; gene duplication; immune system; innate defences; positive Darwinian selection

Figure 1.

Phylogenetic trees of defensins constructed by the neighbour‐joining method (Saitou and Nei, ). Numbers on the branches are percentages of 1000 bootstrap replicates that support that clustering pattern. (a) Human and rhesus monkey α defensins, rooted with rabbit α defensins. (b) Primate and mouse β defensins.

Figure 2.

Plots of the number of nonsynonymous nucleotide substitutions per nonsynonymous site (dN) versus the number of synonymous nucleotide substitutions per synonymous site (dS), estimated by the method of Nei and Gojobori , in the mature α defensin (a) and the remainder of the coding region (b) for α‐defensin genes of human and rhesus monkey. A 45° line is drawn in both panels.



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Further Reading

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Hughes, Austin L(Mar 2008) Defensins: Evolution. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0006136.pub2]