Variation in chicken populations may affect the enzymatic activity of lysozyme

The chicken lysozyme gene encodes a hydrolase that has a key role in defence, especially in ovo. This gene was resequenced in global chicken populations [red, grey, Ceylon and green jungle fowl (JF)] and related bird species. Networks, summary statistics and tests of neutrality indicate that although there is extensive variation at the gene, little is present at coding sites, with the exception of one non‐synonymous site. This segregating site and a further fixed non‐synonymous change between red JF and domestic chicken populations are spatially close to the catalytic sites of the enzyme and so might affect its activity.     

Contrasting evolution of diversity at two disease-associated chicken genes

There have been significant evolutionary pressures on the chicken during both its speciation and its subsequent domestication by man. Infectious diseases are expected to have exerted strong selective pressures during these processes. Consequently, it is likely that genes associated with disease susceptibility or resistance have been subject to some form of selection. Two genes involved in the immune response (interferon-γ and interleukin 1-β) were selected for sequencing in diverse chicken populations from Pakistan, Sri Lanka, Bangladesh, Kenya, Senegal, Burkina Faso and Botswana, as well as six outgroup samples (grey, green, red and Ceylon jungle fowl and grey francolin and bamboo partridge). Haplotype frequencies, tests of neutrality, summary statistics, coalescent simulations and phylogenetic analysis by maximum likelihood were used to determine the population genetic characteristics of the genes. Networks indicate that these chicken genes are most closely related to the red jungle fowl. Interferon-γ had lower diversity and considerable coding sequence conservation, which is consistent with its function as a key inflammatory cytokine of the immune response. In contrast, the pleiotropic cytokine interleukin 1-β had higher diversity and showed signals of balancing selection moderated by recombination, yielding high numbers of diverse alleles, possibly reflecting broader functionality and potential roles in more diseases in different environments. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. An erratum to this article can be found at