Polymorphism and varying selection within the MHC class I of four Anas species

AbstractDucks (Anatidae) are often vectors for the spread of pathogens because of their long-distance migrations. These migrations also expose ducks to a wide variety of pathogens in their wintering and breeding grounds, and, as a consequence, we might expect strong selection on their immune genes. Here, we studied exons 2 and 3 of the MHC class I in four species ofAnas ducks (A. platyrhynchos,A. poecilorhyncha,A. formosa, andA. querquedula) using Illumina-sequencing. Both exons 2 and 3 code for the peptide-binding region of class I molecules; however, most previous studies of birds have only focused on exon 3. Here, we found stronger positive selection on exon 2 than exon 3, as indicated by more species withdN/dS >  1 and higher Wu-Kabat values. There was little evidence that divergence time influenced polymorphism, the numbers of identical alleles (partial α1 or α2 regions) among fourAnas, or selection, suggesting that these widespread species might share similar levels of selection from pathogens. The high similarity of allele numbers, positively selected sites (PSS), conserved motifs, and variable protein sites (VPS) supported the persistence of trans-species polymorphism inAnas for at least 10 million years. Our study revealed exon 2 as a relatively unexplored source of variation in avian MHC class I, which should be considered in future studies.

Source: Immunogenetics - June 30, 2021 Category: Genetics & Stem Cells Source Type: research