Evolutionary dynamics of an expressed MHC class IIβ locus in the Ranidae (Anura) uncovered by genome walking and high-throughput amplicon sequencing

摘要: The Major Histocompatibility Complex (MHC) is a genomic region encoding immune loci that are important and frequently used markers in studies of adaptive genetic variation disease resistance. Given the primary role infectious diseases contributing to global amphibian declines, we characterized hypervariable exon 2 flanking introns MHC Class IIβ chain for 17 species frogs Ranidae, speciose cosmopolitan family facing widespread pathogen infections declines. We find high levels concentrated Peptide Binding Region (PBR) exon. Ten codons under positive selection, nine which located mammal-defined PBR. hypothesize tenth codon (residue 21) an amphibian-specific PBR site may be Trans-species trans-generic polymorphisms evident from exon-based genealogies, co-phylogenetic analyses between intron, mitochondrial based reconstructions reveal incongruent topologies, likely due different locus histories. developed two sets barcoded adapters reliably amplify single functional all screened using both 454 Illumina sequencing methods. These primers provide resource multiplexing directly hundreds samples run, avoiding labour chimeric sequences associated with cloning, enabling population analyses. Although currently limited tested, these protocols useful can serve as starting point future disease, adaptation conservation across range anuran taxa.