Characterization and Evolution of MHC Class II B Genes in Ardeid Birds
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Major histocompatibility complex (MHC) is a multi-gene family that is very suitable to investigate a wide range of open questions in evolutionary ecology. In this study, we characterized two expressed MHC class II B genes (DAB1 and DAB2) in the Grey Heron (Aves: Ardea cinerea). We further developed the primer pairs to amplify and sequence two MHC class II B loci in ten ardeid birds. Phylogenetic analysis revealed that different parts of the genes showed different evolutionary patterns. The exon 2 sequences tended to cluster two gene-specific lineages. In each lineage, exon 2 sequences from several species showed closer relationships than sequences within species, and two shared identical alleles were found between species (Egretta sacra and Nycticorax nycticorax; Egretta garzetta and Bubulcus ibis), supporting the hypothesis of trans-species polymorphism. In contrast, the species-specific intron 2 plus partial exon 3 tree suggested that DAB1 and DAB2 were subject to concerted evolution. GENECONV analyses showed the gene exchange played an important role in the ardeid MHC evolution.
KeywordsMHC II B gene Ardeid birds Trans-species polymorphism Concerted evolution Genetic exchange
We thank Lin Qingxian for his assistance in samples collection. This research was supported by the National Natural Science Foundation of China (Grant code 30970380 and 40876077), the Fujian Natural Science Foundation of China (Grant code 2009J01195 and 2008S0007) and the Program for Innovative Research Team in Science and Technology in Fujian Province University.
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