کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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2430664 | 1553620 | 2016 | 7 صفحه PDF | دانلود رایگان |
• Forty eight full-length Mimi-DAB functional alleles were identified.
• High level of polymorphism in Mimi-DAB functional alleles was discovered.
• Eighteen positively selected sites were located on the Mimi-DAB alleles.
• More DAB alleles detected in miiuy croaker than in other teleost studied to date.
Major histocompatibility complex (MHC) molecules play a vital role in the immune response and are a highly polymorphic gene superfamily in vertebrates. As the molecular marker associated with polymorphism and disease susceptibility/resistance, the polymorphism of MHC genes has been investigated in many tetrapods and teleosts. Most studies were focused on the polymorphism of the second exon, which encodes the peptide-binding region (PBR) in the α1- or β1-domain, but few studies have examined the full-length coding region. To comprehensive investigate the polymorphism of MHC gene, we identified 48 full-length miiuy croaker (Miichthys miiuy) MHC class IIB (Mimi-DAB) functional alleles from 26 miiuy croaker individuals. All of the alleles encode 34 amino acid sequences, and a high level of polymorphism was detected in Mimi-DAB alleles. The rate of non-synonymous substitutions (dN) occurred at a significantly higher frequency than that of synonymous substitutions (dS) in the PBR, and this result suggests that balancing selection maintains polymorphisms at the Mimi-DAB locus. Phylogenetic analysis based on the full-length and exon 2 sequences of Mimi-DAB alleles both showed that the Mimi-DAB alleles were clustered into two major groups. A total of 19 positive selected sites were identified on the Mimi-DAB alleles after testing for positive selection, and 14 sites were predicted to be associated with antigen-binding sites, which suggests that most of selected sites are significant for disease resistance. The polymorphism of Mimi-DAB alleles provides an important resource for analyzing the association between the polymorphism of MHC gene and disease susceptibility/resistance, and for researching the molecular selective breeding of miiuy croaker with enhanced disease resistance.
Journal: Fish & Shellfish Immunology - Volume 54, July 2016, Pages 544–550