Insight into gene evolution within Cervidae and  Bovidae through genetic variation in MHC-DQA in the black muntjac (Muntiacus  crinifrons).
The critical role that the major histocompatibility  complex plays in the immune recognition of parasites and pathogens makes its  evolutionary dynamics exceptionally relevant to ecology, population biology,  and conservation studies. The black muntjac is a rare deer endemic to a small  mountainous region in eastern China. We found that this species has two DQA loci  through cDNA expression and sequence variation analysis. The level of variation  at both DQA loci was found to be extremely low (three alleles for DQA1 and four alleles for DQA2), possibly because of past bottlenecks and  the species' relatively solitary behavior pattern. The ratio of d(N)/d(S) in the putative peptide binding region of  the DQA2 locus (13.36, P = 0.012) was significantly larger than one but  not that of DQA1 (0.94, P = 0.95), suggesting strong positive selection  at the DQA2 but not at the DQA1 locus. This difference might  reflect different sets of evolutionary selection pressures acting on the two  loci. The phylogenetic tree showed that DQA1 alleles from two species of  Cervidae and two of Bovidae grouped together, as did the DQA2 alleles.  However, different genes from the four species were located in separate  branches. These results lead us to suggest that these DQA alleles are  derived from primordial DQA genes from a common ancestor and are  maintained in Cervidae and Bovidae since their divergence around 25.5-27.8  million years ago.
Key Laboratory for the Conservation and Utilization of Important Biological Resources, College of Life Sciences, Anhui Normal University, Wuhu, China. whlong@mail.ahnu.edu.cn
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D000483:Alleles; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D002417:Cattle / Q000235:genetics*; D002681:China; D019143:Evolution, Molecular; D005091:Exons / Q000235:genetics; D005787:Gene Frequency / Q000235:genetics; D056426:Genetic Loci / Q000235:genetics*; D014644:Genetic Variation; D016013:Likelihood Functions; D008285:Major Histocompatibility Complex / Q000235:genetics*; D008969:Molecular Sequence Data; D018668:Muntjacs / Q000235:genetics*; D010802:Phylogeny