Key Laboratory of Ministry of Education for Coast and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen, Fujian, People's Republic of China.
PLoS One. 2013 Sep 3;8(9):e74185. doi: 10.1371/journal.pone.0074185. eCollection 2013.
The major histocompatibility complex (MHC) is an excellent molecular marker for the studies of evolutionary ecology and conservation genetics because it is a family of highly polymorphic genes that play a key role in vertebrate immune response. In this study, the functional genes of MHC Class II B (DAB) were isolated for the first time in a vulnerable species, the Chinese egret (Egrettaeulophotes). Using a full length DNA and cDNA produced by PCR and RACE methods, four potential MHC DAB loci were characterized in the genome of this egret and all four were expressed in liver and blood. At least four copies of the MHC gene complex were similar to two copies of the minimal essential MHC complex of chicken, but are less complex than the multiple copies expressed in passerine species. In MHC polymorphism, 19 alleles of exon 2 were isolated from 48 individuals using PCR. No stop codons or frameshift mutations were found in any of the coding regions. The signatures of positive selection detected in potential peptide-binding regions by Bayesian analysis, suggesting that all of these genes were functional. These data will provide the fundamental basis for further studies to elucidate the mechanisms and significance of MHC molecular adaptation in vulnerable Chinese egret and other ardeids.
主要组织相容性复合体 (MHC) 是进化生态学和保护遗传学研究的极佳分子标记，因为它是一个高度多态性基因家族，在脊椎动物免疫反应中发挥关键作用。在这项研究中，首次从脆弱物种——中国白鹭 (Egrettaeulophotes) 中分离出 MHC 类 II B (DAB) 的功能基因。通过 PCR 和 RACE 方法产生全长 DNA 和 cDNA，在这种白鹭的基因组中鉴定出四个潜在的 MHC DAB 基因座，并且所有四个基因座均在肝脏和血液中表达。至少有四个 MHC 基因座的拷贝与鸡的最小必需 MHC 基因座的两个拷贝相似，但比在雀形目物种中表达的多个拷贝要简单。在 MHC 多态性方面，从 48 个个体中使用 PCR 分离出了 19 个外显子 2 的等位基因。在任何编码区都没有发现终止密码子或移码突变。贝叶斯分析检测到潜在肽结合区的正选择特征，表明所有这些基因都是有功能的。这些数据将为进一步阐明脆弱的中国白鹭和其他鹭科鸟类 MHC 分子适应的机制和意义提供基础。
