Eimes John A, Bollmer Jennifer L, Dunn Peter O, Whittingham Linda A, Wimpee Charles
Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA.
Genetica. 2010 Feb;138(2):265-71. doi: 10.1007/s10709-009-9417-4. Epub 2009 Oct 23.
The major histocompatibility complex (Mhc) of domestic chickens has been characterized as small and relatively simple compared with that of mammals. However, there is growing evidence that the Mhc of many bird lineages may be more complex, even within the Order Galliformes. In this study, we measured genetic variation and balancing selection at Mhc loci in another galliform, the greater prairie-chicken. We cloned and sequenced a 239 bp fragment of Mhc Class II beta-chain (BLB) exon 2 in 14 individuals. There was a total of 10 unique sequences and a minimum of four BLB loci. The d(N)/d(S) ratio at peptide-binding codons was significantly greater than one, suggesting balancing selection is acting on the BLB. We also recovered two YLB sequences, which clustered tightly with YLB sequences from three other species: domestic chicken, black grouse and common quail. The relatively large number of loci revealed in our study suggests that even closely related galliforms differ in the level of Mhc variation and structure.
与哺乳动物相比，家鸡的主要组织相容性复合体（Mhc）具有体积小且相对简单的特点。然而，越来越多的证据表明，许多鸟类谱系的Mhc可能更为复杂，即使在鸡形目内也是如此。在本研究中，我们测定了另一种鸡形目动物——草原榛鸡Mhc基因座的遗传变异和平衡选择。我们克隆并测序了14个个体中Mhc II类β链（BLB）外显子2的一个239 bp片段。共有10个独特序列，且至少有4个BLB基因座。肽结合密码子处的d(N)/d(S)比率显著大于1，表明平衡选择作用于BLB。我们还获得了两个YLB序列，它们与家鸡、黑琴鸡和普通鹌鹑这其他三个物种的YLB序列紧密聚类。我们研究中揭示的相对较多的基因座表明，即使是亲缘关系密切的鸡形目动物，其Mhc变异水平和结构也存在差异。
