牛羊SSR分析及MHC进化机制研究

发布时间：2018-04-29 10:29

本文选题：MHC + 微卫星　；参考：《西南大学》2017年硕士论文

【摘要】：动物遗传多样性是动物遗传育种的基础,而DNA多态性在评估群体遗传多样性和群体遗传结构中起着重要作用。微卫星(Simple Sequence Repeat,SSR)多态性丰富,被广泛应用于评估动物群体的遗传多样性,所反映的群体遗传结构往往与各自地理分布和管理背景相一致。不同地理分布群体在环境适应性方面不尽相同,主要组织相容性复合物(Major Histocompatibility Complex,MHC)在动物适应性免疫中起主要作用。MHC多样性与动物疾病抗性密切相关,但MHC多样性的形成与维持机制尚不清楚。本研究收集了不同地理分布和管理背景的山羊、绵羊和牛共3个物种53个品种(群体)的1439个样本,通过全基因组微卫星标记(以下简称基因组SSR)和MHC区域微卫星标记(以下简称MHC SSR)分析所有群体的遗传多样性,比较两种水平所反映的群体遗传差异,推测MHC可能存在的进化机制,为家畜在抗病育种和提高环境适应性研究中提供基础数据。本研究的主要结果与结论如下:1、通过分析山羊、绵羊和牛的群体遗传多样性,发现基因组SSR反映出的群体间遗传关系与其地理分布及历史起源基本一致。2、通过分析山羊、绵羊和牛MHC SSR位点的遗传参数,发现BM1258位点在3个物种内均高度多态;BF1位点在牛和山羊群体中表现为中度多态,在绵羊群体中高度多态;DYMS1位点在山羊和绵羊群体中低度多态,在牛群体内无多态性。3、实验中山羊、绵羊和牛群体共用的10个基因组SSR位点中6个位点INRA063、SPS113、OarFCB48、TGLA53、OarFCB20、MAF70在所有群体中均高度多态,可作为评估3个物种的群体遗传多样性有效遗传标记。4、通过比较基因组SSR位点和MHC SSR位点在群体中的遗传参数,发现MHC SSR位点在群体内平均杂合度较低,据此推测杂合子优势在修饰MHC多态性中所起的作用可能比较微弱。5、通过系统进化分析,发现基因组SSR水平我国引进的波尔山羊群体与非洲坦桑尼亚地方山羊群体及波尔山羊群体聚为一支,而MHC SSR水平与我国当地山羊群体聚为一支,据此推测MHC这类与免疫密切相关的遗传标记不完全适用于研究群体历史起源与进化关系。6、本实验通过对物种内群体间遗传分化分析,发现各群体MHC SSR的FST值高于基因组SSR,推测MHC区域进化中可能受到了波动选择作用的影响,且MHC区域的稀有等位基因可能是群体在进化过程中根据所处环境中病原体的变化而新产生的等位基因。7、通过对山羊、绵羊和牛物种间群体遗传关系分析,结果表明,与基因组SSR标记相比,MHC SSR标记中物种间分化程度较低,表明MHC区域存在跨物种等位基因的分布,推测MHC区域跨物种等位基因的存在可能与平衡选择相关。
[Abstract]:Animal genetic diversity is the basis of animal genetics and breeding, and DNA polymorphism plays an important role in evaluating population genetic diversity and population genetic structure. Microsatellite simple Sequence repeat SSRs are widely used to evaluate the genetic diversity of animal populations, and the genetic structure of the populations is often consistent with their geographical distribution and management background. The major histocompatibility complex Major Histocompatibility complex (MHC) plays a major role in animal adaptive immunity. MHC diversity is closely related to animal disease resistance. However, the formation and maintenance mechanism of MHC diversity is not clear. In this study, 1439 samples of 53 species (populations) of goat, sheep and cattle from different geographical distribution and management background were collected. The genetic diversity of all populations was analyzed by genomic microsatellite markers (hereinafter referred to as genomic SSRs) and MHC region microsatellite markers (MHC SSRs). The possible evolutionary mechanism of MHC may provide basic data for animal breeding for disease resistance and improvement of environmental adaptability. The main results and conclusions of this study are as follows: 1. By analyzing the population genetic diversity of goats, sheep and cattle, we found that the genetic relationship between the populations reflected by genomic SSR is basically consistent with its geographical distribution and historical origin. The genetic parameters of MHC SSR loci in sheep and cattle showed that BM1258 loci were moderately polymorphic in cattle and goat populations, and low polymorphic in goat and goat populations. There was no polymorphism in cattle. In the experiment, 6 of the 10 genomic SSR loci shared by goat, sheep and cattle were highly polymorphic (INRA063SPS113OarFCB48 / TGLA53OarFCB20MAF70) in all populations. It can be used as an effective genetic marker for evaluating the genetic diversity of three species. By comparing the genetic parameters of genomic SSR loci and MHC SSR loci in populations, it is found that the average heterozygosity of MHC SSR loci in populations is low. It is suggested that heterozygote dominance may play a weaker role in modifying MHC polymorphism. It was found that the level of genomic SSR of Boer goat introduced from China was one with that of African native goat and Boer goat, while the level of MHC SSR was the same as that of local goat. It is inferred that the genetic markers such as MHC, which are closely related to immunity, are not fully applicable to the study of the historical origin and evolution of populations. It was found that the FST value of MHC SSR in each population was higher than that of genomic SSRs, which suggested that the evolution of MHC region might be affected by fluctuating selections. The rare alleles in the MHC region may be the new alleles. 7 in the evolutionary process according to the changes of pathogens in the environment. The genetic relationships among goat, sheep and cattle species were analyzed, and the results showed that, Compared with genomic SSR markers, the differentiation degree among species in MHC SSR markers was lower, indicating that there were cross-species alleles in the MHC region, which suggested that the existence of cross-species alleles in the MHC region might be related to balanced selection.
【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S813

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