4种天鹅线粒体基因组和BLB基因的分子进化研究

发布时间：2019-07-08 19:10

【摘要】：天鹅是雁形目(Anserformes)鸭科(Anatidae)的鸟类,在我国分布的有大天鹅(Cygnus Cygnus)、小天鹅(Cygnus columbianus)和疣鼻天鹅(Cygnus olor),均为国家二级保护动物,具有较高的经济价值。由于人类破坏和自然环境的改变使天鹅的数量正在逐年下降,因此探究天鹅的繁育能力、对疾病的抗病能力显得尤为重要。鸟类BLB基因是与鸟类抗病能力密切相关的基因,随着分子生物学的广泛应用,越来越多的学者关注雁形目鸟类的分子方面的研究,例如利用线粒体基因组重建系统发育树,解决物种的起源和分类的问题；通过MHC基因的测定研究物种的传染病的抗病能力。目前NCBI中已有二十余种雁形目鸟类线粒体基因组的全序列被测出,多种鸟类的BLB分子的序列被公布,但对天鹅的相关研究并不多。本研究获得大天鹅、小天鹅、黑天鹅和疣鼻天鹅四种天鹅的BLB基因的外显子2、3序列,研究天鹅BLB基因的多态性,为雁形目鸟类的MHC研究提供理论资料,有助于研究疾病的防治和物种的保护。并结合线粒体基因组的全序列从分子角度研究天鹅的进化关系,结果如下：1.大天鹅、疣鼻天鹅的线粒体基因组全序列分别长16721 bp和16735 bp,碱基表现出明显的AT偏倚,构建系统进化树显示疣鼻天鹅和黑天鹅先分化,大天鹅和小天鹅后分化。2.本实验获得天鹅BLB序列的结构为3个内含子和4个外显子,其中外显子2长度为270 bp,外显子3长度为282 bp。3. exon 2多态性明显高于exon 3。4. exon 2在进化过程中受正选择压力的影响,exon 3为中性选择,进化过程中更为保守。5.天鹅BLB的exon 2的系统进化树中出现不同物种交叉出现的现象,认为天鹅的BLB基因在进化过程中存在跨物种进化。另外exon 2构建的进化树趋势与mtDNA构建进化树相近。6.综合等位基因的分型情况,分析推断大天鹅的BLB基因至少存在2个基因座。
[Abstract]:Swan is a bird of (Anserformes) Duck family (Anatidae). The big swan (Cygnus), small swan (Cygnus columbianus) and verrucous nose swan (Cygnus olor), are both national second-class protected animals in China, which have high economic value. Because of the destruction of human beings and the change of natural environment, the number of swans is decreasing year by year, so it is particularly important to explore the breeding ability of swans and the disease resistance. Bird BLB gene is closely related to the resistance of birds. With the wide application of molecular biology, more and more scholars pay attention to the molecular research of wild goose birds, such as the reconstruction of phylogenetic trees by using mtDNA genome to solve the problem of species origin and classification, and the determination of MHC gene to study the disease resistance of species. At present, more than 20 species of wild goose birds have been sequenced in NCBI, and the sequences of BLB molecules in many kinds of birds have been published, but there are few studies on swans. In this study, the exons 2 and 3 of BLB gene of swans, small swans, black swans and warts were obtained, and the polymorphism of swan BLB gene was studied, which provided theoretical data for the study of MHC in wild goose birds, and was helpful to study the prevention and treatment of diseases and the protection of species. The evolutionary relationship of swans was studied from a molecular point of view in combination with the complete sequence of mtDNA genomes. The results are as follows: 1. The complete sequence of mtDNA of big swan and warrucous swan showed obvious AT bias in length of 16721 bp and 16735 bp, respectively. the construction of phylogenetic tree showed that swan and black swan differentiated first, big swan and small swan differentiated later. 2. In this experiment, the structure of swan BLB sequence is 3 introns and 4 exons, in which the length of exon 2 is 270 bp, and the length of Exon 3 is 282 bp.3.. The polymorphism of exon 2 was significantly higher than that of exon 3.4. Exon 2 is influenced by positive selection pressure in the process of evolution. Exon 3 is neutral selection, and it is more conservative in the process of evolution. 5. There is a phenomenon that different species cross in the phylogenetic tree of exon 2 of swan BLB, and it is considered that the BLB gene of swan evolves across species in the process of evolution. In addition, the trend of evolutionary tree constructed by exon 2 is similar to that constructed by mtDNA. 6. According to the genotyping of alleles, it was inferred that there were at least two loci of BLB gene in swan.
【学位授予单位】：东北林业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：Q953

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