中文摘要：

为了探讨牦牛（Bos grunniens）胎盘生长因子（PGF）的特征及其在不同来源囊胚中的表达差异,依据黄牛（Bos taurus）PGF基因序列5′端和3′端的保守序列设计特异性引物,RT-PCR克隆得到牦牛PGF基因,利用生物信息学软件对牦牛PGF基因进行特征进行预测分析,同时采取实时荧光定量（RT-qPCR）检测PGF基因在牦牛体外受精囊胚和体内来源囊胚中表达的差异性。结果,本研究成功克隆得到牦牛PGF基因序列（GeneBank登录号：KU902418）,在组成蛋白质的149个氨基酸中,含量最高的是半胱氨酸Cys（27.9%）,最低的是丙氨酸Ala（21.4%）,PGF基因编码的蛋白为亲水性蛋白。同源性分析和系统进化树分析结果表明,牦牛PGF基因与黄牛PGF基因具有高度同源性,为99.3%,表明PGF基因在进化过程中有高度的保守性。实时荧光定量结果显示,体内来源囊胚的PGF基因表达水平显著高于体外囊胚（P〈0.05）,约为体外囊胚的6.3倍。结果表明,PGF基因体外囊胚低水平表达在一定程度上影响囊胚附植。上述研究结果为哺乳动物囊胚附植机制研究提供了一定的理论基础。

英文摘要：

In order to study the characteristics of placental growth factor（PGF） in yak and to determine the expression difference of PGF in different sources of blastocysts,specific primers were designed on the basis of conserved PGF gene sequence of Bos taurus.The PGF sequence was analyzed by bioinformatics,and the differences of different blastocyst sources were detected by the quantitative real-time PCR.The results showed that the PGF gene sequence of yak contained a complete coding sequence（GeneBank accession number：KU902418）,encoding 149 amino acids in which the highest content of cysteine residues was 27.9 percent;the lowest residue was alanine,which took 21.4 percent, and the related protein was hydrophilicity.According to homology analysis,the similarity of PGF gene in bos grunniens was up to 99.3%,suggesting that the PGF gene was conserved in the evolution process.The expression level of PGF gene in vivo blastocysts was about 6.3 times as that many as in vitro by QRT-PCR.The low level of expression in vitro affected the implantation of blastocysts partly,which provided theoretical basis for the study of mammalian blastocyst implantation.