3个不同尼罗罗非鱼(Oreochromis niloticus)群体MHC ⅡA基因多态性和遗传分化

MHC ⅡA Gene in Three Different Populations of Nile tilapia(Oreochromis niloticus)

MHC ⅡA作为主要组织相容性复合体的重要成分之一,在鱼类的免疫系统中发挥重要作用,具有高度多态性。本研究从广东省3个不同养殖地区的91尾尼罗罗非鱼(Oreochromis niloticus)的个体中获得了MHC ⅡA的第二外显子区域序列共501条,长度为647～742 bp。对该序列进行分析,共发现12个不同的等位基因。三个群体中核苷酸序列变异百分比为34.73%～60.78%,氨基酸变异百分比为68.24%～78.82%,其中惠州群体的变异比例最高(60.78%和78.82%)。单倍型多样性和核苷酸多样性分析表明:惠州群体的遗传多样性最为丰富。群体间分化指数(Fst)、中性检测(Tajima检测)、平均基因流、平均K2-P遗传距离和AMOVA分析的各项数据表明MHC ⅡA基因的第二外显子区域在3个不同群体间遗传分化不显著,存在一定的基因交流。本研究发现的MHC ⅡA基因的高度多态性及遗传结果,为尼罗罗非鱼抗病品种的选育以及种质资源的保护奠定了重要的基础资料。

MHCⅡA plays an important role in the immune system with a highly polymorphic of fish as one of the important components of major histocompatibility complexes.In this study,501 exon 2 region sequences in MHCⅡA were obtained from the 91 individuals of Nile tilapia(Oreochromis niloticus)from three different farming areas in Guangdong province.The sequence of exon 2 was 647~742 bp in length.The analysis of this sequence showed that there were 12 different alleles.The percentage of nucleotide sequence variation among the three populations ranged from 34.73%to 60.78%,and the percentage of amino acid variation was 68.24%to 78.82%.Among them,Huizhou population had the highest percentage of variation(60.78%and 78.82%).The analysis of haplotype diversity and nucleotide diversity showed that the genetic diversity of Huizhou population was most abundant.The data of FSTvalue,Tajima test,average gene flow,average K2-P genetic distances,and AMOVA analysis revealed that the second exon region of MHCⅡA gene was not significantly genetic differentiated among three different populations and there was some gene exchange.The high polymorphism and genetic results of MHCⅡA gene found in this study might provide important basic information for the disease resiatance breeding of Nile tilapia and the protection of germplasm resources.