鲂属鱼类线粒体基因组的比较及其系统发育分析

基于GenBank中团头鲂线粒体基因组全序列和三角鲂、厚颌鲂、广东鲂的部分线粒体基因组序列,设计引物扩增出三角鲂、厚颌鲂和广东鲂3种鱼线粒体基因组全序列,同时对4种鲂属鱼类线粒体基因组全序列进行了比较分析。结果表明,4种鲂属鱼类线粒体基因组基因排列顺序完全相同,排列紧密,均包含13个蛋白质编码基因、22个tRNA、2个rRNA、1个非编码控制区(D-loop区)和1个轻链复制起始区(OL区)。除ND6和8个tRNA在L链上编码外,其余的基因均在H链上编码。4种鲂属线粒体基因组13个蛋白质编码基因中,均呈现出较强的A+T偏向性和C碱基偏好。全序列比对结果显示,共有758个变异位点,其中非简约性信息位点有691个,占总变异位点的91.16%,简约性信息位点有67个,仅占总变异位点的8.84%。22个tRNA基因中只有11个存在种间变异,共23个变异位点,主要发生在tRNA三叶草结构的TΨC和DHU臂环上。13个蛋白质编码基因中共检测出626个变异位点,这些变异主要发生在密码子第三位,占总变异位点的82.59%,其中变异位点数最多的是Cyt b基因,达84个,其次是ND 4基因(83个)。因此,Cyt b和ND4基因可作为备选的分子标记,用于鲂属群体间的遗传学研究。基于4种鲂属鱼类线粒体基因组全序列构建的ML树和BI树均显示,三角鲂与厚颌鲂的亲缘关系最近,团头鲂与它们的亲缘关系相对较近,而广东鲂与前述3种鲂属鱼类的亲缘关系均较远。

Comparison of mitochondrial genomes of the genus Megalobrama and their phylogenetic analysis

This study cloned the complete mitochondrial genome sequences of Megalobrama skolkovii,M.pellegrini and M.terminalis based on the complete mitochondrial genome sequences of M. amblycephala and partial mitochondrial genome sequences of M.hoffmanni,M.ellegrini and M.terminalis in the GenBank database.The complete mitochondrial genome sequences of four species in the genus Megalobrama were analyzed.Results showed that all the mitochondrial genomes of the four Megalobrama fishes contained 13 protein-coding genes,22 tRNA genes,2 rRNA genes,a non-coding control region(D-loop)and a replication origin region of the light chain(OL),with identical arrangement and tightly packed.Eight tRNAs and ND6 genes were encoded on the light strand(L strand),and the remainders encoded on the heavy strand(H strand).All 13 protein-coding genes of the mitochondrial genomes from four species of the genus Megalobrama showed a strong bias toward A+T and a bias for C nucleotides.The comparison of the complete mitochondrial genome sequences showed that there were 758 variable sites,including 691 singleton variable sites(accounting for 91.19%),67 parsimony informative sites(only accounting for 8.84%).Eleven of 22 tRNA genes had mutated in Megalobrama,and 23 variable sites were mainly distributed in the TΨC and DHU of the cloverleaf secondary structure.Additionally,626 variable sites of the protein-coding genes were mainly distributed in the third codon position(accounting for 82.59%)and Cyt b gene had the largest number of different loci(84),followed by ND4 gene with 83 loci.Therefore,Cyt b and ND4 could be used as alternative molecular markers for genetics research in the genus Megalobrama groups,which provided a theoretical and technical basis for the rational and efficient use of biological resources and conservation of biological diversity.Both ML and BI phylogenetic trees based on the complete mitochondrial genome sequences from four species showed that M.terminalis and M.pellegrini had the closest genetic relationship,with M.amblycephala being more closely related to them,and M.hoffmanni was farther related to the other species.