白纹方蟹线粒体基因组全序列测定及方蟹总科比较分析

THE COMPLETE MITOCHONDRIAL GENOME OF GRAPSUS ALBOLINEATUS LATREILLE AND COMPARATIVE ANALYSIS OF GRAPSOIDEA

为探讨该总科内部亲缘关系及其与线粒体基因排序之间的相关性,研究以方蟹科(Grapsidae)白纹方蟹(Grapsus albolineatus)为代表种,测定其线粒体基因组全序列。其全长为15577 bp,包含13个蛋白编码基因,22个tRNA基因,2个rRNA基因和1个控制区。基因组碱基组成为33.4%A、12.0%G、20.6%C和34.0%T,具有明显的AT偏向性(67.4%)。除ATP8和ND1以GTG作为起始密码子外,其余蛋白编码基因均以ATN作为起始密码子;除COⅡ和Cyt b以T作为不完全终止密码子外,其余基因均以TAN作为终止密码子。亮氨酸(Leu)和半胱氨酸(Cys)分别是使用频率最高(15.28%)和最低(0.81%)的两种密码子。除tRNA-Ser1缺少DHU臂外,其余tRNA均能形成典型的三叶草结构。基于13个蛋白编码基因的核苷酸序列同时构建了方蟹总科的贝叶斯树(BI)和最大似然树(ML),两种方法构建的系统发育树扑拓结构一致,均显示所有方蟹科(Grapsidae)种类聚在一起,其中白纹方蟹与同属的细纹方蟹(G.tenuicrustatus)的亲缘关系最近;相手蟹科(Sesarmidae)与怪方蟹科(Xenograpsidae)形成姐妹群关系后与地蟹科(Gecarcinidae)聚为一支,三者与方蟹科互为姐妹群,弓蟹科(Varunidae)则为相对独立的一支。研究还比较分析了方蟹总科(Grapsoidea)的线粒体基因排序情况,并发现方蟹总科基因重排和系统发育有着明显的相关性。研究系统地阐述了方蟹总科的系统发育关系,为更好地理解基因重排和系统发育之间的关系提供了理论支撑。

For a long time,the phylogeny of Grapsoidea(Decapoda:Brachyura)has been controversial.Complete mitochondrial genome(mitogenome)provides important information for better understanding of gene rearrangement,molecular evolution and phylogenetic analysis.However,only a few mitogenomes of Grapsidae species have been reported and the phylogenetic status of Grapsidae within Grapsoidea remains unresolved.In order clarify the phylogenetic relationship of Grapsoidea and further explore the correlation between phygeny and mitogenome rearangement,the complete mitogenome of Grapsus albolineatus,the representative species of Grapsidae was sequenced.The total length of this mitogenome is 15577 bp,containing 13 protein-coding genes,22 transfer RNA genes,2 ribosomal RNA genes and a control region.The nucleotide composition is shown as follows:33.4%A,12.0%G,20.6%C,34.0%T,respectively,with a high AT bias(67.4%).Majority protein-coding genes are initiated by the typical start codon ATN,with an exception GTG in ATP8 and ND1,most of them terminate with TAN,while two genes(COⅡand Cyt b)use a single T as a stop codon.Leu(15.8%)and Cys(0.81%)are the most and least frequently used amino acid,respectively.Except for tRNA-Ser1,which lacks DHU arm,all tRNAs have the typical cloverleaf structure.The phylogenetic relationships among Grapsoidea were reconstructed based on nucleotide sequences of 13 PCGs using maximum likelihood(ML)and Bayesian(BI)methods.The phylogenetic trees obtained identical topological structures,which showed that all grapsid crabs clustered into a clade,and G.albolineatus shared the closest relationship with G.tenuicrustatus.Sesarmidae and Xenograpsidae clustered together,and then formed a sister group with Gecarcinidae,and finally form a sister group with Grapsidae.Varunidae formed a separate clade.A significant correlation between gene rearrangement and phylogeny was found in Grapsoidea for the first time.These findings will contribute to a better understanding of gene rearrangement and molecular evolution,as well as provide insights into the phylogenetic studies of Grapsoidea.