德汉劳绵蟹(Lauridromia dehaani)线粒体基因组测定及短尾下目系统发生分析

First Complete Mitochondrial Genome of Lauridromia dehaani and Phylogenetic Analysis of Brachyura

本研究使用高通量测序方法首次获得德汉劳绵蟹(Lauridromia dehaani)的线粒体基因组全序列,确定其线粒体基因组是一个环状DNA,全长15,755 bp,包含37条基因.通过分析比较德汉劳绵蟹线粒体基因组的tRNA二级结构、蛋白编码基因的碱基组成、起始/终止密码子和选择压力,发现trnS 1缺失DHU臂,这种现象在短尾类线粒体基因组中比较常见;不同功能的蛋白编码基因的碱基组成和选择压力不同;cox 1以不常见的ACG作为起始密码子;在多个基因重排断裂点处有长达32 bp以上的间隔序列(最长达130 bp),借此推断发生基因重排的路径.与短尾下目线粒体基因组的祖先排列顺序相比,德汉劳绵蟹呈现一种新的基因排列模式,涉及nad 6、cob、trnH、trnF、trnS 2和trnT等6条基因的重排.使用蛋白编码基因和rRNA基因的联合数据集进行系统发生分析,结果生成了强健的系统发生树,支持短尾下目的各派及亚派之间的关系:(绵蟹总科,人面蟹总科),(蛙蟹总科,真短尾派).另外,两种绵蟹共享短尾类的线粒体基因组中trnH易位特征,并在系统发生树与人面蟹总科的物种形成姐妹群关系,成为短尾下目的基部分支,再次证明绵蟹归置于短尾下目.

The mitochondrial genome of Lauridromia dehaani was firstly determined by using high-throughput sequencing in this research.The results indicated that the complete mitogenome of L.dehaani was 15755 bp in length,containing 37 genes.Comparative mitogenomic features including the secondary structures of tRNAs,nucleotide composition,start/stop codons and selective pressures for protein coding genes indicated special evolution that trnS 1 lack DHU stem arm,which has been commonly observed in brachyuran mitogenomes.AT nucleotide content and selective pressures varied among different functional protein coding genes.Unusual start codon ACG for cox 1 was commonly found in the published primitive crabs.Longer intergenic intervals(32 bp-130 bp)were observed in break point where gene rearranged and guided for deducing the generation of rearrangement.With respect to the ancestral brachyuran mitochondrial gene order,two protein coding genes(nad 6 and cob),and 4 tRNA genes(trnH,trnF,trnS 2 and trnT)were rearranged,which is a novel mitogenomic arrangement pattern.Two dromiids shared a translocation of trnH common in brachyuran mitogenomes,and formed a sister group with species from Homoloidea as basal branch of Brachyura in phylogenetic trees,reconfirming Dromioidea belong to Brachyura.The robust phylogenetic tree among brachyuran section and subsection were generated by using mitochondrial DNA sequence and exhibited relationships as:(Dromioidea,Homoloidea),(Raninoidea,Eubrachyura).