长脚蟹科首个线粒体基因组测定及系统发育分析

The first complete mitochondrial genome of Goneplacidae (Decapoda:Brachyura)and its phylogenetic position among Brachyura

  • 摘要: 【目的】从线粒体基因组水平探究长脚蟹科(Goneplacidae)在短尾次目(Brachyura)中的进化地位,为更好地理解短尾次目分类及演化起源提供理论依据。【方法】以泥脚毛隆背蟹(Entricoplax vestita)为长脚蟹科代表种,测定分析其线粒体基因组全序列特征,并从GenBank下载短尾次目科级阶元代表种的线粒体基因组全序列,然后基于13个蛋白编码基因串联序列,采用PhyloSuite同时构建短尾次目贝叶斯树(BI)和最大似然树(ML)。【结果】泥脚毛隆背蟹线粒体基因组全长为15716 bp,共编码37个基因,包括13个蛋白编码基因、22个tRNA基因和2个rRNA基因;基因组碱基组成为:A(占34.9%)、T(占37.7%)、G(占17.0%)和C(占10.5%),表现出明显的AT偏好性(占72.6%);AT偏倚和GC偏倚均为负值,分别为-0.039和-0.237。所有蛋白编码基因均以ATN为起始密码子;除COIICOIIICyt b基因以T为不完全终止密码子外,其余基因均以TAA或TAG终止;除tRNA-Ser1基因二级结构缺少DHU臂外,其他tRNA基因均能形成典型的三叶草结构;2个rRNA基因均由轻链编码,其中,12S rRNA长度为825 bp(位于tRNA-Val与控制区间),16S rRNA长度为1330 bp(位于tRNA-Leu1与tRNA-Val间)。基于13个蛋白编码基因核苷酸序列构建的短尾次目贝叶斯树(BI)和最大似然树(ML)均显示,长脚蟹科和团扇蟹科(Oziidae)的亲缘关系最近,二者互为姐妹支,再与武蟹科(Panopeidae)和扇蟹科(Xanthidae)聚在一起;蜘蛛蟹科(Majidae)和人面蟹科(Homolidae)为非单系群;馒头蟹总科(Calappoidea)、方蟹总科(Grapsoidea)和沙蟹总科(Ocypodoidea)的非单系性也得到有力支持。【结论】长脚蟹科线粒体基因组与短尾次目祖先型线粒体基因组共享同一基因排序,与十足目祖先型线粒体基因组相比仅tRNA-F-ND5-H基因排序突变成tRNA-H-F-ND5基因排序。长脚蟹科与团扇蟹科的亲缘关系最近,二者拥有最近的共同祖先,同时进一步佐证了蜘蛛蟹科、人面蟹科及馒头蟹总科、方蟹总科和沙蟹总科的非单系性。

     

    Abstract: 【Objective】To explore the evolutionary status of Goneplacidae in Brachyura from the mitochondrial genome level,so as to provide theoretical basis for better understanding the classification and evolutionary origin of Brachyura.【Method】Entricoplax vestita was selected as the representative species of Goneplacidae. The complete mitochondrial genome sequence of E.vestita was determined and analyzed. The complete mitochondrial genome sequence of the representative species was downloaded from GenBank. PhyloSuite was adopted to build a Brachyura Bayesian tree (BI)and a maximum likelihood tree(ML)simultaneously. 【Result】The total length of mitochondrial genome was 15716 bp,encoding 37 genes,including 13 protein coding genes,22 tRNA genes and 2 rRNA genes. The genome base composition was as follows:A(34.9%),T(37.7%),G(17.0%)and C(10.5%),showing obvious AT preference(72.6%);AT skew and GC skew were negative values,which were -0.039 and -0.237,respectively. ATN was the starting codon of all protein-coding genes. Except for COIICOIII and Cyt b genes with T as incomplete termination codon,other genes were terminated with TAA or TAG. Except for the lack of DHU arm in the secondary structure of tRNA-Ser1 gene,other tRNA genes could form typical clover structure. The two rRNA genes were encoded by light chains,in which the length of 12S rRNA was 825 bp(between tRNA-Val and control interval),and the length of 16S rRNA was 1330 bp(between tRNALeu1 and tRNA-Val). Based on the nucleotide sequences of 13 protein-coding genes,both Brachyura Bayes Tree(BI) and maximum likelihood tree(ML)showed that Goneplacidae and Oziidae were closely related,and the two were sister branches and clustered together with Panopeidae and Xanthidae. Majidae and Homolidae were non-monophyletic groups; the non-monophyletic properties of Calappoidea,Grapsoidea and Ocypodoidea were also strongly supported.【Conclusion】Goneplacidae shares the same gene rearrangements with that of ancestral genome of Brachyura;namely only tRNAF-ND5-H cluster changed to tRNA-H-F-ND5 order compared with Decapodamitochondial ancestral genome. Goneplacidae is most closely related to Oziidae,sharing the most recent common ancestor. Also,the results further verify the nonmonophyletic features of Majidae,Homolidae,Calappoidea,Grapsoidea and Ocypodoidea.

     

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