二斑素瓢虫线粒体基因组全序列测定和分析

Complete sequence determination and analysis of mitochondrial genome of Illeis bistigmosa

【目的】在线粒体基因组水平探讨二斑素瓢虫[Illeis bistigmosa(Mulsant,1850)]完整的线粒体基因组结构特征,分析其在瓢虫科(Coccinellidae)内的分类地位,为揭示瓢虫科昆虫的系统发育和进化关系提供理论依据。【方法】通过Illumina二代测序技术对二斑素瓢虫线粒体基因组进行测序,对基因组序列进行拼装和注释,分析其结构特点和碱基组成;使用最大似然法和贝叶斯法构建瓢虫科16个种线粒体基因组的系统发育进化树,分析其在瓢虫科内的系统发育关系。【结果】二斑素瓢虫线粒体基因组序列全长17840 bp,包含13个蛋白质编码基因,22个tRNA基因,2个rRNA基因和1个A+T富含区(A+T rich region)。基因组全序列的AT含量为78.44%,表现明显的A+T偏向性。13个蛋白质编码基因中除cox1基因以TTG为起始密码子外,其余12个基因均以ATN为起始密码子;nad4、nad5、cox2和cox3基因的终止密码子以单独的T结尾。除trnS1和trnP基因外,其余20个tRNAs的二级结构均为典型的三叶草结构,二级结构中有U-U或U-G碱基错配现象。系统发育分析显示,瓢虫亚科的所有物种聚在同一分支,支持该亚科的单系性;二斑素瓢虫与素菌瓢虫属(Illeis)另外2个种[柯氏素菌瓢虫(I.koebelei)和素鞘瓢虫(I.cincta)]聚为一个分支,组成姐妹关系。【结论】获得了二斑素瓢虫的线粒体基因组全序列,二斑素瓢虫线粒体基因组符合瓢虫科昆虫线粒体基因组的一般特征;二斑素瓢虫与柯氏素菌瓢虫和素鞘瓢虫的亲缘关系较近,与传统的形态学分类相一致。

【Objective】The purpose of the study was to characterize the complete mitochondrial genome structure of Illeis bistigmosa(Mulsant,1850)at the level of the mitochondrial genome,to analyze its classification status within Cocci-nellidae,and to provide a theoretical basis for revealing the phylogenetic and evolutionary relationships of Coccinellidae insects.【Method】The mitochondrial genome of I.bistigmosa was sequenced by using Illumina Next-generation sequen-cing technique,and the genome sequence was assembled and annotated to analyze its structural features and base compo-sition.The phylogenetic trees of mitochondrial genomes of 16 Coccinellidae species were constructed by using maximum likelihood and Bayesian methods to analyze their phylogenetic relationships within Coccinellidae.【Result】The mitochon-drial genome sequence of I.bistigmosa was 17840 bp in length,including 13 protein-coding genes,22 tRNA genes,2 rRNA genes,and 1 A+T rich region.The AT content in the whole genome sequence was 78.44%,showing significant A+T bias.Among the 13 protein-coding genes,12 genes used ATN as the start codon,except for the cox1 gene,which had TTG as the start gene.The termination codon of nad4,nad5,cox2,and cox3 genes ended in a separate T.Except for trnS1 and trnP genes,all the remaining 20 tRNAs had the typical clover-leaf-like structure with U-U or U-G base mismatched in the secondary structure.Pgylogenetic analysis showed that all species of Coccinellinae clustered in the same branch,confirming Coccinellinae to be a monophyly.I.bistigmosa grouped with two other species of Illeis(I.koebelei and I.cinc-ta)in a branch,forming a sister relationship.【Conclusion】In this study,the mitochondrial genome complete sequence of I.bistigmosa is obtained.The mitochondrial genome of I.bistigmosa conforms to the general characteristics of Coccinelli-dae mitochondrial genome.I.bistigmosa is closely related to I.koebelei and I.cincta,which is in accordance with the tra-ditional morphological classification.