Luo Qian-Chun, Hao You-Jin, Meng Fengxia, Li Ting-Jing, Ding Yi-Ran, Hua Ya-Qiong, Chen Bin
Institute of Entomology and Molecular Biology, College of Life Sciences, Chongqing Normal University, Chongqing, 401331, People's Republic of China.
National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, 102206, People's Republic of China.
Parasit Vectors. 2016 Jul 21;9(1):406. doi: 10.1186/s13071-016-1694-z.
Culex tritaeniorhynchus and Culex pipiens pallens are the major vectors of the Japanese encephalitis virus and Wuchereria bancrofti, the causative agent of filariasis. The knowledge of mitochondrial genomes has been widely useful for the studies on molecular evolution, phylogenetics and population genetics.
In this study, we sequenced and annotated the mitochondrial (mt) genomes of Cx. tritaeniorhynchus and Cx. p. pallens, and performed a comparative analysis including four known mt genomes of species of the subgenus Culex (Culex). The phylogenetic relationships of Cx. tritaeniorhynchus, Cx. p. pallens and four known Culex mt genome sequences were reconstructed by maximum likelihood based on concatenated protein-coding gene sequences.
Culex tritaeniorhynchus and Cx. p. pallens mt genomes are 14,844 bp and 15,617 bp long, both consists of 13 PCGs, 22 tRNAs, 2 rRNAs and 1 CR (not sequenced for Cx. tritaeniorhynchus). The initiation and termination codons of PCGs are ATN and TAA, respectively, except for COI starting with TCG, and COI and COII terminated with T. tRNAs have the typical clover-leaf secondary structures except for trnS ((AGN)) that is lacking the DHU stem. 16S rRNA and 12S rRNA secondary structures were drawn for the first time for mosquito mt genomes. The control region of Cx. p. pallens mt genome is 747 bp long and with four tandem repeat structures. Phylogenetic analyses demonstrated that the mt genome of Cx. tritaeniorhynchus was significantly separated from the remaining five mt genomes of Culex spp. Culex p. pipiens, Cx. p. pallens and Cx. p. quinquefasciatus formed a monophyletic clade with Cx. p. quinquefasciatus linked in the middle of the clade, and Cx. p. pallens should have the same taxonomic level as Culex p. pipiens and Cx. p. quinquefasciatus.
The mt genomes of Cx. tritaeniorhynchus and Cx. p. pallens share the same gene composition and order with those of two other Culex species. Culex p. pallens of the Pipiens complex should have the same taxonomic level as Culex p. pipiens and Cx. p. quinquefasciatus investigated. We enriched the Culex mt genome data and provided a reference basis for further Culex mt genome sequencing and analyses.
三带喙库蚊和淡色库蚊分别是日本脑炎病毒及丝虫病病原体班氏吴策线虫的主要传播媒介。线粒体基因组知识在分子进化、系统发育学及群体遗传学研究中具有广泛用途。
在本研究中，我们对三带喙库蚊和淡色库蚊的线粒体（mt）基因组进行了测序和注释，并与库蚊亚属（库蚊）中四个已知物种的mt基因组进行了比较分析。基于串联的蛋白质编码基因序列，通过最大似然法重建了三带喙库蚊、淡色库蚊与四个已知库蚊mt基因组序列之间的系统发育关系。
三带喙库蚊和淡色库蚊的mt基因组长度分别为14,844 bp和15,617 bp，均由13个蛋白质编码基因、22个tRNA、2个rRNA和1个控制区（三带喙库蚊未测序）组成。蛋白质编码基因的起始密码子和终止密码子分别为ATN和TAA，但细胞色素氧化酶亚基I（COI）起始于TCG，且COI和细胞色素氧化酶亚基II（COII）以T结尾。除了缺乏二氢尿嘧啶（DHU）茎的trnS（(AGN)）外，tRNA具有典型的三叶草二级结构。首次绘制了蚊类mt基因组的16S rRNA和12S rRNA二级结构。淡色库蚊mt基因组的控制区长747 bp，具有四个串联重复结构。系统发育分析表明，三带喙库蚊的mt基因组与其余五个库蚊物种的mt基因组有显著差异。致倦库蚊、淡色库蚊和白纹伊蚊形成一个单系类群，白纹伊蚊连接在类群中间，淡色库蚊应与致倦库蚊和白纹伊蚊具有相同的分类地位。
三带喙库蚊和淡色库蚊的mt基因组与另外两个库蚊物种具有相同的基因组成和顺序。致倦库蚊复合组中的淡色库蚊应与所研究的致倦库蚊和白纹伊蚊具有相同的分类地位。我们丰富了库蚊mt基因组数据，为进一步的库蚊mt基因组测序和分析提供了参考依据。
