Du Chao, Zhang Lifang, Lu Ting, Ma Jingnan, Zeng Chenjuan, Yue Bisong, Zhang Xiuyue
Key Laboratory of Bio-resources and Eco-environment (Ministry of Education), College of Life Sciences, Sichuan University, Chengdu, 610064, People's Republic of China.
Nanchong Vocational and Technical College, Nanchong, 637131, Sichuan, People's Republic of China.
BMC Genomics. 2017 Sep 6;18(1):698. doi: 10.1186/s12864-017-4102-y.
Insect mitochondrial genomes (mitogenomes) exhibit high diversity in some lineages. The gene rearrangement and large intergenic spacer (IGS) have been reported in several Coleopteran species, although very little is known about mitogenomes of Meloidae.
We determined complete or nearly complete mitogenomes of seven meloid species. The circular genomes encode 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs) and two ribosomal RNAs (rRNAs), and contain a control region, with gene arrangement identical to the ancestral type for insects. The evolutionary rates of all PCGs indicate that their evolution is based on purifying selection. The comparison of tRNA secondary structures indicates diverse substitution patterns in Meloidae. Remarkably, all mitogenomes of the three studied Hycleus species contain two large intergenic spacers (IGSs). IGS1 is located between trnW and trnC, including a 9 bp consensus motif. IGS2 is located between trnS2 (UCN) and nad1, containing discontinuous repeats of a pentanucleotide motif and two 18-bp repeat units in both ends. To date, IGS2 is found only in genera Hycleus across all published Coleopteran mitogenomes. The duplication/random loss model and slipped-strand mispairing are proposed as evolutionary mechanisms for the two IGSs (IGS1, IGS2). The phylogenetic analyses using MrBayes, RAxML, and PhyloBayes methods based on nucleotide and amino acid datasets of 13 PCGs from all published mitogenomes of Tenebrionoids, consistently recover the monophylies of Meloidae and Tenebrionidae. Within Meloidae, the genus Lytta clusters with Epicauta rather than with Mylabris. Although data collected thus far could not resolve the phylogenetic relationships within Meloidae, this study will assist in future mapping of the Meloidae phylogeny.
This study presents mitogenomes of seven meloid beetles. New mitogenomes retain the genomic architecture of the Coleopteran ancestor, but contain two IGSs in the three studied Hycleus species. Comparative analyses of two IGSs suggest that their evolutionary mechanisms are duplication/random loss model and slipped-strand mispairing.
昆虫线粒体基因组（线粒体基因组）在某些谱系中表现出高度多样性。虽然对芫菁科昆虫的线粒体基因组了解甚少，但在几种鞘翅目物种中已报道了基因重排和大的基因间隔区（IGS）。
我们测定了7种芫菁科物种的完整或近乎完整的线粒体基因组。环状基因组编码13个蛋白质编码基因（PCG）、22个转运RNA（tRNA）和两个核糖体RNA（rRNA），并包含一个控制区，其基因排列与昆虫的祖先类型相同。所有PCG的进化速率表明它们的进化基于纯化选择。tRNA二级结构的比较表明芫菁科存在不同的替代模式。值得注意的是，所研究的3种斑芫菁属物种的所有线粒体基因组都包含两个大的基因间隔区（IGS）。IGS1位于trnW和trnC之间，包括一个9bp的共有基序。IGS2位于trnS2（UCN）和nad1之间，包含一个五核苷酸基序的不连续重复序列以及两端的两个18bp重复单元。迄今为止，IGS2仅在所有已发表的鞘翅目线粒体基因组的斑芫菁属中发现。提出了重复/随机丢失模型和滑链错配作为这两个IGS（IGS1、IGS2）的进化机制。使用MrBayes、RAxML和PhyloBayes方法基于所有已发表的拟步甲科线粒体基因组的13个PCG的核苷酸和氨基酸数据集进行的系统发育分析，一致地恢复了芫菁科和拟步甲科的单系性。在芫菁科内，地胆属与豆芫菁属聚类，而不是与绿芫菁属聚类。尽管迄今为止收集的数据无法解决芫菁科内的系统发育关系，但本研究将有助于未来绘制芫菁科系统发育图。
本研究展示了7种芫菁科甲虫的线粒体基因组。新的线粒体基因组保留了鞘翅目祖先的基因组结构，但在所研究的3种斑芫菁属物种中包含两个IGS。对两个IGS的比较分析表明它们的进化机制是重复/随机丢失模型和滑链错配。
