Abstract
Many of true bugs are important insect pests to cultivated crops and some are important vectors of human diseases, but few cladistic analyses have addressed relationships among the seven infraorders of Heteroptera. The Enicocephalomorpha and Nepomorpha are consider the basal groups of Heteroptera, but the basal-most lineage remains unresolved. Here we report the mitochondrial genome of the unique-headed bug Stenopirates sp., the first mitochondrial genome sequenced from Enicocephalomorpha. The Stenopirates sp. mitochondrial genome is a typical circular DNA molecule of 15, 384 bp in length, and contains 37 genes and a large non-coding fragment. The gene order differs substantially from other known insect mitochondrial genomes, with rearrangements of both tRNA genes and protein-coding genes. The overall AT content (82.5%) of Stenopirates sp. is the highest among all the known heteropteran mitochondrial genomes. The strand bias is consistent with other true bugs with negative GC-skew and positive AT-skew for the J-strand. The heteropteran mitochondrial atp8 exhibits the highest evolutionary rate, whereas cox1 appears to have the lowest rate. Furthermore, a negative correlation was observed between the variation of nucleotide substitutions and the GC content of each protein-coding gene. A microsatellite was identified in the putative control region. Finally, phylogenetic reconstruction suggests that Enicocephalomorpha is the sister group to all the remaining Heteroptera.
Highlights
Mitochondrial genome sequences are becoming increasingly important for comprehensive evolutionary and population studies
This genome is a medium level of true bug mt genome size, ranging from 14,935 bp to 17,191 bp [14]
Within true bug mt genomes, the length variation was minimal in protein-coding genes (PCGs), tRNAs, the large and small rRNA subunits, but very different in the putative control region (Figure 2; Table S2)
Summary
Mitochondrial (mt) genome sequences are becoming increasingly important for comprehensive evolutionary and population studies. For the past two decades, mtDNA has been widely regarded as the molecular marker of choice for the phylogenetic analysis in metazoans because of its abundance in animal tissues, the small genome size, faster rate of evolution, low or absence of sequence recombination, and evolutionary conserved gene products [5,6], the applicability of mt genomes as a marker of deeper divergences or highly divergent lineages is still controversial [7,8]. What is the basal-most sister-group of the majority of Heteroptera - the Enicocephalomorpha (orthodoxy) or Nepomorpha [13]? Mt genome sequences of Enicocephalomorpha and Dipsocoromorpha have not been reported. This lack of information impedes our ability to trace the evolution of the basal groups of Heteroptera based on mt genomes
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