Abstract
Animal mitochondrial genomes usually exhibit conserved gene arrangement across major lineages, while those in the Hymenoptera are known to possess frequent rearrangements, as are those of several other orders of insects. Here, we sequenced two complete mitochondrial genomes of Trichogramma japonicum and Trichogramma ostriniae (Hymenoptera: Chalcidoidea: Trichogrammatidae). In total, 37 mitochondrial genes were identified in both species. The same gene arrangement pattern was found in the two species, with extensive gene rearrangement compared with the ancestral insect mitochondrial genome. Most tRNA genes and all protein-coding genes were encoded on the minority strand. In total, 15 tRNA genes and seven protein-coding genes were rearranged. The rearrangements of cox1 and nad2 as well as most tRNA genes were novel. Phylogenetic analysis based on nucleotide sequences of protein-coding genes and on gene arrangement patterns produced identical topologies that support the relationship of (Agaonidae + Pteromalidae) + Trichogrammatidae in Chalcidoidea. CREx analysis revealed eight rearrangement operations occurred from presumed ancestral gene order of Chalcidoidea to form the derived gene order of Trichogramma. Our study shows that gene rearrangement information in Chalcidoidea can potentially contribute to the phylogeny of Chalcidoidea when more mitochondrial genome sequences are available.
Highlights
Animal mitochondrial genomes usually exhibit conserved gene arrangement across major lineages, while those in the Hymenoptera are known to possess frequent rearrangements, as are those of several other orders of insects
We found novel and extensive gene rearrangements in both species compared with the ancestral insect mitochondrial genome
In the mitochondrial genome of T. japonicum, a total of 547 bp of intergenic nucleotides ranging from 1 to 81 bp were found in 17 locations
Summary
Animal mitochondrial genomes usually exhibit conserved gene arrangement across major lineages, while those in the Hymenoptera are known to possess frequent rearrangements, as are those of several other orders of insects. The same gene arrangement pattern was found in the two species, with extensive gene rearrangement compared with the ancestral insect mitochondrial genome. No tight association was found between an increased rate of mitochondrial gene arrangement and the evolution of parasitism in an analysis of the characterization of 67 mitochondrial tRNA gene rearrangements in the Hymenoptera[16]. Gene rearrangement patterns in the Hymenoptera are usually complicated and variable compared with those in most other insect orders[24,25]. The rate of rearrangement of protein-coding genes is lower than that of tRNAs in the Hymenoptera. Increasing knowledge of the mitochondrial genomes of egg parasitoids will provide further insight into their higher-level phylogeny and the evolution of their life histories
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