Phylogenomic Study Of Orthoptera Mitochondrion

Orthoptera is one of the largest families among the insecta with more than20000 described species widely distributed throughout the world especially in tropicalzone, such as locust, cricket, long-horned grasshopper, mole cricket and so on. Theclassification of species in Orthopteran has been controversial and complicate.In this paper, we report the mitochondrial genome of Tettigonia chinensis andConocephalus gladiatus determinded by sub-PCR method, which are representativeinsect in Tettigonioidea. Phylogenomic analysis among mitogenomes of T. chinensis and C.gladiatus and other insect orders was accomplished, and the utility of mitogenome forOrthopteran phylogeny construction was briefly discussed.1. The determined mitochondrial genome sequeces of T. chinensis and C. gladiatus are14,974 bp and 14,591 bp long respectively. T. chinensis mitgenome encodes 13 putativeproteins, 2 rRNAs and 21 tRNAs(excluding tRNA^Ile) while the C. gladiatus mitgenomeencodes 13 putative proteins, 2 rRNAs and 19 tRNAs (excluding tRNA^Ile, tRNA^Met,tRNA^Gln) without A+T-rich region.2. The arrangement of mitochondrial coding genes matches almost with those ofGryllotalpa orientalis. A total of 88 bp overlap regions among T. chinensis mt genomesare found in sixteen locations with a total of 296 bp of intergenic spacer. C. gladiatus hasa 128bp-overlap region and a 38bp-intergenic spacer while the tRNA^Gly almost locatedin COⅢentirely.3. The average A+T content of the T. chinensis and C. gladiatus mitochondrial genomeprotein coding sequence, rRNA and tRNA gene was corresponding well to the A+T biasgenerally observed in insect mitochondrial genomes. The strongest A+T blase is foundat the tRNA^Glu and tRNA^Asp and at third codon positions which are under the lowpurifying selection.4. Common Met start codons could be assigned to nine and six of the proteincoding genes in T. chinensis and C. gladiatus mitogenome respectively. Common stopcodons (TAA and TAG) could be assigned to most of the putative protein sequences.Only the ND5 genes terminate into a single T residue. Leucine, isoleucine, serine,phenylalanineare are the most frequently used amino acids in the mt protein-coding genes.5. All of tRNAs showed typical clover leaf secondary structures and theiranticodons are similar to those found inother Hexapoda animals, tRNAs possessinvariable aminoacyl stem, anticodon loop, and anticodon stem. Most of the sizevariation among tRNAs stemmed from length variation in the TΨC and DHU arms. TheG-U pair is found in all the tRNA genes. The two rRNA genes are conservative in T.chinensis and C. gladiatus.6. Phylogenomic analysis of mitochondrion were performed with maximumparsimony, maximum likelihood and Bayesian inference methods with protein-codinggene data set, putative protein data set and tRNA gene data set. Caelifera ismonophyletic in this study. Excluding the long-brnach attraction, a monophyly of theancient insect order Orthoptera was still not recovered. The reason for the lack ofsupport by the mitogenome sequences is not obvious. Whether the paraphyly ormonophyly of the Orthoptera can't be concluded in the paper. To further ravel thephylogenetic relationships of Orthoptera insects, a larger number of insect orders andmitogenome are required.