| Mitochondrial play a central role in metabolism,disease and aging.They are the site of oxidative phosphorylation,as well as a variety of other biochemical functions. Mitochondrial genome is a genome that separate from the nuclear chromatin,with its own systems for DNA replication,transcription,and commonly is a double-strand closed-circular molecule,and contains 37 genes.Mitochondrial genome is commonly used in studies of molecular phylogenetics,and is the best model for the studies of genome structure,function and evolution.The complete mitochondrial genome sequences for three species of Caelifera, Primnoa arctica,Gomphocerippus rufus and Alulatettix qinlingensis,were sequenced, assembled and annotated.Complete mitogenomes of eight families were compared. The common features of genome structure and organization,sequence and evolution were summarized,these enriches mitochondrial genome data of Orthoptera. Phylogenetic of Acridoidea was reconstructed utilizing 20 insects from Acridoidea and phylogenetic of Cealifera was reconstructed utilizing 10 insects.The conclusions of these studies showed as following:1.The genes arrangement of mitochondrial genome in Primnoa arctica, Gomphocerippus rufus and Alulatettix qinlingensis were identical to that of Locusta migratoria,and were different from ancient insects in that the translocation of tRNAK-tRNAD was rearrangement as tRNAD-tRNAK.This rearrangement was common in mitogenome of Acridoidea.2.Average A+T content of mitogenome from Acridoidea was found higher than that of Tettigonioidea.3.The usage of synonymous codons was markedly correlated with the nucleotide composition at the third codon position.Generally,the codons whose third position are A or T were frequently used.4.The longest space of genes in mitogenome of Acridoidea was usually locates between tRNASer-UCN and ndl.There are 7bp long overlapping regions located between atp8/atp6 and nad4/nad4L.The interspaces and overlapping regions were similar at the feature of number and length in mitogenome of species.5.ATG is the most frequently used starting codon,ATT is the second frequently used one,ATA is the one that being used lessly.TAA is the most frequently used termination codon.Most of nd5 in mitogenome of Orthoptera utilize incomplete termination codon(T/TA) as terminate singnal.6.The mismatched base pairs occur in the tRNA genes,and the majority of these are G-U pairs.7.There was a stem and loop structure located in both A+T rich regions of mitochondrial genome of Primnoa arctica and Gomphocerippus rufus.And the structure was similar with the structure that Saito(2005) found on the same region of L. migratoria.They each has a conserved structure of"TA" on the 5' of the stem and loop structure.8.Phylogenetic analyses confirmed the monophyly of Oedipodidae and Catantopidae of Xia's system,and the monophyly of Acrididae and Arcypteridae were not supported.Monophyly of Oedipodinae and Gomphocerinae in One's system were supported,while monophyly of Catantopinae was not suppoted.Catantopinae, Melanoplinae and Oxyinae formed a sister group.9.The result of reconstruction of systemtic evolution relationship of eight families in Acridoidea concluded that the relationship of evolution is Pyrgomorphidae+Chrotogonidae→Oedipodidae→Pamphagidae→Catantopidae→Acrididae→Gomphoceridae+Arcypteridae.10.This phylogenetic analyses based on mitogenome separated Acridoidea distributing in China into two clades.The first clade is consisted of Chrotogonidae and Pyrgomorphidae,which formed the basic of the tree;the second and large clade is consisted of Catantopidae,Oedipodidae,Acrididae,Gomphoceridae,Arcypteridae and Pamphagidae.These clades are coincident with that in Otte's classification system,and the difference was that Pamphagidae in our study could not be separated from the clade of Acridoidea.
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