Sequencing And Analysis Of Oxya Chinensis,Eirenephilus Longipennis And Traulia Stal Complete Mitochondrial Genome

The Mitochondrial DNA is high polymorphism,rapid evolutionary rate,maternal inheritance and almost lack of intermolecular genetic recombination, Mitochondrial DNA has become a good model for research in gene structure,function,transcription and gene expression. Recently, there were 975 metazoan species which the mitochondfial genomes had been sequenced, including 913 vertebrates, 125 arthropods, among them only two Orthoptera species, Gryllotalpa orientalis and Locusta migratoria, more mitochondrial genomes need to be sequenced in order to resolve the higher levels phylogeny relationship of Orthoptera.In this study, three Catantopidae grasshoppers: O. chinensis,E, longipemmis and T. stal were sequenced, assemlyed, annotated, and analyzed in details using the strategy of sub-PCR based on long PCR and combining with clone sequencing method. Also we compared three grasshoppers with other Orthoptera insect from aspects of comparative genomics. The conclusions drawn from the study as follows:1. The complete mitochondrial genome of O. chinensis,E. longipemmis and T. stal are 15443bp,15621bp and 15768bp respectively, including 13 protein gene, 22 tRNA gene, 2 rRNA gene, and an AT-rich region which is located between the srRNA and tRNA^Ile. The gene orders of these grasshoppers are identical with L. migratoria, all of them have K and D gene inversion. The arrangement of mitochondrial genes is compact, being 65bp,38bp and 47bp gene overlaps in three grasshoppers, especially 7bp between ND4 and ND4L, ATP6 and ATP8. There are 87bp,109bp and 117bp intergenic spacer in three grasshoppers, the biggest intergenic spacer located between ND1 and tRNA^Ser(UCN)).2. The overall AT composition in O. chinensis,E. longipemmis and T. stal mtDNA shows obvious bias, and the AT content of O. chinensis,E. longipemmis and T. stal are 75.9%, 76.0% and 74.6% respectively. The AT content of control region is highest, IrRNA and srRNA are followed, protein-coding region is lowest.3. All protein-coding genes in O. chinensis, E. longipemmis and T. stal are started with typical ATN start codons. ND5 has an incomplete termination codon (T), while other protein-coding genes are terminated with the complete stop codon TAA or TAG.4. All protein-coding genes have codon usage bias in three species, the usage of NNU and UUA is higher, especially UUA of Leu's usage is highest. The content of AT in third position of L-strand protein-coding genes is higest. The biggest AT bias appears in the second position, and the biggest GC bias appears in the third position. The H-strand has more C and A, while GT-rich codons are more preference in L-strand.5. All tRNAs have typical clover-leaf structure except for tRNA^ser(AGN), which is lack of DHU arm. Mismatch of tRNA are concentrated in 3' of amino acid accept arm, there are mostly G-T mismatch,A-A mismatch and T-T mismatch.6. The secondary structure of the domainâ…¢of mtDNA 12s rRNA and the domainâ…£,â…¤of mtDNA 16s rRNA show a little difference to L. migratoria.7. There are 6 conserved blocks in AT-rich region in O. chinensis,E. longipemmis and T. stal: Block A,Block B,Block D,Block E1,Block E2 and Block F. These conserved blocks are related with the regulation of mitochonddal replication and transcription, Block E1 and Block E2 form a conserved stem and loop structure which is potentially associated with the L-strand replication origin.8. We also compared three grasshoppers with other Orthoptera, Lepidoptera, Coleoptera, Hymenoptera, Hemiptera, Phthiraptera, Psocoptera and Thysanoptera species, and get some assumptions about characters of insects mitochondrial genome.This work was supported by CNSF grant. It is the first study on sequencing mitogenomics of O. chinensis,E. longipemmis and T. stal, also it is the first time described gene organization,condon usage bias and other biochemistry characters in the view of comparative genomics. It offers some important clues and data for comprehending the mitochondrial structure, evolution higher level phylogeny relationship of Orthoptera.