Mitochondrial Genome Sequencing Of Three Species Of Cockroaches And Comparative Analysis Of Mitochondrial Genomes Of The Genus Trichosanthes

Tetrigoidea is a superfamily of Caelifera in Orthoptera accoding to the Orthoptera Species File Online(OSF),and was regarded as a primitive taxa with Gryllotalpoidea in Caelifera.About 270 genera and 1500 species are known in this superfamily that was divided seven subfamilies in China.Tetrigoidea,small body size and herbivorous,is mainly in tropical and subtropical places and can be used as a bioindicator in the environmental surveying.The previous studies of Tetrigoidea were mostly involve morphology and single genes,fewer concerned research conducted at the mitochondrial genome scale.We determined nearly the entire mitochondrial genomes of Bolivaritettix yuanbaoshanensis,Systolederus spicupennis and Bolivaritettix sikkinensis by combining NGS and Sanger sequencing technology.The new mitochondrial genomes were annotated with reference to the mitochondrial genome information of Tetrix japonica and Formosatettix qinlingensis.Furthermore,other 27 Orthopterans(including nineteen Acridoidea species,eight Tetrigoidea species,one Eumastacoidea specie,one Gryllotalpoidea specie and two Ensifera species)were used to comparative analysis and the reconstruction phylogenetic relationship.In addition,partial sequences of 28S rRNA were amplified and sequenced to reconstruct the phylogenetic relationship within Tetrigoidea.The main conclusions drawn from this study were listed below:1.The obtained sequences length of Bolivaritettix yuanbaoshanensis,Systolederus spicupennis and Bolivaritettix sikkinensis mitochondrial genomes are 14,905 bp,15,141 bp and 14,908 bp respectively.The gene order of trnK/trnD is the same as Acridoidea;high AT-content and T-skew are in genes or most regions;the second structure of tRNAs are similar to the other insects,the largely different domain caused by base transition mainly is in variable loop,TΨC loop,and DHC loop;the largely different region of rRNAs’ second structures mainly concentrated the end of 5’ terminal regions;2.The comparative analysis shows that the size of mitochondrial genome in Tetrigoidea is smaller than other fanmilies,shorter inter-genes-sequeces(IGS)and longer overlaps(expect B.yuanbaoshanensis),indicating mitogenome with a more compact structure in Tetrigoidea;AT content proportionates to the value of AT-skew in third position of PCGs with most hydrophobic amino acids,indicating that the higher AT-content,the lower A-content in Orthoptera;N-strand has T-skew and C-skew,while J-strand has G-skew in Orthoptera;we also found some specific conserved sequence fragments in Tetrigoidea’s internal gene regions and other tRNA genes,that can be used as a molecular synapomorphy for this genus potentially;the species’ sizes of trnAsp,trnGly,trnIle,tmLys and trnCys are smaller in Tetrigoidea than others caeliferans;in addition,the A+T-rich regions of Tetrigoidea lack the structure of[TA]n and T-stretch;3.The phylogeny of Orthoptera was reconstructed using ML and BI method based on all 13 protein-coding genes in 30 species,and the tree topology supported the monophyly of Tetrigoidea and Acridoidea.B.yuanbaoshanensis and B.sikkinensis form a mini monophyletic group.Genus Thoradonta and Bolivaritettix clustered into a clade on both ML and BI trees,indicating their close relationship.Tridactyloidea species located at the basal position of Caelifera.Besides,Monophyly of family Tetrigidae,Metrodoridae and Scelimenidae was not supported by BI-tree based on partial sequences of 28S rRNA genes.