Mitochondrial genome characteristics and phylogenetic analysis of Thoradonta yunnana (Orthoptera: Tetrigoidea)

【Objective】 By analyzing the characteristics of the mitochondrial genome of Thoradonta yunnana, the phylogenetic relationship of Tetrigoidea was reconstructed, which provided a theoretical basis for further clarifying the genetic relationship and evolutionary position among various groups of Tetrigoidea.【Method】 The mitochondrial genome of T. yunnana was sequenced by Illumina HiSeq 2500 platform next-generation sequencing. Based on the protein-coding genes (PCGs) of 24 species of Tetrigoidea and 2 species of Tridactylidae, the phylogenetic tree was constructed by maximum likelihood(ML) method and Bayesian inference(BI) method respectively.【Result】 The total length of the mitogenome was 17859 bp, including 2 rRNA genes, 22 tRNA genes, 13 PCGs and one non-coding control region. Among the 13 PCGs, except for nad6 gene with TTG as the start codon and nad5 gene with incomplete T as the end codon, all PCGs had ATN as the start codon and end with complete TAA or TAG codon. Among the 22 tRNA genes, only trnS1 lacked the DHU arm, and the rest of the genes were able to fold into a clover leaf secondary structure. A total of six repetitive sequences were identified in the control region of T. yunnana, with repeat unit lengths ranging from 29 bp to 204 bp. The topology of two phylogenetic trees constructed based on 13 PCGs was essentially consistent. Batrachididae and Tripetaloceridae were located at the base of the phylogenetic tree and belonged to the more primitive groups. Scelimenidae, Cladonotidae and Metrodoridae were located in the middle of the developmental tree and belonged to the intermediate group. All species of Tetriginae were clustered into one branch, located at the top of the developmental tree, belonging to a more evolutionary group. 【Conclusion】 The results support the view that Tetriginae is a monophyletic group, and Scelimenidae is a paraphyletic group. To a certain extent, the evolutionary position of the Batrachididae as more primitive groups and Tetriginae in Tetrigoidea as more evolutionary group is verified.