Genomic and phylogenetic analysis of the complete mitochondrial DNA sequence of walnut leaf pest Paleosepharia posticata (Coleoptera: Chrysomeloidea)

Mitochondrial DNA (mitogenome) has been widely used in species identification and comparison among closely related species and is valuable for phylogenetic studies. However, considering the large amount and high biodiversity of coleopteran insects, only about 100 complete or nearly complete mitogenome sequences of coleopterans were found in GenBank, largely limiting the research of biological evolution among coleopteran insects. In this study, the complete mitochondrial sequence of Paleosepharia posticata, an important walnut leaf pest, was determined by the next-generation sequencing technology and verified using Sanger sequencing method. The mitogenome of P. posticata was 15,729 bp with an A + T content of 79.8%, and was very similar with other reported coleopteran insects in genome complement, gene order and nucleotide composition. All of the protein-coding genes started with the typical ATN initiation codons except for nad1 (TTG). The ancestral gene order with trnI-trnQ-trnM located between the A + T-rich region and nad2 and the formerly identified conserved elements of coleopteran mitogenomes, such as the motif 'TAGTA' between trnS(UCN) and nad2, the overlap 'ATGATAA' between atp8 and atp6 genes and poly-T stretch in the A + T-rich region, were also present in the P. posticata mitogenome. A special 'ATGATAA' between nad41 and nad4, which was 'ATGTTAA' in many insect mitogenomes, was observed in the mitogenome of P. posticata and coleopteran species used in this study. Phylogenetic trees inferred from the amino acid and nucleotide sequence data for the 13 protein-coding genes strongly supported the monopoly of Elateriformia, the paraphyly of Staphyliniformia, and the sister relationship of Scarabaeoidea and Staphylinoidea.