The mitochondrial genome of the lepidopteran host cadaver (Thitarodes sp.) of Ophiocordyceps sinensis and related phylogenetic analysis

Abstract

To understand the phylogeny of the host insect (Thitarodes sp.) of the fungus Ophiocordyceps sinensis, we sequenced, annotated and characterized the complete mitochondrial (mt) genome of the host cadaver of a natural O. sinensis. Further, we compared the Thitarodes sp. mt genome with those of the other 7 sequenced Hepialidae and examined the phylogenetic relationships using a constructed Maximum Likelihood (ML) phylogenetic tree and mt genomic features (genetic distances and intergenic spacers). The mt genome is a circular molecule of 16,280bp in length with a high A+T content (81.20%) and contains 13 protein-coding genes (PCGs), 2 rRNA genes, 22 tRNA genes and an AT-rich region. The gene arrangement is identical to the ancestral arrangement but differs from those of other lepidopteran mt genomes because of the arrangement of tRNA genes. The tRNA region, which is located between the AT-rich region and nad2, is trnI/trnQ/trnM (IQM) in Thitarodes sp., rather than the trnM/trnI/trnQ (MIQ) of the Lepidoptera-specific rearrangement. All PCGs begin with the canonical start codons ATN or NTG, except for cox1, which starts with CGA. Most PCGs terminate with the typical stop codon TAA, although some have an incomplete stop codon (T). The 1473bp AT-rich region is located between the rrnS (12S rRNA) and trnI, which is the longest sequenced in a Thitarodes mt genome to date, containing nine 112bp copies and one partial copy of a 55bp sequence. The results derived from the phylogenetic tree, the genetic distances and the intergenic spacers of the mt genome show that the host insect of O. sinensis belongs to the Thitarodes, while Endoclita signifer and Napialus hunanensis form a relatively distinct lineage from Thitarodes. The sequence and full annotation of this moth mt genome will provide more molecular information about the Exoporia within the Lepidoptera, and the clarification of its phylogeny will improve the management of this insect resource and the conservation and sustainable use of this endangered medicinal species in China.