Antimicrobial peptide repertoire of Thitarodes armoricanus, a host species of Ophiocordyceps sinensis, predicted based on de novo transcriptome sequencing and analysis

Abstract

Ophiocordyceps sinensis is an entomopathogenic fungus that parasitizes the larvae of ghost moths. The fungus-caterpillar complex resulting from fungal parasitism is a medicinally and economically important traditional Chinese medicine famous for its tonic, aphrodisiac and immunomodulatory activity. Antimicrobial peptides (AMPs), which play predominant roles in responding to infection of pathogenic microorganisms in the immune system of ghost moths, may remain behind the fungus-caterpillar complex. Thitarodes armoricanus, as a widely distributed ghost moth on the Tibetan Plateau, is the first reported and one of the most common host insects of O. sinensis. However, there is little information about AMPs of T. armoricanus. In this study, high-throughput RNA-seq analysis and transcriptome assembly and annotation of T. armoricanus was performed to explore the AMP repertoire. A total of 41,464 unigenes were obtained by de novo assembly, and 20,080 unigenes including 385 immunity-related candidates were annotated. Among which, 16 AMP nucleotide sequences were identified. Based on their peptide structure, these were further classified as cecropin, defensin, attacin and gloverin AMPs. All identified AMPs are highly conserved in the Hepialidae family with distinct features as in other insect AMPs. In conclusion, this research offers insights into the AMP repertoire of T. armoricanus which gives opportunity for the further study of the AMP-related medical components of the fungus-caterpillar complex. The identified AMPs from T. armoricanus also provide valuable information for a better understanding of the immune mechanism of Thitarodes and the formation of the mysterious entomo-fungal combination.

Keywords: Antimicrobial peptide; Hepialidae; Ophiocordyceps sinensis; Sequencing; Thitarodes armoricanus; Transcriptome.