Characterization of Iflavirus in the Red Flour Beetle, Tribolium castaneum (Coleoptera; Tenebrionidae)

SIMPLE SUMMARY: A model beetle, Tribolium castaneum, carries a positive single-stranded RNA virus Tribolium castaneum iflavirus (TcIV). This study shows that the TcIV is prevalent among different laboratory cultures, different strains, and the same strain maintained in different laboratories, and in the Tribolium cell line TcA. Transovarial transmissions and their prevalence in the nervous system were supported in this study. The novel TcIV, showing no observable pathogenicity, offers an opportunity to study the interaction between the virus and the immune system in this model beetle species. ABSTRACT: Iflavirus is a group of viruses distributed mainly in arthropod species. We surveyed Tribolium castaneum iflavirus (TcIV) in different laboratory strains and in Sequence Read Archives (SRA) in GenBank. TcIV is highly specific to only T. castaneum and is not found in seven other Tenebrionid species, including the closely related species T. freemani. The same strains from different laboratories and different strains displayed largely different degrees of infections in the examination of 50 different lines by using Taqman-based quantitative PCR. We found that ~63% (27 out of 43 strains) of T. castaneum strains in different laboratories are positive for TcIV PCR with large degrees of variation, in the range of seven orders of magnitude, indicating that the TcIV is highly fluctuating depending on the rearing conditions. The TcIV was prevalent in the nervous system with low levels found in the gonad and gut. The transovarial transmission was supported in the experiment with surface-sterilized eggs. Interestingly, TcIV infection did not show observable pathogenicity. TcIV offers an opportunity to study the interaction between the virus and the immune system of this model beetle species.