Characterization of Iflavirus in the red flour beetle, Tribolium castaneum (Coleoptera; Tenebrionidae)

Authors: FATEHI, SOHEILA - Kansas State University; AIKENS, MICHAEL - Kansas State University; PHILLIPS, THOMAS - Kansas State University; BROWN, SUSAN - Kansas State University; ZHU, KUN YAN - Kansas State University; Scully, Erin; PARK, YOONSEONG - Kansas State University

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2023
Publication Date: 2/23/2023
Citation: Fatehi, S., Aikens, M., Phillips, T.W., Brown, S., Zhu, K., Scully, E.D., Park, Y. 2023. Characterization of Iflavirus in the red flour beetle, Tribolium castaneum (Coleoptera; Tenebrionidae). Insects. 14(3). Article 220. https://doi.org/10.3390/insects14030220.
DOI: https://doi.org/10.3390/insects14030220

Interpretive Summary: Iflavirus is a group of viruses that occurs almost exclusively in insects. Infection can have a variety of impacts on the health and fitness of insects, ranging from developmental delays, structural deformities, and reduced reproduction and population growth. Curiously, some iflaviruses do not appear to have any impacts on health and some even provide benefits. Because of their ability to manipulate population growth, iflaviruses have the potential to be developed as pest management tools. Red flour beetle is a high profile pest of flour mills that is occasionally infected by iflavirus. This species has developed resistance to a large number of fumigants and insecticides and alternate means of control are being sought after. Thus, the purpose of this study was to survey different populations of red flour beetle and other species of flour beetles to determine the prevalence of viral infection and document any impacts on health. Iflavirus infection was found in the majority (~63%) of red lour beetle populations surveyed, but not in other flour beetle species. The virus was predominantly detected in the nervous system and viral infection was readily passed from mother to offspring. Although the virus did not appear to negatively impact infected colonies, perturbations to the insect immune system have the potential to disrupt these interactions, which could allow viruses to replicate and proliferate. This could allow them to be developed into pest management tools for red flour beetles and other stored product pests.

Technical Abstract: Iflavirus is a group of viruses distributed mainly in arthropod species. We surveyed Tribolium castaneum iflavirus (TcIV) in different laboratory strains and also 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 examination of 50 different lines by usingTaqman-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 variations, 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. 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 immune system of this model beetle species.