|ZHAO, YAZHOU - Non ARS Employee
|PENG, WEN JUN - Chinese Academy Of Agricultural Sciences
|ROSE, ROBYN - Animal And Plant Health Inspection Service (APHIS)
|LI, JIANGHONG - Non ARS Employee
|LI, ZHIGUO - Non ARS Employee
|SU, SONGKUN - Fujian Agriculture And Forest University
|RODRIGUEZ-GARCIA, CRISTINA - Non ARS Employee
|Chen, Yanping - Judy
Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2018
Publication Date: 1/8/2019
Citation: Zhao, Y., Heerman, M.C., Peng, W., Evans, J.D., Rose, R., Hoffman, G.D., Simone-Finstrom, M., Li, J., Li, Z., Cook, S.C., Su, S., Rodriguez-Garcia, C., Banmeke, O.A., Hamilton, M.C., Chen, Y. 2019. The dynamics of deformed wing virus titer and host defensive gene expression after varroa mite parasitism in honey bees, Apis mellifera. Insects. 10(1):16. https://doi.org/10.3390/insects10010016.
Interpretive Summary: The parasitic mite Varroa in association with Deformed wing virus (DWV) has often have been implicated in colony losses and is responsible for the death of millions of colonies worldwide. However, to date, the underlying mechanisms that facilitate the interactions between the bee, Varroa mite, and virus have not been fully explained. We conducted a study to investigate honey bees' defense responses to Varroa infestation and DWV infection. Our results showed that honey bees could mount rapid and immediate immune responses to threats. However, the immune system slowed down in its normal function two days post the Varroa infestation, leaving the bee vulnerable to expansive viral replication. The critical insights into the defense response upon Varroa and DWV challenges generated in this study may serve as a solid base for future research on the development of therapeutic strategies for honey bee disease treatment and should be of interest to the researchers, graduate students, apiary inspectors, and beekeepers in the honey bee society worldwide.
Technical Abstract: The synergistic interactions between the ectoparasitic mite Varroa destructor and Deformed wing virus (DWV) lead to the reduction in lifespan of the European honey bee Apis mellifera and often have been implicated in colony losses worldwide. However, to date, the underlying processes and mechanisms that form the multipartite interaction between the bee, mite, and virus have not been fully explained. To gain a better understanding of honey bees' defense response to Varroa mite infestation and DWV infection, the DWV titers and transcription profiles of genes originating from RNAi, immunity, wound response, and homeostatic signaling pathways were monitored over a period of eight days. With respect to DWV we observed low viral titers at early timepoints that coincided with high levels of Toll pathway transcription factor Dorsal, and its downstream immune effector molecules Hymenoptaecin, Apidaecin, Abaecin, and Defensin 1. However, we observed a striking increase in viral titers beginning after 2 days that coincided with a decrease in Dorsal levels and its corresponding immune effector molecules, and the Small ubiquitin-like modifier (SUMO), ligase repressor of Dorsal, PIAS3. We observed a similar expression pattern for genes expressing transcripts for the RNA interference (Dicer/Argonaute), wound/homeostatic (Janus Kinase), and tissue growth (Map kinase/Wnt) pathways. Our results demonstrate that on a whole, honey bees are able to mount an immediate, albeit, temporally limited immune and homeostatic response to Varroa and DWV infections, after which down regulation of these pathways leaves the bee vulnerable to expansive viral replication. The critical insights into the defense response upon Varroa and DWV challenges generated in this study may serve as a solid base for future research on the development of effective and efficient disease management strategies in honey bees.