Brief Bio: Dr Emily Remnant is an Academic Fellow and Lecturer in the School of Life and Environmental Sciences at the University of Sydney. Her research investigates evolution in action, using genomics to explore how insects respond to strong selective pressures like parasites and pesticides. She is particularly interested in investigating novel ways to improve the health of beneficial insects like honey bees by examining host-parasite interactions, virus discovery and evolution and honey bee immune responses to viral disease.

Virus evolution, antiviral immunity, honey bee health, host-parasite interactions, RNA interference

Virus silencing in honey bees and their mites

Viruses are some of the most common pathogens contributing to declining honeybee health worldwide. Since the emergence and global spread of the parasitic mite Varroa destructor, one of the most striking observations has been the concurrent increase in virus levels in honeybee colonies. Varroa provides an alternate route of transmission as a mechanical vector, enabling virus particles to directly breach the cuticle of developing bees and replicate to higher levels. Some evidence also exists to suggest that viruses can actively infect mites, facilitating increased transmission via biological vectoring. To better understand the role of Varroa as a vector, we investigated if honeybee viruses actively replicate in Varroa by determining whether they trigger the mite’s antiviral immune response. Using deep sequencing of small RNA in honeybees and Varroa, we examined the RNA interference (RNAi) pathway, a major antiviral immune pathway in insects. We find that multiple honeybee-infecting viruses are actively silenced in Varroa, however mites show distinct degradation profiles that differ from the profiles observed in bees. Our results indicate that viruses are silenced differently between bees and their mite parasites and point to alternate viral RNAi pathways within these two Arthropod lineages, potentially identifying a novel target that may be exploited in Varroa biocontrol. Characterising the antiviral response of the honeybee’s most significant parasite will contribute to a better understanding of the role of this vector in the evolution and spread of honey bee viruses.