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Carr Group: *Priority CASE Project* Pathogenic viruses of bees and aphids: Are plants a common reservoir?

NERC / GFC / OTHER

Supervisor: John Carr (Plant Sciences
Co-Supervisors: Gerard Clover (Plant Health Department, Royal Horticultural Society)
CASE Partner: Royal Horticultural Society, RHS Garden Wisley

Importance of the area of research concerned:

Bee populations and diversity of wild bees (bumblebees, solitary bees etc.) are in decline. In some cases these declines can be attributed to off-target effects of insecticides, changing land use (e.g. urbanization), or the intensification of agriculture. Understanding and reversing these declines clearly requires further research. However, a neglected area of study is how bee health is affected by their interactions with other organisms. Our previous work suggests that insect-pathogenic viruses (belonging to a group known as dicistroviruses) may be passed between different insect types via plant reservoirs (Wamonje et al. 2017). Virus flow between bees, plants and other plant-associated insects (including pests such as aphids) is a completely new area of study that may provide valuable insights into the biotic factors affecting bee survival and the wider interactions of beneficial and pest insects with plants.

Project summary:

Aphids are sap-sucking insects that damage plants and transmit most plant-infecting viruses. However, plant phloem sap can harbour aphid-infecting viruses that do not infect or damage plants but can be lethal to any aphids that feed on the phloem. Curiously, some aphid-infecting viruses have been detected in bees, where they do not appear to cause any disease, and the bees may deposit infectious material on plants during pollination. This prompts several questions: (1) do aphid-pathogenic viruses that use plants as infection reservoirs act as natural 'biocontrol' agents that provide a mutualistic benefit to plants; (2) does bee-plant mutualism extend beyond pollination to include providing plants with viral 'biological weapons' that protect against insect pests, and (3) are bee-pathogenic dicistroviruses disseminated by sap-sucking pest insects such as aphids?

What will the student do?:

Year 1 Exploit the biodiversity of Wisley and other RHS sites to discover examine the diversity of dicistroviruses in plants, aphids, bees (honeybees and many bumblebees and solitary bees), and aphid-associated insects (aphid-farming ants, parasitoid wasps, ladybirds). Methods will include reverse transcription PCR with dicistrovirus-specific primers to detect and sequence dicistroviruses present.
Years 2-3 Establish dicistrovirus-carrying aphid and plant populations from material surveyed in year 1. Dicistroviruses pass horizontally between insects, through plants, or vertically to offspring, facilitating establishment of infected stocks. Pathogenesis differs between insect hosts, e.g. Aphid lethal paralysis virus kills Myzus persicae but replicates asymptomatically in Aphis nerii. Thus, where infection is lethal to one aphid species, another will be used as a maintenance host to transfer virus into plant reservoirs. We will explore if viruses can be transferred via the plant between aphids and bees under lab conditions.

References:

  • Groen, S.C., Jiang S., Murphy, A.M., Cunniffe N.J., Westwood, J.H., Davey, M.P., Bruce, T.J.A., Caulfield, J.C., Furzer, O.J., Reed, A., Robinson, S.I., Miller, E., Davis C.N., Pickett, J.A., Whitney, H.M., Glover, B.J. & Carr, J.P. (2016). Virus infection of plants alters pollinator preference: A payback for susceptible hosts? PLoS Pathogens 12(8): e1005790 http://dx.plos.org/10.1371/journal.ppat.1005790
  • Wamonje, F.O., Michuki, G.N., Braidwood, L.A., Njuguna, J., Mutuku, J.M., Djikeng, A., Harvey, J.J.W. & Carr, J.P. (2017) Viral metagenomics of aphids present in bean and maize plots on mixed-use farms in Kenya reveals the presence of three dicistroviruses including a novel Big Sioux River virus-like dicistrovirus. Virology Journal 14:188. https://doi.org/10.1186/s12985-017-0854-x
  • Carr, J.P., Donnelly, R., Tungadi, T., Murphy, A.M., Jiang, S., Bravo-Cazar, A., Yoon, J.Y., Cunniffe, N.J., Glover, B.J., and Gilligan, C.A.G. (2018). Viral manipulation of plant stress responses and host interactions with insects. Advances in Virus Research 102: 177-197. doi: 10.1016/bs.aivir.2018.06.004.

Applying: To the Cambridge NERC C-CLEAR DTP programme: https://nercdtp.esc.cam.ac.uk/  

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