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Carr Group: Plant Virology: Role of RNA-dependent RNA polymerase in salicylic acid-induced viruses resistance


Supervisor: John Carr (Plant Sciences

Project Summary

Plant-infecting viruses cause serious crop losses but our knowledge of how they cause disease in their plant hosts is incomplete. An improved understanding of disease induction is important not only because it would improve our fundamental less susceptible to disease. Among the most important natural resistance mechanisms are RNA silencing and salicylic acid-induced resistance. RNA silencing is a potent system that allows the plant cell to 'learn' to identify and destroy the genetic material of an invading virus. Salicylic acid (a naturally occurring chemical that is the parent compound of aspirin) is made by plants and used to stimulate resistance to replication and spread of viruses. There are intriguing links between these two antiviral systems. One of these is RNA-dependent RNA polymerase 1 (RDR1) expression and activity – which amplify antiviral RNA silencing – are increased by salicylic acid. We discovered that RDR1 and salicylic acid work synergistically to prevent viruses from invading the meristem. This is important because if we prevent RDR1 and SA from protecting the meristems, virus-induced disease is greatly exacerbated and cuases death of the plant. More recently, we discovered that RDR1 accumulates inside plant cells close to microscopic channels that link cells to their neighbors. Plant viruses exploit these channels, called 'plasmodesmata', as invasion routes to spread between cells. We suspect that the placement of RDR1 in the vicinity of plasmodesmata might be related to the ability of this important antiviral factor to prevent entry of viruses into the meristem and thereby protect plants from the worst effects of the virus. In this project we will:

  1. Confirm the localization of RDR1 at plasmodesmata and determine if salicylic acid causes any change in the accumulation at these sites or redirects RDR1 elsewhere within the cell.
  2. Determine if SA alters the sub-cellular localization of RDR1 or its ubiquitination and phosphorylation states.
  3. Identify proteins that interact with RDR1 using techniques including yeast two-hybrid, co-immunoprecipitation and bimolecular fluorescence complementation.


  • Lee, W.S., Fu, S.F., Li, Z., Murphy, A.M., Dobson, E.A., Garland, L., Chaluvadi, S.R., Lewsey, M.G., Nelson, R.S., and Carr, J.P. 2016. Salicylic acid treatment and expression of an RNA-dependent RNA polymerase 1 transgene inhibits lethal symptoms and meristem invasion during tobacco mosaic virus infection in Nicotiana benthamiana. BMC Plant Biology 16:15 DOI: 10.1186/s12870-016-0705-8
  • Palukaitis, P., Yoon, J.Y., Choi, S.K. and Carr, J.P. 2017. Manipulation of induced resistance to viruses. Current Opinion in Virology 26:141-148. doi: 10.1016/j.coviro.2017.08.001. 


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