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A viral counter defence protein as a probe for cross-talk or functional overlap between host defence pathways.

Reference	BB/D008204/1
Principal Investigator / Supervisor	Professor John Carr
Co-Investigators / Co-Supervisors
Institution	University of Cambridge
Department	Plant Sciences
Funding type	Research
Value (£)	276,249
Status	Completed
Type	Research Grant
Start date	24/04/2006
End date	23/10/2009
Duration	42 months

Abstract

The Cucumber mosaic virus 2b protein is a suppressor of RNAi-mediated silencing of the virus. But it also subverts induced virus resistance mechanism(s) regulated by the plant signal chemical salicylic acid (SA), a key signal in the induction of systemic acquired resistance. This suggests that the two forms of resistance overlap and that the 2b protein is targeting a component common to both types of resistance. Although the effect of the 2b protein on SA-induced resistance has been known for four years it has never been determined exactly how it exerts its effects on this resistance pathway. In this project we will identify: 1. The mechanism(s) of 2b-mediated subversion of SA-induced virus resistance; 2. whether or not the functional domains of the 2b protein involved in subversion of SA-induced resistance are the same as, or different from, those that function in subversion of RNAi-mediated resistance, and 3. If the CMV 2b protein affects resistance to non-viral pathogens via SA as well as non-SA dependent signalling pathways such as those controlled primarily by ethylene and jasmonate.

Summary

Cucumber mosaic virus (CMV) is remarkable in that it attacks more crop and wild plant species than any other and it is one of the two most important viruses of field-grown and glasshouse horticultural crops in the UK and worldwide. An essential contributor to the success of CMV is a recently discovered factor called the 2b protein. This viral protein carries out several tasks but its most important is subverting disease resistance. We know that the 2b protein can inhibit the action of two types of resistance mechanism. One of these is called systemic acquired resistance, in which an attack by one disease-causing organism may stimulate a higher degree of resistance to a very broad range of diverse micro-organisms (viruses, fungi, bacteria). The other resistance mechanism defeated by the 2b protein is based on RNA interference, a phenomenon in which viral genetic material is recognised as foreign and broken down. We will determine how the 2b protein affects two apparently very different defence systems and if, in the process of disrupting systemic acquired resistance against virus infection, the 2b also has the potential to increase the susceptibility of plants to other disease causing micro-organisms.

Committee	Closed Committee - Plant & Microbial Sciences (PMS)
Research Topics	Crop Science, Microbiology, Plant Science
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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