Identification of the domains of cauliflower mosaic virus protein P6 responsible for suppression of RNA silencing and salicylic acid signalling

Laird, J. et al. (2013) Identification of the domains of cauliflower mosaic virus protein P6 responsible for suppression of RNA silencing and salicylic acid signalling. Journal of General Virology, 94(12), pp. 2777-2789. (doi: 10.1099/vir.0.057729-0) (PMID:24088344) (PMCID:PMC3836500)

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Cauliflower mosaic virus (CaMV) encodes a 520 amino acid polypeptide, P6, which participates in several essential activities in the virus lifecycle including suppressing RNA-silencing and salicylic acid-responsive defence signaling. We infected Arabidopsis with CaMV mutants containing short in-frame deletions within the P6 ORF. A deletion in the distal end of Domain D-I (the N-terminal 112 amino acids) of P6 did not affect virus replication but compromised symptom development and curtailed the ability to restore GFP-fluorescence in a GFP-silenced transgenic Arabidopsis line. A deletion in the miniTAV domain was defective in virus replication but retained the capacity to suppress RNA-silencing locally. Symptom expression in CaMV-infected plants is apparently linked to the ability to suppress RNA-silencing. When transiently co-expressed with an elicitor of programmed cell death in Nicotiana tabacum, wild-type P6 suppressed the hypersensitive response (HR), but three mutants, two with deletions within the distal end of Domain D-I and one involving the N-terminal nuclear export signal (NES) were unable to do so. Deleting the N-terminal 20 amino acids also abolished the suppression of PAMP-dependent PR1a expression following agroinfiltration. However the two other deletions in Domain D-I retained this activity, evidence that the mechanisms underlying these functions are not identical. The D-I domain of P6 when expressed alone failed to suppress either cell-death or PR1a expression and is therefore necessary but not sufficient for all three defence suppression activities. Consequently concerns about the biosafety of GM crops carrying truncated ORFVI sequences appear unfounded.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Carr, Mr Craig and Milner, Dr Joel and Smith, Dr Brian and Love, Dr Andrew and Laird, Ms Janet
Authors: Laird, J., McInally, C., Carr, C., Doddiah, S., Yates, G., Chrysanthou, E., Khattab, A., Love, A.J., Geri, C., Sadanandom, A., Smith, B.O., Kobayashi, K., and Milner, J.J.
College/School:College of Medical Veterinary and Life Sciences > School of Molecular Biosciences
College of Medical Veterinary and Life Sciences > School of Life Sciences
Journal Name:Journal of General Virology
Publisher:Society for General Microbiology
ISSN (Online):1465-2099
Copyright Holders:Copyright © 2013 SGM
First Published:First published in Journal of General Virology 49(12):2777-2789
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
419821Defence and defence suppression in plant pathogen interactions - the role of CaMV protein P6Joel MilnerBiotechnology and Biological Sciences Research Council (BBSRC)BB/D017319/1LS - BIOMOLECULAR SCIENCE