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

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.; Milner, J.J.

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


Authors

J. Laird

C. McInally

C. Carr

S. Doddiah

G. Yates

E. Chrysanthou

A. Khattab

A.J. Love

C. Geri

B.O. Smith

K. Kobayashi

J.J. Milner



Abstract

Cauliflower mosaic virus (CaMV) encodes a 520 aa polypeptide, P6, which participates in several essential activities in the virus life cycle including suppressing RNA silencing and salicylic acid-responsive defence signalling. 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 aa) 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 minimum transactivator 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 tomato bushy stunt virus P19, an elicitor of programmed cell death in Nicotiana tabacum, WT P6 suppressed the hypersensitive response, 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 aa also abolished the suppression of pathogen-associated molecular pattern-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 genetically modified crops carrying truncated ORFVI sequences appear unfounded.

Journal Article Type Article
Acceptance Date Sep 19, 2013
Publication Date Dec 1, 2013
Deposit Date Sep 9, 2015
Publicly Available Date Nov 3, 2015
Journal Journal of General Virology
Print ISSN 0022-1317
Electronic ISSN 1465-2099
Publisher Microbiology Society
Peer Reviewed Peer Reviewed
Volume 94
Issue 12
Pages 2777-2789
DOI https://doi.org/10.1099/vir.0.057729-0
Public URL https://durham-repository.worktribe.com/output/1400324

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