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

2013 ◽  
Vol 94 (12) ◽  
pp. 2777-2789 ◽  
Author(s):  
Janet Laird ◽  
Carol McInally ◽  
Craig Carr ◽  
Sowjanya Doddiah ◽  
Gary Yates ◽  
...  
Keyword(s):  
Cell Death ◽  
Salicylic Acid ◽  
Mosaic Virus ◽  
Virus Replication ◽  
Nuclear Export ◽  
Rna Silencing ◽  
Nuclear Export Signal ◽  
Genetically Modified Crops ◽  
Cauliflower Mosaic Virus ◽  
Virus Protein

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.

scholarly journals Cauliflower mosaic virus Protein P6 Inhibits Signaling Responses to Salicylic Acid and Regulates Innate Immunity

PLoS ONE ◽  
2012 ◽  
Vol 7 (10) ◽  
pp. e47535 ◽  
Author(s):  
Andrew J. Love ◽  
Chiara Geri ◽  
Janet Laird ◽  
Craig Carr ◽  
Byung-Wook Yun ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Salicylic Acid ◽  
Mosaic Virus ◽  
Cauliflower Mosaic Virus ◽  
Virus Protein

scholarly journals Cauliflower mosaic virus protein P6 is a suppressor of RNA silencing

2007 ◽  
Vol 88 (12) ◽  
pp. 3439-3444 ◽  
Author(s):  
Andrew J. Love ◽  
Janet Laird ◽  
Justin Holt ◽  
Andrew J. Hamilton ◽  
Ari Sadanandom ◽  
...  
Keyword(s):  
Mosaic Virus ◽  
Symptom Severity ◽  
Rna Silencing ◽  
Transgenic Arabidopsis ◽  
Cauliflower Mosaic Virus ◽  
Virus Protein ◽  
Silencing Suppressor ◽  
Northern Blots ◽  
Gfp Fluorescence ◽  
Suppressor Of Rna Silencing

We infected a transgenic Arabidopsis line (GxA), containing an amplicon-silenced 35S : : GFP transgene, with cauliflower mosaic virus (CaMV), a plant pararetrovirus with a DNA genome. Systemically infected leaves showed strong GFP fluorescence and amplicon transcripts were detectable in Northern blots, indicating that silencing of GFP had been suppressed during CaMV-infection. Transgenic Arabidopsis lines expressing CaMV protein P6, the major genetic determinant of symptom severity, were crossed with GxA. Progeny showed strong GFP fluorescence throughout and amplicon transcripts were detectable in Northern blots, indicating that P6 was suppressing local and systemic silencing. However, levels of 21 nt siRNAs derived from the GFP transgene were not reduced. In CaMV-infected plants, the P6 transgene did not reduce levels of CaMV leader-derived 21 and 24 nt siRNAs relative to levels of CaMV 35S RNA. These results demonstrate that CaMV can efficiently suppress silencing of a GFP transgene, and that P6 acts as a silencing suppressor.

scholarly journals Nucleo-cytoplasmic shuttling of VPg encoded by Wheat yellow mosaic virus requires association with the coat protein

2013 ◽  
Vol 94 (12) ◽  
pp. 2790-2802 ◽  
Author(s):  
Liying Sun ◽  
Bian Jing ◽  
Ida Bagus Andika ◽  
Yingchun Hu ◽  
Bingjian Sun ◽  
...  
Keyword(s):  
Coat Protein ◽  
Nuclear Export ◽  
Fluorescent Protein ◽  
Nuclear Export Signal ◽  
Plant Viruses ◽  
Yellow Mosaic Virus ◽  
Virus Protein ◽  
Wheat Yellow Mosaic Virus ◽  
Nuclear Targeting ◽  
Cytoplasmic Transport

VPg (virus protein, genome-linked) is a multifunctional protein that plays important roles in viral multiplication in the cytoplasm. However, a number of VPgs encoded by plant viruses target the nucleus and this appears to be biologically significant. These VPgs may therefore be translocated between nuclear and cytoplasmic compartments during virus infection, but such nucleo-cytoplasmic transport has not been demonstrated. We report that VPg encoded by Wheat yellow mosaic virus (WYMV, genus Bymovirus, family Potyviridae) accumulated in both the nucleus and cytoplasm of infected cells, but localized exclusively in the nucleus when expressed alone in plants. Computational analyses predicted the presence of a nuclear localization signal (NLS) and a nuclear export signal (NES) in WYMV VPg. Mutational analyses showed that both the N-terminal and the NLS domains of VPg contribute to the efficiency of nuclear targeting. In vitro and in planta assays indicated that VPg interacts with WYMV coat protein (CP) and proteinase 1 (P1) proteins. Observation of VPg fused to a fluorescent protein and subcellular fractionation experiments showed that VPg was translocated to the cytoplasm when co-expressed with CP, but not with P1. Mutations in the NES domain or treatment with leptomycin B prevented VPg translocation to the cytoplasm when co-expressed with CP. Our results suggest that association with CP facilitates the nuclear export of VPg during WYMV infection.

scholarly journals The Suppressor of Transgene RNA Silencing Encoded by Cucumber mosaic virus Interferes with Salicylic Acid-Mediated Virus Resistance

2001 ◽  
Vol 14 (6) ◽  
pp. 715-724 ◽  
Author(s):  
Liang-Hui Ji ◽  
Shou-Wei Ding
Keyword(s):  
Salicylic Acid ◽  
Cucumber Mosaic Virus ◽  
Mosaic Virus ◽  
Virus Resistance ◽  
Rna Silencing ◽  
Defense Mechanism ◽  
Antiviral Defense ◽  
Oxidase Gene ◽  
Systemic Spread ◽  
Systemic Infections

The Cucumber mosaic virus (CMV)-encoded 2b protein (Cmv2b) is a nuclear protein that suppresses transgene RNA silencing in Nicotiana benthamiana. Cmv2b is an important virulence determinant but nonessential for systemic spread in N. glutinosa, in contrast to its indispensable role for systemic infections in cucumber. Here, we report that Cmv2b became essential for systemic infections in older N. glutinosa plants or in young seedlings pre-treated with salicylic acid (SA). Expression of Cmv2b from the genome of either CMV or Tobacco mosaic virus significantly reduced the inhibitory effect of SA on virus accumulation in inoculated leaves and systemic leaves. A close correlation is demonstrated between Cmv2b expression and a reduced SA-dependent induction of the alternative oxidase gene, a component of the recently proposed SA-regulated antiviral defense. These results collectively reveal a novel activity of Cmv2b in the inhibition of SA-mediated virus resistance. We used a N. tabacum line expressing a bacterial nahG transgene that degrades SA to provide evidence for a Cmv2b-sensitive antiviral defense mechanism in tobacco in which SA acts as a positive modifier but not as an essential component. We propose that SA induces virus resistance by potentiating a RNA-silencing antiviral defense that is targeted by Cmv2b.

Salicylic Acid Interferes with Tobacco Mosaic Virus Replication via a Novel Salicylhydroxamic Acid-Sensitive Mechanism

1997 ◽  
Vol 9 (4) ◽  
pp. 547 ◽  
Author(s):  
Stephen Chivasa ◽  
Alex M. Murphy ◽  
Martin Naylor ◽  
John P. Carr
Keyword(s):  
Salicylic Acid ◽  
Tobacco Mosaic Virus ◽  
Mosaic Virus ◽  
Virus Replication ◽  
Salicylhydroxamic Acid

scholarly journals Cauliflower Mosaic Virus Utilizes Processing Bodies to Escape Translational Repression in Arabidopsis

2021 ◽  
Author(s):  
Anders Hafrén ◽  
Gesa Hoffmann ◽  
Amir Mahboubi ◽  
Johannes Hanson ◽  
Damien Garcia
Keyword(s):  
Quality Control ◽  
Mosaic Virus ◽  
Rna Silencing ◽  
Rna Degradation ◽  
Virus Multiplication ◽  
Cauliflower Mosaic Virus ◽  
Translational Repression ◽  
Processing Bodies ◽  
Rna Quality ◽  
Rna Quality Control

Viral infections impose extraordinary RNA stress on a cell, triggering cellular RNA surveillance pathways like RNA decapping, nonsense-mediated decay and RNA silencing. Viruses need to maneuver between these pathways to establish infection and succeed in producing high amounts of viral proteins. Processing bodies (PBs) are integral to RNA triage in eukaryotic cells with several distinct RNA quality control pathways converging for selective RNA regulation. In this study, we investigate the role of Arabidopsis thaliana PBs during Cauliflower Mosaic Virus (CaMV) infection. We find that several PB components are co-opted into viral replication factories and support virus multiplication. This pro-viral role was not associated with RNA decay pathways but instead, we could establish PB components as essential helpers in viral RNA translation. While CaMV is normally resilient to RNA silencing, PB dysfunctions expose the virus to this pathway, similar to previous observations on transgenes. Transgenes, however, undergo RNA Quality Control dependent RNA degradation, whereas CaMV RNA remains stable but becomes translationally repressed through decreased ribosome association, revealing a unique dependence between PBs, RNA silencing and translational repression. Together, our study shows that PB components are co-opted by the virus to maintain efficient translation, a mechanism not associated with canonical PB functions.

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