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

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.

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Effects of DICER-like proteins 2, 3 and 4 on cucumber mosaic virus and tobacco mosaic virus infections in salicylic acid-treated plants

Journal of General Virology ◽

10.1099/vir.0.014555-0 ◽

2009 ◽

Vol 90 (12) ◽

pp. 3010-3014 ◽

Cited By ~ 35

Author(s):

Mathew G. Lewsey ◽

John P. Carr

Keyword(s):

Salicylic Acid ◽

Tobacco Mosaic Virus ◽

Cucumber Mosaic Virus ◽

Mosaic Virus ◽

Rna Silencing ◽

Rna Viruses ◽

Virus Infections ◽

Defence Mechanisms ◽

Triple Mutant ◽

Positive Sense

Salicylic acid (SA)-mediated resistance and RNA silencing are both important plant antiviral defence mechanisms. To investigate overlap between these resistance phenomena, we examined the ability of mutant Arabidopsis thaliana plants lacking DICER-like (DCL) endoribonucleases 2, 3 and 4 to exhibit SA-induced defence. We found that in dcl2/3/4 triple mutant plants, treatment with exogenous SA stimulated resistance to two positive-sense RNA viruses: cucumber mosaic virus and tobacco mosaic virus. We conclude that DCLs 2, 3 and 4, which are the predominant DCL endoribonucleases involved in silencing of positive-sense RNA viruses, are not required for effective SA-induced resistance to these viruses. However, the findings do not exclude RNA silencing from making a contribution to SA-mediated resistance in wild-type plants.

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Reprogramming of RNA silencing triggered by cucumber mosaic virus infection in Arabidopsis

Genome Biology ◽

10.1186/s13059-021-02564-z ◽

2021 ◽

Vol 22 (1) ◽

Author(s):

Maria Luz Annacondia ◽

German Martinez

Keyword(s):

Cucumber Mosaic Virus ◽

Mosaic Virus ◽

Virus Resistance ◽

Rna Silencing ◽

High Throughput Sequencing ◽

Small Interfering Rnas ◽

Genome Wide ◽

Endogenous Genes ◽

Silencing Pathways ◽

Relationship Of

Abstract Background RNA silencing has an important role mediating sequence-specific virus resistance in plants. The complex interaction of viruses with RNA silencing involves the loading of viral small interfering RNAs (vsiRNAs) into its host ARGONAUTE (AGO) proteins. As a side effect of their antiviral activity, vsiRNAs loading into AGO proteins can also mediate the silencing of endogenous genes. Here, we analyze at the genome-wide level both aspects of the interference of cucumber mosaic virus (CMV) with the RNA silencing machinery of Arabidopsis thaliana. Results We observe CMV-derived vsiRNAs affect the levels of endogenous sRNA classes. Furthermore, we analyze the incorporation of vsiRNAs into AGO proteins with a described antiviral role and the viral suppressor of RNA silencing (VSR) 2b, by combining protein immunoprecipitation with sRNA high-throughput sequencing. Interestingly, vsiRNAs represent a substantial percentage of AGO-loaded sRNAs and displace other endogenous sRNAs. As a countermeasure, the VSR 2b loaded vsiRNAs and mRNA-derived siRNAs, which affect the expression of the genes they derive from. Additionally, we analyze how vsiRNAs incorporate into the endogenous RNA silencing pathways by exploring their target mRNAs using parallel analysis of RNA end (PARE) sequencing, which allow us to identify vsiRNA-targeted genes genome-wide. Conclusions This work exemplifies the complex relationship of RNA viruses with the endogenous RNA silencing machinery and the multiple aspects of virus resistance and virulence that this interaction induces.

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Faculty Opinions recommendation of Evidence that RNA silencing functions as an antiviral defense mechanism in fungi.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1090143.543358 ◽

2007 ◽

Author(s):

Herb Arst

Keyword(s):

Rna Silencing ◽

Defense Mechanism ◽

Antiviral Defense

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Analysis of Mechanisms Involved in the Cucumber mosaic virus Satellite RNA-mediated Transgenic Resistance in Tomato Plants

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.2004.17.1.98 ◽

2004 ◽

Vol 17 (1) ◽

pp. 98-108 ◽

Cited By ~ 29

Author(s):

Fabrizio Cillo ◽

Mariella M. Finetti-Sialer ◽

Maria A. Papanice ◽

Donato Gallitelli

Keyword(s):

Cucumber Mosaic Virus ◽

Mosaic Virus ◽

Rna Silencing ◽

Resistance Mechanism ◽

Degradation Process ◽

Transgenic Tomato ◽

Satellite Rna ◽

Total Recovery ◽

Tomato Plants ◽

Free Strain

Transgenic tomato (Lycopersicon esculentum Mill. cv. UC82) plants expressing a benign variant of Cucumber mosaic virus satellite RNA (CMV Tfn-satRNA) were generated. The transformed plants did not produce symptoms when challenged with a satRNA-free strain of CMV (CMV-FL). The same plant lines initially were susceptible to necrosis elicited by a CMV strain supporting a necrogenic variant of satRNA (CMV-77), but a phenotype of total recovery from the necrosis was observed in the newly developing leaves. The features of the observed resistance were analyzed and are consistent with two different mechanisms of resistance. In transgenic plants inoculated with CMV-FL strain, the symptomless phenotype was correlated to the down-regulation of CMV by Tfn-satRNA, amplified from the transgene transcripts, as the first resistance mechanism. On the other hand, the delayed resistance to CMV-77 in transgenic tomato lines was mediated by a degradation process that targets satRNAs in a sequence-specific manner. Evidence is provided for a correlation between a reduced accumulation level of transgenic messenger Tfn-satRNA, the accumulation of small (approximately 23 nucleotides) RNAs with sequence homology to satRNAs, the progressively reduced accumulation of 77-satRNA in infected tissues, and the transition in infected plants from diseased to healthy. Thus, events leading to the degradation of satRNA sequences indicate a role for RNA silencing as the second mechanism determining resistance of transgenic tomato lines.

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Cucumber mosaic virus Infection Transiently Breaks dsRNA-Induced Transgenic Immunity to Potato virus Y in Tobacco

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.2003.16.10.936 ◽

2003 ◽

Vol 16 (10) ◽

pp. 936-944 ◽

Cited By ~ 30

Author(s):

Neena Mitter ◽

Emy Sulistyowati ◽

Ralf G. Dietzgen

Keyword(s):

Cucumber Mosaic Virus ◽

Mosaic Virus ◽

Potato Virus ◽

Potato Virus Y ◽

Defense Mechanism ◽

Transcriptional Gene Silencing ◽

Mrna Levels ◽

Post Transcriptional Gene Silencing ◽

The Stability ◽

High Level

Post-transcriptional gene silencing (PTGS), an intrinsic plant defense mechanism, can be efficiently triggered by double stranded (ds)RNA-producing transgenes and can provide high level virus resistance by specific targeting of cognate viral RNA. The discovery of virus-encoded suppressors of PTGS led to concerns about the stability of such resistance. Here, we show that Cucumber mosaic virus (CMV) is able to suppress dsRNA-induced PTGS and the associated Potato virus Y (PVY) immunity in tobacco. CMV suppression supported only a transient PVY accumulation and did not prevent recovery of the transgenic plants from PVY infection. CMV inoculation resulted in strongly increased transgene mRNA levels due to suppression of PTGS, but accumulation of PVY-specific small interfering (si)RNA was unaffected. However, PVY accumulation in previously immune plants resulted in increased PVY siRNA levels and transgene mRNA was no longer detected, despite the presence of CMV. Transgene mRNA returned to high levels once PVY was no longer detected in CMV-infected plants. Recovered and chronically CMV-infected tissues were immune to further PVY infection.

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Hypovirus Papain-Like Protease p29 Suppresses RNA Silencing in the Natural Fungal Host and in a Heterologous Plant System

Eukaryotic Cell ◽

10.1128/ec.00373-05 ◽

2006 ◽

Vol 5 (6) ◽

pp. 896-904 ◽

Cited By ~ 95

Author(s):

Gerrit C. Segers ◽

Rene van Wezel ◽

Xuemei Zhang ◽

Yiguo Hong ◽

Donald L. Nuss

Keyword(s):

Rna Silencing ◽

Defense Mechanism ◽

Fluorescent Protein ◽

Cryphonectria Parasitica ◽

Fungal Host ◽

Chestnut Blight Fungus ◽

Systemic Spread ◽

Green Fluorescent ◽

Fungal Viruses ◽

Suppressor Of Rna Silencing

ABSTRACT Virulence-attenuating hypoviruses of the species Cryphonectria hypovirus 1 (CHV1) encode a papain-like protease, p29, that shares similarities with the potyvirus-encoded suppressor of RNA silencing HC-Pro. We now report that hypovirus CHV1-EP713-encoded p29 can suppress RNA silencing in the natural host, the chestnut blight fungus Cryphonectria parasitica. Hairpin RNA-triggered silencing was suppressed in C. parasitica strains expressing p29, and transformation of a transgenic green fluorescent protein (GFP)-silenced strain with p29 resulted in an increased number of transformants with elevated GFP expression levels. The CHV1-EP713 p29 protein was also shown to suppress both virus-induced and agroinfiltration-induced RNA silencing and systemic spread of silencing in GFP-expressing transgenic Nicotiana benthamiana line 16c plants. The demonstration that a mycovirus encodes a suppressor of RNA silencing provides circumstantial evidence that RNA silencing in fungi may serve as an antiviral defense mechanism. The observation that a phylogenetically conserved protein of related plant and fungal viruses functions as a suppressor of RNA silencing in both fungi and plants indicates a level of conservation of the mechanisms underlying RNA silencing in these two groups of organisms.

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Cucumber mosaic virus and its 2b RNA silencing suppressor modify plant-aphid interactions in tobacco

Scientific Reports ◽

10.1038/srep00187 ◽

2011 ◽

Vol 1 (1) ◽

Cited By ~ 73

Author(s):

Heiko Ziebell ◽

Alex M. Murphy ◽

Simon C. Groen ◽

Trisna Tungadi ◽

Jack H. Westwood ◽

...

Keyword(s):

Cucumber Mosaic Virus ◽

Mosaic Virus ◽

Rna Silencing ◽

Silencing Suppressor ◽

Rna Silencing Suppressor

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A Novel Methyltransferase Methylates Cucumber Mosaic Virus 1a Protein and Promotes Systemic Spread

Journal of Virology ◽

10.1128/jvi.02518-07 ◽

2008 ◽

Vol 82 (10) ◽

pp. 4823-4833 ◽

Cited By ~ 22

Author(s):

Min Jung Kim ◽

Sung Un Huh ◽

Byung-Kook Ham ◽

Kyung-Hee Paek

Keyword(s):

Cucumber Mosaic Virus ◽

Mosaic Virus ◽

Protein Interactions ◽

Protein Localization ◽

Binding Activity ◽

Virus Infectivity ◽

Gene Encoding ◽

Systemic Spread

ABSTRACT In mammalian and yeast systems, methyltransferases have been implicated in the regulation of diverse processes, such as protein-protein interactions, protein localization, signal transduction, RNA processing, and transcription. The Cucumber mosaic virus (CMV) 1a protein is essential not only for virus replication but also for movement. Using a yeast two-hybrid system with tobacco plants, we have identified a novel gene encoding a methyltransferase that interacts with the CMV 1a protein and have designated this gene Tcoi1 (tobacco CMV 1a-interacting protein 1). Tcoi1 specifically interacted with the methyltransferase domain of CMV 1a, and the expression of Tcoi1 was increased by CMV inoculation. Biochemical studies revealed that the interaction of Tcoi1 with CMV 1a protein was direct and that Tcoi1 methylated CMV 1a protein both in vitro and in vivo. The CMV 1a binding activity of Tcoi1 is in the C-terminal domain, which shows the methyltransferase activity. The overexpression of Tcoi1 enhanced the CMV infection, while the reduced expression of Tcoi1 decreased virus infectivity. These results suggest that Tcoi1 controls the propagation of CMV through an interaction with the CMV 1a protein.

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