scholarly journals Differential Virulence by Strains of Cucumber mosaic virus is Mediated by the 2b Gene

2002 ◽  
Vol 15 (9) ◽  
pp. 947-955 ◽  
Author(s):  
Bu-Jun Shi ◽  
Peter Palukaitis ◽  
Robert H. Symons
Keyword(s):  
Cucumber Mosaic Virus ◽  
Mosaic Virus ◽  
Kinetic Studies ◽  
Transcriptional Gene Silencing ◽  
Long Distance ◽  
Post Transcriptional Gene Silencing ◽  
Subgroup Ii ◽  
2B Protein ◽  
Rna Accumulation ◽  
Long Distance Movement

The approximately 12-kDa 2b protein, encoded by all cucumoviruses, had been shown to play an important role in viral long-distance movement, hypervirulence, and suppression of post-transcriptional gene silencing. The role of the 2b gene in the hypervirulence of Cucumber mosaic virus (CMV) and whether hypervirulence was linked to movement were analyzed using a hybrid virus (CMV-qw), generated by replacing the 2b gene in a subgroup II strain, Q-CMV, with the 2b gene from a subgroup IA strain, WAII-CMV. CMV-qw was more virulent than Q-CMV or WAII-CMV on most of the host plant species tested. Northern blot and nucleotide sequence analyses demonstrated that CMV-qw was stably maintained during the course of infection and upon passage. Kinetic studies revealed that the hypervirulence induced by the hybrid virus was associated with neither increased viral RNA accumulation nor more rapid viral movement per se, suggesting that other functions of the 2b protein are important in determining the hypervirulence.

scholarly journals 2b ORFs encoded by subgroup IB strains of cucumber mosaic virus induce differential virulence on Nicotiana species

2007 ◽  
Vol 88 (9) ◽  
pp. 2596-2604 ◽  
Author(s):  
Zhi-You Du ◽  
Fei-Fei Chen ◽  
Qian-Sheng Liao ◽  
Hua-Rong Zhang ◽  
Yan-Fei Chen ◽  
...  
Keyword(s):  
Cucumber Mosaic Virus ◽  
Mosaic Virus ◽  
Host Species ◽  
Long Distance ◽  
Reading Frame ◽  
Subgroup Ii ◽  
Viral Movement ◽  
2B Protein ◽  
Rna Accumulation ◽  
High Level

Cucumber mosaic virus (CMV)-encoded 2b protein from subgroup IA or subgroup II was shown to be a determinant of virulence in many solanaceous hosts. In this study, the virulence of 2b proteins from subgroup IB strains was analysed using four intraspecies hybrid viruses, which were generated by precise replacement of the 2b open reading frame (ORF) in subgroup IA strain Fny-CMV with the 2b ORFs of four subgroup IB strains, Cb7-CMV, PGs-CMV, Rad35-CMV and Na-CMV, generating FCb72b-CMV, FPGs2b-CMV, FRad352b-CMV and FNa2b-CMV, respectively. FCb72b-CMV was more virulent than Fny-CMV, and was similar in phenotype to its parental virus Cb7-CMV on the three Nicotiana species tested. FNa2b-CMV also was virulent on these host species, equivalent to Fny-CMV or Na-CMV. However, FRad352b-CMV only caused mild mosaic or undetectable symptoms on all the host species tested, and was less virulent than Fny-CMV or Rad35-CMV. FPGs2b-CMV infected all the host species systemically, and induced either mosaic or barely visible symptoms, demonstrating that the inability of PGs-CMV to infect these three Nicotiana species was not due to its 2b protein. The diverse virulence was shown to be mediated by the 2b proteins rather than the C-terminal overlapping parts of the 2a proteins, and was associated with the level of viral progeny RNA accumulation in systemically infected leaves, but not with the rate of long-distance viral movement in host plants. Through analysis of encapsidation of viral RNAs, there was an apparent correlation between the virulence and the high level of encapsidated RNA 2 in virions of Fny-CMV, FCb72b-CMV and FNa2b-CMV.

scholarly journals Sequence-, Tissue-, and Delivery-Specific Targeting of RNA During Post-Transcriptional Gene Silencing

2002 ◽  
Vol 15 (8) ◽  
pp. 753-763 ◽  
Author(s):  
Ezequiel Balmori-Melian ◽  
Robin M. MacDiarmid ◽  
David L. Beck ◽  
Richard C. Gardner ◽  
Richard L. S. Forster
Keyword(s):  
Gene Silencing ◽  
Mosaic Virus ◽  
Viral Vectors ◽  
Transcriptional Gene Silencing ◽  
Wild Type ◽  
Long Distance ◽  
Post Transcriptional Gene Silencing ◽  
In The Wild ◽  
Long Distance Movement ◽  
White Clover Mosaic Virus

Transgenic Nicotiana benthamiana plants expressing an untranslatable version of the coat protein (CP) gene from the Tamarillo mosaic virus (TaMV) were either resistant to TaMV infection or recovered from infection. These phenotypes were the result of a post-transcriptional gene silencing (PTGS) mechanism that targeted TaMV-CP sequences for degradation. The TaMV-CP sequences were degraded when present in the wild-type TaMV potyvirus, in transgene mRNA, or in chimeric viral vectors based on White clover mosaic virus. The more efficiently targeted region was mapped to a 134-nt segment. Differences were observed in the efficiency of targeting during cell-to-cell and long-distance movement of the chimeric viruses. However, the TaMV-CP sequences do not appear to be targeted for degradation when delivered by biolistics.

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

2003 ◽  
Vol 16 (10) ◽  
pp. 936-944 ◽  
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.

scholarly journals The Rate of Cell-to-Cell Movement in Squash of Cucumber Mosaic Virus Is Affected by Sequences of the Capsid Protein

1999 ◽  
Vol 12 (7) ◽  
pp. 628-632 ◽  
Author(s):  
Sek-Man Wong ◽  
Sharon Swee-Chin Thio ◽  
Michael H. Shintaku ◽  
Peter Palukaitis
Keyword(s):  
Amino Acids ◽  
Cucumber Mosaic Virus ◽  
Mosaic Virus ◽  
Capsid Protein ◽  
Cell Movement ◽  
Systemic Infection ◽  
Long Distance ◽  
Local Movement ◽  
Long Distance Movement

The M strain of cucumber mosaic virus (CMV) does not infect squash plants systemically and moves very slowly in inoculated cotyledons. Systemic infection and an increase in the rate of local movement were observed when amino acids 129 or 214 of the M-CMV capsid protein (CP) were altered to those present in the Fny strain of CMV. While the opposite alterations to the CP of Fny-CMV inhibited systemic infection of squash, they did not show the same effects on the rates of both cell-to-cell and long-distance movement. However, the ability of CMV to infect squash systemically was affected by the rate of cell-to-cell movement.

scholarly journals The Weak Small RNA-Binding Activity of the 2b Proteins of Subgroup II Cucumber Mosaic Virus Strains Is Insufficient for RNA Silencing Suppression

2021 ◽  
Vol 12 ◽  
Author(s):  
Yingying Gao ◽  
Jinrui Yang ◽  
Xiaobei Zhang ◽  
Aizhong Chen ◽  
Zhouhang Gu ◽  
...  
Keyword(s):  
Cucumber Mosaic Virus ◽  
Mosaic Virus ◽  
Rna Silencing ◽  
Rna Binding ◽  
Nuclear Accumulation ◽  
Nuclear Localization Sequence ◽  
Binding Ability ◽  
Suppressor Activity ◽  
Subgroup Ii ◽  
2B Protein

The 2b proteins encoded by cucumber mosaic virus (CMV) subgroup I strains suppress RNA silencing primarily by competitively binding small RNAs (sRNAs) in the host cell cytoplasm. Interestingly, 2b proteins encoded by CMV subgroup II strains accumulate predominantly in nuclei. Here we determined that whereas the 2b protein (Fny2b) of subgroup IA strain Fny-CMV is highly effective in suppressing both sense RNA-induced and inverted repeat-induced posttranscriptional gene silencing, the 2b protein (LS2b) of the subgroup II strain LS-CMV was not as effective. Reducing nuclear accumulation of LS2b by mutating a residue in its nuclear localization sequence had no effect on RNA silencing suppressor activity, while attenuated viral symptoms. Electrophoretic mobility shift assays showed that the sRNA binding of LS2b was weaker and more selective than that of Fny2b. The domain determining the differential sRNA-binding ability was delimited to the putative helix α1 region. Moreover, LS2b mutants that completely lost suppressor activity still retained their weak sRNA-binding ability, suggesting that sRNA binding is not sufficient for LS2b to suppress RNA silencing. Considering the subgroup I strain-encoded 2b proteins that require sRNA-binding ability for the suppression of RNA silencing, we suggest that in addition to binding sRNA, the 2b proteins of subgroup II CMV strains would require extra biological activities to achieve RNA silencing inhibition.

scholarly journals Twenty Years of Transgenic Plants Resistant to Cucumber mosaic virus

2008 ◽  
Vol 21 (6) ◽  
pp. 675-684 ◽  
Author(s):  
Marco Morroni ◽  
Jeremy R. Thompson ◽  
Mark Tepfer
Keyword(s):  
Transgenic Plants ◽  
Cucumber Mosaic Virus ◽  
Mosaic Virus ◽  
Transcriptional Gene Silencing ◽  
Effective Strategies ◽  
Resistance Strategies ◽  
Post Transcriptional Gene Silencing ◽  
Viral Coat ◽  
Viral Replicase ◽  
Pathogen Derived Resistance

Plant genetic engineering has promised researchers improved speed and flexibility with regard to the introduction of new traits into cultivated crops. A variety of approaches have been applied to produce virus-resistant transgenic plants, some of which have proven to be remarkably successful. Studies on transgenic resistance to Cucumber mosaic virus probably have been the most intense of any plant virus. Several effective strategies based on pathogen-derived resistance have been identified; namely, resistance mediated by the viral coat protein, the viral replicase, and post-transcriptional gene silencing. Techniques using non-pathogen-derived resistance strategies, some of which could offer broader resistance, generally have proven to be much less effective. Not only do the results obtained so far provide a useful guide to help focus on future strategies, but they also suggest that there are a number of possible mechanisms involved in conferring these resistances. Further detailed studies on the interplay between viral transgene-derived molecules and their host are needed in order to elucidate the mechanisms of resistance and pathogenicity.

Identification a coat protein region of cucumber mosaic virus (CMV) essential for long-distance movement in cucumber

2011 ◽  
Vol 156 (12) ◽  
pp. 2279-2283 ◽  
Author(s):  
Katalin Salánki ◽  
László Kiss ◽  
Ákos Gellért ◽  
Ervin Balázs
Keyword(s):  
Coat Protein ◽  
Cucumber Mosaic Virus ◽  
Mosaic Virus ◽  
Long Distance ◽  
Coat Protein Region ◽  
Long Distance Movement

scholarly journals A Cucumber Mosaic Virus (CMV) RNA 1 Transgene Mediates Suppression of the Homologous Viral RNA 1 Constitutively and Prevents CMV Entry into the Phloem

2001 ◽  
Vol 75 (19) ◽  
pp. 9114-9120 ◽  
Author(s):  
Tomas Canto ◽  
Peter Palukaitis
Keyword(s):  
Cucumber Mosaic Virus ◽  
Mosaic Virus ◽  
Tobacco Rattle Virus ◽  
Resistance Mechanism ◽  
Systemic Infection ◽  
Viral Rna ◽  
Systemic Resistance ◽  
Long Distance ◽  
Steady State Levels ◽  
Rna Accumulation

ABSTRACT Resistance to Cucumber mosaic virus (CMV) in tobacco lines transformed with CMV RNA 1 is characterized by reduced virus accumulation in the inoculated leaf, with specific suppression of accumulation of the homologous viral RNA 1, and by the absence of systemic infection. We show that the suppression of viral RNA 1 occurs in protoplasts from resistant transgenic plants and therefore is not due to a host response activated by the cell-to-cell spread of virus. In contrast, suppression of Tobacco rattle virus vectors carrying CMV RNA 1 sequences did not occur in protoplasts from resistant plants. Furthermore, steady-state levels of transgene mRNA 1 were higher in resistant than in susceptible lines. Thus, the data indicate that sequence homology is not sufficient to induce suppression. Grafting experiments using transgenic resistant or susceptible rootstocks and scions demonstrated that the resistance mechanism exhibited an additional barrier to phloem entry, preventing CMV from moving a long distance in resistant plants. On the other hand, virus from susceptible rootstocks could systemically infect grafted resistant scions via the phloem. Analysis of viral RNA accumulation in the infected scions showed that the mechanism that suppresses the accumulation of viral RNA 1 at the single-cell level was overcome. The data indicate that this transgene-mediated systemic resistance probably is not based on a posttranscriptional gene-silencing mechanism.

scholarly journals A Viral Protein Suppresses siRNA-directed Interference in Tobacco Mosaic Virus Infection

2005 ◽  
Vol 37 (4) ◽  
pp. 248-253 ◽  
Author(s):  
Ming-Min Zhao ◽  
De-Rong An ◽  
Guang-Hua Huang ◽  
Zu-Hua He ◽  
Jiang-Ye Chen
Keyword(s):  
Tobacco Mosaic Virus ◽  
Mosaic Virus ◽  
Plant Viruses ◽  
Negative Control ◽  
Transcriptional Gene Silencing ◽  
Potato Virus A ◽  
Post Transcriptional Gene Silencing ◽  
Tobacco Mosaic Virus Infection ◽  
Helper Component Proteinase ◽  
Rna Accumulation

Abstract Plant viruses encode suppressors of post-transcriptional gene silencing (PTGS), an adaptive defense response that limits virus replication and its spread in plants. The helper component proteinase (HC-Pro) of the potato virus A (PVA, genus Potyvirus) suppresses PTGS of silenced transgenes. Here, the effect of HC-Pro on siRNA-directed interference in the tobacco mosaic virus (TMV) was examined by using a transient Agrobacterium tumefaciens-based delivery system in intact tissues. It was shown that the interference effect was completely blocked by co-infiltration with HC-Pro plus siRNA constructs in both systemic and hypersensitive hosts. In the system host, all plants agro-infiltrated with HC-Pro plus siRNA constructs displayed the same symptoms as the negative control. Meanwhile, TMV RNA accumulation was found to be abundant in the upper leaves using reverse transcriptase-PCR (RT-PCR) and Northern blot assays. On the contrary, plants agro-infiltrated with the siRNA construct alone were free of symptoms. Therefore, our study suggests that the transient expression of HC-Pro inhibited the siRNA-directed host defenses against TMV infection.

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