scholarly journals The 2b protein and the C-terminus of the 2a protein of cucumber mosaic virus subgroup I strains both play a role in viral RNA accumulation and induction of symptoms

Virology ◽  
2008 ◽  
Vol 380 (2) ◽  
pp. 363-370 ◽  
Author(s):  
Zhiyou Du ◽  
Feifei Chen ◽  
Zhijing Zhao ◽  
Qiansheng Liao ◽  
Peter Palukaitis ◽  
...  
Keyword(s):  
Cucumber Mosaic Virus ◽  
Mosaic Virus ◽  
Viral Rna ◽  
C Terminus ◽  
2B Protein ◽  
Rna Accumulation

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 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 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 Symptom induction and RNA silencing suppression by the cucumber mosaic virus 2b protein

2010 ◽  
Vol 5 (6) ◽  
pp. 705-708 ◽  
Author(s):  
Mathew G. Lewsey ◽  
Inmaculada González ◽  
Natalia O. Kalinina ◽  
Peter Palukaitis ◽  
Tomas Canto ◽  
...  
Keyword(s):  
Cucumber Mosaic Virus ◽  
Mosaic Virus ◽  
Rna Silencing ◽  
2B Protein ◽  
Silencing Suppression

scholarly journals RNA Binding by the Brome Mosaic Virus Capsid Protein and the Regulation of Viral RNA Accumulation

2009 ◽  
Vol 391 (2) ◽  
pp. 314-326 ◽  
Author(s):  
Guanghui Yi ◽  
Robert C. Vaughan ◽  
Ian Yarbrough ◽  
S. Dharmaiah ◽  
C. Cheng Kao
Keyword(s):  
Mosaic Virus ◽  
Capsid Protein ◽  
Rna Binding ◽  
Brome Mosaic Virus ◽  
Viral Rna ◽  
Virus Capsid ◽  
Rna Accumulation ◽  
Virus Capsid Protein

scholarly journals A subpopulation of RNA 1 of Cucumber mosaic virus contains 3′ termini originating from RNAs 2 or 3

2001 ◽  
Vol 82 (4) ◽  
pp. 941-945 ◽  
Author(s):  
Tomas Canto ◽  
Seung Kook Choi ◽  
Peter Palukaitis
Keyword(s):  
Cucumber Mosaic Virus ◽  
Mosaic Virus ◽  
Viral Rna ◽  
Template Switching ◽  
Wild Type ◽  
Coding Region ◽  
Tobacco Plants ◽  
Viral Rnas ◽  
Virus Cdna ◽  
Cdna Fragments

Tobacco plants transgenic for RNA 1 of Cucumber mosaic virus and inoculated with transcript of RNAs 2 and 3 regenerated viral RNA 1 from the transgenic mRNA, and the plants became systemically infected by the reconstituted virus. cDNA fragments corresponding to the 3′ non-coding region (NCR) of viral RNA 1 were amplified, cloned and sequenced. In some clones the termini of the 3′ NCR corresponded to those of viral RNAs 2 or 3. This suggested that in some cases RNA 1 may have been regenerated during replication by a template switching mechanism between the inoculated transcript RNAs and the mRNA. However, encapsidated, recombinant RNA 1 with the 3′ NCR ends originating from RNAs 2 or 3 also was found in virus samples that had been passaged exclusively through non-transgenic plants. Thus, these chimeras occur naturally due to recombination between wild-type viral RNAs, and they are found encapsidated in low, but detectable amounts.

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.

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