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

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.

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

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.2002.15.9.947 ◽

2002 ◽

Vol 15 (9) ◽

pp. 947-955 ◽

Cited By ~ 55

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.

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

Frontiers in Microbiology ◽

10.3389/fmicb.2021.760937 ◽

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

Journal of Virology ◽

10.1128/jvi.75.19.9114-9120.2001 ◽

2001 ◽

Vol 75 (19) ◽

pp. 9114-9120 ◽

Cited By ~ 27

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.

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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 ◽

10.1016/j.virol.2008.07.036 ◽

2008 ◽

Vol 380 (2) ◽

pp. 363-370 ◽

Cited By ~ 31

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

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The 3' untranslated region of cucumber mosaic virus (CMV) subgroup II RNA3 arose by interspecific recombination between CMV and tomato aspermy virus

Journal of General Virology ◽

10.1099/vir.0.011452-0 ◽

2009 ◽

Vol 90 (9) ◽

pp. 2293-2298 ◽

Cited By ~ 8

Author(s):

J. R. Thompson ◽

M. Tepfer

Keyword(s):

Cucumber Mosaic Virus ◽

Mosaic Virus ◽

Untranslated Region ◽

Tomato Aspermy Virus ◽

Subgroup Ii ◽

Interspecific Recombination

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Development of Cucumber mosaic virus as a vector modifiable for different host species to produce therapeutic proteins

Planta ◽

10.1007/s00425-006-0346-5 ◽

2006 ◽

Vol 225 (2) ◽

pp. 277-286 ◽

Cited By ~ 31

Author(s):

Kouki Matsuo ◽

Jin- Sung Hong ◽

Noriko Tabayashi ◽

Akira Ito ◽

Chikara Masuta ◽

...

Keyword(s):

Cucumber Mosaic Virus ◽

Mosaic Virus ◽

Host Species ◽

Therapeutic Proteins

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First Report of Cucumber mosaic virus in Desert Rose in Taiwan

Plant Disease ◽

10.1094/pdis-11-11-0917 ◽

2012 ◽

Vol 96 (4) ◽

pp. 593-593 ◽

Cited By ~ 1

Author(s):

Y. K. Chen ◽

Y. S. Chang ◽

Y. W. Lin ◽

M. Y. Wu

Keyword(s):

Cucumber Mosaic Virus ◽

Mosaic Virus ◽

Chenopodium Quinoa ◽

Rabbit Antiserum ◽

Serological Tests ◽

Reading Frame ◽

First Report ◽

Reverse Transcription Pcr ◽

Wilt Virus ◽

Line Patterns

Desert rose (Adenium obesum (Forssk.) Roem. & Schult, family Apocynaceae) is native to southeastern Africa, and is a perennial potted ornamental with colorful flowers that are popular in Taiwan. Symptoms of mosaic and chlorotic ringspots and line patterns on leaves were observed in July 2010, on all eight plants in a private garden in Potzu, Chiayi, Taiwan. Spherical virus particles with a diameter of approximately 28 nm were observed in crude sap prepared from symptomatic leaves. Virus culture was established by successive local lesion isolation in Chenopodium quinoa and was maintained in the systemic host Nicotiana tabacum van Hicks. The virus was mechanically transmissible to indicator plants and induced symptoms similar to those incited by Cucumber mosaic virus (CMV). Observed symptoms included local lesions on inoculated leaves of C. amaranticolor and systemic mosaic in Cucumis sativus, Lycopersicon esculentum, N. benthamiana, N. glutinosa, and N. rustica. On N. tabacum, necrotic ringspots developed on inoculated leaves followed by systemic mosaic. Serological tests using ELISA assays and western blotting indicated that the virus reacted positively to a rabbit antiserum prepared to CMV (4). Amplicons of an expected size (1.1 kb) were obtained in reverse transcription-PCR with primers specific to the 3′-half of CMV RNA 3 (3) using total RNA extracted from infected desert rose and N. tabacum. The amplified cDNA fragment was cloned and sequenced (GenBank Accession No. AB667971). Nucleotide sequences of the coat protein open reading frame (CP ORF) (657 nt) had 92 to 96% and 76 to 77% sequence identity to those of CMV in subgroups I (GenBank Accession Nos. NC_001440, D00385, M57602, D28780, and AB008777) and II (GenBank Accession Nos. L15336, AF127976, AF198103, and M21464), respectively. Desert roses infected by Tomato spotted wilt virus (TSWV) (1) and CMV (2) have been reported previously. In spite of the plants showing mosaic symptoms similar to that caused by CMV (2) and chlorotic ringspots and line patterns caused by TSWV (1), only CMV was detected in and isolated from these infected desert roses. However, the possibility of mixed infection of CMV and other viruses were not excluded in this research. To our knowledge, this is the first report of CMV infection in desert rose plants occurring in Taiwan. References: (1) S. Adkins and C. A. Baker. Plant Dis. 89:526, 2005. (2) C. A. Baker et al. Plant Dis. 87:1007, 2003. (3) Y. K. Chen et al. Arch. Virol. 146:1631, 2001. (4) Y. K. Chen and C. C. Yang. Plant Dis. 89:529, 2005.

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First report of a cucumber mosaic virus (CMV) subgroup II isolate infecting pea in Pakistan

Journal of Plant Pathology ◽

10.1007/s42161-018-0105-z ◽

2018 ◽

Vol 100 (3) ◽

pp. 597-597

Author(s):

Muhammad Ahsan ◽

Muhammad Ashfaq

Keyword(s):

Cucumber Mosaic Virus ◽

Mosaic Virus ◽

First Report ◽

Subgroup Ii

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First Report of Cucumber mosaic virus Subgroup II Infecting Lycopersicon esculentum in India

Plant Disease ◽

10.1094/pd-90-1457b ◽

2006 ◽

Vol 90 (11) ◽

pp. 1457-1457 ◽

Cited By ~ 15

Author(s):

N. Sudhakar ◽

D. Nagendra-Prasad ◽

N. Mohan ◽

K. Murugesan

Keyword(s):

Coat Protein ◽

Cucumber Mosaic Virus ◽

Mosaic Virus ◽

Tamil Nadu ◽

Indian Subcontinent ◽

Enzyme Linked Immunosorbent Assay ◽

Infected Leaf ◽

Polymorphism Analysis ◽

First Report ◽

Subgroup Ii

During a survey in January 2006 near Salem in Tamil Nadu (south India), Cucumber mosaic virus was observed infecting tomatoes with an incidence of more than 70%. Plants exhibiting severe mosaic, leaf puckering, and stunted growth were collected, and the virus was identified using diagnostic hosts, evaluation of physical properties of the virus, compound enzyme-linked immunosorbent assay (ELISA) (ELISA Lab, Washington State University, Prosser), reverse-transcription polymerase chain reaction (RT-PCR), and restriction fragment length polymorphism analysis (DSMZ, S. Winter, Germany). To determine the specific CMV subgroup, total RNA was extracted from 50 infected leaf samples using the RNeasy plant RNA isolation kit (Qiagen, Hilden, Germany) and tested for the presence of the complete CMV coat protein gene using specific primers as described by Rizos et al. (1). A fragment of the coat protein was amplified and subsequently digested with MspI to reveal a pattern of two fragments (336 and 538 bp), indicating CMV subgroup II. No evidence of mixed infection with CMV subgroup I was obtained when CMV isolates representing subgroups I (PV-0419) and II (PV-0420), available at the DSMZ Plant Virus Collection, were used as controls. Only CMV subgroup I has been found to predominantly infect tomato in the Indian subcontinent, although Verma et al. (2) identified CMV subgroup II infecting Pelargonium spp., an ornamental plant. To our knowledge, this is the first report of CMV subgroup II infecting tomato crops in India. References: (1) H. Rizos et al. J. Gen. Virol. 73:2099, 1992. (2) N. Verma et al. J. Biol. Sci. 31:47, 2006.

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