Elevated Carbon Dioxide Levels Decreases Cucumber Mosaic Virus Accumulation in Correlation with Greater Accumulation of rgs-CaM, an Inhibitor of a Viral Suppressor of RNAi

Plant viruses cause a range of plant diseases symptoms that are often responsible for significant crop production losses and the severity and spread of the symptoms may be affected by climate change. While the increase in anthropogenic activities has caused a critical problem of increased CO2 levels in the atmosphere, these elevated CO2 levels have been reported to reduce virus disease severity in some plant species. In such instances, it is not clear if the plant defense mechanisms are being enhanced or virus-mediated mechanisms to overcome plant resistance are being defeated. Additionally, a few studies have been attempted in this area to determine if reduced disease is the norm or the exception under enhanced CO2 levels. In the present study, the effects of elevated CO2 levels (750 ppm vs. 390 ppm) on RNAi-mediated resistance of Nicotiana tabacum against the cucumber mosaic virus (CMV), and the activity of viral suppressor of RNAi (VSR) 2b protein of CMV were evaluated. On the one hand, our results showed that elevated CO2 decreased the transcription of dicer-like protein 2 (DCL2), DCL4, and argonaut 1 (AGO1) genes with functions related to RNAi-mediated resistance when infected by CMV, which is contradictory with the decreased CMV copy numbers under elevated CO2. On the other hand, we found that elevated CO2 increased the calcium concentration and expression of the calcium-binding protein rgs-CaM in tobacco plants when infected by CMV, which directly weakened the function of 2b protein, the VSR of CMV, and therefore decreased the infection efficiency of the virus and suppressed the severity of CMV in tobacco plants under elevated CO2. This study provides molecular insights into the ecological implications underlying the development of prevention strategies against plant virus infection in the context of climate change.

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The 2b Silencing Suppressor of a Mild Strain of Cucumber mosaic virus Alone Is Sufficient for Synergistic Interaction with Tobacco mosaic virus and Induction of Severe Leaf Malformation in 2b-Transgenic Tobacco Plants

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-12-10-0290 ◽

2011 ◽

Vol 24 (6) ◽

pp. 685-693 ◽

Cited By ~ 9

Author(s):

Shahid A. Siddiqui ◽

Jari P. T. Valkonen ◽

Minna-Liisa Rajamäki ◽

Kirsi Lehto

Keyword(s):

Tobacco Mosaic Virus ◽

Cucumber Mosaic Virus ◽

Mosaic Virus ◽

Transgenic Tobacco ◽

Transgenic Tobacco Plants ◽

Mild Strain ◽

Tobacco Plants ◽

2B Protein ◽

Synergistic Relationship ◽

Severe Leaf

Tobacco plants infected simultaneously by Tobacco mosaic virus (TMV) and Cucumber mosaic virus (CMV) are known to produce a specific synergistic disease in which the emerging leaves are filiformic. Similar developmental malformations are also caused to a lesser extent by the severe strains (e.g., Fny) of CMV alone, but mild strains (e.g., Kin) cause them only in mixed infection with TMV. We show here that transgenic tobacco plants expressing 2b protein of CMV-Kin produce filiformic symptoms when infected with TMV, indicating that only 2b protein is needed from CMV-Kin for this synergistic relationship. On the other hand, transgenic plants that express either the wild-type TMV genome or a modified TMV genome with its coat protein deleted or movement protein (MP) inactivated also develop filiformic or at least distinctly narrow leaves, while plants expressing the MP alone do not develop any malformations when infected with CMV-Kin. These results show that either TMV helicase/replicase protein or active TMV replication are required for this synergistic effect. The effect appears to be related to an efficient depletion of silencing machinery, caused jointly by both viral silencing suppressors, i.e., CMV 2b protein and the TMV 126-kDa replicase subunit.

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The 2b protein of cucumber mosaic virus is essential for viral infection of the shoot apical meristem and for efficient invasion of leaf primordia in infected tobacco plants

Journal of General Virology ◽

10.1099/vir.0.013219-0 ◽

2009 ◽

Vol 90 (12) ◽

pp. 3015-3021 ◽

Cited By ~ 23

Author(s):

Anurag Sunpapao ◽

Takashi Nakai ◽

Fang Dong ◽

Tomofumi Mochizuki ◽

Satoshi T. Ohki

Keyword(s):

Cucumber Mosaic Virus ◽

Mosaic Virus ◽

Shoot Apical Meristem ◽

Rna Silencing ◽

Apical Meristem ◽

Leaf Primordia ◽

Shoot Meristem ◽

Tobacco Plants ◽

2B Protein ◽

Infected Tobacco

It has been reported previously that a 2b protein-defective mutant of the cucumber mosaic virus (CMV) Pepo strain (Δ2b) induces only mild symptoms in systemically infected tobacco plants. To clarify further the role of the 2b protein as an RNA silencing suppressor in mosaic symptom expression during CMV infection, this study monitored the sequential distribution of Δ2b in the shoot meristem and leaf primordia (LP) of inoculated tobacco. Time-course histochemical observations revealed that Δ2b was distributed in the shoot meristem at 7 days post-inoculation (p.i.), but could not invade shoot apical meristem (SAM) and quickly disappeared from the shoot meristem, whereas wild-type (Pepo) transiently appeared in SAM from 4 to 10 days p.i. In LP, Δ2b signals were detected only at 14 and 21 days p.i., whereas dense Pepo signals were observed in LP from 4 to 18 days p.i. Northern blot analysis showed that small interfering RNA (siRNA) derived from Δ2b RNA accumulated earlier in the shoot meristem and LP than that of Pepo. However, a similar amount of siRNA was detected in both Pepo- and Δ2b-infected plants at late time points. Tissue printing analysis of the inoculated leaves indicated that the areas infected by Pepo increased faster than those infected by Δ2b, whereas accumulation of Δ2b in protoplasts was similar to that of Pepo. These findings suggest that the 2b protein of the CMV Pepo strain determines virulence by facilitating the distribution of CMV in the shoot meristem and LP via prevention of RNA silencing and/or acceleration of cell-to-cell movement.

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Topical Application of Double-Stranded RNA Targeting 2b and CP Genes of Cucumber mosaic virus Protects Plants against Local and Systemic Viral Infection

Plants ◽

10.3390/plants10050963 ◽

2021 ◽

Vol 10 (5) ◽

pp. 963

Author(s):

Maria C. Holeva ◽

Athanasios Sklavounos ◽

Rajendran Rajeswaran ◽

Mikhail M. Pooggin ◽

Andreas E. Voloudakis

Keyword(s):

Cucumber Mosaic Virus ◽

Mosaic Virus ◽

Topical Application ◽

Plant Virus ◽

Plant Protection ◽

Post Inoculation ◽

Tobacco Plants ◽

Double Stranded Rna

Cucumber mosaic virus (CMV) is a destructive plant virus with worldwide distribution and the broadest host range of any known plant virus, as well as a model plant virus for understanding plant–virus interactions. Since the discovery of RNA interference (RNAi) as a major antiviral defense, RNAi-based technologies have been developed for plant protection against viral diseases. In plants and animals, a key trigger of RNAi is double-stranded RNA (dsRNA) processed by Dicer and Dicer-like (DCL) family proteins in small interfering RNAs (siRNAs). In the present study, dsRNAs for coat protein (CP) and 2b genes of CMV were produced in vitro and in vivo and applied onto tobacco plants representing a systemic solanaceous host as well as on a local host plant Chenopodium quinoa. Both dsRNA treatments protected plants from local and systemic infection with CMV, but not against infection with unrelated viruses, confirming sequence specificity of antiviral RNAi. Antiviral RNAi was effective when dsRNAs were applied simultaneously with or four days prior to CMV inoculation, but not four days post inoculation. In vivo-produced dsRNAs were more effective than the in vitro-produced; in treatments with in vivo dsRNAs, dsRNA-CP was more effective than dsRNA-2b, while the effects were opposite with in vitro dsRNAs. Illumina sequencing of small RNAs from in vivo dsRNA-CP treated and non-treated tobacco plants revealed that interference with CMV infection in systemic leaves coincides with strongly reduced accumulation of virus-derived 21- and 22-nucleotide (nt) siRNAs, likely generated by tobacco DCL4 and DCL2, respectively. While the 21-nt class of viral siRNAs was predominant in non-treated plants, 21-nt and 22-nt classes accumulated at almost equal (but low) levels in dsRNA treated plants, suggesting that dsRNA treatment may boost DCL2 activity. Taken together, our findings confirm the efficacy of topical application of dsRNA for plant protection against viruses and shed more light on the mechanism of antiviral RNAi.

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Comparative studies on RNA-dependent RNA polymerases in cucumber mosaic virus infected cucumber and tobacco, and uninfected tobacco plants

Biochemistry ◽

10.1021/bi00256a020 ◽

1982 ◽

Vol 21 (13) ◽

pp. 3161-3167 ◽

Cited By ~ 12

Author(s):

Yoichi Takanami ◽

Heinz Fraenkel-Conrat

Keyword(s):

Cucumber Mosaic Virus ◽

Mosaic Virus ◽

Comparative Studies ◽

Rna Polymerases ◽

Tobacco Plants

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Dalmatian Toadflax (Linaria dalmatica): New Host for Cucumber Mosaic Virus

Weed Technology ◽

10.1614/wt-06-005.1 ◽

2007 ◽

Vol 21 (1) ◽

pp. 41-44 ◽

Cited By ~ 1

Author(s):

Courtney L. Pariera Dinkins ◽

Sue K. Brumfield ◽

Robert K. D. Peterson ◽

William E. Grey ◽

Sharlene E. Sing

Keyword(s):

Cucumber Mosaic Virus ◽

Mosaic Virus ◽

Aphid Transmission ◽

Negative Control ◽

Enzyme Linked Immunosorbent Assay ◽

New Host ◽

Tobacco Plants ◽

Linaria Dalmatica ◽

Mechanical Methods ◽

Dalmatian Toadflax

To date, there have been no reports of Dalmatian toadflax serving as a host for cucumber mosaic virus (CMV). Infestations of Dalmatian toadflax may serve as a reservoir of CMV, thereby facilitating aphid transmission of CMV to both agricultural crops and native plants. The goal of this study was to determine whether Dalmatian toadflax is a host for CMV. Dalmatian toadflax seedlings were randomly assigned to two treatments (18 replicates/treatment): no inoculation (control) and inoculation with CMV (Fast New York strain). The Dalmatian toadflax seedlings were inoculated by standard mechanical methods and tested for the presence of CMV using enzyme-linked immunosorbent assay (ELISA). Ten of the 18 CMV-inoculated toadflax plants tested positive for the virus; 6 of the 18 displayed systemic mosaic chlorosis and leaf curling. All control plants tested negative. Transmission electron microscopy obtained from CMV-positive plants confirmed the presence of CMV based on physical properties. To verify CMV infestation, tobacco plants were assigned to the following treatments (six replicates/treatment): no inoculation (control), CMV-negative (control) inoculation, and a CMV-positive inoculation. Plants were inoculated by standard methods. Five of the 6 tobacco plants treated with the CMV-positive inoculum tested positive for CMV using ELISA. All control plants tested negative for the virus.

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