scholarly journals Lettuce chlorosis virus P23 Suppresses RNA Silencing and Induces Local Necrosis with Increased Severity at Raised Temperatures

2016 ◽  
Vol 106 (6) ◽  
pp. 653-662 ◽  
Author(s):  
Kenji Kubota ◽  
James C. K. Ng
Keyword(s):  
Rna Silencing ◽  
Elevated Temperatures ◽  
Fluorescent Protein ◽  
Plant Viruses ◽  
Suppressor Activity ◽  
Systemic Movement ◽  
Symptom Modulation ◽  
Green Fluorescent ◽  
Rna Accumulation ◽  
Local Necrosis

RNA silencing functions as an antivirus defense strategy in plants, one that plant viruses counter by producing viral suppressors of RNA silencing (VSRs). VSRs have been identified in three members of the genus Crinivirus but they do not all share identical suppression mechanisms. Here, we used Agrobacterium co-infiltration assays to investigate the suppressor activity of proteins encoded by Lettuce chlorosis virus (LCV). Of 7 LCV proteins (1b, P23, HSP70 homolog, P60, CP, CPm, and P27) tested for the suppression of silencing of green fluorescent protein (GFP) expression in wild-type Nicotiana benthamiana plants, only P23 suppressed the onset of local silencing. Small-interfering (si)RNA accumulation was reduced in leaves co-infiltrated with P23, suggesting that P23 inhibited the accumulation or enhanced the degradation of siRNA. P23 also inhibited the cell-to-cell and systemic movement of RNA silencing in GFP-expressing transgenic N. benthamiana plants. Expression of P23 via agroinfiltration of N. benthamiana leaves induced local necrosis that increased in severity at elevated temperatures, a novelty given that a direct temperature effect on necrosis severity has not been reported for the other crinivirus VSRs. These results further affirm the sophistication of crinivirus VSRs in mediating the evasion of host’s antiviral defenses and in symptom modulation.

scholarly journals Modification of Small RNAs Associated with Suppression of RNA Silencing by Tobamovirus Replicase Protein

2007 ◽  
Vol 81 (19) ◽  
pp. 10379-10388 ◽  
Author(s):  
Hannes Vogler ◽  
Rashid Akbergenov ◽  
Padubidri V. Shivaprasad ◽  
Vy Dang ◽  
Monika Fasler ◽  
...  
Keyword(s):  
Small Rnas ◽  
Rna Silencing ◽  
Fluorescent Protein ◽  
Plant Viruses ◽  
Micro Rna ◽  
Silencing Suppressor ◽  
Small Interfering Rnas ◽  
Suppressor Activity ◽  
Virus Family ◽  
Green Fluorescent

ABSTRACT Plant viruses act as triggers and targets of RNA silencing and have evolved proteins to suppress this plant defense response during infection. Although Tobacco mosaic tobamovirus (TMV) triggers the production of virus-specific small interfering RNAs (siRNAs), this does not lead to efficient silencing of TMV nor is a TMV-green fluorescent protein (GFP) hybrid able to induce silencing of a GFP-transgene in Nicotiana benthamiana, indicating that a TMV silencing suppressor is active and acts downstream of siRNA production. On the other hand, TMV-GFP is unable to spread into cells in which GFP silencing is established, suggesting that the viral silencing suppressor cannot revert silencing that is already established. Although previous evidence indicates that the tobamovirus silencing suppressing activity resides in the viral 126-kDa small replicase subunit, the mechanism of silencing suppression by this virus family is not known. Here, we connect the silencing suppressing activity of this protein with our previous finding that Oilseed rape mosaic tobamovirus infection leads to interference with HEN1-mediated methylation of siRNA and micro-RNA (miRNA). We demonstrate that TMV infection similarly leads to interference with HEN1-mediated methylation of small RNAs and that this interference and the formation of virus-induced disease symptoms are linked to the silencing suppressor activity of the 126-kDa protein. Moreover, we show that also Turnip crinkle virus interferes with the methylation of siRNA but, in contrast to tobamoviruses, not with the methylation of miRNA.

scholarly journals Identification of the Potential Virulence Factors and RNA Silencing Suppressors of Mulberry Mosaic Dwarf-Associated Geminivirus

Viruses ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 472 ◽  
Author(s):  
Xiuling Yang ◽  
Yanxiang Ren ◽  
Shaoshuang Sun ◽  
Dongxue Wang ◽  
Fanfan Zhang ◽  
...  
Keyword(s):  
Virulence Factors ◽  
Rna Silencing ◽  
Fluorescent Protein ◽  
Potato Virus X ◽  
Defense Responses ◽  
Plant Viruses ◽  
Silencing Suppressor ◽  
Long Distance ◽  
Suppressor Activity ◽  
Rna Silencing Suppressor

Plant viruses encode virulence factors or RNA silencing suppressors to reprogram plant cellular processes or to fine-tune host RNA silencing-mediated defense responses. In a previous study, Mulberry mosaic dwarf-associated virus (MMDaV), a novel, highly divergent geminivirus, has been identified from a Chinese mulberry tree showing mosaic and dwarfing symptoms, but the functions of its encoded proteins are unknown. In this study, all seven proteins encoded by MMDaV were screened for potential virulence and RNA silencing suppressor activities. We found that V2, RepA, and Rep affect the pathogenicity of a heterologous potato virus X. We showed that V2 could inhibit local RNA silencing and long-distance movement of the RNA silencing signal, but not short-range spread of the green fluorescent protein (GFP) silencing signal in Nicotiana benthamiana 16c plants. In addition, V2 localized to both subnuclear foci and the cytoplasm. Deletion mutagenesis of V2 showed that the basic motif from amino acids 61 to 76 was crucial for V2 to form subnuclear foci and for suppression of RNA silencing. Although the V2 protein encoded by begomoviruses or a curtovirus has been shown to have silencing suppressor activity, this is the first identification of an RNA silencing suppressor from a woody plant-infecting geminivirus.

scholarly journals Functional Characterization of RNA Silencing Suppressor P0 from Pea Mild Chlorosis Virus

2020 ◽  
Vol 21 (19) ◽  
pp. 7136
Author(s):  
Qian Sun ◽  
Tao Zhuo ◽  
Tianyu Zhao ◽  
Cuiji Zhou ◽  
Yuanyuan Li ◽  
...  
Keyword(s):  
Rna Silencing ◽  
Fluorescent Protein ◽  
Functional Characterization ◽  
Plant Viruses ◽  
C Terminus ◽  
Systemic Rna ◽  
Green Fluorescent ◽  
Leafroll Virus ◽  
F Box Protein ◽  
Viral Suppressors

To counteract host antiviral RNA silencing, plant viruses encode numerous viral suppressors of RNA silencing (VSRs). P0 proteins have been identified as VSRs in many poleroviruses. However, their suppressor function has not been fully characterized. Here, we investigated the function of P0 from pea mild chlorosis virus (PMCV) in the suppression of local and systemic RNA silencing via green fluorescent protein (GFP) co-infiltration assays in wild-type and GFP-transgenic Nicotiana benthamiana (line 16c). Amino acid deletion analysis showed that N-terminal residues Asn 2 and Val 3, but not the C-terminus residues from 230–270 aa, were necessary for PMCV P0 (P0PM) VSR activity. P0PM acted as an F-box protein, and triple LPP mutation (62LPxx79P) at the F-box-like motif abolished its VSR activity. In addition, P0PM failed to interact with S-phase kinase-associated protein 1 (SKP1), which was consistent with previous findings of P0 from potato leafroll virus. These data further support the notion that VSR activity of P0 is independent of P0–SKP1 interaction. Furthermore, we examined the effect of P0PM on ARGONAUTE1 (AGO1) protein stability, and co-expression analysis showed that P0PM triggered AGO1 degradation. Taken together, our findings suggest that P0PM promotes degradation of AGO1 to suppress RNA silencing independent of SKP1 interaction.

scholarly journals A Versatile Assay for the Identification of RNA Silencing Suppressors Based on Complementation of Viral Movement

2008 ◽  
Vol 21 (7) ◽  
pp. 879-890 ◽  
Author(s):  
Jason G. Powers ◽  
Tim L. Sit ◽  
Feng Qu ◽  
T. Jack Morris ◽  
Kook-Hyung Kim ◽  
...  
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Rna Silencing ◽  
Fluorescent Protein ◽  
Wide Spectrum ◽  
Cell Movement ◽  
Suppressor Activity ◽  
Reading Frame ◽  
Movement Proteins ◽  
In Trans ◽  
Green Fluorescent

The cell-to-cell movement of Turnip crinkle virus (TCV) in Nicotiana benthamiana requires the presence of its coat protein (CP), a known suppressor of RNA silencing. RNA transcripts of a TCV construct containing a reporter gene (green fluorescent protein) (TCV-sGFP) in place of the CP open reading frame generated foci of three to five cells. TCV CP delivered in trans by Agrobacterium tumefaciens infiltration potentiated movement of TCV-sGFP and increased foci diameter, on average, by a factor of four. Deletion of the TCV movement proteins in TCV-sGFP (construct TCVΔ92-sGFP) abolished the movement complementation ability of TCV CP. Other known suppressors of RNA silencing from a wide spectrum of viruses also complemented the movement of TCV-sGFP when delivered in trans by Agrobacterium tumefaciens. These include suppressors from nonplant viruses with no known plant movement function, demonstrating that this assay is based solely on RNA silencing suppression. While the TCV-sGFP construct is primarily used as an infectious RNA transcript, it was also subcloned for direct expression from Agrobacterium tumefaciens for simple quantification of suppressor activity based on fluorescence levels in whole leaves. Thus, this system provides the flexibility to assay for suppressor activity in either the cytoplasm or nucleus, depending on the construct employed.

scholarly journals RNA Silencing Suppression by a Second Copy of the P1 Serine Protease of Cucumber Vein Yellowing Ipomovirus, a Member of the Family Potyviridae That Lacks the Cysteine Protease HCPro

2006 ◽  
Vol 80 (20) ◽  
pp. 10055-10063 ◽  
Author(s):  
Adrian Valli ◽  
Ana Montserrat Martín-Hernández ◽  
Juan José López-Moya ◽  
Juan Antonio García
Keyword(s):  
Rna Silencing ◽  
Fluorescent Protein ◽  
Serine Proteinase ◽  
Plum Pox Virus ◽  
Coding Region ◽  
Long Distance ◽  
Systemic Spread ◽  
The Family ◽  
Silencing Suppression ◽  
Green Fluorescent

ABSTRACT The P1 protein of viruses of the family Potyviridae is a serine proteinase, which is highly variable in length and sequence, and its role in the virus infection cycle is not clear. One of the proposed activities of P1 is to assist HCPro, the product that viruses of the genus Potyvirus use to counteract antiviral defense mediated by RNA silencing. Indeed, an HCPro-coding region is present in all the genomes of members of the genera Potyvirus, Rymovirus, and Tritimovirus that have been sequenced. However, it was recently reported that a sequence coding for HCPro is lacking in the genome of Cucumber vein yellowing virus (CVYV), a member of the genus Ipomovirus, the fourth monopartite genus of the family. In this study, we provide further evidence that P1 enhances the activity of HCPro in members of the genus Potyvirus and show that it is duplicated in the ipomovirus CVYV. The two CVYV P1 copies are arranged in tandem, and the second copy (P1b) has RNA silencing suppression activity. CVYV P1b suppressed RNA silencing induced either by sense green fluorescent protein (GFP) mRNA or by a GFP inverted repeat RNA, indicating that CVYV P1b acts downstream of the formation of double-stranded RNA. CVYV P1b also suppressed local silencing in agroinfiltrated patches of transgenic Nicotiana benthamiana line 16c and delayed its propagation to the neighboring cells. However, neither the short-distance nor long-distance systemic spread of silencing of the GFP transgene was completely blocked by CVYV P1b. CVYV P1b and P1-HCPro from the potyvirus Plum pox virus showed very similar behaviors in all the assays carried out, suggesting that evolution has found a way to counteract RNA silencing by similar mechanisms using very different proteins in viruses of the same family.

scholarly journals Negative-Strand Tospoviruses and Tenuiviruses Carry a Gene for a Suppressor of Gene Silencing at Analogous Genomic Positions

2003 ◽  
Vol 77 (2) ◽  
pp. 1329-1336 ◽  
Author(s):  
Etienne Bucher ◽  
Titia Sijen ◽  
Peter de Haan ◽  
Rob Goldbach ◽  
Marcel Prins
Keyword(s):  
Rna Silencing ◽  
Tomato Spotted Wilt Virus ◽  
Fluorescent Protein ◽  
Negative Strand ◽  
Tomato Spotted Wilt ◽  
Ns3 Protein ◽  
Genes Encoding ◽  
Green Fluorescent ◽  
Wilt Virus ◽  
Suppressor Of Rna Silencing

ABSTRACT Posttranscriptional silencing of a green fluorescent protein (GFP) transgene in Nicotiana benthamiana plants was suppressed when these plants were infected with Tomato spotted wilt virus (TSWV), a plant-infecting member of the Bunyaviridae. Infection with TSWV resulted in complete reactivation of GFP expression, similar to the case for Potato virus Y, but distinct from that for Cucumber mosaic virus, two viruses known to carry genes encoding silencing suppressor proteins. Agrobacterium-based leaf injections with individual TSWV genes identified the NSS gene to be responsible for the RNA silencing-suppressing activity displayed by this virus. The absence of short interfering RNAs in NSS-expressing leaf sectors suggests that the tospoviral NSS protein interferes with the intrinsic RNA silencing present in plants. Suppression of RNA silencing was also observed when the NS3 protein of the Rice hoja blanca tenuivirus, a nonenveloped negative-strand virus, was expressed. These results indicate that plant-infecting negative-strand RNA viruses carry a gene for a suppressor of RNA silencing.

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

2006 ◽  
Vol 5 (6) ◽  
pp. 896-904 ◽  
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.

scholarly journals The Use of Green Fluorescent Protein-Tagged Recombinant Viruses to Test Lettuce mosaic virus Resistance in Lettuce

2002 ◽  
Vol 92 (2) ◽  
pp. 169-176 ◽  
Author(s):  
T. Candresse ◽  
O. Le Gall ◽  
B. Maisonneuve ◽  
S. German-Retana ◽  
E. Redondo
Keyword(s):  
Green Fluorescent Protein ◽  
Mosaic Virus ◽  
Fluorescent Protein ◽  
Lettuce Mosaic Virus ◽  
Recombinant Viruses ◽  
Systemic Movement ◽  
Resistance Breaking ◽  
Recessive Genes ◽  
Lettuce Breeding ◽  
Green Fluorescent

Seed certification and the use of cultivars containing one of two, probably allelic, recessive genes, mo11 and mo12, are the principal control methods for Lettuce mosaic virus (LMV) in lettuce. Although for a few LMV isolates, mo12 confers resistance with most isolates, the genes mo11 or mo12 confer a tolerance, and virus accumulation is readily detected in mo1-carrying plants. This phenotype complicates evaluation of the resistance status, in particular for mo11, for which there are no viral strains against which a true resistance is expressed. Two green fluorescent protein (GFP)-tagged viruses were constructed, derived from a non-resistance breaking isolate (LMV-0) and from a resistance-breaking isolate (LMV-E). An evaluation of 101 cultivars of known status was carried out with these recombinant viruses. Using the LMV-0-derived recombinant, identification of mo1-carrying cultivars was simple because, contrary to its wild-type parent, systemic movement of LMV-0-GFP was abolished in resistant plants. This assay detected four cases of misidentification of resistance status. In all these cases, further tests confirmed that the prior resistance status information was incorrect, so that a 100% correlation was observed between LMV-0-GFP behavior and the mo1 resistance status. Similarly, the LMV-E-derived recombinant allowed the identification of mo12 lettuce lines because its systemic movement was restricted in mo12 lines but not in susceptible or in mo11 lines. The tagged viruses were able to systemically invade another host, pea, irrespective of its resistance status against another member of the genus Potyvirus, Pea seed-borne mosaic virus. The use of these recombinant viruses could therefore greatly facilitate LMV resistance evaluation and speed up lettuce breeding programs.

scholarly journals Phenotypes and Functional Effects Caused by Various Viral RNA Silencing Suppressors in Transgenic Nicotiana benthamiana and N. tabacum

2008 ◽  
Vol 21 (2) ◽  
pp. 178-187 ◽  
Author(s):  
Shahid Aslam Siddiqui ◽  
Cecilia Sarmiento ◽  
Erkki Truve ◽  
Harry Lehto ◽  
Kirsi Lehto
Keyword(s):  
Mosaic Virus ◽  
Potato Virus ◽  
Nicotiana Benthamiana ◽  
Rna Silencing ◽  
Fluorescent Protein ◽  
Potato Virus X ◽  
Mottle Virus ◽  
African Cassava Mosaic Virus ◽  
Rice Yellow Mottle Virus ◽  
Green Fluorescent

RNA silencing suppressor genes derived from six virus genera were transformed into Nicotiana benthamiana and N. tabacum plants. These suppressors were P1 of Rice yellow mottle virus (RYMV), P1 of Cocksfoot mottle virus, P19 of Tomato bushy stunt virus, P25 of Potato virus X, HcPro of Potato virus Y (strain N), 2b of Cucumber mosaic virus (strain Kin), and AC2 of African cassava mosaic virus (ACMV). HcPro caused the most severe phenotypes in both Nicotiana spp. AC2 also produced severe effects in N. tabacum but a much milder phenotype in N. benthamiana, although both HcPro and AC2 affected the leaf tissues of the two Nicotiana spp. in similar ways, causing hyperplasia and hypoplasia, respectively. P1-RYMV caused high lethality in the N. benthamiana plants but only mild effects in the N. tabacum plants. Phenotypic alterations produced by the other transgenes were minor in both species. Interestingly, the suppressors had very different effects on crucifer-infecting Tobamovirus (crTMV) infections. AC2 enhanced both spread and brightness of the crTMV-green fluorescent protein (GFP) lesions, whereas 2b and both P1 suppressors enhanced spread but not brightness of these lesions. P19 promoted spread of the infection into new foci within the infiltrated leaf, whereas HcPro and P25 suppressed the spread of crTMV-GFP lesions.

scholarly journals Peanut Clump Virus RNA-1-Encoded P15 Regulates Viral RNA Accumulation but Is Not Abundant at Viral RNA Replication Sites

2001 ◽  
Vol 75 (4) ◽  
pp. 1941-1948 ◽  
Author(s):  
Patrice Dunoyer ◽  
Etienne Herzog ◽  
Odile Hemmer ◽  
Christophe Ritzenthaler ◽  
Christiane Fritsch
Keyword(s):  
Laser Scanning ◽  
Fluorescent Protein ◽  
Laser Scanning Confocal Microscopy ◽  
Viral Rna ◽  
Epifluorescence Microscopy ◽  
Scanning Confocal Microscopy ◽  
Virus Rna ◽  
Green Fluorescent ◽  
Rna Accumulation

ABSTRACT RNA-1 of peanut clump pecluvirus (PCV) encodes N-terminally overlapping proteins which contain helicase-like (P131) and polymerase-like (P191) domains and is able to replicate in the absence of RNA-2 in protoplasts of tobacco BY-2 cells. RNA-1 also encodes P15, which is expressed via a subgenomic RNA. To investigate the role of P15, we analyzed RNA accumulation in tobacco BY-2 protoplasts inoculated with RNA-1 containing mutations in P15. For all the mutants, the amount of progeny RNA-1 produced was significantly lower than that obtained for wild-type RNA-1. If RNA-2 was included in the inoculum, the accumulation of both progeny RNAs was diminished, but near-normal yields of both could be recovered if the inoculum was supplemented with a small, chimeric viral replicon expressing P15, demonstrating that P15 has an effect on viral RNA accumulation. To further analyze the role of P15, transcripts were produced expressing P15 fused to enhanced green fluorescent protein (EGFP). Following inoculation to protoplasts, epifluorescence microscopy revealed that P15 accumulated as spots around the nucleus and in the cytoplasm. Intracellular sites of viral RNA synthesis were visualized by laser scanning confocal microscopy of infected protoplasts labeled with 5-bromouridine 5′-triphosphate (BrUTP). BrUTP labeling also occured in spots distributed within the cytoplasm and around the nucleus. However, the BrUTP-labeled RNA and EGFP/P15 very rarely colocalized, suggesting that P15 does not act primarily at sites of viral replication but intervenes indirectly to control viral accumulation levels.

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