The Experts below are selected from a list of 3249 Experts worldwide ranked by ideXlab platform
Jozsef Burgyan - One of the best experts on this subject based on the ideXlab platform.
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defective interfering rna hinders the activity of a tombusvirus encoded Posttranscriptional Gene Silencing suppressor
Journal of Virology, 2005Co-Authors: Zoltan Havelda, Csaba Hornyik, Anna Valoczi, Jozsef BurgyanAbstract:Defective interfering (DI) RNAs are subviral replicons originating from the viral genome and are associated with many plant RNA viruses and nearly all animal RNA viruses. The presence of DI RNAs in tombusvirus-infected plants reduces the accumulation of helper virus RNA and results in the development of attenuated symptoms similar to those caused by tombusviruses defective in p19, the Posttranscriptional Gene Silencing (PTGS) suppressor. In situ analysis of infected plants containing DI RNAs revealed that the extent of virus infection was spatially restricted as was found for p19-defective tombusvirus. Previously, p19 was shown to suppress PTGS by sequestering the small interfering RNAs (siRNAs), which act as the specificity determinant for PTGS. Our results demonstrate that DI RNAs dramatically elevate the level of virus-specific siRNAs in viral infections, resulting in the saturation of p19 and the accumulation of unbound siRNAs. Moreover, we showed that, at low temperature, where PTGS is inhibited, DI RNAs are not able to efficiently interfere with virus accumulation and protect the plants. These data show that the activation of PTGS plays a pivotal role in DI RNA-mediated interference. Our data also support a role for 21-nucleotide siRNAs in PTGS signaling.
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in situ characterization of cymbidium ringspot tombusvirus infection induced Posttranscriptional Gene Silencing in nicotiana benthamiana
Journal of Virology, 2003Co-Authors: Zoltan Havelda, Csaba Hornyik, Aniello Crescenzi, Jozsef BurgyanAbstract:In plants, Posttranscriptional Gene Silencing (PTGS) is an ancient and effective defense mechanism against viral infection. A number of viruses encode proteins that suppress virus-activated PTGS. The p19 protein of tombusviruses is a potent PTGS suppressor which interferes with the onset of PTGS-Generated systemic signaling and is not required for viral replication or for viral movement in Nicotiana benthamiana. This unique feature of p19 suppressor allowed us to analyze the mechanism of PTGS-based host defense and its viral suppression without interfering with other viral functions. In contrast to the necrotic symptoms caused by wild-type tombusvirus, the infection of p19-defective mutant virus results in the development of a typical PTGS-associated recovery phenotype in N. benthamiana. In this report we show the effect of PTGS on the viral infection process for N. benthamiana infected with either wild-type Cymbidium Ringspot Tombusvirus (CymRSV) or a p19-defective mutant (Cym19stop). In situ analyses of different virus-derived products revealed that PTGS is not able to reduce accumulation of virus in primary infected cells regardless of the presence of p19 PTGS suppressor. We also showed that both CymRSV and Cym19stop viruses move systemically in the vasculature, with similar efficiencies. However, in contrast to the uniform accumulation of CymRSV throughout systemically infected leaves, the presence of Cym19stop virus was confined to and around the vascular bundles. These results suggest that the role of p19 is to prevent the onset of mobile signal-induced systemic PTGS ahead of the viral infection front, leading to Generalized infection.
Yiguo Hong - One of the best experts on this subject based on the ideXlab platform.
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functional characterization of the nuclear localization signal for a suppressor of Posttranscriptional Gene Silencing
Journal of Virology, 2003Co-Authors: Xiangli Dong, Rene Van Wezel, John Stanley, Yiguo HongAbstract:The nucleus-localized C2 protein of Tomato yellow leaf curl virus-China (TYLCV-C) is an active suppressor of Posttranscriptional Gene Silencing (PTGS). Consistently, infection with TYLCV-C resulted in PTGS arrest in plants. The C2 protein possesses a functional, arginine-rich nuclear localization signal within the basic amino acid-rich region 17KVQHRIAKKTTRRRR31. When expressed from potato virus X, C2-RRRR31DVGG (in which the four consecutive arginine residues 28RRRR31 were replaced with DVGG) that had been tagged with a green fluorescent protein (GFP) failed to transport GFP into nuclei and was dysfunctional in inducing necrosis and suppressing PTGS in plants. Amino acid substitution mutants C2-K17D-GFP, C2-HR21DV-GFP, and C2-KK25DI-GFP localized to nuclei and produced necrosis, but only C2-K17D-GFP suppressed PTGS. The N-terminal portions C21-31 and C217-31 fused in frame to GFP were capable of targeting GFP to nuclei, but neither caused necrosis nor affected PTGS. Our data establish that nuclear localization is likely required for C2 protein to function in C2-mediated induction of necrosis and suppression of PTGS, which may follow diverse pathways in plants. Possible mechanisms of how the C2 protein involves these biological functions are discussed.
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contribution of the zinc finger to zinc and dna binding by a suppressor of Posttranscriptional Gene Silencing
Journal of Virology, 2003Co-Authors: Rene Van Wezel, Zirong Wu, John Stanley, Yiguo HongAbstract:The zinc finger C36-X1-C38-X7-C46-X6-H53 of the nuclearly localized C2 protein of Tomato yellow leaf curl virus China is involved in pathogenicity and suppression of Posttranscriptional Gene Silencing (PTGS). Here, we demonstrate that the zinc finger is indispensable for the C2 protein to bind zinc and DNA. Mutation of cysteine residue C36, C38, or C46 reduced the zinc and DNA binding capacity of C2 protein. When expressed from potato virus X, all three mutants, C2-C36R, C2-C38N, and C2-C46I, tagged with a green fluorescent protein (GFP) were still capable of transporting GFP into but aggregated abnormally in nuclei. Our data establish that zinc- and DNA-binding activity correlates with C2-mediated pathoGenesis and PTGS suppression.
Zoltan Havelda - One of the best experts on this subject based on the ideXlab platform.
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defective interfering rna hinders the activity of a tombusvirus encoded Posttranscriptional Gene Silencing suppressor
Journal of Virology, 2005Co-Authors: Zoltan Havelda, Csaba Hornyik, Anna Valoczi, Jozsef BurgyanAbstract:Defective interfering (DI) RNAs are subviral replicons originating from the viral genome and are associated with many plant RNA viruses and nearly all animal RNA viruses. The presence of DI RNAs in tombusvirus-infected plants reduces the accumulation of helper virus RNA and results in the development of attenuated symptoms similar to those caused by tombusviruses defective in p19, the Posttranscriptional Gene Silencing (PTGS) suppressor. In situ analysis of infected plants containing DI RNAs revealed that the extent of virus infection was spatially restricted as was found for p19-defective tombusvirus. Previously, p19 was shown to suppress PTGS by sequestering the small interfering RNAs (siRNAs), which act as the specificity determinant for PTGS. Our results demonstrate that DI RNAs dramatically elevate the level of virus-specific siRNAs in viral infections, resulting in the saturation of p19 and the accumulation of unbound siRNAs. Moreover, we showed that, at low temperature, where PTGS is inhibited, DI RNAs are not able to efficiently interfere with virus accumulation and protect the plants. These data show that the activation of PTGS plays a pivotal role in DI RNA-mediated interference. Our data also support a role for 21-nucleotide siRNAs in PTGS signaling.
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in situ characterization of cymbidium ringspot tombusvirus infection induced Posttranscriptional Gene Silencing in nicotiana benthamiana
Journal of Virology, 2003Co-Authors: Zoltan Havelda, Csaba Hornyik, Aniello Crescenzi, Jozsef BurgyanAbstract:In plants, Posttranscriptional Gene Silencing (PTGS) is an ancient and effective defense mechanism against viral infection. A number of viruses encode proteins that suppress virus-activated PTGS. The p19 protein of tombusviruses is a potent PTGS suppressor which interferes with the onset of PTGS-Generated systemic signaling and is not required for viral replication or for viral movement in Nicotiana benthamiana. This unique feature of p19 suppressor allowed us to analyze the mechanism of PTGS-based host defense and its viral suppression without interfering with other viral functions. In contrast to the necrotic symptoms caused by wild-type tombusvirus, the infection of p19-defective mutant virus results in the development of a typical PTGS-associated recovery phenotype in N. benthamiana. In this report we show the effect of PTGS on the viral infection process for N. benthamiana infected with either wild-type Cymbidium Ringspot Tombusvirus (CymRSV) or a p19-defective mutant (Cym19stop). In situ analyses of different virus-derived products revealed that PTGS is not able to reduce accumulation of virus in primary infected cells regardless of the presence of p19 PTGS suppressor. We also showed that both CymRSV and Cym19stop viruses move systemically in the vasculature, with similar efficiencies. However, in contrast to the uniform accumulation of CymRSV throughout systemically infected leaves, the presence of Cym19stop virus was confined to and around the vascular bundles. These results suggest that the role of p19 is to prevent the onset of mobile signal-induced systemic PTGS ahead of the viral infection front, leading to Generalized infection.
Frederick Meins - One of the best experts on this subject based on the ideXlab platform.
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high molecular weight rnas and small interfering rnas induce systemic Posttranscriptional Gene Silencing in plants
Proceedings of the National Academy of Sciences of the United States of America, 2002Co-Authors: Ulrich Klahre, Patrice Crete, Sabrina Leuenberger, Victor Alejandro Iglesias, Frederick MeinsAbstract:Posttranscriptional Gene Silencing (PTGS) in transgenic plants is an epiGenetic form of RNA degradation related to PTGS and RNA interference (RNAi) in fungi and animals. Evidence suggests that transGene loci and RNA viruses can Generate double-stranded RNAs similar in sequence to the transcribed region of target Genes, which then undergo endonucleolytic cleavage to Generate small interfering RNAs (siRNA) that promote degradation of cognate RNAs. The silent state in transgenic plants and in Caenorhabditis elegans can spread systemically, implying that mobile Silencing signals exist. Neither the chemical nature of these signals nor their exact source in the PTGS pathway is known. Here, we use a positive marker system and real-time monitoring of green fluorescent protein expression to show that large sense, antisense, and double-stranded RNAs as well as double-stranded siRNAs delivered biolistically into plant cells trigger Silencing capable of spreading locally and systemically. Systemically silenced leaves show greatly reduced levels of target RNA and accumulate siRNAs, confirming that RNA can induce systemic PTGS. The induced siRNAs represent parts of the target RNA that are outside of the region of homology with the triggering siRNA. Our results imply that siRNAs themselves or intermediates induced by siRNAs could comprise Silencing signals and that these signals induce self-amplifying production of siRNAs.
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β 1 3 glucanase and chitinase transGenes in hybrids show distinctive and independent patterns of Posttranscriptional Gene Silencing
Planta, 2001Co-Authors: Christian Kunz, Hanspeter Schob, Gerd Leubnermetzger, Eugene Glazov, Frederick MeinsAbstract:Nicotiana sylvestris Speg. & Comes transformed with a tobacco class-I β-1,3-glucanase (GLU I ) cDNA driven by CaMV 35S RNA expression signals exhibits Posttranscriptional Gene Silencing (PTGS) which is triggered between the cotyledon and two-leaf stages of seedling development and is postmeiotically reset to the high-expressing state during seed development. The incidence of GLU I PTGS in sibling plants differed for the two different transformants tested and increased with the number of T-DNA loci. Comparison of host class-I and class-II β-1,3-glucanase Gene expression suggests that a similarity of 60–70% in the coding-region is required for PTGS of the homologous host Genes. The GLU I transformants exhibited a spatial gradient in PTGS, in which expression of the silent phenotype gradually increased in successive leaves toward the bottom of the plant. In contrast, transformants carrying an unrelated tobacco class I chitinase (CHN I ) cDNA in the same expression vector exhibited discontinuous patterns of PTGS with adjacent high-expressing and silent leaves. The GLU I- and CHN I-specific patterns were maintained in hybrids homozygous for both T-DNA's indicating that two different transGenes present in the same genome can exhibit independent and distinctive patterns of PTGS. This implies that the nature of the transGene rather than a General pre-pattern of competence for PTGS or propagation of the silent state are important for pattern determination.
Hervé Vaucheret - One of the best experts on this subject based on the ideXlab platform.
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the nuclear ribonucleoprotein smd1 interplays with splicing rna quality control and Posttranscriptional Gene Silencing in arabidopsis
The Plant Cell, 2016Co-Authors: Emilie Elviramatelot, Nathalie Bouteiller, Florian Bardou, Federico Ariel, Vincent Jauvion, Ivan Le Masson, Martin Crespi, Hervé VaucheretAbstract:RNA quality control (RQC) eliminates aberrant RNAs based on their atypical structure, whereas Posttranscriptional Gene Silencing (PTGS) eliminates both aberrant and functional RNAs through the sequence-specific action of short interfering RNAs (siRNAs). The Arabidopsis thaliana mutant smd1b was identified in a Genetic screen for PTGS deficiency, revealing the involvement of SmD1, a component of the Smith (Sm) complex, in PTGS. The smd1a and smd1b single mutants are viable, but the smd1a smd1b double mutant is embryo-lethal, indicating that SmD1 function is essential. SmD1b resides in nucleoli and nucleoplasmic speckles, colocalizing with the splicing-related factor SR34. Consistent with this, the smd1b mutant exhibits intron retention at certain endogenous mRNAs. SmD1 binds to RNAs transcribed from silenced transGenes but not nonsilenced ones, indicating a direct role in PTGS. Yet, mutations in the RQC factors UPFRAMESHIFT3, EXORIBONUCLEASE2 (XRN2), XRN3, and XRN4 restore PTGS in smd1b, indicating that SmD1 is not essential for but rather facilitates PTGS. Moreover, the smd1b mtr4 double mutant is embryo-lethal, suggesting that SmD1 is essential for mRNA TRANSPORT REGULATOR4-dependent RQC. These results indicate that SmD1 interplays with splicing, RQC, and PTGS. We propose that SmD1 facilitates PTGS by protecting transGene-derived aberrant RNAs from degradation by RQC in the nucleus, allowing sufficient amounts to enter cytoplasmic siRNA bodies to activate PTGS.
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second site mutaGenesis of a hypomorphic argonaute1 allele identifies superkiller3 as an endogenous suppressor of transGene Posttranscriptional Gene Silencing
Plant Physiology, 2015Co-Authors: Agnes Yu, Taline Elmayan, Baptiste Saudemont, Nathalie Bouteiller, Jean Sébastien Parent, Jean-benoit Morel, Gersende Lepere, Emilie Elviramatelot, Hervé VaucheretAbstract:Second-site mutaGenesis was performed on the argonaute1-33 (ago1-33) hypomorphic mutant, which exhibits reduced sense transGene Posttranscriptional Gene Silencing (S-PTGS). Mutations in FIERY1, a positive regulator of the cytoplasmic 5′-to-3′ EXORIBONUCLEASE4 (XRN4), and in SUPERKILLER3 (SKI3), a member of the SKI complex that threads RNAs directly to the 3′-to-5′ exoribonuclease of the cytoplasmic exosome, compensated AGO1 partial deficiency and restored S-PTGS with 100% efficiency. Moreover, xrn4 and ski3 single mutations provoked the entry of nonsilenced transGenes into S-PTGS and enhanced S-PTGS on partially silenced transGenes, indicating that cytoplasmic 5′-to-3′ and 3′-to-5′ RNA degradation Generally counteract S-PTGS, likely by reducing the amount of transGene aberrant RNAs that are used by the S-PTGS pathway to build up small interfering RNAs that guide transGene RNA cleavage by AGO1. Constructs Generating improperly terminated transGene messenger RNAs (mRNAs) were not more sensitive to ski3 or xrn4 than regular constructs, suggesting that improperly terminated transGene mRNAs not only are degraded from both the 3′ end but also from the 5′ end, likely after decapping. The facts that impairment of either 5′-to-3′ or 3′-to-5′ RNA degradation is sufficient to provoke the entry of transGene RNA into the S-PTGS pathway, whereas simultaneous impairment of both pathways is necessary to provoke the entry of endogenous mRNA into the S-PTGS pathway, suggest poor RNA quality upon the transcription of transGenes integrated at random genomic locations.
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Second-site mutaGenesis of a hypomorphic argonaute1 allele identifies SUPERKILLER3 as an endogenous suppressor of transGene Posttranscriptional Gene Silencing
Plant Physiology, 2015Co-Authors: Agnes Yu, Taline Elmayan, Baptiste Saudemont, Nathalie Bouteiller, Emilie Elvira-matelot, Jean Sébastien Parent, Jean-benoit Morel, Jun Cao, Gersende Lepere, Hervé VaucheretAbstract:© 2015 American Society of Plant Biologists. All rights reserved. Second-site mutaGenesis was performed on the argonaute1-33 (ago1-33) hypomorphic mutant, which exhibits reduced sense transGene Posttranscriptional Gene Silencing (S-PTGS). Mutations in FIERY1, a positive regulator of the cytoplasmic 59-to-39 EXORIBONUCLEASE4 (XRN4), and in SUPERKILLER3 (SKI3), a member of the SKI complex that threads RNAs directly to the 39-to-59 exoribonuclease of the cytoplasmic exosome, compensated AGO1 partial deficiency and restored S-PTGS with 100% efficiency. Moreover, xrn4 and ski3 single mutations provoked the entry of nonsilenced transGenes into S-PTGS and enhanced S-PTGS on partially silenced transGenes, indicating that cytoplasmic 5′-to-3′ and 3′-to-5′ RNA degradation Generally counteract S-PTGS, likely by reducing the amount of transGene aberrant RNAs that are used by the S-PTGS pathway to build up small interfering RNAs that guide transGene RNA cleavage by AGO1. Constructs Generating improperly terminated transGene messenger RNAs (mRNAs) were not more sensitive to ski3 or xrn4 than regular constructs, suggesting that improperly terminated transGene mRNAs not only are degraded from both the 3′ end but also from the 5′ end, likely after decapping. The facts that impairment of either 5′-to-3′ or 3′-to-5′ RNA degradation is sufficient to provoke the entry of transGene RNA into the S-PTGS pathway, whereas simultaneous impairment of both pathways is necessary to provoke the entry of endogenous mRNA into the S-PTGS pathway, suggest poor RNA quality upon the transcription of transGenes integrated at random genomic locations.
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Mutations in the Arabidopsis H3K4me2/3 Demethylase JMJ14 Suppress Posttranscriptional Gene Silencing by Decreasing TransGene Transcription
The Plant Cell, 2012Co-Authors: Ivan Le Masson, Taline Elmayan, Nathalie Bouteiller, Vincent Jauvion, Maud Rivard, Hervé VaucheretAbstract:Posttranscriptional Gene Silencing (PTGS) mediated by sense transGenes (S-PTGS) results in RNA degradation and DNA methylation of the transcribed region. Through a forward Genetic screen, a mutant defective in the Histone3 Lysine4 di/trimethyl (H3K4me2/3) demethylase Jumonji-C (JmjC) domain-containing protein14 (JMJ14) was identified. This mutant reactivates various transGenes silenced by S-PTGS and shows reduced Histone3 Lysine9 Lysine14 acetylation (H3K9K14Ac) levels, reduced polymerase II occupancy, reduced transGene transcription, and increased DNA methylation in the promoter region, consistent with the hypothesis that high levels of transcription are required to trigger S-PTGS. The jmj14 mutation also reduces the expression of transGenes that do not trigger S-PTGS. Moreover, expression of transGenes that undergo S-PTGS in a wild-type background is reduced in jmj14 sgs3 double mutants compared with PTGS-deficient sgs3 mutants, indicating that JMJ14 is required for high levels of transcription in a PTGS-independent manner. Whereas endogenous loci regulated by JMJ14 exhibit increased H3K4me2 and H3K4me3 levels in the jmj14 mutant, transGene loci exhibit unchanged H3K4me2 and decreased H3K4me3 levels. Because jmj14 mutations impair PTGS of transGenes expressed under various plant or viral promoters, we hypothesize that JMJ14 demethylation activity is prevented by antagonistic epiGenetic marks specifically imposed at transGene loci. Removing JMJ14 likely allows other H3K4 demethylases encoded by the Arabidopsis thaliana genome to act on transGenes and reduce transcription levels, thus preventing the triggering of S-PTGS.
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mutations in the arabidopsis h3k4me2 3 demethylase jmj14 suppress Posttranscriptional Gene Silencing by decreasing transGene transcription
The Plant Cell, 2012Co-Authors: Ivan Le Masson, Taline Elmayan, Nathalie Bouteiller, Vincent Jauvion, Maud Rivard, Hervé VaucheretAbstract:Posttranscriptional Gene Silencing (PTGS) mediated by sense transGenes (S-PTGS) results in RNA degradation and DNA methylation of the transcribed region. Through a forward Genetic screen, a mutant defective in the Histone3 Lysine4 di/trimethyl (H3K4me2/3) demethylase Jumonji-C (JmjC) domain-containing protein14 (JMJ14) was identified. This mutant reactivates various transGenes silenced by S-PTGS and shows reduced Histone3 Lysine9 Lysine14 acetylation (H3K9K14Ac) levels, reduced polymerase II occupancy, reduced transGene transcription, and increased DNA methylation in the promoter region, consistent with the hypothesis that high levels of transcription are required to trigger S-PTGS. The jmj14 mutation also reduces the expression of transGenes that do not trigger S-PTGS. Moreover, expression of transGenes that undergo S-PTGS in a wild-type background is reduced in jmj14 sgs3 double mutants compared with PTGS-deficient sgs3 mutants, indicating that JMJ14 is required for high levels of transcription in a PTGS-independent manner. Whereas endogenous loci regulated by JMJ14 exhibit increased H3K4me2 and H3K4me3 levels in the jmj14 mutant, transGene loci exhibit unchanged H3K4me2 and decreased H3K4me3 levels. Because jmj14 mutations impair PTGS of transGenes expressed under various plant or viral promoters, we hypothesize that JMJ14 demethylation activity is prevented by antagonistic epiGenetic marks specifically imposed at transGene loci. Removing JMJ14 likely allows other H3K4 demethylases encoded by the Arabidopsis thaliana genome to act on transGenes and reduce transcription levels, thus preventing the triggering of S-PTGS.