RNA Silencing against Geminivirus: Complementary Action of Posttranscriptional Gene Silencing and Transcriptional Gene Silencing in Host Recovery

Rodríguez-Negrete, Edgar A.; Carrillo-Tripp, Jimena; Rivera-Bustamante, R. F.

doi:10.1128/jvi.01474-08

Cited by 154 publications

(127 citation statements)

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“…Meanwhile, plants with the FWA transgene in the BSCTV C2 transgenic background were found to be insensitive to host de novo methylation, suggesting that BSCTV C2 effects were not restricted to the viral genome and interfered with the host cellular de novo DNA methylation process. Recently, several studies also strongly supported that the methylation-related TGS is a very important defense mechanism against geminiviruses in plant hosts (Raja et al, 2008;Rodríguez-Negrete et al, 2009), and BCTV L2 can suppress the TGS defense and cause the reduction of methylation in both the viral and plant host genomes (Raja et al, 2008;Buchmann et al, 2009). Clearly, during invasion of the plant host by geminiviruses, viral suppressors such as BSCTV C2 can perturb the de novo methylation machinery by different mechanisms, resulting in a hypomethylation of the host cell and facilitation of viral replication.…”

Section: De Novo Methylation-mediated Gene Silencing Targets the Viramentioning

confidence: 94%

BSCTV C2 Attenuates the Degradation of SAMDC1 to Suppress DNA Methylation-Mediated Gene Silencing in Arabidopsis

et al. 2011

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Plant viruses are excellent tools for studying microbial-plant interactions as well as the complexities of host activities. Our study focuses on the role of C2 encoded by Beet severe curly top virus (BSCTV) in the virus-plant interaction. Using BSCTV C2 as bait in a yeast two-hybrid screen, a C2-interacting protein, S-adenosyl-methionine decarboxylase 1 (SAMDC1), was identified from an Arabidopsis thaliana cDNA library. The interaction was confirmed by an in vitro pull-down assay and a firefly luciferase complemention imaging assay in planta. Biochemical analysis further showed that the degradation of the SAMDC1 protein was inhibited by MG132, a 26S proteasome inhibitor, and that C2 could attenuate the degradation of the SAMDC1 protein. Genetic analysis showed that loss of function of SAMDC1 resulted in reduced susceptibility to BSCTV infection and reduced viral DNA accumulation, similar to the effect of BSCTV C2 deficiency. Bisulfite sequencing analysis further showed that C2 deficiency caused enhanced DNA methylation of the viral genome in infected plants. We also showed that C2 can suppress de novo methylation in the FWA transgenic assay in the C2 transgene background. Overexpression of SAMDC1 can mimic the suppressive activity of C2 against green fluorescent protein-directed silencing. These results suggest that C2 interferes with the host defense mechanism of DNA methylation-mediated gene silencing by attenuating the 26S proteasome-mediated degradation of SAMDC1.

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Section: De Novo Methylation-mediated Gene Silencing Targets the Viramentioning

confidence: 94%

BSCTV C2 Attenuates the Degradation of SAMDC1 to Suppress DNA Methylation-Mediated Gene Silencing in Arabidopsis

et al. 2011

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“…Étant donné qu'AGO2, AGO4 et AGO7 recrutent majoritairement les sARN avec une adénosine en 5'-terminal et AGO5 les sARN commençant par une cytosine, leur association avec le RISC antiviral n'est pas à exclure [24,32,33]. De même, AGO4 et AGO6 étant responsables du silencing transcriptionnel chez Arabidopsis, leur rôle potentiel dans la défense contre les virus à ADN est probable [34,35].…”

Section: Revuesunclassified

La bataille du silence

Dunoyer

2009

Med Sci (Paris)

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505 SYNTHÈSE REVUESDécouvert au début des années 1990 [1,2], le méca-nisme du « RNA silencing » a complètement révolu-tionné notre façon d'appréhender la régulation de l'expression du génome chez les eucaryotes. Le terme « RNA silencing » (que nous préférons garder dans son appellation anglophone) englobe, de manière générale, l'ensemble des mécanismes conduisant à la suppression de l'expression de gènes, au niveau transcriptionnel ou post-transcriptionnel, via des interactions séquence-spécifiques médiées par l'ARN. Présent de l'algue unicellulaire Chlamydomonas reinhartii à l'homme, et hautement conservé chez la quasi-totalité des organismes eucaryotes, le RNA silencing joue un rôle essentiel dans un grand nombre de processus biologiques, par exemple le maintien de la stabilité des génomes (en réprimant le mouvement des éléments mobiles du génome que sont les transposons) ou le contrôle de l'expression de gènes au cours du développement, nécessaire à leur bon déroule-ment et inversement participe à de nombreuses pathologies comme le cancer (➜) [3, 4, 61].Dans tous les cas, l'ARN double brin (ARNdb) est la molécule clé initiatrice du silencing [5]. L'ARNdb peut être produit in vivo soit par transcription de séquences génomiques organisées en répétitions inversées, à partir de promoteurs convergents ou via l'action d'ARN polymérases ARN-dépendantes (RdRp) d'origine endogène ou virale qui convertiront un ARN simple brin (ARNsb) en ARNdb. Cet ARNdb est reconnu par une enzyme de type RNase III appelée Dicer [6] qui va produire la seconde catégorie de molécules ubiquitaires du RNA silencing que sont les petits ARN (small ARN ou sARN) [7,8] (Figure 1). Ces sARN, de 21-24nt de longueur, vont ensuite être incorporés dans un complexe multiprotéique appelé RISC (RNA-induced silencing complex) où ils serviront de guide pour lui permettre de retrouver, de manière séquence-spécifique, tout espèce d'acides nucléiques présentant une séquence complémentaire [9]. Selon la nature du complexe RISC impliqué, cette reconnaissance entraînera une répression de l'expression du gène, soit post-transcriptionnelle, par clivage endonucléolytique ou inhibition de la traduction de l'ARN > Le RNA silencing est un mécanisme opéré par de petites molécules d'ARN qui inhibent l'expression de gènes tant au niveau transcriptionnel que post-transcriptionnel via des interactions séquence-spécifiques. Conservé chez la plupart des eucaryotes, ce phénomène est impliqué dans le maintien de l'intégrité des génomes ou dans la régulation de facteurs spécifiques au cours du développement, aussi bien chez les animaux que chez les plantes. Chez ces dernières, le RNA silencing joue également un rôle crucial dans la défense antivirale. Pour contrer cette réponse, les virus ont développé une batterie de stratégies pour inhiber ce mécanisme. Cette revue détaille les mécanismes du RNA silencing et de son inhibition au cours des interactions plante/ virus et suggère les possibles conséquences de cette bataille moléculaire sur l'évolution de leur génomes respectifs. <

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“…In combination with random hexamer primers, circular DNA can be amplified preferentially from plant samples without any prior knowledge of the sequence. Therefore, it was intriguing to test this technique for the identification of C modifications by restriction analysis and bisulfite sequencing.Geminiviruses induce small interfering RNAs (siRNAs) (2,7,62,73), which may lead to posttranscriptional (PTGS) as well as transcriptional (TGS) gene silencing (4,65). This interplay of PTGS and TGS has been understood as part of the plant defense pathways (reviewed in references 16, 64, 75, and 76).…”

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confidence: 99%

“…Geminiviruses induce small interfering RNAs (siRNAs) (2,7,62,73), which may lead to posttranscriptional (PTGS) as well as transcriptional (TGS) gene silencing (4,65). This interplay of PTGS and TGS has been understood as part of the plant defense pathways (reviewed in references 16, 64, 75, and 76).…”

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Conformation-Selective Methylation of Geminivirus DNA

Paprotka

Deuschle

Metzler

et al. 2011

J Virol

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Geminiviruses with small circular single-stranded DNA genomes replicate in plant cell nuclei by using various double-stranded DNA (dsDNA) intermediates: distinct open circular and covalently closed circular as well as heterogeneous linear DNA. Their DNA may be methylated partially at cytosine residues, as detected previously by bisulfite sequencing and subsequent PCR. In order to determine the methylation patterns of the circular molecules, the DNAs of tomato yellow leaf curl Sardinia virus (TYLCSV) and Abutilon mosaic virus were investigated utilizing bisulfite treatment followed by rolling circle amplification. Shotgun sequencing of the products yielded a randomly distributed 50% rate of C maintenance after the bisulfite reaction for both viruses. However, controls with unmethylated single-stranded bacteriophage DNA resulted in the same level of C maintenance. Only one short DNA stretch within the C2/C3 promoter of TYLCSV showed hyperprotection of C, with the protection rate exceeding the threshold of the mean value plus 1 standard deviation. Similarly, the use of methylation-sensitive restriction enzymes suggested that geminiviruses escape silencing by methylation very efficiently, by either a rolling circle or recombination-dependent replication mode. In contrast, attempts to detect methylated bases positively by using methylcytosine-specific antibodies detected methylated DNA only in heterogeneous linear dsDNA, and methylation-dependent restriction enzymes revealed that the viral heterogeneous linear dsDNA was methylated preferentially.Methylation of DNA is commonly investigated using methylation-sensitive restriction enzymes and bisulfite sequencing, which converts unmethylated cytosines into uracil. The products are usually amplified by PCR and sequenced after bacterial cloning (14, 23). The critical steps in various protocols are the complete conversion of unmethylated cytosines to uracil (26, 78) and the design of appropriate primers for the converted DNA (reviewed in references 58 and 85). Several bioinformatic tools have been developed to analyze the results (9, 46-48, 66, 71), including recent improvements for the analysis of plant DNA cytosine methylation (27,35).Eukaryotes methylate cytosine at C 5 by methyltransferases, which differ between plants, fungi, and mammals (reviewed in reference 25). In mammals, symmetric CpG sites are usually preferred, whereas nearly every cytosine residue in plant DNA can be methylated (reviewed in reference 5). As a result, only 2 to 8% of mammalian DNA is methylated, compared to up to 50% of DNA in higher plants (reviewed in reference 84). The methylation status is highly dynamic. In plants, demethylation is mediated by DNA glycosylases and strand cleavage (84), a mechanism which would inactivate single-stranded DNA (ssDNA). In addition to C-methylation, N 6 -adenine methylation is well known for bacteria but rarely described for plants (19,74).The circular ssDNA-containing geminiviruses (reviewed in reference 37) are important plant pathogens causing severe damag...

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RNA Silencing against Geminivirus: Complementary Action of Posttranscriptional Gene Silencing and Transcriptional Gene Silencing in Host Recovery

Cited by 154 publications

References 59 publications

BSCTV C2 Attenuates the Degradation of SAMDC1 to Suppress DNA Methylation-Mediated Gene Silencing in Arabidopsis

BSCTV C2 Attenuates the Degradation of SAMDC1 to Suppress DNA Methylation-Mediated Gene Silencing in Arabidopsis

La bataille du silence

Conformation-Selective Methylation of Geminivirus DNA

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