scholarly journals Effects of the Crinivirus Coat Protein–Interacting Plant Protein SAHH on Post-Transcriptional RNA Silencing and Its Suppression

2013 ◽  
Vol 26 (9) ◽  
pp. 1004-1015 ◽  
Author(s):  
M. Carmen Cañizares ◽  
Rosa Lozano-Durán ◽  
Tomás Canto ◽  
Eduardo R. Bejarano ◽  
David M. Bisaro ◽  
...  
Keyword(s):  
Coat Protein ◽  
Rna Silencing ◽  
Rna Degradation ◽  
Plant Viruses ◽  
Plant Protein ◽  
Transcriptional Gene Silencing ◽  
Small Interfering Rnas ◽  
Post Transcriptional Gene Silencing ◽  
Secondary Sirnas ◽  
Tomato Chlorosis Virus

In plants, post-transcriptional gene silencing (PTGS) is a sequence-specific mechanism of RNA degradation induced by double-stranded RNA (dsRNA), which is processed into small interfering RNAs (siRNAs). siRNAs are methylated and, thereby, stabilized by the activity of the S-adenosylmethionine-dependent RNA methyltransferase HEN1. PTGS is amplified by host-encoded RNA-dependent RNA polymerases (RDR), which generate dsRNA that is processed into secondary siRNAs. To counteract this RNA silencing-mediated response of the host, plant viruses express proteins with silencing suppression activity. Here, we report that the coat protein (CP) of crinivirus (family Closteroviridae, genus Crinivirus) Tomato chlorosis virus, a known suppressor of silencing, interacts with S-adenosylhomocysteine hydrolase (SAHH), a plant protein essential for sustaining the methyl cycle and S-adenosylmethionine-dependent methyltransferase activity. Our results show that, by contributing to an increased accumulation of secondary siRNAs generated by the action of RDR6, SAHH enhances local RNA silencing. Although downregulation of SAHH prevents local silencing, it enhances the spread of systemic silencing. Our results also show that SAHH is important in the suppression of local RNA silencing not only by the crinivirus Tomato chlorosis virus CP but also by the multifunctional helper component-proteinase of the potyvirus Potato virus Y.

scholarly journals The Coat Protein of Turnip Crinkle Virus Suppresses Posttranscriptional Gene Silencing at an Early Initiation Step

2003 ◽  
Vol 77 (1) ◽  
pp. 511-522 ◽  
Author(s):  
Feng Qu ◽  
Tao Ren ◽  
T. Jack Morris
Keyword(s):  
Coat Protein ◽  
Gene Silencing ◽  
Rna Silencing ◽  
Rna Degradation ◽  
Plant Viruses ◽  
Early Initiation ◽  
Turnip Crinkle Virus ◽  
Small Interfering Rnas ◽  
Posttranscriptional Gene Silencing ◽  
Initiation Step

ABSTRACT Posttranscriptional gene silencing (PTGS), or RNA silencing, is a sequence-specific RNA degradation process that targets foreign RNA, including viral and transposon RNA for destruction. Several RNA plant viruses have been shown to encode suppressors of PTGS in order to survive this host defense. We report here that the coat protein (CP) of Turnip crinkle virus (TCV) strongly suppresses PTGS. The Agrobacterium infiltration system was used to demonstrate that TCV CP suppressed the local PTGS as strongly as several previously reported virus-coded suppressors and that the action of TCV CP eliminated the small interfering RNAs associated with PTGS. We have also shown that the TCV CP must be present at the time of silencing initiation to be an effective suppressor. TCV CP was able to suppress PTGS induced by sense, antisense, and double-stranded RNAs, and it prevented systemic silencing. These data suggest that TCV CP functions to suppress RNA silencing at an early initiation step, likely by interfering the function of the Dicer-like RNase in plants.

scholarly journals FIERY1 promotes microRNA accumulation by suppressing rRNA-derived small interfering RNAs in Arabidopsis

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Chenjiang You ◽  
Wenrong He ◽  
Runlai Hang ◽  
Cuiju Zhang ◽  
Xiaofeng Cao ◽  
...  
Keyword(s):  
Rna Degradation ◽  
Transcriptional Gene Silencing ◽  
Rrna Processing ◽  
Small Interfering Rnas ◽  
Post Transcriptional Gene Silencing ◽  
Processing Defects ◽  
And Function ◽  
Mirna Abundance ◽  
Unknown Link

Abstract Plant microRNAs (miRNAs) associate with ARGONAUTE1 (AGO1) to direct post-transcriptional gene silencing and regulate numerous biological processes. Although AGO1 predominantly binds miRNAs in vivo, it also associates with endogenous small interfering RNAs (siRNAs). It is unclear whether the miRNA/siRNA balance affects miRNA activities. Here we report that FIERY1 (FRY1), which is involved in 5′−3′ RNA degradation, regulates miRNA abundance and function by suppressing the biogenesis of ribosomal RNA-derived siRNAs (risiRNAs). In mutants of FRY1 and the nuclear 5′−3′ exonuclease genes XRN2 and XRN3, we find that a large number of 21-nt risiRNAs are generated through an endogenous siRNA biogenesis pathway. The production of risiRNAs correlates with pre-rRNA processing defects in these mutants. We also show that these risiRNAs are loaded into AGO1, causing reduced loading of miRNAs. This study reveals a previously unknown link between rRNA processing and miRNA accumulation.

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

2008 ◽  
Vol 83 (3) ◽  
pp. 1332-1340 ◽  
Author(s):  
Edgar A. Rodríguez-Negrete ◽  
Jimena Carrillo-Tripp ◽  
Rafael F. Rivera-Bustamante
Keyword(s):  
Gene Silencing ◽  
Intergenic Region ◽  
Rna Silencing ◽  
Methylation Status ◽  
Inverse Correlation ◽  
Plant Viruses ◽  
Transcriptional Gene Silencing ◽  
Small Interfering Rnas ◽  
Coding Region ◽  
Natural Defense

ABSTRACT RNA silencing in plants is a natural defense system mechanism against invading nucleic acids such as viruses. Geminiviruses, a family of plant viruses characterized by a circular, single-stranded DNA genome, are thought to be both inducers and targets of RNA silencing. Some natural geminivirus-host interactions lead to symptom remission or host recovery, a process commonly associated with RNA silencing-mediated defense. Pepper golden mosaic virus (PepGMV)-infected pepper plants show a recovery phenotype, which has been associated with the presence of virus-derived small RNAs. The results presented here suggest that PepGMV is targeted by both posttranscriptional and transcriptional gene silencing mechanisms. Two types of virus-related small interfering RNAs (siRNAs) were detected: siRNAs of 21 to 22 nucleotides (nt) in size that are related to the coding regions (Rep, TrAP, REn, and movement protein genes) and a 24-nt population primarily associated to the intergenic regions. Methylation levels of the PepGMV A intergenic and coat protein (CP) coding region were measured by a bisulfite sequencing approach. An inverse correlation was observed between the methylation status of the intergenic region and the concentration of viral DNA and symptom severity. The intergenic region also showed a methylation profile conserved in all times analyzed. The CP region, on the other hand, did not show a defined profile, and its methylation density was significantly lower than the one found on the intergenic region. The participation of both PTGS and TGS mechanisms in host recovery is discussed.

scholarly journals Identification of an RNA-silencing suppressor in the genome of Grapevine virus A

2006 ◽  
Vol 87 (8) ◽  
pp. 2387-2395 ◽  
Author(s):  
Z. Sh. Zhou ◽  
M. Dell'Orco ◽  
P. Saldarelli ◽  
C. Turturo ◽  
A. Minafra ◽  
...  
Keyword(s):  
Fluorescent Protein ◽  
Higher Plants ◽  
Ectopic Expression ◽  
Rna Degradation ◽  
Plant Viruses ◽  
Transcriptional Gene Silencing ◽  
Small Interfering Rnas ◽  
Grapevine Virus ◽  
Transient Expression Assay ◽  
Grapevine Virus A

Higher plants use post-transcriptional gene silencing (PTGS), an RNA-degradation system, as a defence mechanism against viral infections. To counteract this, plant viruses encode and express PTGS suppressor proteins. Four of the five proteins encoded by the Grapevine virus A (GVA) genome were screened using a green fluorescent protein (GFP)-based transient expression assay, and the expression product of ORF5 (protein p10) was identified as a suppressor of silencing. ORF5 p10 suppressed local and systemic silencing induced by a transiently expressed single-stranded sense RNA. This protein was active towards both a transgene and exogenous GFP mRNAs. Ectopic expression of GVA-ORF5 by a Potato virus X vector enhanced symptom severity. The findings that p10 markedly reduces the levels of small interfering RNAs (siRNAs) and that the recombinant protein is able to bind single-stranded and double-stranded forms of siRNAs and microRNAs, suggest the existence of a potential mechanism of suppression based on RNA sequestering.

scholarly journals Inhibition of RNA silencing by the coat protein of Pelargonium flower break virus: distinctions from closely related suppressors

2009 ◽  
Vol 90 (2) ◽  
pp. 519-525 ◽  
Author(s):  
Sandra Martínez-Turiño ◽  
Carmen Hernández
Keyword(s):  
Coat Protein ◽  
Potato Virus ◽  
Rna Silencing ◽  
Potato Virus X ◽  
Plant Viruses ◽  
Small Interfering Rnas ◽  
Silencing Suppression ◽  
Viral Suppressors

Viral-derived double-stranded RNAs (dsRNAs) activate RNA silencing, generating small interfering RNAs (siRNAs) which are incorporated into an RNA-induced silencing complex (RISC) that promotes homology-dependent degradation of cognate RNAs. To counteract this, plant viruses express RNA silencing suppressors. Here, we show that the coat protein (CP) of Pelargonium flower break virus (PFBV), a member of the genus Carmovirus, is able to efficiently inhibit RNA silencing. Interestingly, PFBV CP blocked both sense RNA- and dsRNA-triggered RNA silencing and did not preclude generation of siRNAs, which is in contrast with the abilities that have been reported for other carmoviral CPs. We have also found that PFBV CP can bind siRNAs and that this ability correlates with silencing suppression activity and enhancement of potato virus X pathogenicity. Collectively, the results indicate that PFBV CP inhibits RNA silencing by sequestering siRNAs and preventing their incorporation into a RISC, thus behaving similarly to unrelated viral suppressors but dissimilarly to orthologous ones.

scholarly journals Trigger and suppression of antiviral defenses by grapevine Pinot gris virus (GPGV): novel insights into virus-host interaction

2021 ◽  
Author(s):  
Giulia Tarquini ◽  
Laura Pagliari ◽  
Paolo Ermacora ◽  
Rita Musetti ◽  
Giuseppe Firrao
Keyword(s):  
Rna Silencing ◽  
Infectious Clone ◽  
Transcriptional Gene Silencing ◽  
Antiviral Defense ◽  
Small Interfering Rnas ◽  
Host Interaction ◽  
Post Transcriptional Gene Silencing ◽  
Gene Expression Analyses ◽  
Grapevine Pinot Gris Virus

Grapevine Pinot gris virus (GPGV) is an emerging trichovirus that has been putatively associated with a novel grapevine disease known as grapevine leaf mottling and deformation (GLMD). Yet the role of GPGV in GLMD disease is poorly understood since it has been detected both in symptomatic and symptomless grapevines. We exploited a recently constructed GPGV infectious clone (pRI::GPGV-vir) to induce an antiviral response in Nicotiana benthamiana plants. In silico prediction of virus-derived small interfering RNAs (vsiRNAs) and gene expression analyses revealed the involvement of DCL4, AGO5 and RDR6 genes during GPGV infection, suggesting the activation of the post-transcriptional gene-silencing (PTGS) pathway as a plant antiviral defense. PTGS suppression assays in transgenic N. benthamiana 16c plants revealed the ability of the GPGV coat protein to suppress RNA silencing. This work provides novel insights on the interaction between GPGV and its host, revealing the ability of the virus to trigger and suppress antiviral RNA silencing.

scholarly journals Tomato ringspot virus Coat Protein Binds to ARGONAUTE 1 and Suppresses the Translation Repression of a Reporter Gene

2014 ◽  
Vol 27 (9) ◽  
pp. 933-943 ◽  
Author(s):  
Rajita A. Karran ◽  
Hélène Sanfaçon
Keyword(s):  
Coat Protein ◽  
Reporter Gene ◽  
Rna Silencing ◽  
Fluorescent Protein ◽  
Plant Viruses ◽  
Ringspot Virus ◽  
Small Interfering Rnas ◽  
Gfp Expression ◽  
Translation Repression ◽  
Tomato Ringspot Virus

RNA silencing regulates plant gene expression and antiviral defenses and functions by cleaving target RNAs or repressing translation. As a counter defense, many plant viruses encode suppressor proteins that sequester small RNAs or inactivate Argonaute (AGO) proteins. All known plant virus silencing suppressor activities eventually inhibit the degradation of target mRNAs. Using a transiently expressed green fluorescent protein (GFP) reporter gene, we show that Tomato ringspot virus (ToRSV) coat protein (CP) is a suppressor of RNA silencing that enhances GFP expression but does not prevent the degradation of the GFP mRNA or the accumulation of GFP small interfering RNAs (siRNAs). Coexpression of the CP with GFP resulted in increased association of residual GFP mRNAs with polysome fractions and reduced association of GFP siRNAs with monosome fractions. AGO1 was co-immunoprecipitated with the CP and CP expression destabilized AGO1. A WG motif within the CP was critical for the enhanced GFP expression, AGO1 interaction, and AGO1 destabilization, suggesting that the ToRSV CP acts as an AGO-hook protein and competes for AGO binding with a plant cellular GW/WG protein involved in translation repression.

scholarly journals Comparative reactions of recombinant papaya ringspot viruses with chimeric coat protein (CP) genes and wild-type viruses on CP-transgenic papaya

2001 ◽  
Vol 82 (11) ◽  
pp. 2827-2836 ◽  
Author(s):  
Chu-Hui Chiang ◽  
Ju-Jung Wang ◽  
Fuh-Jyh Jan ◽  
Shyi-Dong Yeh ◽  
Dennis Gonsalves
Keyword(s):  
Coat Protein ◽  
Sequence Similarity ◽  
Transcriptional Gene Silencing ◽  
Papaya Ringspot Virus ◽  
Wild Type ◽  
Coding Region ◽  
Transgenic Papaya ◽  
Cp Gene ◽  
Post Transcriptional Gene Silencing

Transgenic papaya cultivars SunUp and Rainbow express the coat protein (CP) gene of the mild mutant of papaya ringspot virus (PRSV) HA. Both cultivars are resistant to PRSV HA and other Hawaii isolates through homology-dependent resistance via post-transcriptional gene silencing. However, Rainbow, which is hemizygous for the CP gene, is susceptible to PRSV isolates from outside Hawaii, while the CP-homozygous SunUp is resistant to most isolates but susceptible to the YK isolate from Taiwan. To investigate the role of CP sequence similarity in overcoming the resistance of Rainbow, PRSV HA recombinants with various CP segments of the YK isolate were constructed and evaluated on Rainbow, SunUp and non-transgenic papaya. Non-transgenic papaya were severely infected by all recombinants, but Rainbow plants developed a variety of symptoms. On Rainbow, a recombinant with the entire CP gene of YK caused severe symptoms, while recombinants with only partial YK CP sequences produced a range of milder symptoms. Interestingly, a recombinant with a YK segment from the 5′ region of the CP gene caused very mild, transient symptoms, whereas recombinants with YK segments from the middle and 3′ parts of the CP gene caused prominent and lasting symptoms. SunUp was resistant to all but two recombinants, which contained the entire CP gene or the central and 3′-end regions of the CP gene and the 3′ non-coding region of YK, and the resulting symptoms were mild. It is concluded that the position of the heterologous sequences in the recombinants influences their pathogenicity on Rainbow.

scholarly journals An atypical class of non-coding small RNAs produced in rice leaves upon bacterial infection

2021 ◽  
Author(s):  
Ganna Reshetnyak ◽  
Jonathan M. Jacobs ◽  
Florence Auguy ◽  
Coline Sciallano ◽  
Lisa Claude ◽  
...  
Keyword(s):  
Gene Silencing ◽  
Stress Responses ◽  
Small Rnas ◽  
Early Stage ◽  
Kinase Domain ◽  
Transcriptional Gene Silencing ◽  
Small Interfering Rnas ◽  
Post Transcriptional Gene Silencing ◽  
Virulent Strains ◽  
Microbe Interactions

ABSTRACTNon-coding small RNAs (sRNA) act as mediators of gene silencing and regulate plant growth, development and stress responses. Early insights into plant sRNAs established a role in antiviral defense and they are now extensively studied across plant-microbe interactions. Here, sRNA sequencing discovered a class of sRNA in rice (Oryza sativa) specifically associated with foliar diseases caused by Xanthomonas oryzae bacteria. Xanthomonas-induced small RNAs (xisRNAs) loci were distinctively upregulated in response to diverse virulent strains at an early stage of infection producing a single duplex of 20-22nt sRNAs. xisRNAs production was dependent on the Type III secretion system, a major bacterial virulence factor for host colonization. xisRNA loci overlap with annotated transcripts sequences often encoding protein kinase domain proteins. A number of the corresponding rice cis-genes have documented functions in immune signaling and some xisRNA loci coincide with the coding sequence of a conserved kinase motif. xisRNAs exhibit features of small interfering RNAs and their biosynthesis depend on canonical components OsDCL1 and OsHEN1. xisRNA induction possibly mediates post-transcriptional gene silencing but they do not broadly suppress cis-genes expression on the basis of mRNA-seq data. Overall, our results identify a group of unusual sRNAs with a potential role in plant-microbe interactions.

scholarly journals RNA Silencing and Plant Viral Diseases

2012 ◽  
Vol 25 (10) ◽  
pp. 1275-1285 ◽  
Author(s):  
Ming-Bo Wang ◽  
Chikara Masuta ◽  
Neil A. Smith ◽  
Hanako Shimura
Keyword(s):  
Rna Silencing ◽  
Defense Mechanisms ◽  
Critical Role ◽  
Viral Disease ◽  
Rna Degradation ◽  
Degradation Pathway ◽  
Plant Viruses ◽  
Direct Role ◽  
Dna Viruses ◽  
Disease Induction

RNA silencing plays a critical role in plant resistance against viruses, with multiple silencing factors participating in antiviral defense. Both RNA and DNA viruses are targeted by the small RNA-directed RNA degradation pathway, with DNA viruses being also targeted by RNA-directed DNA methylation. To evade RNA silencing, plant viruses have evolved a variety of counter-defense mechanisms such as expressing RNA-silencing suppressors or adopting silencing-resistant RNA structures. This constant defense–counter defense arms race is likely to have played a major role in defining viral host specificity and in shaping viral and possibly host genomes. Recent studies have provided evidence that RNA silencing also plays a direct role in viral disease induction in plants, with viral RNA-silencing suppressors and viral siRNAs as potentially the dominant players in viral pathogenicity. However, questions remain as to whether RNA silencing is the principal mediator of viral pathogenicity or if other RNA-silencing-independent mechanisms also account for viral disease induction. RNA silencing has been exploited as a powerful tool for engineering virus resistance in plants as well as in animals. Further understanding of the role of RNA silencing in plant–virus interactions and viral symptom induction is likely to result in novel anti-viral strategies in both plants and animals.

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