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Questions and Answers
What are the two types of gene silencing?
What are the two types of gene silencing?
RNA silencing mechanisms are unique to plants and invertebrates.
RNA silencing mechanisms are unique to plants and invertebrates.
False (B)
What are the three phases of RNA silencing?
What are the three phases of RNA silencing?
What type of enzyme processes dsRNA into short, 21-24 nt long, small RNA (sRNA) duplexes?
What type of enzyme processes dsRNA into short, 21-24 nt long, small RNA (sRNA) duplexes?
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What enzyme stabilizes sRNA at the 3' end?
What enzyme stabilizes sRNA at the 3' end?
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What protein exports sRNA from the nucleus?
What protein exports sRNA from the nucleus?
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What protein is involved in the silencing complex that induces slicing or translational repression of target RNAs for PTGS?
What protein is involved in the silencing complex that induces slicing or translational repression of target RNAs for PTGS?
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What protein is involved in the RITS complex that causes histone and/or DNA methylation for TGS?
What protein is involved in the RITS complex that causes histone and/or DNA methylation for TGS?
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Which of these are classes of small RNAs identified in plants?
Which of these are classes of small RNAs identified in plants?
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The production of viral siRNAs (vsiRNAs) is a hallmark of the antiviral silencing response.
The production of viral siRNAs (vsiRNAs) is a hallmark of the antiviral silencing response.
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Which DCL is mainly responsible for vsiRNA production from RNA virus infections?
Which DCL is mainly responsible for vsiRNA production from RNA virus infections?
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What type of protein is involved in viral silencing suppression?
What type of protein is involved in viral silencing suppression?
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Which of these mechanisms can be used to block the mounting of antiviral silencing?
Which of these mechanisms can be used to block the mounting of antiviral silencing?
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What is the name of the suppressor protein encoded by tombusviruses that sequesters siRNAs?
What is the name of the suppressor protein encoded by tombusviruses that sequesters siRNAs?
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P19 sequesters both siRNAs and miRNAs.
P19 sequesters both siRNAs and miRNAs.
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The suppressor protein PO from poleroviruses possesses RNA binding activity.
The suppressor protein PO from poleroviruses possesses RNA binding activity.
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PO enhances the degradation of multiple AGOS through the proteasome pathway.
PO enhances the degradation of multiple AGOS through the proteasome pathway.
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What protein encoded by Sweet potato mild mottle ipomovirus (SPMMV) can directly interact with siRNA-loaded AGO1?
What protein encoded by Sweet potato mild mottle ipomovirus (SPMMV) can directly interact with siRNA-loaded AGO1?
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What kind of motifs are involved in the interaction of SPMMV P1 protein with AGO1?
What kind of motifs are involved in the interaction of SPMMV P1 protein with AGO1?
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What is the name of the TCV suppressor protein that can suppress silencing at multiple levels?
What is the name of the TCV suppressor protein that can suppress silencing at multiple levels?
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The p38 suppressor protein binds to both loaded and unloaded AGOs.
The p38 suppressor protein binds to both loaded and unloaded AGOs.
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The p37 protein encoded by Pelargonium line pattern virus (PLPV) mainly acts by sequestering siRNAs.
The p37 protein encoded by Pelargonium line pattern virus (PLPV) mainly acts by sequestering siRNAs.
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What protein has the characteristic of binding ss-sRNAs but not dsRNA?
What protein has the characteristic of binding ss-sRNAs but not dsRNA?
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What is the name of the protein encoded by Rice stripe virus that can suppress GFP silencing and also prevent long distance spread of silencing signal?
What is the name of the protein encoded by Rice stripe virus that can suppress GFP silencing and also prevent long distance spread of silencing signal?
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What are the main functions of host RDRs (RDR1, RDR2, and RDR6)?
What are the main functions of host RDRs (RDR1, RDR2, and RDR6)?
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What is the name of the protein in Tomato yellow leaf curl virus that directly interacts with SGS3 to block silencing amplification?
What is the name of the protein in Tomato yellow leaf curl virus that directly interacts with SGS3 to block silencing amplification?
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What is the name of the protein encoded by potexviruses that can inhibit RDR6/SGS3-dependent dsRNA synthesis?
What is the name of the protein encoded by potexviruses that can inhibit RDR6/SGS3-dependent dsRNA synthesis?
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The suppressor protein 2b encoded by CMV can only prevent the spread of the silencing signal.
The suppressor protein 2b encoded by CMV can only prevent the spread of the silencing signal.
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The 2b suppressor protein can also interact with AGO4.
The 2b suppressor protein can also interact with AGO4.
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What is the name of the host protein that interacts with potyviral HC-Pro?
What is the name of the host protein that interacts with potyviral HC-Pro?
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RgsCAM can directly bind to HC-Pro and block its dsRNA binding activity.
RgsCAM can directly bind to HC-Pro and block its dsRNA binding activity.
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It has been experimentally proven that the release of R-gene based defense is the cause of the inhibitory action of pathogen-encoded suppressors of silencing.
It has been experimentally proven that the release of R-gene based defense is the cause of the inhibitory action of pathogen-encoded suppressors of silencing.
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What is the name of the host hormone that is involved in local and systemic antiviral defense responses?
What is the name of the host hormone that is involved in local and systemic antiviral defense responses?
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What is the name of the viral suppressor that inhibits SA-induced gene expression through NPR1?
What is the name of the viral suppressor that inhibits SA-induced gene expression through NPR1?
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Viral suppressors can be utilized as tools to unravel the molecular mechanisms of both antiviral and endogenous RNA silencing.
Viral suppressors can be utilized as tools to unravel the molecular mechanisms of both antiviral and endogenous RNA silencing.
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The use of viral suppressors can aid in the development of transgenic plants in biotechnology.
The use of viral suppressors can aid in the development of transgenic plants in biotechnology.
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Why are viral suppressors important for the arms race between host and pathogen?
Why are viral suppressors important for the arms race between host and pathogen?
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Viral suppressors are only effective against antiviral silencing and not against endogenous silencing.
Viral suppressors are only effective against antiviral silencing and not against endogenous silencing.
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Viral suppressors can only block one or a few steps in the RNA silencing pathway.
Viral suppressors can only block one or a few steps in the RNA silencing pathway.
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The suppressor protein PO from poleroviruses is more effective in suppressing silencing at a single cell level compared to siRNA binding proteins.
The suppressor protein PO from poleroviruses is more effective in suppressing silencing at a single cell level compared to siRNA binding proteins.
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Suppression of antiviral silencing can be detrimental to host endogenous silencing.
Suppression of antiviral silencing can be detrimental to host endogenous silencing.
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Overexpression of VSRs can be a factor in the development of viral symptoms, however VSRs themselves may not be directly responsible for virus-induced symptoms in all cases.
Overexpression of VSRs can be a factor in the development of viral symptoms, however VSRs themselves may not be directly responsible for virus-induced symptoms in all cases.
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Viral suppressors have the potential to be used to develop new plant breeding technologies through epigenetic modifications.
Viral suppressors have the potential to be used to develop new plant breeding technologies through epigenetic modifications.
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The use of natural host-virus pairs is an important approach in the future for furthering our understanding of viral silencing.
The use of natural host-virus pairs is an important approach in the future for furthering our understanding of viral silencing.
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Study Notes
Viral Silencing Suppressors
- RNA silencing is a gene inactivation process regulated by homology-dependent mechanisms, playing a vital role in antiviral defense in biological systems.
- Viruses have evolved viral suppressors of RNA silencing to counteract host antiviral responses, enabling coexistence.
- Viral suppressors of silencing (VSRs) can have other functions besides silencing suppression during viral infection, often in complex ways that are still not fully understood.
- VSRs impact various steps of antiviral silencing in plants, including initiation, effector phase, and amplification.
- Understanding VSRs is important for improving crop plants and for molecular biology/biotechnology applications.
Plant Viruses
- Plant viruses, a significant class of pathogens, reduce crop yield and quality.
- Different types of plant viruses (positive-sense, negative-sense, double-stranded RNA/DNA) utilize different replication strategies.
- Viruses interact with plant host factors to manipulate biochemical events and molecular interactions crucial for virus replication and movement.
- Viruses can spread within plants via plasmodesmata or vascular systems.
- Host defenses against viruses include programmed hypersensitive reaction (HR), systemic acquired resistance (SAR), ubiquitin/26S proteasome system activation (UPS), and RNA silencing.
RNA Silencing Pathways
- RNA silencing is fundamental for gene regulation in eukaryotes, influencing various biological processes.
- It can operate at the transcriptional (TGS) or post-transcriptional (PTGS) levels.
- RNAi pathways involve processing of double-stranded RNA (dsRNA) into small RNAs (sRNAs) by Dicer (DCL).
- sRNAs bind Argonaute proteins, forming RISC (RNA-induced silencing complex) for targeted slicing, transcript repression or amplification of silencing responses .
- sRNAs also bind RITS (RNA-induced transcriptional silencing) for histone/DNA methylation.
Antiviral Silencing Host Factors
- Viral siRNAs (vsiRNAs) are a hallmark of antiviral silencing, produced from various viral dsRNA sources.
- DCL proteins are crucial in the initiation phase processing viral dsRNA into vsiRNAs.
- DCL4 is most critical for RNA virus response, with DCL2 having a supporting role.
- DCL3 plays a minor role against RNA viruses and a more important role in defense against DNA viruses.
- DCL1 is a positive regulator in vsiRNA production, applicable for both RNA and DNA viruses.
Actions of Viral Suppressors of RNA Silencing
- VSRs employ various strategies to evade host silencing, including blocking initiation, arresting RISC assembly, or impairing silencing amplification.
- Some VSRs bind dsRNAs to prevent RISC assembly.
- VSRs can destabilize AGO proteins essential for RISC activity.
- VSRs act on silencing amplification, suppressing RDR functions.
- VSRs can modulate AGO protein levels and homeostasis through silencing pathways.
VSR Interactions with Host Factors
- VSRs can modulate host factors that regulate silencing, affecting hormone signaling or general host defenses (e.g. influencing SA/JA pathways).
- VSRs can interact with other silencing factors, forming complexes to regulate host functions.
- VSRs can regulate the steps of the silencing pathway to their advantage/benefit.
Limitations of VSRs' Suppressor Strength
- Some VSRs may selectively affect antiviral versus endogenous silencing pathways, impacting specific components or pathways in different ways.
VSRs as Tools
- VSRs can be used in molecular research to unravel RNA silencing pathways (antiviral and endogenous).
- VSRs have applications in biotechnology.
- VSRs can be used in diagnostics especially in the detection of microRNAs.
Conclusions
- VSRs play a major regulatory role in the complex interactions between host and pathogen, impacting various host defenses.
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Description
Explore the fascinating world of viral silencing suppressors (VSRs) and their roles in plant antiviral defenses. This quiz delves into how viruses counteract host responses and the implications for crop improvement and biotechnology. Test your knowledge on the interactions between plant viruses and their hosts.
