Limits...
Viral suppressors of RNA silencing hinder exogenous and endogenous small RNA pathways in Drosophila.

Berry B, Deddouche S, Kirschner D, Imler JL, Antoniewski C - PLoS ONE (2009)

Bottom Line: While VSRs in Drosophila melanogaster were shown to inhibit RNAi through different modes of action, whether they act on other silencing pathways remained unexplored.Here we show that expression of various plant and insect VSRs in transgenic flies does not perturb the Drosophila microRNA (miRNA) pathway; but in contrast, inhibits antiviral RNAi and the RNA silencing response triggered by inverted repeat transcripts, and injection of dsRNA or siRNA.Strikingly, these VSRs also suppressed transposon silencing by endogenous siRNAs (endo-siRNAs).

View Article: PubMed Central - PubMed

Affiliation: Institut Pasteur, Drosophila Genetics and Epigenetics, CNRS-URA2578, Paris, France.

ABSTRACT

Background: In plants and insects, RNA interference (RNAi) is the main responder against viruses and shapes the basis of antiviral immunity. Viruses counter this defense by expressing viral suppressors of RNAi (VSRs). While VSRs in Drosophila melanogaster were shown to inhibit RNAi through different modes of action, whether they act on other silencing pathways remained unexplored.

Methodology/principal findings: Here we show that expression of various plant and insect VSRs in transgenic flies does not perturb the Drosophila microRNA (miRNA) pathway; but in contrast, inhibits antiviral RNAi and the RNA silencing response triggered by inverted repeat transcripts, and injection of dsRNA or siRNA. Strikingly, these VSRs also suppressed transposon silencing by endogenous siRNAs (endo-siRNAs).

Conclusions/significance: Our findings identify VSRs as tools to unravel small RNA pathways in insects and suggest a cosuppression of antiviral RNAi and endo-siRNA silencing by viruses during fly infections.

Show MeSH

Related in: MedlinePlus

Hypersensitivity to DCV infection.(A) An Act5C>GAL4 driver line was crossed to UAS>VSR transgenic lines (▪) or to w1118 control strain (□). 20 females from the progeny of these crosses were challenged by an intrathoracic injection of a control Tris solution (---) or a DCV suspension corresponding to 102 LD50 (–) and survival was monitored daily. (B) An hsp>GAL4 driver line was crossed to UAS>VSR transgenic lines. 20 females from the progeny of these crosses were challenged by an injection of the control Tris solution (---) or a the DCV suspension (–) under heat shock (▪) or non heat shock (□) conditions. Plotted values represent the mean±SEM (standard error to the mean) of three independent experiments.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2689938&req=5

pone-0005866-g002: Hypersensitivity to DCV infection.(A) An Act5C>GAL4 driver line was crossed to UAS>VSR transgenic lines (▪) or to w1118 control strain (□). 20 females from the progeny of these crosses were challenged by an intrathoracic injection of a control Tris solution (---) or a DCV suspension corresponding to 102 LD50 (–) and survival was monitored daily. (B) An hsp>GAL4 driver line was crossed to UAS>VSR transgenic lines. 20 females from the progeny of these crosses were challenged by an injection of the control Tris solution (---) or a the DCV suspension (–) under heat shock (▪) or non heat shock (□) conditions. Plotted values represent the mean±SEM (standard error to the mean) of three independent experiments.

Mentions: To further characterize the impact of the suppressors on antiviral RNAi, we tested their effect on fly susceptibility to infection by the Drosophila C virus (DCV), a common Drosophila pathogen. Upon DCV inoculation of wild type flies, 50% of animals died after 6 to 7 days (Fig. 2A). The survival was similar for flies expressing P25, P38, HcPro or P0 under the control of the ubiquitous Actin5C-GAL4 driver (data not shown), paralleling the lack of effect of these proteins on the replication of the FHV RNA1ΔB2. In contrast, flies expressing B2, 1A, P19, P21 and P15 under the control of the ubiquitous Actin5C>GAL4 driver showed a more rapid course of disease and died faster after inoculation with DCV (Fig. 2A and data not shown). Similar results were obtained when these suppressors were expressed under the control of the heat-shock>GAL4 driver after heat shock induction (Fig. 2B). These data show that the B2 and 1A insect VSRs, as well as the P19, P15 and P21 plant VSRs act as potent inhibitors of antiviral RNAi in flies.


Viral suppressors of RNA silencing hinder exogenous and endogenous small RNA pathways in Drosophila.

Berry B, Deddouche S, Kirschner D, Imler JL, Antoniewski C - PLoS ONE (2009)

Hypersensitivity to DCV infection.(A) An Act5C>GAL4 driver line was crossed to UAS>VSR transgenic lines (▪) or to w1118 control strain (□). 20 females from the progeny of these crosses were challenged by an intrathoracic injection of a control Tris solution (---) or a DCV suspension corresponding to 102 LD50 (–) and survival was monitored daily. (B) An hsp>GAL4 driver line was crossed to UAS>VSR transgenic lines. 20 females from the progeny of these crosses were challenged by an injection of the control Tris solution (---) or a the DCV suspension (–) under heat shock (▪) or non heat shock (□) conditions. Plotted values represent the mean±SEM (standard error to the mean) of three independent experiments.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2689938&req=5

pone-0005866-g002: Hypersensitivity to DCV infection.(A) An Act5C>GAL4 driver line was crossed to UAS>VSR transgenic lines (▪) or to w1118 control strain (□). 20 females from the progeny of these crosses were challenged by an intrathoracic injection of a control Tris solution (---) or a DCV suspension corresponding to 102 LD50 (–) and survival was monitored daily. (B) An hsp>GAL4 driver line was crossed to UAS>VSR transgenic lines. 20 females from the progeny of these crosses were challenged by an injection of the control Tris solution (---) or a the DCV suspension (–) under heat shock (▪) or non heat shock (□) conditions. Plotted values represent the mean±SEM (standard error to the mean) of three independent experiments.
Mentions: To further characterize the impact of the suppressors on antiviral RNAi, we tested their effect on fly susceptibility to infection by the Drosophila C virus (DCV), a common Drosophila pathogen. Upon DCV inoculation of wild type flies, 50% of animals died after 6 to 7 days (Fig. 2A). The survival was similar for flies expressing P25, P38, HcPro or P0 under the control of the ubiquitous Actin5C-GAL4 driver (data not shown), paralleling the lack of effect of these proteins on the replication of the FHV RNA1ΔB2. In contrast, flies expressing B2, 1A, P19, P21 and P15 under the control of the ubiquitous Actin5C>GAL4 driver showed a more rapid course of disease and died faster after inoculation with DCV (Fig. 2A and data not shown). Similar results were obtained when these suppressors were expressed under the control of the heat-shock>GAL4 driver after heat shock induction (Fig. 2B). These data show that the B2 and 1A insect VSRs, as well as the P19, P15 and P21 plant VSRs act as potent inhibitors of antiviral RNAi in flies.

Bottom Line: While VSRs in Drosophila melanogaster were shown to inhibit RNAi through different modes of action, whether they act on other silencing pathways remained unexplored.Here we show that expression of various plant and insect VSRs in transgenic flies does not perturb the Drosophila microRNA (miRNA) pathway; but in contrast, inhibits antiviral RNAi and the RNA silencing response triggered by inverted repeat transcripts, and injection of dsRNA or siRNA.Strikingly, these VSRs also suppressed transposon silencing by endogenous siRNAs (endo-siRNAs).

View Article: PubMed Central - PubMed

Affiliation: Institut Pasteur, Drosophila Genetics and Epigenetics, CNRS-URA2578, Paris, France.

ABSTRACT

Background: In plants and insects, RNA interference (RNAi) is the main responder against viruses and shapes the basis of antiviral immunity. Viruses counter this defense by expressing viral suppressors of RNAi (VSRs). While VSRs in Drosophila melanogaster were shown to inhibit RNAi through different modes of action, whether they act on other silencing pathways remained unexplored.

Methodology/principal findings: Here we show that expression of various plant and insect VSRs in transgenic flies does not perturb the Drosophila microRNA (miRNA) pathway; but in contrast, inhibits antiviral RNAi and the RNA silencing response triggered by inverted repeat transcripts, and injection of dsRNA or siRNA. Strikingly, these VSRs also suppressed transposon silencing by endogenous siRNAs (endo-siRNAs).

Conclusions/significance: Our findings identify VSRs as tools to unravel small RNA pathways in insects and suggest a cosuppression of antiviral RNAi and endo-siRNA silencing by viruses during fly infections.

Show MeSH
Related in: MedlinePlus