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Review
. 2015 Oct:27:111-7.
doi: 10.1016/j.pbi.2015.06.013. Epub 2015 Jul 17.

Antiviral roles of plant ARGONAUTES

Alberto Carbonell  1 , James C Carrington  2
Affiliations
Review

Antiviral roles of plant ARGONAUTES

Alberto Carbonell et al. Curr Opin Plant Biol. 2015 Oct.

Abstract

ARGONAUTES (AGOs) are the effector proteins functioning in eukaryotic RNA silencing pathways. AGOs associate with small RNAs and are programmed to target complementary RNA or DNA. Plant viruses induce a potent and specific antiviral RNA silencing host response in which AGOs play a central role. Antiviral AGOs associate with virus-derived small RNAs to repress complementary viral RNAs or DNAs, or with endogenous small RNAs to regulate host gene expression and promote antiviral defense. Here, we review recent progress towards understanding the roles of plant AGOs in antiviral defense. We also discuss the strategies that viruses have evolved to modulate, attenuate or suppress AGO antiviral functions.

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Conflict of interest statement

Conflict of interest

There is no conflict of interest relating to this article.

Figures

Figure 1
Figure 1
ARGONAUTE functions in plant antiviral RNA silencing. (a) AGOs programmed with vsiRNAs repress viral RNA through slicing or translation inhibition in PTGS, or through hypermethylation of viral DNA in TGS. AGO1 and AGO2 are the main antiviral AGOs against RNA viruses, with AGO5, AGO7 and AGO10 having minor roles in some cases. AGO4 is the main antiviral AGO against DNA viruses. (b–d) AGOs programmed with plant small RNAs promote antiviral defense. (b) In Arabidopsis, virus infection triggers the production of endogenous vasiRNAs that work mainly through AGO2 to repress transcripts from genes mostly related to response to biotic and abiotic stimuli and ribosomal RNA. (c) In rice, plant virus infection induces the accumulation of AGO18 which sequesters miR168 away from AGO1, and consequently induces AGO1 accumulation at elevated levels necessary for antiviral defense. (d) In infected Arabidopsis, AGO4 can bind to plant small RNAs to regulate host transcriptional response to infection and promote antiviral defense. Light blue and grey boxes include steps in PTGS or TGS, respectively.
Figure 2
Figure 2
Viral strategies to modulate or suppress plant RNA silencing. (a) VsiRNAs hijack plant AGOs to target sufficiently complementary host transcripts and induce symptoms. (b) Virus encoded VSRs suppress AGO functions at multiple levels. VSRs can impede AGO association with vsiRNAs, promote AGO degradation, down-regulate AGO1 levels by interfering with its homeostasis or inactivate programmed AGO/vsiRNA complexes. Light blue and grey boxes include steps unique to PTGS or TGS, respectively.
See this image and copyright information in PMC

References

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