Viral RNA silencing suppressors inhibit the microRNA pathway at an intermediate step.

By Elisabeth J. Chapman, Alexey I. Prokhnevsky, K. Gopinath, V. Dolja, James C. Carrington. Genes & Development, 2004

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RNA silencing suppressors from different plant viruses are structurally diverse. In addition to inhibiting the antiviral silencing response to condition susceptibility, many suppressors are pathogenicity factors that cause disease or developmental abnormalities. Here, unrelated suppressors from multiple viruses were shown to inhibit microRNA (miRNA) activities and trigger an overlapping series of severe developmental defects in transgenic Arabidopsis thaliana. This suggests that interference with miRNA-directed processes may be a general feature contributing to pathogenicity of many viruses. A normally labile intermediate in the miRNA biogenesis/RNA-induced silencing complex (RISC) assembly pathway, miRNA*, accumulated specifically in the presence of suppressors (P1/HC-Pro, p21, or p19) that inhibited miRNA-guided cleavage of target mRNAs. Both p21 and p19, but not P1/HC-Pro, interacted with miRNA/miRNA* complexes and hairpin RNA-derived short interfering RNAs (siRNAs) in vivo. In addition, p21 bound to synthetic miRNA/miRNA* and siRNA duplexes in vitro. We propose that several different suppressors act by distinct mechanisms to inhibit the incorporation of small RNAs into active RISCs.

Subfields: Plant Science

View Paper: https://www.semanticscholar.org/paper/37c7d2693495efeaa72d9c52a609c082cee57ddc

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Citations in the corpus

Antiviral immunity directed by small RNAs. (2007, unknown): “Therefore, VSR transgenic plants frequently exhibit recurrent developmental anomalies resembling those of hyl1, ago1, or dcl1 mutants (Chapman et al., 2004; Dunoyer et al., 2004; Zhang et al., 2006; Figure 3D).”
Functions of microRNAs and related small RNAs in plants (2006, background): “The fact that some viral suppressors interfere with both the siRNA-mediated immune response and the miRNA pathway is likely due to an effect on steps shared by the miRNA and siRNA pathway”
Perspective: machines for RNAi. (2005, background): “) Consistent with the view that miRNA are initially born as duplexes, from which the mature miRNA is selected and the miR* strand degraded, p19 protein and another suppressor of RNA silencing, p21 protein, stabilize miR* strands and lead to the accumulation of miR/miR* duplexes in plants (Chapman et”
Plant microRNA: a small regulatory molecule with big impact. (2006, background): “Recently, several studies have shown that these suppressors are involved in the regulation of several miRNA activities (Kasschau et al., 2003; Chen et al., 2004; Chapman et al., 2004; Llave, 2004).”
Post-transcriptional small RNA pathways in plants: mechanisms and regulations. (2006, background): “Viruses also inhibit the miRNA pathway to some extent (Mallory et al. 2002; Kasschau et al. 2003; Chapman et al. 2004; Dunoyer et al. 2004).”
Specificity of ARGONAUTE7-miR390 interaction and dual functionality in TAS3 trans-acting siRNA formation. (2008, methodology): “Immunoprecipitation Immunoprecipitation and subsequent RNA isolation were done using HA antibody (clone 12CA5, Roche) (Chapman et al., 2004).”
Cucumber mosaic virus-encoded 2b suppressor inhibits Arabidopsis Argonaute1 cleavage activity to counter plant defense. (2006, background): “…evolved suppressor proteins to block host RNA silencing at various stages of the siRNA pathways and in many cases miRNA pathways as well (Anandalakshmi et al. 1998; Brigneti et al. 1998; Kasschau and Carrington 1998; Chapman et al. 2004; Chen et al. 2004; Dunoyer et al. 2004; Mlotshwa et al. 2005).”
Roles of plant small RNAs in biotic stress responses. (2009, background): “Indeed, VSRoverexpressing plants often exhibit developmental anomalies typical of miRNA pathway mutants, which are usually considered to be side effects of primary inhibition of vsRNAdirected antiviral silencing (15, 27).”
RNA silencing in plants (2004, background): “However, in most instances, including the prototype HCPro suppressor from potyviruses, there are conflicting data about their mechanism of actio”
MicroRNAS and their regulatory roles in plants. (2006, background): “In addition, plants that express certain viral inhibitors of small RNA processing or function, such as HC-Pro and P19, exhibit developmental defects reminiscent of dcl1 mutants (26, 28, 36, 55, 86).”
MicroRNA-Directed Regulation of Arabidopsis AUXIN RESPONSE FACTOR17 Is Essential for Proper Development and Modulates Expression of Early Auxin Response Genesw⃞ (2005, background): “…2004; Vazquez et al., 2004a), and plants expressing viral suppressors of gene silencing that alter miRNA accumulation (Mallory et al., 2002; Kasschau et al., 2003; Chapman et al., 2004; Chen et al., 2004; Dunoyer et al., 2004) display dramatic anomalies during vegetative and floral development.”
RNA silencing: Methods and protocols (2006, background): “It is intriguing that Cucumber mosaic virus, a cytoplasmic RNA virus, codes for a nuclear protein (2b) that suppresses RNA silencing (8, 30) and also interferes with RNA-directed DNA methylation (14).”