AUTHOR=Shen Wan-Xia , Au Phil Chi Khang , Shi Bu-Jun , Smith Neil A. , Dennis Elizabeth S. , Guo Hui-Shan , Zhou Chang-Yong , Wang Ming-Bo 

TITLE=Satellite RNAs interfere with the function of viral RNA silencing suppressors

JOURNAL=Frontiers in Plant Science

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2015.00281

DOI=10.3389/fpls.2015.00281

ISSN=1664-462X

ABSTRACT=<p>Viral satellite RNAs (satRNAs) are small subviral RNAs and depend on the helper virus for replication and spread. satRNAs can attenuate helper virus-induced symptoms, the mechanism of which remains unclear. Here, we show that two virus-encoded suppressors of RNA silencing (VSRs), <italic>Cucumber mosaic virus</italic> (CMV) 2b and <italic>Tombusvirus</italic> P19, suppress hairpin RNA (hpRNA)-induced silencing of a <italic>β-glucuronidase</italic> (GUS) gene in <italic>Nicotiana benthamiana</italic>. This suppression can be overcome by CMV Y-satellite RNA (Y-Sat) via the Y-Sat-derived small interfering RNAs (siRNAs), which bind to the VSRs and displace the bound hpGUS-derived siRNAs. We also show that microRNA target gene expression in <italic>N. tabacum</italic> was elevated by CMV infection, presumably due to function of the 2b VSR, but this upregulation of microRNA target genes was reversed in the presence of Y-Sat. These results suggest that satRNA infection minimizes the effect of VSRs on host siRNA and microRNA-directed silencing. Our results suggest that the high abundance of satRNA-derived siRNAs contributes to symptom attenuation by binding helper virus-encoded VSRs, minimizing the capacity of the VSRs to bind host siRNA and miRNA and interfere with their function.</p>