Virus-induced diseases cause severe damage to cultivated plants, resulting in crop losses. Certain plant–virus interactions allow disease recovery at later stages of infection and have the potential to reveal important molecular targets for achieving disease control. Although recovery is known to involve antiviral RNA silencing1,2, the specific components of the many plant RNA silencing pathways3 required for recovery are not known. We found that Arabidopsis thaliana plants infected with oilseed rape mosaic virus (ORMV) undergo symptom recovery. The recovered leaves contain infectious, replicating virus, but exhibit a loss of viral suppressor of RNA silencing (VSR) protein activity. We demonstrate that recovery depends on the 21–22 nt siRNA-mediated post-transcriptional gene silencing (PTGS) pathway and on components of a transcriptional gene silencing (TGS) pathway that is known to facilitate non-cell-autonomous silencing signalling. Collectively, our observations indicate that recovery reflects the establishment of a tolerant state in infected tissues and occurs following robust delivery of antiviral secondary siRNAs from source to sink tissues, and establishment of a dosage able to block the VSR activity involved in the formation of disease symptoms.
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This work was supported by funding from the Swiss National Science Foundation (SNF, grant 124940 and 144084 to MH, grant 126329 to FV), the Agence National de la Recherche Scientifique (ANR, grants ANR-08-BLAN-0244 and ANR-13-KBBE-005 to M.H.), the Région Alsace (PhD fellowship to N.P.) and the Centre National de la Recherche Scientifique (CNRS, grant PICS06702 to E.J.P. and M.H.). We would like to thank E. Bucher and T. Blevins for helpful discussions and suggestions, and P. Dunoyer and R. Stadler for providing the SUC:SUL and SUC:GFP Arabidopsis lines, respectively. We thank P. Dunoyer for also providing the Col-0 lines expressing the TBSV p19 and the BYV p21 VSRs. We are grateful to M. Pooggin (INRA, Montpellier) for the anti-P125/P182 antibody. Furthermore, we would like to thank M. Böhrer and T. Blevins for their support with RNA blotting and hybridization, and M. DiDonato, A. Niehl, K. Amari and D. Windels for other technical assistance, discussions and critical comments.
The authors declare no competing interests.
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Kørner, C.J., Pitzalis, N., Peña, E.J. et al. Crosstalk between PTGS and TGS pathways in natural antiviral immunity and disease recovery. Nature Plants 4, 157–164 (2018). https://doi.org/10.1038/s41477-018-0117-x
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