Antiviral roles of plant ARGONAUTES

[EN] 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. We thank members of the Carrington lab for useful and crucial discussions, and apologize to those colleagues whose work could not be cited because of space and reference limitations. This work was supported by grants from the National Science Foundation (MCB-1231726 and MCB-1330562) and National Institutes of Health (AI043288) to James C Carrington, and from the European Commission (H2020-MSCA-IF-2014-655841) to Alberto Carbonell. Carbonell, A.; Carrington, JC. (2015). Antiviral roles of plant ARGONAUTES. Current Opinion in Plant Biology. 27:111-117. https://doi.org/10.1016/j.pbi.2015.06.013 Meister, G. (2013). Argonaute proteins: functional insights and emerging roles. Nature Reviews Genetics, 14(7), 447-459. doi:10.1038/nrg3462 Poulsen, C., Vaucheret, H., & Brodersen, P. (2013). Lessons on RNA Silencing Mechanisms in Plants from Eukaryotic Argonaute Structures. The Plant Cell, 25(1), 22-37. doi:10.1105/tpc.112.105643 Martínez de Alba, A. E., Elvira-Matelot, E., & Vaucheret, H. (2013). Gene silencing in plants: A diversity of pathways. Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms, 1829(12), 1300-1308. doi:10.1016/j.bbagrm.2013.10.005 Csorba, T., Kontra, L., & Burgyán, J. (2015). viral silencing suppressors: Tools forged to fine-tune host-pathogen coexistence. Virology, 479-480, 85-103. doi:10.1016/j.virol.2015.02.028 Vaucheret, H. (2008). Plant ARGONAUTES. Trends in Plant Science, 13(7), 350-358. doi:10.1016/j.tplants.2008.04.007 Morel, J.-B., Godon, C., Mourrain, P., Béclin, C., Boutet, S., Feuerbach, F., … Vaucheret, H. (2002). Fertile Hypomorphic ARGONAUTE (ago1) Mutants Impaired in Post-Transcriptional Gene Silencing and Virus Resistance. The Plant Cell, 14(3), 629-639. doi:10.1105/tpc.010358 Qu, F., Ye, X., & Morris, T. J. (2008). A