RNA-dependent RNA polymerase 1 in potato (Solanum tuberosum) and its relationship to other plant RNA-dependent RNA polymerases

Abstract

Cellular RNA-dependent RNA polymerases (RDR) catalyze synthesis of double stranded RNAs that can serve to initiate or amplify RNA silencing. Arabidopsis thaliana has six RDR genes; RDRs 1, 2 and 6 have roles in anti-viral RNA silencing. RDR6 is constitutively expressed but RDR1 expression is elevated following plant treatment with defensive phytohormones. RDR1 also contributes to basal virus resistance. RDR1 has been studied in several species including A. thaliana, tobacco (Nicotiana tabacum), N. benthamiana, N. attenuata and tomato (Solanum lycopersicum) but not to our knowledge in potato (S. tuberosum). StRDR1 was identified and shown to be salicylic acid-responsive. StRDR1 transcript accumulation decreased in transgenic potato plants constitutively expressing a hairpin construct and these plants were challenged with three viruses: potato virus Y, potato virus X, and tobacco mosaic virus. Suppression of StRDR1 gene expression did not increase the susceptibility of potato to these viruses. Phylogenetic analysis of RDR genes present in potato and in a range of other plant species identified a new RDR gene family, not present in potato and found only in Rosids (but apparently lost in the Rosid A. thaliana) for which we propose the name RDR7.LJRH was supported by a studentship co-funded by the James Hutton Institute (formerly Scottish Crop Research Institute) and the UK Biotechnological and Biological Sciences Research Council (BBSRC). Work in the JPC lab is funded by The Leverhulme Trust (RPG-2012-667), BBSRC (BB/D014376/1, BB/J011762/1) and the Cambridge University Newton Trust. SFB was funded by Leverhulme grant F/09-741/G to Professor Beverley Glover. KG was funded by an EMBO Short Term Fellowship. Work in the PP lab is funded by grant number NRF-2013R1A2A2A01016282 from the Korean National Research Foundation.This is the author accepted manuscript. The final version is available from Nature Publishing Group via https://doi.org/10.1038/srep2308