The Influence of RNA-Dependent RNA Polymerase 1 on Potato virus Y Infection and on Other Antiviral Response Genes

Abstract

The gene encoding RNA-dependent RNA polymerase 1 (RDR1) is involved in basal resistance to several viruses. Expression of the RDR1 gene also is induced in resistance to Tobacco mosaic virus (TMV) mediated by the N gene in tobacco (Nicotiana tabacum cv. Samsun NN) in an incompatible hypersensitive response, as well as in a compatible response against Potato virus Y (PVY). Reducing the accumulation of NtRDR1 transcripts by RNA inhibition mediated by transgenic expression of a double-stranded RNA hairpin corresponding to part of the RDR1 gene resulted in little or no induction of accumulation of RDR1 transcripts after infection by PVY. Plants with lower accumulation of RDR1 transcripts showed much higher accumulation levels of PVY. Reduced accumulation of NtRDR1 transcripts also resulted in lower or no induced expression of three other antiviral, defense-related genes after infection by PVY. These genes encoded a mitochondrial alternative oxidase, an inhibitor of virus replication (IVR), and a transcription factor, ERF5, all involved in resistance to infection by TMV, as well as RDR6, involved in RNA silencing. The extent of the effect on the induced NtIVR and NtERF5 genes correlated with the extent of suppression of the NtRDR1 gene.

RNA-Dependent RNA Polymerase 1 from Nicotiana tabacum Suppresses RNA Silencing and Enhances Viral Infection in Nicotiana benthamiana

“…The fact that downregulation of Nt-RDR1 in transgenic tobacco enhanced susceptibility to PVX and PVY (Xie et al, 2001;Rakhshandehroo et al, 2009) contrasts with our result that PVX and PVY accumulation and symptoms were enhanced in N. benthamiana expressing Nt-RDR1 compared with wildtype N. benthamiana (Figure 6). These results suggest that PVX and PVY are restricted in tobacco by an efficient RDR1-and SA-mediated defense pathway, but this antiviral mechanism was not able to compensate for the suppression of the RDR6-mediated antiviral silencing in the Nt-RDR1-expressing N. benthamiana plants.…”

Characterization of a Viral Synergism in the MonocotBrachypodium distachyonReveals Distinctly Altered Host Molecular Processes Associated with Disease

“…Brachypodium has seven DCL, four DRB, two HEN, 14 AGO, six RDR, and three SILENCING DEFECTIVE3 (SDE3)-like genes (data not shown). In contrast with the Pepino mosaic virus, Turnip yellow mosaic virus, and PVY responses (Rakhshandehroo et al, 2009;Hanssen et al, 2011;Jakubiec et al, 2012), expression of DCL, DRB, AGO, HEN, and RDR genes in Brachypodium was not affected by PMV or PMV+SPMV infections (data not shown), although we cannot rule out changes in protein level or activity or changes that occur transiently. However, expression of an SDE3-like helicase was suppressed in both PMV and PMV+SPMV infections (Supplemental Table S1).…”

“…For example, tomato (Solanum lycopersicum) plants infected with Pepino mosaic virus, a Potexvirus, activates multiple Dicer-like (DCL) and AGO genes during the infection (Hanssen et al, 2011). Similarly, Arabidopsis DRB4 expression is induced upon infection of Turnip yellow mosaic virus (Jakubiec et al, 2012), and expression of RDR1 is up-regulated in tobacco plants infected with Tobacco mosaic virus (Xie et al, 2001) and PVY (Rakhshandehroo et al, 2009). Brachypodium has seven DCL, four DRB, two HEN, 14 AGO, six RDR, and three SILENCING DEFECTIVE3 (SDE3)-like genes (data not shown).…”

Effects of DICER-like proteins 2, 3 and 4 on cucumber mosaic virus and tobacco mosaic virus infections in salicylic acid-treated plants

“…Furthermore, RNA-dependent RNA polymerase 1 (RDR1), a component of the antiviral RNA silencing machinery, is induced by SA treatment and tobacco mosaic virus (TMV) infection (Gilliland et al, 2003;Xie et al, 2001;Yang et al, 2004;Yu et al, 2003). Inhibition of RDR1 expression results in hypersusceptibility to certain RNA viruses, including TMV and potato virus Y (Rakhshandehroo et al, 2009;Xie et al, 2001;Yang et al, 2004;Yu et al, 2003). Additionally, there is evidence that SA potentiates RNA silencing against the potyvirus plum pox virus in tobacco (Alamillo et al, 2006).…”