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 (RDRs) 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.

Differential expression of cucumber RNA‐dependent RNA polymerase 1 genes during antiviral defence and resistance

“…The role of CsRDR1a in defence against virus infection is less clear, as it was induced only moderately, in line with the induction levels described for RDR1 from plants that contain only a single RDR1 (Alamillo et al ., ; Rakhshandehroo et al ., ; Xie et al ., ; Yu et al ., ), or two almost identical RDR1 s (e.g. potato and barley) (Hunter et al ., ; Madsen et al ., ).…”

“…Furthermore, the absence of a functional RDR1 in N. benthamiana can explain the enhanced susceptibility of this species to many plant viruses (Yang et al, 2004). However, suppression of RDR1 in potato is not associated with increased virus susceptibility (Hunter et al, 2016). By contrast, the constitutive expression of RDR1, observed in a transgenic cucumber Line 823 (Cucumis sativus L.), causes broad potyvirus resistance (Leibman et al, 2011).…”

Quantitative trait loci affecting intensity of violet flower colour in potato

“…Two genes encoding RDR1, StRDR1a (PGSC0003DMG400031261) and StRDR1b (PGSC0003DMG400031261), have been identified in the potato reference genome DM 1-3 on chromosome V (Hunter et al 2016). The location of those genes on reference physical map did not correspond precisely to our genetic map data (Table 2).…”

“…The location of those genes on reference physical map did not correspond precisely to our genetic map data (Table 2). Hunter et al (2016) (Hunter et al 2016). Plant RDRs are grouped in seven families (Hunter et al 2016) and their functions include those processes where dsRNA and siRNAs are involved: development, reproduction, biotic and abiotic stress responses.…”

“…Hunter et al (2016) (Hunter et al 2016). Plant RDRs are grouped in seven families (Hunter et al 2016) and their functions include those processes where dsRNA and siRNAs are involved: development, reproduction, biotic and abiotic stress responses. The RDR6 in A. thaliana has been associated with siRNA-producing locus TAS4, which produces ta-siRNAs that target transcripts of MYB transcription factors regulating enzymes in the anthocyanin biosynthesis (Willmann et al 2011).…”