Fig. 3.

The effects of MtRDR1 expression and SA treatment on the recovery of N. benthamiana plants from TMV-induced plant death. a Five-week-old transgenic control (plants transformed with an ‘empty’ transformation vector: EV-control) and MtRDR1-transgenic (MtRDR1) plants were pre-treated with a solution of 1 mM SA in 0.05 % (v/v) ethanol (+SA) or a 0.05 % (v/v) ethanol control solution prior to inoculation with TMV U1. Plants were monitored over a 5-week period and the number of plants killed by the virus recorded. With the transgenic control plant group, TMV U1 had killed all plants within 31 days of inoculation. Pre-treatment with 1 mM SA delayed plant death by a few days but did not prevent it. TMV U1-induced plant death was suppressed in all the MtRDR1-expressing N. benthamiana plants, regardless of whether they were treated with water or with SA. b Symptoms at 75 days post-inoculation with TMV U1 in transgenic control and MtRDR1-transgenic N. benthamiana plants. MtRDR1-transgenic plants pre-treated with SA (+) or treated with control solution (-) recovered but SA-treated plant growth was more vigorous (scale bar = 8 cm). Data and photographs are from one experiment, out of a total of four independent experiments. c Western blot analysis of TMV using anti-TMV coat protein (TMV CP) serum shows that TMV was present in the newly emerged, green leaf tissue in recovering MtRDR1-transgenic plants treated with SA (+) or control solution (-). Leaf samples taken at 75 days post-inoculation or mock-inoculation (each lane is loaded with protein extracted from one plant). Equal loading was confirmed by Ponceau S staining of the western blot membrane with the position of the ribulose 1,5-bisphosphate carboxylase/oxygenase large subunit (LSU) indicated