Fig. 2.

SA treatment enhances RDR1-mediated exclusion of TMV from tissue adjacent to the apical meristem. Empty vector control (plants transformed with an ‘empty’ transformation vector), non-transformed and MtRDR1-transgenic plants were treated with 1 mM SA in 0.05 % (v/v) ethanol (+) or a control solution of 0.05 % (v/v) ethanol (-) prior to inoculation with TMV.GFP. By 14 days post-inoculation the upper leaves of all plants with and without SA treatment showed TMV.GFP fluorescence in the upper leaves. However, when leaves were removed from the stem it was apparent under epifluorescence microscopy (a) that spread of TMV.GFP into tissue adjacent to meristems of non-transgenic and control transgenic plants was inhibited by SA treatment and that in MtRDR1-transgenic plants, the virus did not enter stem tissue adjacent to the meristem (scale bar, 2 mm). (b) Stems (with leaves removed) of TMV.GFP infected plants were observed under a UV lamp and photographed with a digital camera, revealing that in MtRDR1-transgenic plants the exclusion of TMV.GFP from stem tissue proximal to the meristem was enhanced in SA-treated plants. Photographs in (a) and (b) are from two independent experiments (scale bar = 1 cm)