Figure 3.

Expression of PSTVd-related RNAs in transgenic N. benthamiana. Total cellular RNA isolated from PSTVd-infected plants was fractionated by electrophoresis under denaturing conditions, and duplicate blots were hybridized with probes specific for either (+)PSTVd (Left) or (−)PSTVd (Right) RNAs. Samples isolated from transgenic plants (lanes 3–6) contained equal amounts (≈50 pg) of (+) or (−)PSTVd RNAs. The purified (+) and (−)PSTVd RNA transcripts analyzed in lanes 1, 2, 7, and 8 provide mobility standards for circular (C) and linear (L) molecules; samples in lanes 2 and 8 were incubated with wheat germ extract before analysis. Note that monomeric linear (−)PSTVd RNA (arrow) is only detectable in those plants in which it is expressed constitutively. The light area visible in lanes 4–6 (Right) opposite the circular standard in lane 8 is caused by the presence of large amount of circular (+)PSTVd progeny migrating at that position.