Northern blot analysis of PVX genomic and subgenomic RNAs in systemically infected N. benthamiana plants. RNA samples (5 μg) were extracted from leaves of mock-inoculated plants (lane 1) and plants infected with PVX/GFP (lane 2), PVX/C2-GFP (lane 3), PVX/C21-31-GFP (lane 4), PVX/C217-31-GFP (lane 5), PVX/C2-K17D-GFP (lane 6), PVX/C2-HR21DV-GFP (lane 7), PVX/C2-KK25DI-GFP (lane 8), and PVX/C2-RRRR31DVGG-GFP (lane 9) and harvested 13 days p.i. Blots were hybridized with DIG-labeled probes specific for C2 (A) and gfp (B) sequences. Equal loading of samples was verified by ethidium bromide staining of host ribosomal rRNA. The positions of PVX genomic (g) and subgenomic (sg) RNAs are indicated.