RNA gel blot analysis of siRNAs in ihprolC-PP197 transgenic plants. Panel A. Northern blot analysis of siRNAs in T0 plants. Low molecular weight RNA was isolated from control untransformed plant (lane 1) and transgenic lines 29, 2, 9, 8 and 13 (lanes 2, 3, 4, 5 and 6, respectively). Panel B. Northern blot analysis of siRNAs in T1 plants. Low molecular weight RNA isolated from untransformed control plant (lane 1) and transgenic lines 2, 9 and 13 (lanes 2, 3 and 4, respectively). Approximatly 40 μg of low molecular weight RNA per sample was loaded. SiRNAs were detected by hybridisation with hydrolised single stranded 32P-labeled RNA probe corresponding to the 134–330 region of the PPV genome. 21 and 23 nt-long RNA oligoribonucleotides were used as molecular standards.