FIG. 4.

Autoradiogram of a Northern blot with RNA samples incubated under both self-cleavage and non-self-cleavage conditions. Lane 1, synthetic, minus-strand, monomeric PLMVd without snap-cooling; lane 2, RNA sample from healthy leaves incubated without snap-cooling; lanes 3 and 4, RNA samples from healthy leaves mixed with 0.5 ng of synthetic 3′,5′-C-PLMVd transcripts (of positive polarity) and incubated without and with snap-cooling, respectively; lanes 5 and 6, RNA samples isolated from PLMVd-infected leaves either without or with prior self-cleavage, respectively. Adjacent to the gel, the positions of the C-PLMVd and L-PLMVd transcripts are used as size references, and ori indicates the origin. The panels including lanes 1 and 2 and lanes 5 and 6 were overexposed in order to allow for the detection of any trace products.