FIG. 2.

Detection by Northern blot analysis of the CChMVd-specific small RNAs associated with PTGS. Nucleic acid preparations from leaves of healthy (H) chrysanthemum plants and those infected with a nonsymptomatic (NS) or a symptomatic (S) strain of CChMVd were separated in a 15% denaturing polyacrylamide gel and hybridized with full-length radioactive riboprobes for the detection of positive and negative viroid strands. Positions of the 24- and 20-mer DNA markers are at the right, and the signals corresponding to the small RNAs are indicated by an arrowhead at the left. The bands visible in the upper part of the gel lanes containing the infected extracts are mainly generated by unit- and shorter-than-unit-length CChMVd RNAs. The weak signals observed in the upper part of the gel lanes containing the healthy extracts result from nonspecific hybridization.