CMV and PVY, but not PVX, suppress PTGS in TSC. RNA blot hybridization
with a CHN cDNA probe and immunoblot analyses of leaves
from sibling STSC plants (STSC1–STSC4). Tissues were harvested from
the inoculated leaf just before inoculation (0), from leaves showing
systemic virus infection 10–15 DPI (V), and from leaves showing
systemic virus infection 2 days later after treatment of plants with
20-ppm ethylene (+ET). Total RNA (10 μg) was hybridized with a
CHN48 cDNA probe, which detects CHN48 and
CHN50 RNA (CHN RNA). The double bands detected with the
probe have been described earlier and may result from alternative
polyadenylation (26). Equal loading was confirmed by rehybridization
with a probe for 18S rRNA. Immunoblot analyses of equal volumes of
protein extracts of the same tissues used for RNA analyses are shown at
the bottom. The positions of the class I chitinases CHN48, its
truncated form ΔCHN48 and CHN50, and the class II chitinases (CHN II)
are indicated.