PLANT PHYSIOLOGY , Vol 113, Issue 4 1253-1263, Copyright © 1997 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
RNase Activity Decreases following a Heat Shock in Wheat Leaves and Correlates with Its Posttranslational Modification
S. C. Chang and D. R. Gallie
Department of Biochemistry, University of California, Riverside, California 92521-0129
Heat shock results in a coordinate loss of translational efficiency and an
increase in mRNA stability in plants. The thermally mediated increase in
mRNA half-life could be a result of decreased expression and/or regulation
of intracellular RNase enzyme activity. We have examined the fate of both
acidic and neutral RNases in wheat seedlings that were subjected to a
thermal stress. We observed that the activity of all detectable RNases
decreased following a heat shock, which was a function of both the
temperature and length of the heat shock. In contrast, no reduction in
nuclease activity was observed following any heat-shock treatment.
Antibodies raised against one of the major RNases was used in western
analysis to demonstrate that the RNase protein level did not decrease
following a heat shock, and the data suggest that the observed decrease in
RNase activity in heat-shocked leaves may be due to modification of the
protein. Two-dimensional gel/western analysis of this RNase revealed three
isoforms. The most acidic isoform predominated in control leaves, whereas
the most basic isoform predominated in leaves following a heat shock and
correlated with the heat-shock-induced reduction in RNase activity and
increase in mRNA half-life. These data suggest that RNase activity may be
regulated posttranslationally following heat shock as a means to reduce RNA
turnover until recovery ensues.
