RNase Activity Decreases following a Heat Shock in Wheat Leaves and Correlates with Its Posttranslational Modification |
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| Authors: | Chang S. C. Gallie D. R. |
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| Affiliation: | Department of Biochemistry, University of California, Riverside, California 92521-0129. |
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| Abstract: | 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. |
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