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Slow heating of barley aleurone layers to heat-shock temperature preserves heat-shock-sensitive cellular properties¹

Department of Biology, Knox College, Galesburg, Illinois 61401 USA

In barley (Hordeum vulgare L. cv. Himalaya) aleurone layers, heat shock causes the selective suppression of -amylase synthesis by destabilizing this secretory protein's mRNA. The lamellar stacks of the endoplasmic reticulum (ER), which serve as the site of -amylase mRNA translation, are dissociated by heat shock, suggesting that heat-shock-induced changes in ER may be important in selectively targeting -amylase mRNAs for destabilization. We have found that samples maintained at heat-shock temperature (40°C) for 18 h recover the ability to synthesize -amylase and that the ER membranes in these samples contain membrane phospholipids with enhanced levels of fatty acid saturation. This present study investigated whether gradual warming to 40°C over 3–6 h (ramping) would preserve -amylase synthesis by permitting ER membrane phospholipid retailoring during the gradual temperature increase. Analyses by sodium dodecyl-sulfate polyacrylamide gel electrophoresis revealed that -amylase synthesis was markedly increased in ramped samples. Furthermore, northern hybridization analyses and transmission electron microscopy showed that these samples had increased -amylase mRNA levels and stacks of ER lamellae, respectively. Gas chromatographic analyses of ER membrane phospholipids indicated that the fatty acids of ramped samples were more saturated than their heat-shocked counterparts. These data indicate that heat-induced increases in aleurone ER membrane phospholipid fatty acid saturation may be important in maintaining secretory protein expression at normally nonpermissive heat-shock temperatures.

Key Words: -amylase • barley aleurone layer • endoplasmic reticulum • heat shock • heat stress • mRNA stability • phospholipid fatty acid saturation • thermotolerance

This article has been cited by other articles:

				M. K. Johnston, N. P. Jacob, and M. R. Brodl Heat Shock-Induced Changes in Lipid and Protein Metabolism in the Endoplasmic Reticulum of Barley Aleurone Layers Plant Cell Physiol., January 1, 2007; 48(1): 31 - 41. [Abstract] [Full Text] [PDF]

				A. E. Shaw and M. R. Brodl Heat shock response of warm-incubated barley aleurone layers Am. J. Botany, January 1, 2003; 90(1): 40 - 48. [Abstract] [Full Text] [PDF]