PLANT PHYSIOLOGY , Vol 110, Issue 2 571-581, Copyright © 1996 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Effect of Gibberellin and Heat Shock on the Lipid Composition of Endoplasmic Reticulum in Barley Aleurone Layers
K. K. Grindstaff, L. A. Fielding and M. R. Brodl
Department of Biology, Knox College, Galesburg, Illinois 61401
The heat-shock responses of barley (Hordeum vulgare L. cv Hi- malaya)
aleurone layers incubated with or without gibberellic acid (GA3) were
compared. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis
revealed that heat shock blocked the synthesis and secretion of secretory
proteins from GA3-treated layers but not untreated layers. This suppression
of secretory protein synthesis has been correlated with changes in
endoplasmic reticulum (ER) membranes (F.C. Belanger, M. R. Brodl, T.-h.D.
Ho [1986] Proc Natl Acad Sci USA 83: 1354-1358; L. Sticher, A.K. Biswas,
D.S. Bush, R.L. Jones [1990] Plant Physiol 92: 506-513). Our secretion data
suggested that the ER membranes of aleurone layers incubated without GA3
may be more heat shock tolerant. To investigate this, the lipid profiles of
membrane extracts in aleurone layers labeled with [14C]glycerol were
examined. Heat shock markedly increased [14C]glycerol incorporation into
phosphatidylcholine (PC), and gas chromatography revealed an increase in
the amount of saturated fatty acids associated with thin layer
chromatography-purified PC in GA3-treated layers. In contrast, aleurone
layers incubated without GA3 at normal temperature contained PC-associated
fatty acids with a greater degree of saturation than GA3-treated layers.
Heat shock modestly increased the degree of fatty acid saturation in
untreated aleurone layers. This same trend was noted in fatty acids
isolated from ER membranes purified by continuous sucrose density
centrifugation. We propose that increased fatty acid saturation may help
sustain ER membrane function in heat-shocked aleurone layers incubated in
the absence of GA3.
