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.
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机译:比较了在有或没有赤霉素(GA3)的条件下孵育的大麦(大麦(Hordeum vulgare L. cv Hi-malaya))糊粉层的热激响应。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳显示,热激阻止了GA3处理层而非未处理层的分泌蛋白的合成和分泌。分泌蛋白合成的这种抑制与内质网(ER)膜的变化有关(FC Belanger,MR Brodl,T.-hD Ho [1986] Proc Natl Acad Sci USA 83:1354-1358; L. Sticher,AK Biswas ,DS Bush,RL Jones [1990] Plant Physiol 92:506-513)。我们的分泌数据表明,未经GA3孵育的糊粉层的ER膜可能更耐热。为了对此进行研究,检查了用[14C]甘油标记的糊粉层中膜提取物的脂质谱。热激显着增加了[14C]甘油掺入磷脂酰胆碱(PC)中的含量,气相色谱显示在GA3处理的层中与薄层色谱纯化的PC相关的饱和脂肪酸的量增加。相反,在常温下不加GA3的情况下孵育的糊粉层所含的PC相关脂肪酸的饱和度要高于GA3处理的层。热激适度增加了未经处理的糊粉层中脂肪酸的饱和度。从通过连续蔗糖密度离心纯化的ER膜分离的脂肪酸中也注意到了相同的趋势。我们提出增加的脂肪酸饱和度可能有助于在没有GA3的情况下孵育的热激糊粉层中维持ER膜功能。
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