Behzadipour M, Ratajczak R, Faist K, Pawlitschek P, Trémolières A, Kluge M
Institut für Botanik, Technische Universität Darmstadt, Schnittspahnstrasse 10, D-64287 Darmstadt, Germany.
J Membr Biol. 1998 Nov 1;166(1):61-70. doi: 10.1007/s002329900447.
The present study deals with the phenotypic adaptation of tonoplast fluidity in the CAM plant Kalanchoë daigremontiana to changes in growth temperature. Tonoplast fluidity was characterized by measuring fluorescence depolarization in membranes labeled with fluorescent fatty acid analogues and by following formation of eximeres in membranes labeled by eximere-forming fluorophores. With both techniques it was found that exposure of the plants to higher growth temperature compared with the control decreased the fluidity of the tonoplast while exposure to lower growth temperature caused the opposite. Three hours of high temperature treatment (raised from 25 degreesC to 35 degreesC; "heat shock") were sufficient to decrease the tonoplast fluidity to roughly the same extent as growth under high temperature for 30 days. The phenotypic response of tonoplast fluidity to changes in growth temperature was found only in the complete membrane, not however in the lipid matrix deprived of the membrane proteins. Heat treatments of the plants decreased the lipid/protein ratio while exposure to low temperature (for 30 days) increased it. Heat treatments led to a decrease in the percentage of linolenic acid (C18:3) and linoleic acid (C18:2), heat shock and low temperature treatments induced an increase in the percentage of linoleic acid (C18:3), with concomitant decrease in the percentage of linoleic acid (C18:2). However, in the case of heat shock, increase in linolenic acid concerned mainly monogalactosyldiacylglycerol, while with low temperature treatment linoleic acid increased in phosphatidylcholine. Both treatment of the plants with high and low temperature led to a slight decrease in the contribution of phosphatidylcholine and phosphoethanolamine to the total phospholipid content of the tonoplast. High-temperature treatment of the plants not only decreased the phospholipid/protein ratio in the tonoplast, but also led to the occurrence of a 35 kDa polypeptide in the tonoplast which cross-reacted with an antiserum against the tonoplast H+-ATPase holoenzyme. The important role of membrane proteins in bringing about the phenotypic rigidization of the tonoplast was mimicked by reconstitution experiments showing that incorporation of the proteins isolated from the tonoplast into phosphatidylcholine vesicles decreased the fluidity of this membrane system. As to be expected from the analyses in the natural membrane, the degree of this effect depended on the phospholipid/protein ratio.
本研究探讨了景天科酸代谢（CAM）植物落地生根液泡膜流动性对生长温度变化的表型适应性。通过测量用荧光脂肪酸类似物标记的膜中的荧光去极化以及跟踪用形成准分子的荧光团标记的膜中准分子的形成来表征液泡膜流动性。使用这两种技术均发现，与对照相比，将植物暴露于较高生长温度会降低液泡膜的流动性，而暴露于较低生长温度则会产生相反的效果。三小时的高温处理（从25℃升至35℃；“热激”）足以使液泡膜流动性降低到与在高温下生长30天大致相同的程度。仅在完整膜中发现了液泡膜流动性对生长温度变化的表型反应，而在去除膜蛋白的脂质基质中未发现。对植物进行热处理会降低脂质/蛋白质比率，而暴露于低温（30天）则会使其升高。热处理导致亚麻酸（C18:3）和亚油酸（C18:2）的百分比降低，热激和低温处理导致亚麻酸（C18:3）百分比增加，同时亚油酸（C18:2）百分比降低。然而，在热激的情况下，亚麻酸的增加主要涉及单半乳糖基二酰基甘油，而在低温处理时，亚油酸在磷脂酰胆碱中增加。高温和低温处理植物均导致磷脂酰胆碱和磷酸乙醇胺在液泡膜总磷脂含量中的贡献略有降低。对植物进行高温处理不仅会降低液泡膜中的磷脂/蛋白质比率，还会导致液泡膜中出现一种35 kDa的多肽，该多肽与抗液泡膜H + -ATPase全酶的抗血清发生交叉反应。重组实验模拟了膜蛋白在导致液泡膜表型僵化方面的重要作用，该实验表明，将从液泡膜中分离的蛋白质掺入磷脂酰胆碱囊泡中会降低该膜系统的流动性。正如从天然膜分析中所预期的那样，这种效应的程度取决于磷脂/蛋白质比率。
