FORMATION OF OLEOSOMES (STORAGE LIPID BODIES) DURING EMBRYOGENESIS AND THEIR BREAKDOWN DURING SEEDLING DEVELOPMENT IN COTYLEDONS OF SINAPIS-ALBA L
FORMATION OF OLEOSOMES (STORAGE LIPID BODIES) DURING EMBRYOGENESIS AND THEIR BREAKDOWN DURING SEEDLING DEVELOPMENT IN COTYLEDONS OF SINAPIS-ALBA L
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DOI：
10.1007/bf00392002
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发表时间：
1978-01-01
期刊：
影响因子：
4.3
通讯作者：
SCHOPFER, P
中科院分区：
文献类型：
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作者：
BERGFELD, R;HONG, YN;SCHOPFER, P
对发育中的芥子子叶进行的电子显微镜和生化研究，没有为普遍接受的假设提供证据，即储脂组织的油小体起源于内质网，并被单位或半单位膜所包围。授粉后12-14天，第一个脂滴出现在靠近叶绿体表面的细胞质中。随后，这些新生的脂滴在这个阶段缺乏任何可检测到的边界结构，被粗面内质网池包围。同时，在脂质/水界面上可以检测到厚度约为3 nm的嗜奥斯膜。在萌发幼苗的子叶细胞中，脂肪降解的离心式前锋从中央液泡(S)向细胞外围移动，留下塌陷的油小体外壳，其脂质含量被耗尽(球囊)。虽然球囊在横截面上看起来是三部分的，但它们在结构上与内质网膜不同。通过有机溶剂提取脂类，可将油体包衣从油体制剂中分离出来。涂层材料不溶于Triton X-100或脱氧胆酸盐等洗涤剂，在电子显微镜下显示出三部分的片层结构(类似于坍塌的球囊)。经十二烷基硫酸盐溶解后，聚丙烯酰胺凝胶电泳法显示了与内质网膜不同的多肽组成(9条主要条带)。此外，脱脂油体涂层和脱脂内质网膜的浮力密度也有很大的不同。油质体脂积聚在底层细胞质中，并被内质网特定区域合成的蛋白质元素从头开始形成的板层结构所包围。
EM and biochemical investigations of developing embryonic mustard cotyledons provided no evidence for the widely accepted hypothesis that oleosomes of fat-storing tissues originate from the endoplasmic reticulum and are surrounded by a unit- or half-unit membrane. The first lipid droplets appear (about 12-14 days after pollination) in the ground cytoplasm near the surface of plastids. Subsequently these nascent lipid droplets, which lack any detectable boundary structure at this stage, become encircled by a cisterna of rough endoplasmic reticulum. At the same time an osmiophilic coat of about 3 nm thickness becomes detectable at the lipid/water interface. In the cotyledon cells of germinating seedlings a centrifugally moving front of fat degradation moves from the central vacuole(s) towards the cell periphery, leaving behind collapsed coats of oleosomes which are depleted of their lipid contents (saccules). Although saccules appear tripartite in cross section, they are structurally different from endoplasmic reticulum membranes. The oleosome coats can be isolated from oleosome preparations by extracting lipids with organic solvents. The coat material is insoluble in detergents like Triton X-100 or deoxycholate and shows a tripartite, lamellar structure (similar to collapsed saccules) under the electron microscope. Upon dissolution with dodecylsulfate, polyacrylamide gel electrophoresis revealed a polypeptide composition (9 major bands) which is qualitatively different from that of the endoplasmic reticulum membrane. Also the buoyant densities of defatted oleosome coats and defatted endoplasmic reticulum membranes are very different. Oleosome lipids accumulate in the ground cytoplasm and are bounded by a lamellar structure originating de novo from proteinaceous elements synthesized by specific regions of the endoplasmic reticulum.