Abteilung Zellphysiologie, Botanisches Institut der Universität, Menzingerstraße 67, D-8000, München 19, Federal Republic of Germany.
Planta. 1978 Jan;140(2):163-9. doi: 10.1007/BF00384916.
Spherosomes (oleosomes) of cotyledons of rape (Brassica napus L.), sunflower (Helianthus annuus L.), and watermelon (Citrullus vulgaris, Schrad.) seedlings are delimited by a "half unit membrane" that appears to be continuous with each of the osmiophilic layers of a tripartite unit membrane forming a handlelike appendix of the spherosomes. Prior to any noticeable utilization of the spherosomal storage fat, ribosomes were found to be attached to these "handles". At later stages appendices of the spherosomes are smooth, showing a diameter of about 22 nm that greatly exceeds the thickness of any other unit membrane profiles identical in structure and diameter osomes appears to be continuous with the thick lipid layer of the handles. In intermediate stages of fat depletion the spherosomal bodies become invaginated with cytoplasmic material. Finally vesicles with cytoplasmic contents surrounded by a membrane with a typically thick lipid layer are left in the cells. Membrane profiles indentical in structure and diameter to the spherosomal appendices were also present in electron micrographs of the lipolytic membrane fraction recovered from sucrose density gradients after centrifugation of a microsomal cell fraction. The ultrastructural observations are taken for evidence that the spherosomal appendices represent the lipase-carrying membranes isolated previously (Theimer and Rosnitschek, 1978). A novel hypothesis for development and utilization of fat-storing spherosomes is also proposed.
油菜籽(甘蓝型油菜)、向日葵(向日葵)和西瓜(西瓜)幼苗子叶的球体(油体)由一个“半单位膜”限定,该膜似乎与形成球体柄状附件的三分体单位膜的每个亲脂层连续。在明显利用球体储存脂肪之前,发现核糖体附着在这些“手柄”上。在后期,球体的附件变得光滑,直径约为 22nm,大大超过任何其他结构和直径相同的单位膜轮廓的厚度。球体似乎与手柄的厚脂层连续。在脂肪耗尽的中间阶段,球体的主体向内凹陷,伴有细胞质物质。最后,在细胞中留下带有典型厚脂层的膜的含有细胞质内容物的小泡。在蔗糖密度梯度离心后,从微粒体细胞部分回收的脂解膜部分的电子显微镜照片中,也存在与球体附件结构和直径相同的膜轮廓。超微结构观察结果表明,球体附件代表先前分离的携带脂肪酶的膜(Theimer 和 Rosnitschek,1978)。还提出了一种关于脂肪储存球体发育和利用的新假说。