Osafune T, Ehara T, Yokota A, Hase E
Department of Microbiology, Tokyo Medical College, Japan.
J Electron Microsc (Tokyo). 1992 Dec;41(6):469-74.
Wax-rich cells of Euglena gracilis Z grown in the dark without agitation were subjected to freeze-substitution procedures in electron microscopy, which gave intact images of wax accumulated as globules in the cytoplasm. The proplastids in these wax-rich cells were shown to contain no extensive internal structures. When these cells were transferred to an inorganic medium containing ammonium salt and aerated in the dark the specific activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) increased concurrently with the development of a prolamellar body and a rudimentary pyrenoid. When cell sections were labeled with antisera prepared against RuBisCO subunits followed by protein A-gold, gold particles (RuBisCO) were localized in a narrow peripheral region between the plastid envelope and the prolamellar body during an earlier phase of the dark incubation of cells. Subsequently, immunogold particles were concentrated over the rudimentary pyrenoid formed at a site adjacent to the prolamellar body, while the stroma was only slightly labeled with gold particles. It was postulated that the small subunits of RuBisCO made in the cytoplasm combined with the plastid-made large subunits to form the holoenzyme at the peripheral region near the prolamellar body before transfer to the rudimentary pyrenoid.
在黑暗中不搅拌培养的纤细裸藻富含蜡质的细胞，在电子显微镜下进行了冷冻置换处理，从而获得了蜡质以球状形式积累在细胞质中的完整图像。这些富含蜡质的细胞中的原质体显示没有广泛的内部结构。当这些细胞转移到含有铵盐的无机培养基中并在黑暗中通气时，核酮糖-1,5-二磷酸羧化酶/加氧酶（RuBisCO）的比活性随着原片层体和雏形淀粉核的发育而同时增加。当用针对RuBisCO亚基制备的抗血清标记细胞切片，随后用蛋白A-金标记时，在细胞黑暗孵育的早期阶段，金颗粒（RuBisCO）定位在质体包膜和原片层体之间的狭窄周边区域。随后，免疫金颗粒集中在与原片层体相邻部位形成的雏形淀粉核上，而基质仅被金颗粒轻微标记。据推测，在细胞质中产生的RuBisCO小亚基与质体产生的大亚基结合，在转移到雏形淀粉核之前，在靠近原片层体的周边区域形成全酶。
