Division of Plastids by a Plastid-Dividing Ring in Cyanidium caldarium
Division of Plastids by a Plastid-Dividing Ring in Cyanidium caldarium
复制标题
Cyanidium caldarium 中质体分隔环对质体的划分
DOI：
10.1007/978-3-7091-9008-1_16
复制
发表时间：
1988
影响因子：
2.9
通讯作者：
T. Kuroiwa
中科院分区：
文献类型：
--
作者：
T. Mita;T. Kuroiwa
在同步的单细胞藻蓝藻RK-1细胞群中研究了质体分裂环的精细结构和功能及其在生命周期中的命运。4′，6-二氨基-2-苯基吲哚（DAPI）和罗丹明phalloidin染色后用荧光显微镜观察细胞，冷冻取代固定和免疫金细胞化学后用电镜观察细胞。年轻的细胞包含一个叶绿体，一个细胞核和一个线粒体，这些细胞器在细胞质分裂之前按这个顺序分裂。由于两次内孢子分裂，母细胞分裂形成四个子内孢子细胞，每个子内孢子细胞包含细胞核、叶绿体和线粒体。细胞松弛素B （20 μ/ml）对细胞核分裂无抑制作用，但对质体分裂有明显抑制作用。相比之下，cremart （10 μg/ml）对质体分裂无抑制作用，但对细胞核分裂有抑制作用。利用罗丹明-phalloidin染色技术，我们已经明确了一束肌动蛋白样细丝位于哑铃状叶绿体收缩峡部周围。在电镜下，叶绿体第一次和第二次分裂时，在叶绿体赤道区周围的细胞质中分别可见宽度约为60 nm和30 nm的PD环。PD环由许多直径约4.5 nm的细丝组成，这些细丝沿圆周排列。PD环的细丝似乎是由直径40 - 90nm的小的电子密度颗粒形成的，就在收缩的峡部形成之前。环逐渐产生深沟的尺寸类似于那些PD环。最后，叶绿体的内容物仿佛被PD环分隔成两部分，形成两个子叶绿体。这些结果以及免疫金细胞化学和电镜数据表明，PD环由肌动蛋白样细丝组成，是叶绿体分裂的重要参与者。
The fine structure and function of the plastid-dividing (PD) ring and its fate during the life cycle have been studied in a synchronized population of cells of the unicellular alga Cyanidium caldarium RK-1. Cells were examined by using epifluorescence microscopy after staining with 4′,6-diamidino-2-phenylindole (DAPI) and rhodaminphalloidin, and by electron microscopy after freeze-substitution fixation and immuno-gold cytochemistry. The young cell contains a single chloroplast, a cell nucleus and a mitochondrion, and these organelles divide in that order just prior to cytokinesis. As a result of two endospore divisions, the mother cell divides to form four daughter endospore cells each of which contains a cell nucleus, chloroplast, and mitochondrion. Cytochalasin B (20 μ/ml) does not inhibit the division of cell nuclei but markedly inhibit the division of plastids. By contrast, cremart (10 μg/ml) does not inhibit the division of plastids but does inhibit division of cell nuclei. Using the rhodamin-phalloidin staining technique, we have clarified that a bundle of actin-like filaments is located around the constricted isthmus of the dumbbell-shaped chloroplast. Under the electron microscope, the PD rings, of about 60 nm and 30 nm in width, are seen in the cytoplasm around the equatorial region of the dividing chloroplasts during the first and second chloroplast divisions, respectively. The PD ring consists of numerous fine filaments of about 4.5 nm in diameter which are aligned circumferentially. The fine filaments of the PD ring appear to be formed from small somewhat-electron dense granules, 40–90 nm in diameter, just before the formation of the constricted isthmus. The ring progressively generates a deep furrow with dimensions similar to those of the PD ring. Finally, the contents of chloroplast are separated into two parts, as if by the PD ring, to form two daughter chloroplasts. These results and the data obtained by immuno-gold cytochemistry and electron microscopy suggest that the PD ring consists of actin-like filaments and is an important participant in the division of the chloroplast.