Studies on the plastid-dividing apparatus by immuno-electron microscopy

我们是第一个确定的质体分裂appratus，这是位于细胞质中靠近外被膜在收缩的峡分裂叶绿体在红色的Cyanidium caldarium。本课题的目的是研究从低等真核生物Cyanidium caldarium RK-1到高等植物的质体分裂器的精细结构和功能。在低等真核生物中，电子密度较高的小体首先分裂成许多电子密度较高的颗粒，然后它们沿叶绿体赤道区沿着，在赤道区电子密度较高的颗粒形成细丝。免疫电镜观察证实，这些细丝为肌动蛋白样细丝。质体分裂器的细丝按照它们整个区域的最长轴排列。这束细丝开始收缩并产生一条深沟。由于在藻类、苔藓、蕨类和高等植物包括培养细胞的质体中广泛观察到类似的结构，质体分裂器似乎是植物质体分裂的基本结构。利用各种离心和生物化学技术，已经开发了从烟草培养细胞的原生质体中分离质体的方法。然而，很难清楚地将质体分裂器与分裂的质体分离。

We were the first to identify the plastid-dividing appratus, which is located in the cytoplasm close to the outer envelope membrane at the constricted isthmus of dividing chloroplasts in the red alga Cyanidium caldarium. The project has been performed in an aim to identify the fine structures and function of plastiddividing apparatus in many plants from lower eukaryote Cyanidium caldarium RK-1 to higher plants. In lower eukaryotes, some-what electron dense body is fragmented into many, somewhat electron-dense granules as the first step and then they are alighed along the equatorial region of the chloroplast and fine filaments are formed from the somewhat electron dense granules in the equatorial region. The fine filaments have been identified as actin-like filaments by an immuno-electron microscopy. The fine filaments of the plastid-dividing apparatus align themselves according to the longest axis of their overall domain. The bundle of fine filaments begins to contract and generates a deep furrow. Since similar structures as observed extensively in the plastids of algae, moss, fern and higher plants including cultured cells, the plastid-dividing apparatus appears to be an essential structure for the division of plastids in plants. The method for isolation of plastids from the protoplasts of the tabacco cultured cells has been developed using various centrifugations and biochemical techniques. However, it was difficult to isolate clearly the plastid-dividing apparatus from the dividing plastids.