A study of identification of the proteins and their genes which compose the dividing apparatus of mitochondria and plastids

在透射电子显微镜下，叶绿体分裂环可分为两个(或三个)电子致密环：外膜胞液面上的外环，有时膜间隙的中环，内被膜基质面上的内环。FtsZ环在细菌分裂中起着核心作用，也参与了叶绿体的分裂，并被认为是蓝藻内共生过程中的叶绿体。这两种结构之间的关系尚不清楚，尽管有关于它们是否相同的讨论，但利用红藻Bluanidoschyzon merolae的同步叶绿体进行的生化和免疫细胞化学研究表明，叶绿体FtsZ环是明显的，可以从叶绿体分裂环中分离出来。FtsZ环位于基质中，面向内包被远侧的内质体分割环。FtsZ环和内外叶绿体分裂环在叶绿体分裂前依次形成。FtsZ环在叶绿体分裂环解离之前的收缩后期消失，此时收缩仍在进行中。我们的结果表明，基于FtsZ环的系统起源于叶绿体祖先蓝藻，而基于叶绿体分裂环的系统可能起源于宿主真核细胞，形成一个复合体，以不同的方式参与叶绿体的分裂。

The plastid-dividing ring can be detected by transmission electron microscopy as two (or three) electron-dense rings: and outer ring on the cytosolic face of the outer envelope, occasionally a middle ring in the intermembrane space, and an inner ring on the stromal face of the inner envelope. The FtsZ ring, which plays a central role in bacterial division, also is involved in plastid division and is believed to have descended to plastids from cyanobacterial endosymbiosis. The relationship between the two structures is not known, although there is discussion regarding whether they are identical, biochemical and immunocytochemical investigations, using synchronized chloroplasts of the red alga Cyanidoschyzon merolae, showed that the plastid FtsZ ring is distinct and separable from the plastid-dividing ring. The FtsZ ring localizes in stroma and faces the inner plastid-dividing ring at the far side from the inner envelope. The FtsZ ring and the inner and outer plastid-dividing ring form in that order before plastid division. The FtsZ ring disappears at the late stage of constriction before dissociation of the plastid-dividing ring, when the constriction is still in progress. Our results suggest that the FtsZ ring-based system, which originated from a plastid ancestor, cyanobacteria, and the plastid-dividing ring-based system, which probably originated from host eukaryotic cells, form a complex and are involved in plastid division by distinct modes.