Sato Mayuko, Mogi Yuko, Nishikawa Toshikazu, Miyamura Shinichi, Nagumo Tamotsu, Kawano Shigeyuki
Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Bldg. FSB-601, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8562, Japan.
Planta. 2009 Mar;229(4):781-91. doi: 10.1007/s00425-008-0872-4. Epub 2008 Dec 19.
The cyanelles of glaucocystophytes are probably the most primitive of known extant plastids and the closest to cyanobacteria. Their kidney shape and FtsZ arc during the early stage of division define cyanelle division. In order to deepen and expand earlier results (Planta 227:177-187, 2007), cells of Cyanophora paradoxa were fixed with two different chemical and two different freeze-fixation methods. In addition, cyanelles from C. paradoxa were isolated to observe the surface structure of dividing cyanelles using field emission scanning electron microscopy (FE-SEM). A shallow furrow started on one side of the division plane. The furrow subsequently extended, covering the entire division circle, and then invaginated deeply, becoming clearly visible. The typical FtsZ arc was 2.3-3.4 microm long. This length matches that of the cleavage furrow observed using FE-SEM. The cyanelle cleavage furrows are from one-fourth to one-half of the circumference of the division plane. The shallow furrow that appears on the cyanelle outer surface effectively changes the division plane. Using freeze-fixation methods, the electron-dense stroma and peptidoglycan could be distinguished. In addition, an electron-dense belt structure (the cyanelle ring) was observed inside the leading edge at the cyanelle division plane. The FtsZ arc is located at the division plane ahead of the cyanelle ring. Immunogold-TEM localization shows that FtsZ is located interiorly of the cyanelle ring. The lack of an outer PD ring, together with the arch-shaped furrow, suggests that the mechanical force of the initial (arch shaped) septum furrow constriction comes from inside the cyanelle.
蓝隐藻的蓝小体可能是已知现存质体中最原始的，也是最接近蓝细菌的。它们在分裂早期的肾形和FtsZ弧决定了蓝小体的分裂。为了深化和扩展早期研究结果（《植物》227:177 - 187, 2007），对蓝氏拟甲藻的细胞采用两种不同的化学固定方法和两种不同的冷冻固定方法进行固定。此外，分离出蓝氏拟甲藻的蓝小体，利用场发射扫描电子显微镜（FE - SEM）观察分裂蓝小体的表面结构。一条浅沟在分裂平面的一侧开始形成。这条沟随后延伸，覆盖整个分裂环，然后深深内陷，变得清晰可见。典型的FtsZ弧长2.3 - 3.4微米。这个长度与用FE - SEM观察到的分裂沟长度相符。蓝小体的分裂沟为分裂平面周长的四分之一到二分之一。蓝小体外表面出现的浅沟有效地改变了分裂平面。采用冷冻固定方法，可以区分电子致密的基质和肽聚糖。此外，在蓝小体分裂平面的前缘内部观察到一种电子致密的带状结构（蓝小体环）。FtsZ弧位于蓝小体环前方的分裂平面处。免疫金 - 透射电镜定位显示FtsZ位于蓝小体环的内部。缺乏外部的PD环以及拱形沟表明，初始（拱形）隔膜沟收缩的机械力来自蓝小体内部。
