Basal body and flagellar development during the vegetative cell cycle and the sexual cycle of Chlamydomonas reinhardii.
Basal body and flagellar development during the vegetative cell cycle and the sexual cycle of Chlamydomonas reinhardii.
复制标题
DOI：
--
复制
发表时间：
1974-12
影响因子：
4
通讯作者：
T. Cavalier-smith
中科院分区：
文献类型：
--
作者：
T. Cavalier-smith
用光学显微镜和电子显微镜研究了单细胞绿色莱茵衣原体在同步培养的营养细胞周期和性生活周期中的基体发育和鞭毛退化与生长。鞭毛退化，在营养细胞分裂之前逐渐缩短，在性周期中细胞融合后几小时也是如此。在营养细胞中，基体通过其过渡纤维保持附着在质膜上，并且在分裂期间不作为纺锤体极处的中心粒。在受精卵的基体和相关的微管根和横纹连接都溶解，并通过6.5小时后交配的鞭毛器和相关结构的所有痕迹已经消失。它们在整个接合孢子成熟过程中缺席6天，然后在减数分裂开始后的接合孢子萌发过程中重新组装。发育中的接合孢子中的基体组装发生在质膜附近（在没有预先存在的基体的情况下），通过中间阶段由围绕中央“侧手翻”的九个单个A-小管组成。在营养细胞中，组装是类似的（并且发生在细胞分裂之前），除了新的基体通过无定形物质物理地附着在旧的基体上。在营养细胞中，无定形盘，这可能是更早的阶段，在基体发展中出现在同一位置的9单线发展的基体。9-单线态结构形成后，加入B和C纤维，基体伸长至其成熟长度。然后组装微管根、条纹连接和鞭毛。鞭毛的退化和生长都是渐进的和连续的，鞭毛基部的过渡区首先形成，最后分解。生长和退化鞭毛的轴丝尖端存在无定形物质，表明轴丝的生长或缩短是通过其尖端的顺序组装或拆卸实现的。在均质化的细胞中，基体通过它们的条纹状连接保持牢固的相互连接。鞭毛过渡区，部分膜和4个微管根，也保持附着;新的发展中的基体，如果存在的话。这些结构在匀浆中保存良好，并且可以看到新的精细结构细节。这些结果进行了讨论，并不支持的想法，基体具有遗传连续性。有人建议，基体的发展，可以最好地理解，如果区分所需的信息，以指定一个基体的结构，并需要指定其位置和方向。
Basal body development and flagellar regression and growth in the unicellular green alga Chlamydomonas reinhardii were studied by light and electron microscopy during the vegetative cell cycle in synchronous cultures and during the sexual life cycle. Flagella regress by gradual shortening prior to vegetative cell division and also a few hours after cell fusion in the sexual cycle. In vegetative cells basal bodies remain attached to the plasma membrane by their transitional fibres and do not act as centrioles at the spindle poles during division. In zygotes the basal bodies and associated microtubular roots and cross-striated connexions all dissolve, and by 6.5 h after mating all traces of flagellar apparatus and associated structures have disappeared. They remain absent for 6 days throughout zygospore maturation and then are reassembled during zygospore germination, after meiosis has begun. Basal body assembly in developing zygospores occurs close to the plasma membrane (in the absence of pre-existing basal bodies) via an intermediate stage consisting of nine single A-tubules surrounding a central ‘cartwheel’. Assembly is similar in vegetative cells (and occurs prior to cell division), except that new basal bodies are physically attached to old ones by amorphous material. In vegetative cells, amorphous disks, which may possibly be still earlier stages in basal-body development occur in the same location as 9-singlet developing basal bodies. After the 9-singlet structure is formed, B and C fibres are added and the basal body elongates to its mature length. Microtubular roots, striated connexions and flagella are then assembled. Both flagellar regression and growth are gradual and sequential, the transitional region at the base of the flagellum being formed first and broken down last. The presence of amorphous material at the tip of the axoneme of growing and regressing flagella suggests that the axoneme grows or shortens by the sequential assembly or disassembly at its tip. In homogenized cells basal bodies remain firmly attached to each other by their striated connexions. The flagellar transitional region, and parts of the membrane and of the 4 microtubular roots, also remain attached; so also do new developing basal bodies, if present. These structures are well preserved in homogenates and new fine-structural details can be seen. These results are discussed, and lend no support to the idea that basal bodies have genetic continuity. It is suggested that basal body development can be best understood if a distinction is made between the information needed to specify the structure of a basal body and that needed to specify its location and orientation.