Salisbury J L, Sanders M A, Harpst L
Developmental Genetics and Anatomy, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106.
J Cell Biol. 1987 Oct;105(4):1799-805. doi: 10.1083/jcb.105.4.1799.
When Chlamydomonas cells are deflagellated by pH shock or mechanical shear the nucleus rapidly moves toward the flagellar basal apparatus at the anterior end of the cell. During flagellar regeneration the nucleus returns to a more central position within the cell. The nucleus is connected to the flagellar apparatus by a system of fibers, the flagellar roots (rhizoplasts), which undergo a dramatic contraction that coincides with anterior nuclear movement. A corresponding extension of the root system, back to its preshock configuration is observed as the nucleus retracts to a central position. Anterior displacement of the nucleus and flagellar root contraction require free calcium in the medium. Nuclear movement and flagellar root contraction and extension are not sensitive to inhibitors of protein synthesis (cycloheximide), or drugs that influence either microtubules (colchicine) or actin-based microfilaments (cytochalasin D). Detergent-extracted cell models contract and extend their flagellar roots and move their nuclei in response to alterations of free calcium levels in the medium. Cycles of nuclear movement in detergent-extracted models require ATP to potentiate the contractile mechanism for subsequent calcium-induced contraction. Flagellar root contraction and nuclear movement in Chlamydomonas may be causally related to signaling of induction of flagellar precursor genes or to the transport of flagellar precursors or their messages to sites of synthesis or assembly near the basal apparatus of the cell.
当衣藻细胞因pH值冲击或机械剪切而失去鞭毛时，细胞核会迅速移向细胞前端的鞭毛基部装置。在鞭毛再生过程中，细胞核会回到细胞内更中心的位置。细胞核通过一个纤维系统——鞭毛根（根质体）与鞭毛装置相连，鞭毛根会发生剧烈收缩，这与细胞核向前移动同时发生。当细胞核缩回至中心位置时，可以观察到根系相应地伸展，恢复到冲击前的形态。细胞核向前移位和鞭毛根收缩需要培养基中有游离钙。细胞核移动以及鞭毛根收缩和伸展对蛋白质合成抑制剂（放线菌酮）、影响微管（秋水仙碱）或肌动蛋白微丝（细胞松弛素D）的药物不敏感。用去污剂处理过的细胞模型会根据培养基中游离钙水平的变化收缩和伸展其鞭毛根并移动细胞核。去污剂处理过的模型中的细胞核移动循环需要ATP来增强后续钙诱导收缩的收缩机制。衣藻中的鞭毛根收缩和细胞核移动可能与鞭毛前体基因诱导的信号传导、鞭毛前体或其信使向细胞基部装置附近的合成或组装位点的运输存在因果关系。
