Study on the induction of cell apex and its developent

通过细胞离心和红光偏振光照射，在原丝体侧壁上诱导出一个新的细胞顶点。分析了分支的发育过程，描述了分支形成过程中细胞骨架模式的变化。在白光照射7小时诱导细胞分裂后，对原体细胞进行基本离心，使细胞核脱位到原体细胞基部。原体在离心后立即或在黑暗中孵育两天后转移到连续偏振红光下。细胞在红色和深色条件下均发生分裂。如果细胞分裂发生在离原丝体顶端平均250 μ m以下的地方，一个新的原丝体顶端从非常接近顶细胞和/或基细胞分裂壁的侧壁上分枝出来。然而，如果原丝体的一部分，不管细胞分裂壁如何，在微束偏振红光照射下，一个新的…More分支只在照射部位发育。研究了核在新分支发育过程中的行为。细胞分裂后，在红色和黑暗条件下，两个细胞核都远离分裂部位。在全细胞红光照射下，细胞增厚发生在细胞分裂壁附近，而细胞核位于远离分支部位的地方。当一个新的顶端开始生长时，一个细胞核回到分支位置并爬进新的分支。另一方面，在微束照射下，当一个核进入微束时，一个新的尖分化。值得注意的是，纺锤形的细胞核可以从原来的顶端或底部进入一个分支，这表明细胞核没有头和尾。同时还观察了微管和微丝在发酵过程中的变化。在细胞增厚之前，在未来分支部位出现了微管带，类似于前期带或亚根尖环结构（Murata and Wada 1989）。微管从新的顶端向外扩散。少

A new cell apex was induced as a branch on a side wall of a protonema by cell centrifugation and polarized red light irradiation. A developmental process of the branch was analyzed and changes on cytoskeletal pattern during the branch formation were described.A protonemal cell was centrifuged basipetally to dislocate a nucleus to the protonemal basal part after an induction of cell division by irradiation with white light for 7 hr. The protonemata were transferred to the continuous polarized red light immediately after the centrifugation or after two days incubation in the dark. Cell division was taken place under the red or the dark condition. If the cell division occurred at more than 250 um below in average from the tip of protonemata, a new protonemal apex branched out from a side wall very close to the cell dividing wall of an apical and/or basal cell. However, if a part of protonema, irrespective of cell dividing wall, was irradiated with a microbeam of polarized red light, a new … More branch developed only at the irradiated site. Behavior of a nucleus during the process of new branch development were investigated.After the cell division, both nuclei moved away from the division site both in red and dark conditions. Under whole cell irradiation with red light, cell thicking occurred near the cell dividing wall but nuclei localized far from the branching site. When a new apex started to grow, a nucleus came back to the branching site and crawled into the new branch. On the other hand, under microbeam irradiation, a new apex was differentiated when a nucleus moved into the beam. It is note worthy that a spindle-shaped uncleus can get into a branch from their former tip or bottom, indicating that a nucleus has not head and tail.Changes of mictotubuled and microfilaments during the process were also observed. A microtubule band like a preprophase band or subapical ring structure (Murata and Wada 1989) appeared tentatively at the future branching site before cell thickning. Fun-like pattern of microtubuled spread out from the new apex. Less