Dependency of the slime mold development on the cell-cycle position at the onset of starvation

本文采用诱导良好同步的方法，分析了盘状盘齿钢鞘Ax-2的发育与饥饿开始时细胞周期的关系，并特别参考了极化细胞团（段塞）形成过程中的分选行为。不同细胞周期位置的饥饿细胞在进一步培养中表现出不同的发育特征。例如，在有丝分裂和分裂前的细胞被分类到迁移鼻涕虫的前柄区，而在g2期的大部分时间里饥饿的细胞被分类到后孢子区。细胞聚集和尖端形成的时间进程也有很大的变化，与细胞周期有关，g2期后期饥饿的细胞发育最快。不同的趋化性和内聚性通常被认为是盘基骨门发育过程中细胞分选的重要因素。事实上，在细胞周期的任何特定阶段，在饥饿的细胞中检测到对趋化剂cAMP的趋化能力的显着差异。抗edta内聚性也因细胞周期的不同而不同，在聚集速度更快的细胞中更强。此外，我们还认为，无论营养是否存在，Ax-2细胞都可能将自己的周期推进到g2期的某个特定点，并在营养剥夺的情况下从这个点进入分化阶段。这里讨论了细胞周期相关事件的可能意义，特别强调了这种有机体的模式形成。

The relationship between the development of Dictyostelium discoideum Ax-2 and the cell cycle at the onset of starvation was analysed with special reference to sorting behaviors during the formation of polarized cell masses (slug), using a method for inducing good synchrony. Cells starved at different cell-cycle positions showed different developmental features during further culture. For example, cells just before mitosis and dividing cells were sorted out into the anterior prestalk zone of migrating slugs, while cells starved during most of the G_2-phase, into the posterior prespore zone. Time courses of cell aggregatiion and tip formation were also found to vary greatly in a cell-cycle-related manner, and cells starved during the late G_2-phase showed the most rapid development. Differential chemotaxis and cohesiveness are generally considered to be important for cell sorting in Dictyostelium development. In fact, remarkable differences in the chemotactic ability to a chemoattactant, cAMP, were detected among cells starved at any particular phase of the cell cycle. EDTA-resistant cohesiveness was also acquired differently depending on the cell cycle, and it was stronger in the cells showing more rapid aggregation. Moreover, it was suggested that Ax-2 cells may advance their own cycle to a particular point in G_2-phase, irrespective of the presence and absence of nutrients, and enter differentiation phase from this point in concert with nutritional deprivation. The possible significance of the cell-cycle-related events presented here is discussed, with special emphasis on the pattern fromation of this organism.