| Research Abstract |
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.
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