Pattern Formation in a Cell-Cycle Dependent Manner during the Development of Dictyostelium discoideum: (pattern formation/cell sorting/cell cycle/PS-point/Dictyostelium discoideum).

Abstract

strain Ax-2, cells grow axenically and multiply by binary fission with a doubling time of about 7.2 hr provided sufficient nutrients are supplied. Upon exhaustion of the nutrient supply, starving cell populations start differentiating with the acquisition of aggregation competence and aggregate to form multicellular structures by che- motaxis to 3’,5’-cyclic adenosine monophosphate (CAMP) (2, 15). During aggregation, cells also acquire EDTA-resistant cohesiveness (9). The cell aggregate (mound) thus formed exerts orga- nized movement and zonal differentiation as a migrating pseudoplasmodium (slug), and even- tually develops into a sorocarp consisting of a mass of spores (sorus), a supporting cellular stalk, and a basal disc. Differentiation of the two cell types, anterior prestalk and posterior prespore cells, is evident at the slug stage. The growth and differentiation in Ax-2 cells are temporarily sepa- rated from each other and easily controlled by nutritional conditions. In addition, determinations of the fate map of cell types are simpler than in other organisms. Accordingly, this organism has been particularly useful for elucidating the molecu- lar mechanism of growthidifferentiation transition and also the regulatory mechanisms controlling eukaryotic cell-type determination and pattern formation. There have been numerous studies on the following developmental stages: 1 ) growth and preaggregation, 2) aggregation, 3) tip formation and prestalk/prespore differentiation, 4) slug formation and migration, and 5) culmination and terminal stalk/spore differentlation. The studies