The timing of cell-type-specific differentiation in Dictyostelium discoideum.

We have used two-dimensional gel electrophoresis to identify over 30 proteins which are specific to one or other of the two cell types of Dictyostelium discoideum, either at the slug stage or in mature fruiting bodies. Our results support the idea that there is a continuous developmental program that begins in prespore cells at the hemispherical mound stage (10-12 hr) and results in spore differentiation (24 hr). Prestalk differentiation, on the other hand, appeared largely unrelated to stalk differentiation, which was first detectable at the onset of culmination (18 hr). We have also used this approach to study the differentiation of stalk-only mutants and have found that the cells can switch from spore to stalk differentiation as late as 2 hr before the end of the wild-type developmental program.