Fig. 4. Differentiation of rtoA-/mdrA1-/mdrA2- cells. Cells were grown in low-density monolayer culture overnight, with a field of the cells being videotaped. The medium was then gently changed to conditioned starvation buffer, and 6 hours later cAMP was added to induce the expression of cell-type-specific markers. Eighteen hours after starvation the cells were fixed, the videotape was turned off, and the cells were stained for the prestalk marker CP2 and the prespore marker SP70. The time of cytokinesis and the fate of the sister cell for each positive cell were then determined by examining the videotape. Open circles mark the phase that SP70-positive prespore cells happened to be in at the time of starvation, whereas filled squares mark where CP2-positive prestalk cells happened to be.
