CELLS AT THE CENTER OF DICTYOSTELIUM AGGREGATES BECOME SPORES

The cellular slime mold Dictyostelium discoideum undergoes a developme ntal life cycle on starvation to generate a fruiting body consisting o f a mass of spores supported on a stalk of dead, vacuolated cells. The choice between alternative cell fates is influenced by a variety of f actors including cell cycle position at the onset of starvation. We pr esent evidence to suggest that the cell cycle position influences cell fate by determining the position of cells in the early aggregate. The existence of a strain which cannot initiate development on its own bu t which can respond to signals generated by nonmutant cells has allowe d us to investigate the eventual cell fate of the initiating cells whi ch are, by definition, at the center of the early aggregate. Cells whi ch have a propensity to become prespore cells show an increased effici ency in initiating development of this strain. Labeling the initiating cells by the expression of green fluorescent protein reveals that the se cells become spores. The higher levels of expression of genes chara cteristic of early development in cells with a prespore tendency are c onsistent with the earlier expression of the components of relay in pr espore cells. (C) 1997 Academic Press.