RTOA LINKS INITIAL CELL-TYPE CHOICE TO THE CELL-CYCLE IN DICTYOSTELIUM

In Dictyostelium, initial cell type choice is correlated with the cell -cycle phase of the cell at the time of starvation. We have isolated a mutant, ratioA (rtoA), with a defect in this mechanism that results i n an abnormally high percentage of prestalk cells. The rtoA gene has b een cloned and sequenced and codes for a novel protein. The cell cycle is normal in rtoA. In the wild type, prestalk cells differentiate fro m those cells in S or early G(2) phase at starvation and prespore cell s from cells in late G(2) or M phase at starvation. In rtoA mutants, b oth prestalk and prespore cells originate randomly from cells in any p hase of the cell cycle at starvation.