• calcium;
  • Dictyostelium cell cycle;
  • cell differentiation

Levels of intracellular calcium, (Ca2+)i, from different stages of cell cycle of Dictyostelium discoideum were monitored using the fluorescent Ca2+-sensitive dye, Indo 1. Combinations of Ca2+-ionophore (A23187) and Ca2+-chelator (EGTA) resulted in the inhibition of progression of cell cycle. This delay was caused due to block in G2/M[RIGHTWARDS ARROW]S phase transition of the cell cycle. Rescue of the cell cycle progression was made with 0.5m m of exogenous Ca2+. High (Ca2+)ilevels overlapped with the S-phase, of the cell cycle.

Results indicate that a high (Ca2+)ilevel during S-phase is not required for cell cycle progression but for cell-type choice mechanism at the onset of starvation, and these cells tend to follow the prestalk pathway.