Mitochondrial DNA replication but no nuclear DNA replication during development of Dictyostelium.

Dictyostelium discoideum cells initiate development when nutrients are depleted. DNA synthesis decreases rapidly thereafter but resumes during late aggregation, only in prespore cells. This observation has been previously interpreted as indicating progression of prespore cells through the cell cycle during development. We show that developmental DNA replication occurs only in mitochondria and not in nuclei. We also show that the prestalk morphogen known as differentiation-inducing factor 1 can inhibit mitochondrial respiration. A model is proposed for cell type divergence, based on competition to become prespores, that involves mitochondrial replication in prespore cells and reduction of mitochondrial activity in prestalk cells.