A cell type-specific effect of calcium on pattern formation and differentiation in dictyostelium discoideum

Abstract

Spatial gradients of sequestered and free cellular calcium (Ca²⁺) exist in the slug of Dictyostelium discoideum (Maeda and Maeda, 1973; Tirlapur et al., 1991; Azhar et al., 1995; Cubitt et al., 1995). When we vary intracellular Ca²⁺ with the help of calcium buffers and the ionophore Br-A23187, there are striking effects on slug morphology, patterning and cell differentiation. In the presence of a calcium ionophore, high external Ca²⁺ levels lead to an increase of intracellular sequestered and free Ca²⁺, the formation of long slugs, a decrease in the fraction of genetically defined prespore cells and 'stalky' fruiting bodies. Conversely, a lowering of external Ca²⁺ levels results in a decrease of intracellular Ca²⁺, the formation of short slugs, an increase in the prespore fraction and 'spory' fruiting bodies. We infer that Ca²⁺ plays a significant morphogenetic role in D. discoideum development, by selectively promoting the prestalk pathway relative to the prespore pathway.