Specific Induction by Zinc of Dictyostelium Stalk Cell Differentiation

Abstract

Zinc is found in a variety of organisms and has been suggested to be essential for many cellular functions. We report here that zinc ions (Zn2+) have a specific and striking effect on cell differentiation in the simple eukaryote, Dictyostelium discoideum. In its asexual reproduction phase, solitary cells gather to form multicellular fruiting bodies consisting of spores and stalk cells. In vitro studies have revealed endogenous factors required for the differentiation of these two cell types. For stalk cell differentiation, these are cyclic AMP and a putative morphogen, a unique chlorinated alkylphenone named differentiation-inducing factor (DIF). With millimolar concentrations of Zn2+, however, cells neglect these requirements altogether and differentiate in vitro into mature stalk cells without the addition of cAMP and/or DIF, expressing stalk-specific markers, wst34 (protein) and ecmB (gene), but not ecmA. Zn2+-induced stalk cell formation is thus distinct from normal stalk cell formation and this system would provide a clue to elucidate the mechanism of stalk cell differentiation.