The distribution of the stalk cell differentiation inducing factor and other lipids during the differentiation of Dictyostelium discoideum

Abstract

The production of the stalk cell differentiation inducing factor (DIF) is restricted to the differentiation phase of the Dictyostelium discoideum life cycle. By the migrating pseudoplasmodial stage, the majority of the accumulated DIF is localized outside the pseudoplasmodia and the remaining pseudoplasmodial DIF is distributed between the intracellular and intercellular compartments. These results indicate possible reasons for the failure to detect gradients of DIF along the migrating pseudoplasmodia. De novo synthesized sterol is also localized predominantly outside the pseudoplasmodia. In contrast the majority of the de novo synthesized polar lipid and steryl ester are within the pseudoplasmodium. Of the de novo synthesized intracellular components, the polar lipid is almost entirely membrane bound and, although most of the sterol and steryl ester are also membrane bound, significant amounts are cytosolic. Intracellular DIF is also detectable in both membrane and cytosolic fractions.