The role of DIF-1 signaling in Dictyostelium development

We have constructed a mutant blocked in the biosynthesis of DIF-1, a chlori nated signal molecule proposed to induce differentiation of both major pres talk cell types formed during Dictyostelium development. Surprisingly, the mutant still forms slugs retaining one prestalk cell type, the pstA cells, and can form mature stalk cells. However, the other major prestalk cell typ e, the pstO cells, is missing. Normal pstO cell differentiation and their p atterning in the slug are restored by development on a uniform concentratio n of DIF-1. We conclude that pstO and pstA cells are in fact induced by sep arate signals and that DIF-1 is the pstO inducer. Positional information, i n the form of DIF-1 gradients, is evidently not required for pstO cell indu ction.