Studies on the accumulation of the differentiation-inducing factor (DIF) in high-cell-density monolayers of Dictyostelium discoideum

Abstract

A number of factors that have been shown to influence cell type determination in Dictyostelium discoideum were assessed for their effects on the accumulation of the stalk cell differentiation-inducing factor (DIF) in high-cell-density monolayers of strain V12-M2. DIF accumulation is markedly enhanced by low pH, butyrate, and the proton pump inhibitor diethylstilbestrol (DES), conditions that induce stalk cell formation in low-cell-density monolayers in the absence of added DIF. These results are discussed in relation to a model for cell type determination recently proposed by (J. D. Gross, M. J. Peacey, and R. Pogge Von Strandmann (1988, Differentiation, 38: 91–98). DIF accumulates in high-cell-density monolayers after the cells have become independent of cyclic AMP for stalk cell formation. This accumulation is greatly enhanced by the addition of cyclic AMP. This result may explain why cyclic AMP stimulates stalk cell formation in low-density monolayers in the presence of suboptimal levels of DIF, following preincubation in the presence of saturating levels of cyclic AMP ( L. Kwong, A. Sobolewski, and G. Weeks, 1988, Differentiation 37 ,1–6 ). Adenosine has no effect on DIF accumulation in high-cell-density monolayers.