Developmental regulation of a stalk cell differentiation-inducing factor in Dictyostelium discoideum

Previous work has shown that cells developing at high density release a low-molecular-weight factor that can induce isolated Dictyostelium discoideum amoebae of strain V12M2 to differentiate into stalk cells in the presence of cyclic AMP. We now show that this differentiation-inducing factor, called DIF, can be extracted from cells during normal development and that its production is strongly developmentally regulated. DIF is not detectable in vegetative cells but rises dramatically after aggregation to reach a peak during slug migration. DIF levels are very low in two mutants defective in aggregation. The postaggregative synthesis of DIF is stimulated by the addition of extracellular cyclic AMP. We propose that DIF is a morphogen controlling prestalk cell differentiation.