Selective induction of stalk-cell-specific proteins in Dictyostelium.

We compared the proteins synthesized and accumulated by Dictyostelium discoideum amoebae in response to the morphogenetic factor termed differentiation-inducing factor (DIF) to assess the proposed ability of DIF to regulate the choice of differentiation pathway. When amoebae of a mutant strain with low endogenous DIF levels were given DIF, they dramatically increased the expression of 21 of 23 proteins preferentially found in stalk cells, but drastically repressed 4 major spore-specific proteins. Most of the induced proteins were also expressed in amoebae of a developmentally competent strain developing at low cell densities and exposed to DIF, low extracellular pH, or the proton pump inhibitor diethylstilbestrol; this suggests that an intracellular acidification may be a key part of the mechanism of DIF action. We conclude from the similar morphology and extensive homology of proteins of DIF-induced and stalk cells that most stalk-pathway functions are DIF dependent.