A Oohata | PubMed Health

PubMed1983

Dictyostelium mutants lacking DIF, a putative morphogen.

DIF is an endogenous extracellular signal that may control differentiation of D. discoideum cells. It is a dialyzable, lipid-like factor that induces stalk cell formation among isolated amebae incubated in vitro with cAMP. To examine the consequences of DIF deprivation, we have isolated several mutant strains that are impaired in DIF accumulation, and whose inability to make stalk cells in vitro and during normal development on agar can be corrected by the addition of exogenous DIF. Little DIF is made by the mutants, and morphological development on agar stops after the cells have aggregated, but before a slug forms. In these DIF-deprived conditions, prespore cells can differentiate, but prestalk cells cannot.

Cell Differentiation↗

PubMed1977

Separation and biochemical characterization of the two cell types present in the pseudoplasmodium of Dictyostelium mucoroides.

The pseudoplasmodium (slug) of the cellular slime mould, Dictyostelium mucoroides consists of prestalk and prespore cells. These 2 differentiated types of cells were separated by modification of the previous methods using density-gradient centrifugation. Major improvements made in the present study were the use of a density column of different specific gravities and the use of a discontinuous gradient rather than a continuous one. With these improvements, it became possible to obtain efficiently a large number of prestalk and prespore cells. After separation of the 2 types of cells, activities and electrophoretic patterns of some developmentally regulated enzymes were compared. The hydrolases such as beta-glucosidase, beta-galactosidase, acetylglucosaminidase and alkaline phosphatase showed higher activities in the prestalk than in the prespore cells. The results are consistent with the fact that more autophagic vacuoles are present in the prestalk than in the prespore cells. On the other hand, UDP-galactose polysaccharide transferase was almost exclusively found in the prespore cells. Electrophoresis on polyacrylamide gels of slug, prestalk and prespore extracts showed that one among 4 isozymes of beta-galactosidase recognized in the slug extract was present only in the prestalk extract. Electrophoretic patterns of acid phosphatase revealed that one of the two isozymes present in the slug was specifically found in the prestalk cell. Finding of such prestalk specific isozymes was significant, since no specific markers have been known for the prestalk cell.

Acetylglucosaminidase↗