Cell type conversion in isolated prestalk and prespore fragments of the cellular slime mold Dictyostelium discoideum

Abstract

Fragmentation of a slug of D. discoideum causes conversion between the two types of differentiated cells (prestalk and prespore cells) in order to reestablish their normal proportion in each fragment. A quantitative study of the kinetics of such a process was made by determining the proportion of prespore cell contained in a fragment. Conversion from prestalk cell to prespore cell (in a prestalk isolate) occurred after a lag phase of about 3 hr and was complete within 7 to 8 hr of incubation. Conversion from prespore cell to prestalk cell (in a prespore isolate) occurred without a lag and was complete within 3 to 4 hr of incubation. Both types of conversion were inhibited at low temperatures and in the presence of 200 μg/ml cycloheximide of 125 μg/ml actinomycin D. Conversion from the prestalk cell to the prespore cell was completely inhibited in the presence of 10 mM LiCl, while the reverse conversion was not affected. All the cells in a prespore isolate were eventually converted to the prestalk cell. This is also the case with an intact slug.