Developmental regulation of cell-type-enriched mRNAs in Dictyostelium discoideum

We describe sixteen new families of cDNA clones representing mRNAs that are expressed preferentially in either prespore or prestalk cells during development of Dictyostelium discoideum and two new mRNAs that are expressed in a non-cell-type-specific manner. None of the prespore-enriched mRNAs are detectable in Dictyostelium cells until 13-15 h of development but then they increase dramatically and peak at 18-22 h. Upon dissociation of developing aggregates, all these mRNAs rapidly decay to low levels. In marked contrast to data presented for prespore genes by other workers, cyclic AMP either has no effect on the mRNA levels in dissociated cells or is only weakly effective in restoring normal expression. A prestalk-enriched mRNA examined, 5G mRNA, is similarly expressed late in development but is also expressed in vegetative cells. The level of 5G mRNA is only moderately affected by cell disaggregation.