Regulation of dictyostelium discoideum mRNAs specific for prespore or prestalk cells

Abstract

Prespore and prestalk cells in Dictyostelium discoideum aggregates can be separated by density gradient centrifugation. Using poly(A+) RNA from the fractionated cells to probe a cDNA library of mRNAs from postaggregation cells, we were able to identify six cDNA clones representing RNAs enriched in prespore or prestalk cells. Remarkably, transcripts of six of seven cDNA clones, previously selected to encode mRNAs present in postaggregating cells but low or absent in growing cells, also are enriched in RNA from either prestalk or prespore cells. By hybridization of cDNA probes to nitrocellulose blots of formaldehyde RNA gels, these 13 mRNA species have been examined with respect to cell type specificity, temporal pattern of accumulation, and affect of disaggregation and cAMP on accumulation. Aggregation-stage mRNAs tend to fit into three different classes. All prespore mRNAs are similar in all aspects of their regulation, while prestalk mRNAs fall into two co-regulated classes. All mRNAs that are present at significant levels during growth and differentiation are found in both cell types at comparable levels. Our results indicate that there is coordinate control of expression of genes specific for the two principal cell types.