Molecular cloning of cell-type-specific cDNAs exhibiting new types of developmental regulation in Dictyostelium discoideum

By screening cDNA libraries from NC-4 cells, we have obtained five prespore-specific and two prestalk-specific cDNA clones. The two classes of prespore genes began to be expressed at the tipped aggregate stage: one class was expressed throughout development, while the other was shut off during culmination. Another class of prespore genes was expressed in vegetative cells but only in prespore cells at the later stages. Prestalk-specific genes were first expressed at the tipped aggregate stage concurrently with the two prespore gene classes, indicating the importance of this stage for transcriptional regulation in both prestalk and prespore differentiation. Except for the first prespore gene class, these represent new cell-type-specific genes as to their temporal pattern of expression.