Essential for normal culmination. May function as a transcriptional regulator. Expressed in the prestalk cells that constitute the slug tip (pstA cells) and in prespore cells (at protein level). Not expressed in the band of prestalk cells that lies behind the slug tip (pstO cells). Highly expressed in pstO derived papilla cells during culmination. Accumulates during aggregation and remains constant throughout culmination. Induced by acaA in the slug tip. Induced by dstA in prestalk cells, but not in prespore cells. Mutants fail to culminate. Development is normal until migratory slugs are formed, but slugs lacking cudA fail to culminate in the dark or in low level unidirectional light. In overhead light slugs lacking cudA eventually form defective fruiting bodies that lack both mature stalk cells and mature spore cells.