Fig. 2. Expression of rblA. (A) Northern blot showing expression beginning at 12 hours. (B) ß-Galactosidase activity in extracts of developing cells carrying the rblA::pgal reporter, detected using chemoluminescence. Two independent clones were measured. The gray curves (left scale) show vegetative activity and an increase beginning at 8-10 hours; the black curves (right scale) show an ultimate 200-fold upregulation. (C) Colony lift of growing clone of rblA::pgal cells, stained with X-gal and counterstained with Ponceau Red. The heavy red band (left) is the clone edge, made up of proliferating cells. Multicellular stages (slugs and fruiting bodies) are on the right. Expression is visible only at multicellular stages.