Fig. 1. ACG promoter activity in developing structures. (A-C) D. discoideum wild-type cells were transformed with vector ACG::gal, which contains a gene fusion of the ACG promoter and the ß-galactosidase reporter gene. Cells were starved on nitrocellulose filters supported by PB agar and developing structures were fixed and stained with X-Gal. (A) aggregate; (B) standing slug; (C) mature fruiting body. (D,E) D. discoideum wild-type cells were transformed with vector ACG::ile-gal, where ile-gal encodes a labile form of ß-galactosidase with a 30-minute half-life. Slugs (D) and mid-culminants (E) were stained with X-Gal. Scale bars: 100 µm.