Fig. 6. gtaC^- null mutant cells exhibit defects in pstB cell and basal disc cell differentiation. Wild-type and gtaC^- mutant cells were transformed with representative prestalk and prespore reporter genes, and developed and stained for β-galactosidase activity at the slug (A) and early culminant (B) stages. ecmB-lacZ expression was aberrant as many staining cells were found at the rear of slugs and was absent from the basal disc. Brackets highlight the pstB cell population. Arrows indicate basal disc. Expression of all other markers was normal at the slug stage. However, ecmAO and ecmA-lacZ expression was absent at the expected position of the basal disc in mutant structures. Scale bars: 0.25 mm.