Fig. 7. pstB cells do not sort to the prestalk-prespore border at any developmental stage. Wild type and gtaC^- mutant ecmB-lacZ transformants were stained at the tip mound (A,D), early finger (B,E) and standing (C,F) slug stages. A collection of staining cells is visible towards the prestalk-prespore boundary in wild-type specimens as soon as morphological pattern appears. In mutant specimens, staining cells always appeared to be scattered throughout the prespore zone and became concentrated towards the rear as development progressed. Scale bars: 0.25 mm.