Fig. 4. Development of cGMP-mutant cell strains. Mutant cells were starved as a monolayer on non-nutrient agar plates. Pictures of developing cells were taken at 5 hours after the start of starvation. gc-null cells lack cGMP synthesis, whereas gpbC-null cells lack the cGMP-target protein GbpC that mediates cell polarity. sGCN, expressed in gc-null cells, is catalytically active but cytosolic. sGCcat is catalytically inactive but localizes to the anterior of the cell, an event that previously was shown to stabilize the leading edge in a spatial gradient.