Figure 6. A scheme for the regulation of pspA gene expression.

The scheme hypothesises a general activator of transcription (yellow-boxed) that has the potential to direct transcription in all cells in the slug. However, DimB acts in pstO cells in its repressor form (red-boxed) to prevent the activator functioning. Not shown here is a proposed functionally redundant repressor that can subsume the role of DimB as a repressor of pspA in a dimB- strain. The ecmA promoter is hyper-active in pstO cells of the DimB null strain, so is shown as being co-repressed by the DimB repressor form. In pstB cells the ecmB gene is directly induced by the activating form (green-boxed) of DimB.