Abstract
In response to the signaling polyketide DIF-1 DimB directly activates transcription of the ecmB gene in pstB cells; a subset of the prestalk cells that are the precursors of the basal disc. We show that the promoter of pspA, a prespore-specific gene, also contains a DimB binding site. Mutation of this site causes ectopic expression in the prestalk region and ChIP analysis shows that DIF-1 induces binding of DimB to the pspA promoter. DIF-1 represses pspA gene expression in a suspension cell assay but this repression is abrogated in a dimB null strain. These results suggest a coupled control mechanism, whereby the same DIF-DimB signaling pathway that directly activates ecmB gene expression directly represses pspA gene expression.
Highlights
Biological systems frequently employ coupled control mechanisms to effect on-off switching because they ensure a tightly coordinated regulation
In the Dictyostelium asexual life cycle a single cell type can differentiate as either a prestalk or a prespore cell. This switch is governed by a form of coupled control whereby the same extracellular signaling molecule, DIF-1, both induces certain types of prestalk differentiation and represses prespore differentiation [1,2]
DimB is required for DIF inducibility of ecmA and DimB accumulates in the nucleus and binds to the ecmA promoter when cells are treated with DIF [8,9]
Summary
Biological systems frequently employ coupled control mechanisms to effect on-off switching because they ensure a tightly coordinated regulation. In the Dictyostelium asexual life cycle a single cell type can differentiate as either a prestalk or a prespore cell. This switch is governed by a form of coupled control whereby the same extracellular signaling molecule, DIF-1 (hereafter termed DIF), both induces certain types of prestalk differentiation and represses prespore differentiation [1,2]. DIF induces expression of the related ecmB gene in pstB cells, the immediate precursors of the lower cup and outer basal disc of the culminant. This induction too depends directly upon DimB [10]
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