Practice question

High ambient extracellular cAMP acts as positional cue favoring prespore differentiation through sustained protein kinase A activation. At millimolar levels, cAMP saturates desensitization mechanisms, maintaining intracellular messenger elevated, inducing transcription of prespore-specific genes encoding spore coat proteins while repressing prestalk markers. Low-density monolayer experiments show cAMP plus conditioned medium induces prespore markers, whereas DIF-1 alone induces prestalk. High cAMP therefore mirrors posterior slug environment where prespore cells reside. Prestalk formation prefers low cAMP together with DIF-1, vegetative growth requires folate, slug dispersal demands low cAMP oscillations, highlighting dosage-dependent fate specification mechanism.