Practice question

Ammonia, catabolic byproduct accumulating within slug interior, influences cell fate and timing of culmination. Elevated ammonia increases intracellular cAMP via inhibition of RegA phosphodiesterase, activates PKA, and promotes prespore gene expression while suppressing prestalk vacuolization. Tip region, where ammonia volatilizes, maintains lower concentration permitting prestalk differentiation. In vitro monolayer assays demonstrate ammonium chloride addition favors prespore markers and inhibits ecmB induction. Low ammonia would favor prestalk. Ammonia does not directly drive migration or division but acts as diffusible inhibitor linking nitrogen metabolism to developmental decision, ensuring prespore bias in regions of high metabolic activity.