Ammonia is produced by growing amoebae and by cells throughout development via oxidative degradation of exogenously obtained or endogenous proteins. Protein degradation is the primary source of nitrogen, carbon, and energy for growing and developing cells. Ammonia production/concentration is a reflection of the producing cell type and of the macro- and/or micro-environment of the cell. Developing Dictyostelium cells thus use ammonia as a signal for monitoring the environment, the morphological changes and the differentiation events that have occurred, and thus their progression through the developmental program.

Ammonia singnaling affects a number of processes/steps during development. The numbers below correspond to the numbers in the above schematic drawing of the developmental program:

1. alters rate of movement of chemotaxing amoeba.

2. modulates prestalk and prespore gene expression.

3. mediates choice between migrating slug verses terminal differentiation/culmination.

3. modulates cAMP dependent protein kinase A activity.

4. modulates chemotaxis of anterior like cells (ALCs) during slug migration to maintain proper prestalk/prespore ratios.

4. regulates cell proportioning and differentiation.

5. inhibits stalk cell differentiation.

5. promotes spore differentiation.

6. mediates spacing of raised sori of mature fruiting bodies.