DIF‐1 induces its own breakdown in Dictyostelium.

DIF‐1 is a novel chlorinated alkyl phenone which induces differentiation of prestalk cells in Dictyostelium discoideum. It is broken down and inactivated by a cytoplasmic enzyme, DIF‐1 3(5)‐dechlorinase (hereafter referred to as DIF‐1 dechlorinase), which is found only in prestalk cells. We show that DIF‐1 dechlorinase levels are induced at least 50‐fold when cells are treated with DIF‐1. This response is rapid‐‐enzyme activity doubles within 15 min and is fully induced within an hour‐‐and occurs early in development, before other prestalk markers can be induced by DIF‐1. Maximum inducibility is seen towards the end of aggregation, when DIF‐1 dechlorinase is barely detectable in uninduced cells. The dose‐dependence reveals a threshold concentration of DIF‐1 (15 nM) below which almost no response is seen. Cyclic AMP, which is the chemoattractant during aggregation and plays a key role in later development, suppresses the induction of DIF‐1 dechlorinase by DIF‐1. We conclude that induction of DIF‐1 dechlorinase is one of the first steps on the developmental pathway which leads to prestalk cell differentiation, and suggest that the resulting negative feedback on DIF‐1 levels is an important part of the mechanism by which cells decide whether to become prestalk or prespore cells.