DIF signalling and cell fate

The DIFs are a family of secreted chlorinated molecules that control cell f ate during development of Dictyostelium cells in culture and probably durin g normal development too. They induce stalk cell differentiation and suppre ss spore cell formation. The biosynthetic and inactivation pathways of DIF- 1 (the major bioactivity) have been worked out. DIF-1 is probably synthesis ed in prespore cells and inactivated in prestalk cells, by dechlorination. Thus, each cell type tends to alter DIF-1 level so as to favour differentia tion of the other cell type. This relationship leads to a model for cell-ty pe proportioning during normal development.