METABOLIC PATHWAYS FOR DIFFERENTIATION-INDUCING FACTOR-I AND THEIR REGULATION ARE CONSERVED BETWEEN CLOSELY-RELATED DICTYOSTELIUM SPECIES, BUT NOT BETWEEN DISTANT MEMBERS OF THE FAMILY

There is suggestive evidence that a conserved signalling system involv ing differentiation inducing factor-1 (DIF-1) controls stalk cell diff erentiation in a variety of slime mould species. In the standard labor atory species, Dictyostelium discoideum, DIF-1 is first inactivated by dechlorination catalysed by DIF-1 dechlorinase, then by several hydro xylation events, so that eventually about 12 metabolites are produced. If DIF-1 is used as a signal molecule in other species, they too must be able to metabolize it. We report here that the essentials of DIF-1 metabolism are conserved in D. mucoroides, the closest relative of D. discoideum. Both the dechlorinase and hydroxylase enzymes were presen t in D. mucoroides, and living cells of both species produced a simila r spectrum of metabolites from [H-3]DIF-1. Furthermore, DIF-1 dechlori nase was induced by DIF-1, as in D. discoideum, and this induction was repressed by ammonia and cAMP. DIF-1 dechlorinase could not be detect ed in cell extracts from D. minutum or Poly-sphondylium violaceum. How ever, Living cells of both species are able to metabolize DIF-1; P. vi olaceum seems to produce a small amount of the monodechlorinated compo und, DIF-3, but all other metabolites from both species appear to be u nique. Thus all investigated species can metabolize DIF-1, but the exa ct route of metabolism is not highly conserved.