Fig. 7. The regulation of DIF-1 production by DIF in living cells. (A) TLC showing the inhibition of DIF-1 synthesis by DIF-1. Accumulation of the DIF-1 metabolites, DIF-3 and DM3, is inhibited in parallel with DIF-1. (B) Quantitation of the results shown in A; (C) effect of compounds related to DIF-1 on DIF-1 synthesis. All these compounds are produced during development and therefore are potential regulators of DIF-1 synthesis: DIF-2 is a homologue of DIF-1 with one fewer carbon atom in the alkyl side chain, DIF-3 is produced from DIF-1 by a single dechlorination; DM3 is produced from DIF-3 by an oxidation of the side chain. Cells of strain V12M2 were incubated for 12 hour in submerged culture with cAMP and ³⁶Cl^–. DIF-1 or related compounds were added at the start of the experiment, as indicated. Labelled compounds were extracted from cells and media, resolved by TLC and quantitated using a Phosphorimager. Data are typical of three experiments.