Fig. 5. dimB^- mutant cells fail to induce prestalk markers and stalk cells in response to DIF-1. (A) Stalk cell induction was measured in response to DIF-1 in the cAMP removal assay. The assay was repeated at least three times and a representative example is shown. Wild-type cells (AX4) differentiated as stalk cells, whereas mutants defective either in dimA or in dimB, or in both (dimAB^-) failed to do so. (B) In the dimB^- mutant, a prestalk reporter (ecmAO/lacZ) was non responsive to DIF-1, whereas a prespore marker (cotB/lacZ) was repressed as in the wild type. The results are means of three experiments where each assay was performed in triplicate. (C) The dimB^- mutant did not show rapid induction of prestalk gene expression (ecmA or ecmB) in culture, although the prespore gene (cotB) was repressed. After treatment with cAMP for 9 hours, samples were incubated with or without DIF-1 for 3 hours. Expression levels were normalized to IG7 and compared with or without DIF-1. In the case of ecmA and ecmB, fold increase is shown, and for cotB fold decrease. Broken line indicates no change.