Fig. 9. gtaC^- mutant defects are phenocopied by DIF signalling mutants. (A) Expression of ecmB-lacZ at the slug stage. In wild-type structures clusters of high expressing cells are found at the prestalk/prespore boundary (pstB cells). In DIF signalling mutants (gtaC^-, dimA^-, dimB^- and dmtA), these cells are mostly found clustered towards the slug rear. (B) Basal disc differentiation is aberrant in DIF signalling mutants. st-lacZ expression was used to label the stalk and basal disc. Although staining can be observed in the stalk proper in mutant fruiting bodies, no staining is present in the basal disc. (C) The basal disc is absent from DIF signalling mutants. The arrowhead shows the basal disc of a typical wild-type fruiting body. Although a morphological fruiting body with stalk and spore is formed in each DIF signalling mutant, the basal disc structure is much reduced or absent. Scale bars: 0.25 mm.