Fig. 7. Induction of stalk cell differentiation by DIF-1. Comparison of the DIF-1 sensitivity of AX2 cells and an Ax2/gskA– strain. Ax2 (black circles) and gskA-null mutant cells (white circles) were plated at low density (10⁴ cells/cm²⁾ in stalk medium in 5 mM camp). After 24 hours incubation, cAMP was washed off and replaced with DIF at varying concentrations for a further 24 hours. Stalk cells were counted and expressed as a percentage of total number plated. Data are expressed as mean±s.e.m., and represent the combination of two clones analysed in triplicate. (B) Comparison of the effect of cAMP on AX2 cells, a random integrant and an Ax2/gskA– strain. Cells were treated as in A, but incubated in 100 nM DIF±5 mM cAMP, as indicated. (C) Comparison of the effect of cAMP on AX2 cells and an Ax2/gskA– strain using different inductive concentrations of DIF-1 Cells were treated as in A, but incubated in 100, 10 or 5 nM DIF ±5 mM cAMP, as indicated.