Copper up-regulation of cuoA (panel A), cuoB (panel B), or cuoC (panel C) promoter during development. Strains JM51AZY, JM51BZY, and JM51CDWZY (see Table 1) were incubated on CF agar plates containing 0 (□), 20 (▪), 40 (•) or 60 μM (▴) copper sulfate. β-Galactosidase specific activity in cell extracts was determined as described in Materials and Methods. Error bars indicate standard deviations.