FIG. 4.

Expression of β-galactosidase by mse^S and pseudo-urs1^S SMK1 promoter plasmids during sporulation. Yeast strain LNY150 transformed with a plasmid expressing β-galactosidase under the control of the wild-type (A), pseudo-urs1^S (B), mse^S (C), or pseudo-urs1^S mse^S (D) −139 promoter (pMDP89, pMDP119, pMDP174, or pMDP176, respectively) was synchronously sporulated, and β-galactosidase levels (expressed as units per milligram of total protein) were determined at 2-h intervals. The experiment was performed at least twice for each promoter with similar results.