FIG. 1.

Smp1 transcription factor modulates HOG1-mediated STL1 gene expression. (A) Yeast multicopy plasmids capable of inducing STL1-LacZ expression in wild-type cells were isolated, and their dependence on HOG1 was assayed in wild-type cells (YEN2) and hog1Δ cells (YEN7). A representative filter β-galactosidase assay demonstrating induction of STL1-LacZ by several positive clones from the screening is shown. (B) Smp1 modulates expression of STL1-LacZ. Wild-type, hog1Δ, and smp1Δ strains containing the STL1-LacZ reporter system (strains YEN2, YEN7, and YEN48) were transformed with a control plasmid or a multicopy plasmid expressing SMP1. β-Galactosidase activity was assayed in cells that were grown to mid-log phase and that were subjected (open bars) or not subjected (control; filled bars) to hyperosmotic stress (0.4 M NaCl for 35 min). β-Galactosidase activity is given in nanomoles per minute per milligram and is the result of the measurement in quadruplicate of results for two independent transformants.