MET3 promoter-controlled expression of SFL1. The wild-type, sfl1/sfl1, and MET3p-SFL1/sfl1 strains were pregrown in minimal media at 30°C with or without methionine/cysteine (+M/C and −M/C, respectively), diluted, and inoculated to the same cell density in fresh medium. Filamentation was induced with the addition of GlcNAc to the medium. Note that filamentation is blocked in cells overexpressing SFL1 (bottom right panel). Bar, 10 μm.