Fig. 1. Osmotic stress generates SICS at cell tips and perturbs septation. (A) Wild-type cells grown to mid-log phase in YES media were fixed and processed for Calcofluor staining at the indicated times after the addition of sorbitol to a final concentration of 1.2 M. Sorbitol treatment induced SICS at one (cell 1) or both (cells 2 and 3) cell tips and, later, away from tips (arrow in inset; the boxed cell highlighted in the 120-minute panel is shown magnified 2x in the inset). Long cells containing one septum (asterisk in the 120-minute panel), or two or three septa (180-minute panel) appeared following sorbitol treatment. (B) Cells were fixed 60 minutes post-stress and stained with the indicated final concentrations of Calcofluor white. (C) Sorbitol-treated wild-type cells were fixed 180 minutes post-stress, and were stained with DAPI and Calcofluor (left-hand panel) and TRITC-phalloidin (right-hand panel) to localize chromatin and F-actin, respectively. (D,E) Wild-type cells were grown to mid-log phase and subjected to the indicated stresses. Cells were fixed and processed for Calcofluor-white staining 30 minutes (D,E) and 60 minutes (E) post-stress (n=200). Scale bars: 5 µm.