cdc15_ΔSH3 cells are viable but exhibit cytokinesis defects. (A) cdc15_ΔSH3 cells were grown to midlog phase, fixed, and stained with DAPI and methyl blue to visualize DNA and cell walls, respectively. The asterisk indicates a cell with both cell separation and cytokinesis defects, the arrow marks a “paired” cell, the arrowhead denotes a cell with impaired cell separation, and the double arrowhead marks a cell with a “kissing nuclei” phenotype. The boxed area is from a separate micrograph but was included to demonstrate all of the phenotypes scored. (B) Denatured lysates were prepared from wild-type, cdc15_ΔSH3, and cdc15_ΔSH3-FLAG₃ cells grown at 32°C and immunoblotted with anti-Cdc15 serum or anti–α-tubulin for loading control. (C) Wild-type, cdc15_ΔSH3-FLAG₃, and cdc15_ΔSH3 cells were grown at the temperatures indicated, fixed, and imaged as in A (n = 200). (D) cdc15-GFP and cdc15_ΔSH3-GFP cells were grown to midlog phase at 25°C and imaged. Arrows indicate interphase cells, asterisks indicate contractile rings that have not begun constriction, and arrowheads mark constricting rings. The insets show a cell in which nodes of Cdc15_ΔSH3 are present. BF, bright field. Bars: (A) 10 μm; (D) 5 μm.