Fig. 1. Clp1p is essential when cell division structures are mildly perturbed and ensures the completion of cytokinesis. (A) Cells of the indicated genotype were streaked to YES plates and assayed for colony formation after 3 days at 30°C (left) and 32°C (right). (B) Cells of indicated genotype were cultured to exponential growth phase at 24°C and then shifted to 32°C for 5 hours, fixed and then stained with aniline blue and DAPI to visualize cell wall/septa and nuclei respectively. Septa are indicated with arrowheads. Scale bar 10 µm. (C) Septum formation in group I cytokinesis mutants at semi-permissive temperatures in the presence or absence of Clp1p. Cells of the indicated genotype were cultured to exponential growth phase at 24°C, shifted to 32°C for 5 hours, fixed and then stained with aniline blue and DAPI to visualize cell wall/septa and nuclei respectively. (D) Wild-type and clp1 cells were cultured to exponential growth phase at 24°C, synchronized in early G2 by centrifugal elutriation and then treated with a low dose (0.2 µM) of Lat A or DMSO (solvent control) and cultured at 32°C. Cells were subsequently fixed at 30 minute intervals and stained with DAPI (nuclei) and aniline blue (cell wall/septa). (E) Wild-type and clp1 cells treated as in Fig. 1D (at t=240 minutes) and stained with both DAPI (nuclei) and aniline blue (cell wall/septa). Imperfect, but functional, septa are indicated with arrowheads. Scale bar 10 µm. (F) Tenfold serial dilutions of wild-type and clp1 cells grown on YES plates containing either 0.25 µM Lat A or DMSO. Images were captured after 3 days growth at 32°C. (G) Wild-type and clp1 cells were cultured to exponential growth phase at 24°C, synchronized in early G2 by centrifugal elutriation and then treated with a low dose (0.2 µM) of Lat A or DMSO (solvent control) and cultured at 32°C. Cell number was determined using a haemocytometer.