Figure 1.

Temperature-sensitive defects in actin ring formation of rng2 mutant cells. (A, B) After growing at 25°C, rng2^ts (A) and wild-type (B) cells were shifted to 36°C and fixed after 0, 30, 60, or 90 min incubation before being stained for DNA and F-actin. Arrowheads indicate abnormal actin assembly in the medial region. (C) Percentage of binucleate cells. (D) Percentage of binucleate cells without normal CR. As these data include late telophase and septating cells, the CR was not found in about 20% of wild-type cells. Data are expressed as the means±s.d. (error bars) of three independent experiments. More than 120 cells were counted for each point. Note that rng2^ts cells tended to aggregate, which prevented their correct observation, so we analysed cells outside of aggregates. (E, F) Phenotypes of rng2^ts mutant cells at anaphase. Wild-type (E) or rng2^ts (F) cells expressing GFP-atb2 (α-tubulin) were fixed and then stained for DNA and F-actin after 30 min incubation at 36°C. Cells with a long mitotic spindle were photographed. The percentages of cells with the depicted phenotypes are shown. About 40 cells from two independent experiments were observed for each strain. Asterisks and an arrowhead indicate the CR and the abnormal accumulation of F-actin, respectively. (G, H) Localization of Rlc1-GFP in the CR. After growing at 25°C, wild-type (G) or rng2^ts (H) cells expressing Rlc1-GFP were fixed and then stained for DNA and F-actin. The percentages of cells with the depicted phenotypes are shown. More than 60 cells from two independent experiments were observed for each strain. Bars: 5 μm.