Effects of pressure stress on the fission yeast Schizosaccharomyces pombe cold-sensitive mutant nda3

To investigate the influence of pressure stress on the cell cycle of Schizo saccharomyces pombe, we used a cold-sensitive nda3-KM311 mutant which arres ts cell division at a step similar to the mitotic prophase, proposed by Hir aoka and colleagues (Cell 39 (1984) 349-358), under the restrictive tempera ture, 20 degrees C. The nda3-KM311 cells were first aerobically grown at 30 degrees C, transferred to 20 degrees C for 4 h and shifted to a permissive temperature of 36 degrees C for 15 min. The cells were treated with 100-20 0 MPa pressure and studied by electron and fluorescence microscopy. At 100 MPa, the nuclear membrane was damaged and the matrix of mitochondria had an electron-dense area. At 150 MPa, the nuclear membrane was broken over broa d areas; numerous small vacuoles had fused into large pieces. Actin patches were concentrated in the central region and actin rings were seen in the 2 0 degrees C-grown cells. Even at 100 MPa, specific actin distribution was l ost. Although at 100 MPa, long and fine actin cables were seen all over the cells, large actin patches and the actin rings remained in the center of t he cell. They changed into thick and short cables at 150 MPa and above 200 MPa they decomposed but the actin ring was visible even with faint fluoresc ence. Immunoelectron microscopic observation confirmed this phenomenon. (C) 1999 Federation of European Microbiological Societies. Published by Elsevi er Science B.V. All rights reserved.