POLARITY, SPATIAL-ORGANIZATION OF CYTOSKELETON, AND NUCLEAR DIVISION IN MORPHOLOGICALLY ALTERED CELLS OF SCHIZOSACCHAROMYCES-POMBE

To gain more information about the determination of cell polarity and its relationship to the organisation of cytoskeleton, we have examined the mycelial mutant sep1-1 and the multinucleate multipolar syncytia of the triple mutant sep1-1 spl1-1 cdc4-8 by indirect immunofluorescen ce techniques. We have found that polarity is predetermined by the sha pe of the cell. During transition from mitosis to interphase the micro tubules of the arising cytoplasmic cytoskeleton gradually form a baske t-like pattern that reflects the curvatures of the cell envelope. The presumable growing poles, where actin accumulates, usually correlates with the sites where the cell tapers and the microtubules converge. Ho wever, no growth can be launched at these sites if the cell surface ha s not been properly processed. Mitosis and meiosis are not affected si gnificantly by changes in cell morphology and polarity, but larger cel ls are less effective during sporulation. The azygotic asci produced b y multinucleate syncytia frequently contain over 20 ascospores.