ISOLATION AND CHARACTERIZATION OF POS MUTANTS DEFECTIVE IN CORRECT POSITIONING OF SEPTUM IN SCHIZOSACCHAROMYCES-POMBE

We have isolated mutants of fission yeast defective in correct positio ning of septum. In visual screening, we obtained 16 clones showing une qual septation at restrictive temperature, which were classified into three complementation groups. At restrictive temperature, all the muta nts underwent nuclear division normally. In cytokinesis, however, a co ntractile ring was formed at the site independent of the mitotic spind le. These results suggest that positional information for cytokinesis are not accurately transmitted to the cell equator. Furthermore, all t he mutants frequently displayed incorrect orientation and/or distortio n of septum, which suggests that the septum positioning is closely rel ated to correct orientation and organization of septum.