Abstract

In the fission yeast Schizosaccharomyces pombe, twenty sporulation-specific genes (spo1–spo20) have been identified and analyzed. We found that a mutation designated spo14–221 caused cold-sensitive sporulation: ascospores were formed at 30°C but not at 23°C. Nuclear staining with 4′,6-diamidino-2-phenylindole revealed that a strain with this mutation completed meiosis even at the restrictive temperature. Electron microscopy showed that assembly of forespore membranes during meiosis II was abnormal and incomplete in the mutant cultured at 23°C. Temperature-shift experiments indicated that the cold-sensitive period began during early meiosis I and terminated with the end of meiosis II. These results suggest that the product of the spo14 gene is synthesized and executes its function prior to the expression of the sporulation-deficient phenotype of the mutant, prior to the formation of the abnormal forespore membrane.

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