INDUCTION OF MEIOSIS AND SPORULATION IN DIFFERENTLY AGED CELLS OF SACCHAROMYCES CEREVISIAE

It has been known that age 0 cells of Saccharomyces cerevisiae, lacking any bud scar, hardly form any spore, while the cells of age 1 or more sporulate abundantly. Based on this finding we attempted to elucidate at what stage of cell age the age 0 cells acquire sporulation activity. Aliquots of the synchronous culture started from small age 0 cells were transferred to sporulation media at time intervals and sporulation in each culture was examined. Results showed that age 0 cells were endowed with the sporulating ability just before the first bud initiation. The sporulation ability decreased after the first budding and increased again at the stage of the second budding. The fluorescent staining of the resultant asci revealed that most asci derived from cultures just before the initiation of the first budding carried neither bud nor bud scar. It was also observed that the number of spores per ascus changed with the cellular age. Cells in synchronous culture of large cells, most of which bear more than one bud scar showed similar changes in the sporulating ability during their cell cycle. Addition of tomato juice to the culture media preceding sporulation stimulated the sporulating ability.