METABOLIC FLUXES REGULATE THE SUCCESS OF SPORULATION IN SACCHAROMYCES-CEREVISIAE

In this work we investigated to what extent cellular metabolism and en ergetics regulate sporulation in Saccharomyces cerevisiae and which me tabolic pathways are involved in such regulation, Sporulation, meiosis , and associated metabolic fluxes in S. cerevisiae strain CH1211 were studied in several experimental protocols involving changes of carbon source (acetate, lactate, or pyruvate) or cell density in sporulation medium, or changing the phase of batch growth at which cells were harv ested before transfer to sporulation medium. In acetate-based sporulat ion medium, the rate at which cells utilized glyoxylate and gluconeoge nic pathways correlated positively with the percentage of asci per cel l at 72 h, In contrast, in lactate sporulation medium the frequency of sporulation correlated negatively with both the rate of lactate consu mption and the fluxes through gluconeogenesis and the pyruvate-carboxy lase catalyzed step. In the presence of lactate, the respiratory capac ity did correlate positively with the percentage of asci per cell. The experimental data suggest that acetate limits fluxes to anabolic prec ursors during sporulation. In contrast, sporulation on lactate appears to be influenced by catabolic processes or, even more precisely, by t he respiratory capacity of yeast cells. The results obtained are discu ssed in terms of the hypothesis that an imbalance between anabolic and catabolic fluxes may be required for an efficient sporulation. (C) 19 96 Academic Press, Inc.