Carbohydrate metabolism during ascospore development in yeast

Abstract

Carbohydrate metabolism, under sporulation conditions, was compared in sporulating and nonsporulating diploids of Saccharomyces cerevisiae. Total carbohydrate was fractionated into trehalose, glycogen, mannan, and an alkali insoluble fraction composed of glucan and insoluble glycogen. The behavior of 3 fractions was essentially the same in both sporulating and nonsporulating strains; trehalose, mannan, and the insoluble fraction were all synthesized to about the same extent regardless of a strain's ability to undergo meiosis or sporulation. In contrast, aspects of soluble glycogen metabolism depended on sporulation. Although glycogen synthesis took place in both sporulating and nonsporulating strains, only sporulating strains exhibited a period of glycogen degradation, which coincided with the final maturation of ascospores. The carbohydrate composition of spores isolated from mature asci was also determined. Spores contained all components present in vegetative cells, but in different proportions. In cells, the most abundant carbohydrate was mannan, followed by glycogen, then trehalose, and finally the alkali insoluble fraction; in spores, trehalose was most abundant, followed by the alkali insoluble fraction, glycogen, and mannan in that order.