Sugar uptake during early ascosporulation in Saccharomyces cerevisiae

The uptake rates of several sugars were examined in cells of Saccharomyces cerevisiae during early ascosporulation. The pH optimum of glucose uptake was about 7 both in the vegetative cells and in the cells after transfer to the sporulation medium. The glucose uptake rate of the cells 3 h after transfer to sporulation medium was about two-fold higher than that of vegetative cells. Uptake rates of glucose, mannose, and galactose increased during the first 3 h and then decreased slightly. The uptake rate of lactose increased throughout the 4 h period of observation, and the uptake rate of 2-deoxy-glucose was constant but at a very low level. Uptake rates of xylose and rhamnose, using the 3,5-dinitrosalicyclic acid method, were below detection levels.