ULTRASTRUCTURAL-STUDY OF THE YEAST TONOPLAST DURING THE SHIFT FROM EXPONENTIAL TO STATIONARY PHASE

The vacuolar membrane or tonoplast of Saccharomyces cerevisiae changes dramatically during the transition from exponential to stationary phase. Stereological studies of thin sections reveal an increase in vacuole volume, changes in the tonoplast surface area, and a decrease in the surface to volume ratio of the vacuole. Freeze-fracture studies demonstrate changes in the distributions and frequencies of the tonoplast intramembranous particles. At one stage, rows of intramembranous particles surround polygonal areas depleted of particles. This stage is preceded and followed by stages during which the distribution of particles is dispersed. The particle distribution patterns are explained in terms of the fluid mosaic membrane model. © 1979 Academic Press, Inc.