Fine structure of ascospore development in the yeast Saccharomyces cerevisiae

Abstract

In the yeast Saccharomyces cerevisiae, ascospore development is initiated through the movement of nuclear material and cytoplasm into an envelope, or prospore wall. The prospore wall is first observed at the cytoplasmic side of the spindle plaque during the second meiotic division. When the 'prospores' attain their full size, the envelope closes and the ascospore becomes spherical. At this stage the central, electron-transparent, zone of the prospore wall becomes more prominent. Eventually the central zone expands into the mature cell wall. This description is based on observations of glutaraldehyde-fixed cells, and it differs in some details from reports based on KMnO4-fixed yeast cells.