Saccharomyces cerevisiae seems to be a particularly suitable model organism for studying eukaryotic differentiation.
It is a unicellular eukaryote that can be approached with microbial genetic techniques. It undergoes meiosis and sporulation, a process analogous to gametogenesis in higher organisms. During meiosis, genetic recombination and chromosome segregation occur, leading to the generation of new genotypes. Sporulation takes place in a single cell, thereby eliminating the necessity of studying complex cell-cell interactions that occur during differentiation of multicellular organisms. The intent here is to introduce the sporulation practicum of S. cerevisiae. Background information is provided for facilitating the selection of strains and sporulation methods. The accompanying article (1) summarizes methods of growth, handling, and biochemical analysis of S. cerevisiae. Overview S. cerevisiae initiates meiosis and ascospore formation in response to specific starvation conditions. These processes are coordinately regulated and are accompanied by major biochemical and morphological changes. A single diploid cell forms an ascus
Morphological Changes
Vegetatively growing cells complete their cell cycle and arrest in Gl phase within several hours after transfer to a sporulation medium. The cells gradually change their shape from elongated to almost round, increase in size, and eventually form tetrahedral asci, each containing four spores easily visible in a phase-contrast microscope. The percentage of asci and time of their appearance vary with strain and sporulation conditions. Strains that sporulate well produce from 80