Cell cycle dependency of sporulation in Saccharomyces cerevisiae.

The study of sporulation in Saccharomyces cerevisiae is complicated by the fact that not all cells in the population complete sporulation and that the kinetics of development of those which do are not synchronous. By separating vegetative cells by zonal rotor centrifugation into fractions of increasing cell volume and hence progressive stages of the vegetative cell cycle, it was possible to observe sporulation of more homogeneous, synchronous populations. The capacity of S. cerevisiae to complete sporulation is low for small single cells at the beginning of the cell cycle and is greatest for large budded cells about to divide. The capacity of a cell to complete sporulation thus appears to be directly related to the stage in the vegetative cell cycle from which it was taken. The use of synchronously sporulating cultures made it possible to examine very early decision events leading to the commitment of a cell to sporulation. In addition, differences in the capacity of a mother and daughter cell produced by cell scission were examined.