The Cell Cycle in the Fission Yeast, Schizosaccharomyces pombe. V. Relationship between Cell Size and Division Delay due to Heat Shock

Abstract

The relationship between cell size and division delay due to a single heat shock has been investigated in individual cells of Schizosaccharomyces pombe. The heat shock was applied to an asynchronously growing culture, to a hydroxyurea-synchronized culture in which the cell size was larger than normal, and a hydroxyurea-synchronized culture incubated in a starvation medium which could divide twice but barely elongated. After the heat shock was applied, cells were transferred to a small chamber and observed continuously.
Regardless of the experimental situation, the period from the end of heat treatment to cell division was negatively proportional to cell size at the end of heat shock, except that the time from the end of heat shock to division in cells larger than a particular size was consistently minimal. In addition, cells grown in a rich medium, regardless of the cell size at the end of heat shock, divided at the critical size which had been found for exponentially proliferating cells, but cells larger than the particular size divided above the critical size. Homeo-stasis at division also was maintained in shocked cells grown in a rich medium.
Our results are explained by the "set-back" hypothesis (22) and are discussed in relation to our "effector-producer" hypothesis (14).