Growth Pattern of Single Fission Yeast Cells Is Bilinear and Depends on Temperature and DNA Synthesis

Abstract

Cell growth and division have to be tightly coordinated to keep the cell size constant over generations. Changes in cell size can be easily studied in the fission yeast Schizosaccharomyces pombe because these cells have a cylindrical shape and grow only at the cell ends. However, the growth pattern of single cells is currently unclear. Linear, exponential, and bilinear growth models have been proposed. Here we measured the length of single fission yeast cells with high spatial precision and temporal resolution over the whole cell cycle by using time-lapse confocal microscopy of cells with green fluorescent protein-labeled plasma membrane. We show that the growth profile between cell separation and the subsequent mitosis is bilinear, consisting of two linear segments separated by a rate-change point (RCP). The change in growth rate occurred at the same relative time during the cell cycle and at the same relative extension for different temperatures. The growth rate before the RCP was independent of temperature, whereas the growth rate after the RCP increased with an increase in temperature, leading to clear bilinear growth profiles at higher temperatures. The RCP was not directly related to the initiation of growth at the new end (new end take-off). When DNA synthesis was inhibited by hydroxyurea, the RCP was not detected. This result suggests that completion of DNA synthesis is required for the increase in growth rate. We conclude that the growth of fission yeast cells is not a simple exponential growth, but a complex process with precise rates regulated by the events during the cell cycle.

Cell size and growth regulation in the Arabidopsis thaliana apical stem cell niche

“…At least in some environmental conditions, various bacteria (23,24) and budding yeast (8,25,26) grow at constant rates per unit size (constant relative growth rates) throughout the cell cycle, and metazoan lymphoblasts (27) and human osteosarcoma cells (28) grow at constant relative rates during certain cell cycle phases, whereas fission yeast has been reported to show bilinear growth (two distinct phases of a constant absolute growth rate) (29). In plant tissues where wall-wall contacts between cell neighbors impose additional growth constraints compared with single cells, constant relative growth rates have been tacitly assumed (12,14,30), but this assumption and whether growth rate varies through the cell cycle have not been tested experimentally.…”

Molecular mechanism of size control in development and human diseases

“…By measuring a single cell growth rate during the cell cycle progression in both yeast and mammalian cells, several groups have discovered that the cell growth rate during the cell cycle is not constant but changes during the cell cycle stages. The cell growth rate is high during G1 phase but is decreased during mitosis [154][155][156][157], suggesting that cell division may inhibit cell growth. It has been proposed that increased Cdk activity and polarized actin cytoskeleton during mitosis may be responsible for the inhibition of cell growth [148].…”

Variability and constancy in cellular growth of Arabidopsis sepals

“…They also observed S curves for the growth of leaves, petals, anthers, carpels, pedicels, and filaments (Mündermann et al, 2005). In contrast, the growth in size of individual bacteria or fission yeast cells have been shown to fit bilinear curves (Reshes et al, 2008;Baumgärtner and Toli c-Nørrelykke, 2009).…”