A model for how fission yeast cells scale their size with ploidy

Yamashita Ichirou

It has long been known that eukaryotic cells with more DNA content are larger in cell size. However, no molecular mechanisms for this universal rule have been given. In the fission yeast Schizosaccharomyces pombe, diploid cells grow faster at 1.5-fold rate than haploid cells during the same cycle time. Here I discovered that cell division genes control not only cell growth or cell extension rate (CER) but also cycle time dose-dependently in diploid cells. These genes are well-known regulators for Cdc2, a conserved master regulator of eukaryotic cell cycle, such as inhibitors (wee1+ and pom1+) and activators (cdc25+ and nim1+). Actin content and its dynamics between monomer and polymer forms also control CER and cycle time through nuclear accumulation of Wee1 and Cdc25. Remarkably, doubling these genes in haploids reproduced CER of diploids. I propose a model in which regulatory cascades for Cdc2 activity govern the cell-size scaling with ploidy.

actin

cdc25

nim1

ploidy

scaling

wee1

eng

© Copyright by Ichiro Yamashita 2020

[Created] 2020-04-28