Lipid Droplets are Polarized during G2 Phase and Increase in Number at the Septum after its Formation in Fission Yeast Cells

Abstract

Lipid droplets are now being appreciated as active organelles involved in a variety of cellular processes and not just inert storage depots for neutral lipids. There is evidence that lipid droplet dynamics are linked to cell cycle progression in both budding and fission yeast. In fission yeast, S. pombe, the number of lipid droplets follows an oscillatory cycle where the number increases during G2 phase and is roughly halved when the septum forms at the end of M phase. We observe that droplets are polarized to the cell tips in a temperature sensitive mutant (cdc25), whose cell cycle is arrested in late G2 phase at 36 C well before formation of the septum. Here, we investigate the mechanisms for this distribution. We also present data showing that the number of lipid droplets locally increases on both sides of the septum in the daughter cells. The droplets are later distributed throughout the cells.