A cell cycle cue triggers cell growth resumption after division

The decoupling of the fundamental processes of cell division and growth is important for maintaining cell integrity. Through a chemical approach, we delayed the clock that controls when cells separate, uncoupling cell division and cell growth. This led to polarized cell growth before the cells completed separation. Using fluorescent markers to denote the cell’s stage in the cell cycle, we observed that only cells that were in mitosis exhibited this uncoupling. Previously it was thought that growth resumption occurred after completion of cell division, but this observation suggests that growth is triggered earlier, from a mitotic cue. This mitotic cue allows the tips to become better equipped to compete with the septum, causing the septum not to separate. Cdc42, a conserved GTPase that is a master regulator of cell division and polarity in eukaryotes, appears at the septum and remains there until the cells separate then oscillates between the cell tips. However, in the uncoupled cells, Cdc42 leaves during septum formation, before the cells separate and is found at the tips. Further investigations into the specific cues could lead to a better understanding of what this cell cycle trigger is and how this cue affects Cdc42 at the tips.