Single-cell analysis of growth in budding yeast and bacteria reveals a common size regulation strategy

TL;DR

This study reveals that both budding yeast and bacteria use a similar incremental size control strategy, where cells add a constant volume between specific cell cycle events, challenging previous assumptions about size regulation mechanisms.

Contribution

The paper demonstrates that budding yeast employs an incremental size control model similar to bacteria, with volume added between budding events rather than from birth to division.

Findings

Cell size control in yeast is well described by the incremental model.

Yeast adds volume between budding events, not from birth to division.

A common size regulation strategy exists for yeast and bacteria.

Abstract

To maintain a constant cell size, dividing cells have to coordinate cell cycle events with cell growth. This coordination has for long been supposed to rely on the existence of size thresholds determining cell cycle progression [1]. In budding yeast, size is controlled at the G1/S transition [11]. In agreement with this hypothesis, the size at birth influences the time spent in G1: smaller cells have a longer G1 period [3]. Nevertheless, even though cells born smaller have a longer G1, the compensation is imperfect and they still bud at smaller cell sizes. In bacteria, several recent studies have shown that the incremental model of size control, in which size is controlled by addition of a constant volume (in contrast to a size threshold), is able to quantitatively explain the experimental data on 4 different bacterial species [6, 5, 6, 7]. Here, we report on experimental results for the budding yeast Saccharomyces cerevisiae, finding, surprisingly, that cell size control in this organism is very well described by the incremental model, suggesting a common strategy for cell size control with bacteria. Additionally, we argue that for S. cerevisiae the volume increment is not added from birth to division, but rather between two budding events.