Optimal segregation of proteins: phase transitions and symmetry breaking

TL;DR

This paper presents a theoretical framework analyzing how asymmetric protein segregation during cell division can optimize population fitness, revealing phase transitions and symmetry breaking phenomena in evolutionary strategies.

Contribution

It introduces a general model linking protein segregation asymmetry to population fitness, uncovering phase transitions and differences based on protein benefit or detriment.

Findings

Population fitness depends on segregation asymmetry.

Phase transition occurs between symmetric and asymmetric segregation.

Different transition types for beneficial versus deleterious proteins.

Abstract

Asymmetric segregation of key proteins at cell division -- be it a beneficial or deleterious protein -- is ubiquitous in unicellular organisms and often considered as an evolved trait to increase fitness in a stressed environment. Here, we provide a general framework to describe the evolutionary origin of this asymmetric segregation. We compute the population fitness as a function of the protein segregation asymmetry $a$, and show that the value of $a$ which optimizes the population growth manifests a phase transition between symmetric and asymmetric partitioning phases. Surprisingly, the nature of phase transition is different for the case of beneficial proteins as opposed to proteins which decrease the single-cell growth rate. Our study elucidates the optimization problem faced by evolution in the context of protein segregation, and motivates further investigation of asymmetric protein segregation in biological systems.