# Congruence between noise and plasticity in protein expression

## TL;DR

The study finds that nonessential genes in E. coli show a link between protein expression variability and sensitivity to environmental changes, while essential genes do not.

## Contribution

The paper provides empirical evidence of a coupling between noise and plasticity in protein expression that depends on gene essentiality.

## Key findings

- Essential genes in Escherichia coli exhibit lower noise and plasticity compared to nonessential genes.
- Nonessential genes show a positive correlation between noise and plasticity in protein expression.
- The study uses flow cytometry to measure both noise and plasticity from the same dataset in E. coli.

## Abstract

Gene expression responds to various types of perturbations, such as mutations, environmental changes, and stochastic molecular noises. These different types of variability are often interdependent, where genes sensitive to one perturbation tend to be sensitive to others. However, the relationship between plasticity (variability in response to environmental changes) and noise (variability among cells under the same conditions) in gene expression remains debatable. Previous studies predicted a positive correlation between plasticity and noise in nonessential genes, but these were often measured at different levels: plasticity at the mRNA level and noise at the protein level. This methodological discrepancy complicates the understanding of their relationship. We addressed this by measuring protein expression in Escherichia coli, quantifying both plasticity and noise from the same dataset using flow cytometry. Essential genes exhibited lower noise and plasticity than nonessential genes. Nonessential genes showed a positive correlation between noise and plasticity, while essential genes did not. This study provides empirical evidence of essentiality-dependent coupling between noise and plasticity in protein expression, highlighting the organization of different types of variabilities.