Relevance of phenotypic noise to adaptation and evolution

Area of Science:

• Cellular Biology
• Systems Biology
• Evolutionary Biology

Background:

• Biological processes exhibit inherent noise, particularly evident in stochastic gene expression.
• Phenotypic noise plays a critical role in how organisms adapt to diverse environments.
• This noise is also fundamental to the evolutionary development of robustness against genetic mutations.

Purpose of the Study:

• To demonstrate that phenotypic noise is essential for organism adaptation and the evolution of robustness.
• To elucidate a novel, generic mechanism for the selection of adaptive cellular states driven by noise.
• To investigate the role of noise in the evolution of gene networks for robustness against mutations.

Main Methods:

• Model simulations were employed to confirm the selection of adaptive states.
• Simulations of a stochastic gene expression network undergoing mutation and selection were used.
• Analysis of protein concentration dynamics (synthesis, dilution, degradation) in relation to cell growth.

Main Results:

• Stochastic gene expression noise inherently selects for adaptive cellular states in growing cells, independent of specific signaling networks.
• An adaptive state is less susceptible to noise due to high synthesis and dilution rates compared to non-adaptive states.
• A threshold level of gene expression noise is necessary for gene networks to evolve robustness against both noise and mutations.

Conclusions:

• Phenotypic noise is a key driver for both adaptation to environmental changes and the evolution of robustness in biological systems.
• Noise shapes the robustness of gene networks, influencing their resilience to intrinsic fluctuations and external mutations.
• A direct relationship exists between developmental robustness and mutational robustness, mediated by noise.