Environment-dependent epistasis increases phenotypic diversity in gene regulatory networks

Area of Science:

• Evolutionary biology
• Systems biology
• Synthetic biology

Background:

• Mutations in gene regulatory networks (GRNs) can be detrimental or drive evolutionary innovation.
• Epistasis, where mutation effects depend on genetic background, complicates understanding GRN evolution.
• Environmental context significantly influences epistatic interactions.

Purpose of the Study:

• To systematically investigate the impact of pairwise and triplet epistasis on GRN expression patterns.
• To explore how environmental gradients modulate epistatic effects within GRNs.
• To understand the role of environment-dependent epistasis in generating phenotypic diversity.

Main Methods:

• Utilized synthetic biology tools in *Escherichia coli* to construct and assay mutant GRN genotypes.
• Applied an inducer gradient across a spatial domain to simulate environmental variation.
• Quantified gene expression patterns resulting from various combinations of mutations.

Main Results:

• Observed a significant prevalence of epistasis in GRN expression patterns.
• Demonstrated that epistasis magnitude and sign vary across the inducer gradient.
• Discovered that environment-dependent epistasis generates a wider range of expression phenotypes than predicted without it.

Conclusions:

• Environment-dependent epistasis is a crucial factor in generating phenotypic diversity within GRNs.
• These findings provide insights into the evolution of hybrid incompatibilities and novel traits.
• Synthetic biology offers a powerful approach to dissect complex genetic interactions in evolutionary contexts.