Different levels of catabolite repression optimize growth in stable and variable environments

Area of Science:

• Microbiology
• Genetics
• Evolutionary Biology

Background:

• Organisms adapt to environmental shifts by altering gene expression.
• Transcriptional reprogramming is time- and energy-consuming, potentially causing maladaptation.
• Understanding adaptation dynamics is crucial for predicting organismal responses to environmental change.

Purpose of the Study:

• Investigate transcriptional reprogramming and fitness dynamics in Saccharomyces cerevisiae under changing carbon environments.
• Analyze how environmental variability influences carbon catabolite repression strategies.
• Identify genetic underpinnings of distinct adaptation strategies.

Main Methods:

• Population and single-cell analyses of yeast growth and gene expression.
• Evolutionary experiments with varying carbon source frequencies and durations.
• Whole-genome sequencing of evolved mutants.

Main Results:

• Observed heterogeneity in yeast strain adaptation speed and uniformity.
• Evolved mutants demonstrated distinct "specialist" and "generalist" carbon catabolite repression strategies.
• Mutations in regulatory genes (e.g., HXK2, STD1) altered metabolic gene regulation and transcriptional noise, enabling stochastic sensing.

Conclusions:

• Environmental stability versus variability favors different transcriptional reprogramming and growth strategies.
• Specialist strategies optimize growth in stable environments but are slow to adapt.
• Generalist strategies offer faster adaptation but reduce fitness in stable, glucose-rich conditions.