Dominant constraints on the evolution of rhythmic gene expression

Area of Science:

• Evolutionary biology
• Chronobiology
• Genomics

Background:

• Circadian clocks, crucial for daily physiological rhythms, exhibit conserved autoregulatory feedback loops in core transcriptional regulators across diverse species.
• While the core clock mechanisms are conserved, the principles governing circadian gene expression output remain largely unexplored.

Purpose of the Study:

• To investigate whether conserved design principles, similar to core clock mechanisms, govern rhythmic gene expression across species.
• To identify common patterns in rhythmic gene expression and explore the evolutionary pressures shaping them.

Main Methods:

• Comparative analysis of rhythmic gene expression in eight diverse species.
• Large-scale computational simulations to test hypotheses regarding energetic constraints on gene expression evolution.

Main Results:

• Identified four common distribution patterns of cycling gene expression across the studied species.
• Computational simulations supported the hypothesis that reduced energetic costs constrain the evolution of rhythmic gene expression.
• Demonstrated that selective pressure against high energy expenditure regenerates observed cycling gene patterns and influences peaks of rhythmic expression.

Conclusions:

• Circadian regulation imposes selective pressure that efficiently removes unnecessary gene products, significantly impacting transcriptome evolution.
• Energetic cost is a key evolutionary constraint shaping the patterns of rhythmic gene expression in circadian clocks.