Differential paralog divergence modulates genome evolution across yeast species

Area of Science:

• Evolutionary Biology
• Genetics
• Microbiology

Background:

• Evolutionary trajectories are shaped by both selective pressures and inherent genetic differences.
• Discerning historical genetic variations between species is challenging.
• Experimental evolution offers a controlled method to compare evolutionary potential.

Purpose of the Study:

• To investigate if experimental evolution selects for similar adaptive mutations across different yeast species.
• To explore how genetic background influences adaptive evolution in Saccharomyces species.
• To understand the role of paralog divergence in driving genome evolution.

Main Methods:

• Experimental evolution of Saccharomyces cerevisiae, S. paradoxus, S. mikatae, S. uvarum, and hybrids under sulfate limitation.
• Analysis of gene amplification (SUL1 and SUL2) as an adaptive mechanism.
• Fitness assays of gene deletions and amplifications.
• Gene expression analysis using chimeric promoter-ORF constructs.

Main Results:

• Saccharomyces cerevisiae consistently amplified the high-affinity SUL1 gene.
• S. paradoxus and S. mikatae populations amplified SUL1, while S. uvarum selected for SUL2 amplification.
• S. uvarum SUL2 conferred greater fitness under sulfate limitation than S. uvarum SUL1.
• Differential fitness was primarily attributed to regulatory changes in the S. uvarum SUL1 promoter.

Conclusions:

• Yeast species exhibit differential sub-functionalization of sulfate transporters due to recent noncoding sequence changes.
• Paralog divergence in genetic background significantly influences adaptive evolution and genome changes.
• Experimental evolution highlights species-specific adaptive strategies in response to environmental challenges.