Genome duplication in a long-term multicellularity evolution experiment

Area of Science:

• Evolutionary biology
• Genomics
• Yeast research

Background:

• Whole-genome duplication (WGD) is common in eukaryotes and drives evolution.
• Polyploid genome instability poses challenges to understanding WGD origins and persistence.
• The evolutionary dynamics of WGD, especially its role in adaptation, require empirical investigation.

Purpose of the Study:

• To investigate the rapid evolution and long-term persistence of whole-genome duplication (WGD) in Saccharomyces cerevisiae under specific selective pressures.
• To understand the mechanisms by which WGD arises, is maintained, and facilitates adaptation in a multicellular context.
• To provide empirical insights into the evolutionary consequences of WGD in a long-term experimental evolution setting.

Main Methods:

• Utilized the Multicellularity Long Term Evolution Experiment (MuLTEE) with Saccharomyces cerevisiae.
• Applied synthetic reconstruction and biophysical modeling to analyze tetraploidy.
• Employed counter-selection experiments to assess fitness benefits and maintenance of tetraploidy.

Main Results:

• Diploid yeast rapidly evolved tetraploidy within 50 days under selection for larger multicellular size.
• Tetraploid yeast persisted for over 5,000 generations despite genomic instability.
• Tetraploidy conferred immediate fitness advantages by increasing cell size and cluster formation, maintaining its persistence.
• Tetraploidy facilitated further adaptation, including the evolution of multicellularity via aneuploidy.

Conclusions:

• WGD can rapidly evolve and persist when providing immediate adaptive benefits under specific environmental conditions.
• Selection actively maintains WGD, overcoming typical reversion to diploidy, and enabling long-term evolutionary innovation.
• WGD acts as a crucial facilitator for novel adaptations by increasing genetic variation and enabling new evolutionary pathways.