Asexual Experimental Evolution of Yeast Does Not Curtail Transposable Elements.

Area of Science:

• Evolutionary biology
• Genetics
• Molecular biology

Background:

• Transposable elements (TEs) are mobile DNA sequences.
• The role of sexual reproduction in the proliferation and regulation of TEs is debated.
• Previous studies suggested asexual reproduction reduces TE load, but this is questioned.

Purpose of the Study:

• To re-evaluate the impact of sexual versus asexual reproduction on transposable element (TE) loads in yeast.
• To investigate the evolutionary dynamics of TEs in yeast under different experimental conditions.
• To determine the primary mechanisms maintaining TE loads in yeast populations.

Main Methods:

• Analysis of yeast experimental evolution data sets with varying genomic sequencing coverages.
• Examination of asexual mutation accumulation lines under minimal selection.
• Quantification of transposition and excision rates of TEs in yeast.

Main Results:

• Purported TE load reduction in asexual evolution was likely an artifact of low sequencing coverage.
• Stable TE loads were observed in both sexual and asexual experimental evolution with sufficient coverage.
• TE transposition and excision rates increased in slower-growing yeast environments, but not significantly differently.

Conclusions:

• Yeast TE loads are maintained by a balance between transposition and excision, not strong selection.
• The influence of sex on TE proliferation in yeast remains uncertain.
• Previous conclusions about sex driving TE evolutionary success in yeast require re-evaluation due to methodological limitations.