Deleterious transposable elements and the extinction of asexuals

Area of Science:

• Evolutionary biology
• Genetics
• Molecular biology

Background:

• Transposable elements are widespread in genomes of sexually reproducing species.
• Active transposable elements can proliferate rapidly, posing a threat to genome stability.
• Purifying selection can limit transposon copy number, especially when selection intensifies with increasing copy number.

Purpose of the Study:

• To investigate the mechanisms by which sexual reproduction restrains the intragenomic proliferation of transposable elements.
• To understand the evolutionary advantage of sex in managing transposable elements compared to asexual reproduction.

Main Methods:

• The study discusses theoretical models of selection acting on transposable elements in sexual populations.
• It considers mechanisms like ectopic crossing-over and homologous recombination under negative epistasis.
• Meiosis-associated controls on transposon activity are also hypothesized.

Main Results:

• Synergistic purifying selection, enhanced by increasing copy number, effectively controls transposable elements in sexual species.
• Mechanisms such as ectopic recombination and negative epistasis contribute to this control.
• Asexual lineages may face extinction due to unchecked transposon proliferation, lacking these sexual reproduction-associated controls.

Conclusions:

• Sexual reproduction provides crucial mechanisms to limit the intragenomic proliferation of transposable elements.
• The ability to restrain transposon activity is a significant component of the evolutionary advantage of sex over asex.
• Failure to control transposable elements can lead to genome instability and potentially extinction in asexual lineages.