Horizontal Transfer Can Drive a Greater Transposable Element Load in Large Populations

Area of Science:

• Genomics
• Evolutionary Biology
• Molecular Biology

Background:

• Genomes contain euchromatin and heterochromatin, with transposable elements (TEs) influencing these domains.
• Understanding TE abundance is key to comprehending genome structure and chromatin landscapes.
• The role of genetic drift in TE accumulation is debated, particularly in small populations where mildly deleterious alleles may fix.

Purpose of the Study:

• To investigate the impact of horizontal transfer (HT) exposure rates on transposable element (TE) abundance in populations.
• To determine how population size and recombination rates influence TE copy number and genomic load.
• To explore the interplay between drift, HT, and TE dynamics in shaping genome architecture.

Main Methods:

• Utilized simulation approaches to model TE dynamics.
• Employed analytical methods to derive theoretical predictions.
• Examined the influence of population size, HT exposure rate, and recombination on TE establishment.

Main Results:

• When genetic drift effects are weak, HT exposure rate significantly determines genomic TE copy number.
• Larger populations, with exposure rates proportional to size, are predicted to have a higher TE load due to increased exposure to rare HT events.
• Higher recombination rates increase the probability of TE establishment.

Conclusions:

• Horizontal transfer exposure rate is a critical factor in controlling TE abundance, especially in populations with weak drift.
• Population size can have a counterintuitive effect, potentially leading to a higher TE burden in larger populations.
• Recombination rates play a role in TE proliferation, impacting genome evolution and defense mechanisms.