Transposable Element Diversity Remains High in Gigantic Genomes

Area of Science:

• Genomics
• Evolutionary Biology
• Molecular Biology

Background:

• Transposable elements (TEs) are mobile DNA sequences that shape genome evolution.
• Ecological diversity models are used to study TE communities within genomes.
• Previous research suggested TE diversity decreases with increasing genome size.

Purpose of the Study:

• To investigate TE diversity in Plethodon salamanders with exceptionally large genomes.
• To test the hypothesis that large genomes lead to reduced TE diversity.
• To compare TE diversity across species with independent genome expansion events.

Main Methods:

• Utilized Oxford Nanopore sequencing for low-coverage genomic data.
• Analyzed four Plethodon species representing two independent genome expansions.
• Classified transposable elements into superfamilies and calculated diversity indices (Simpson's, Shannon's).

Main Results:

• Identified over 40 TE superfamilies, comprising 22-27% of the analyzed genomes.
• Found nearly identical TE diversity index values between smaller and larger genomes within each clade.
• Observed high TE diversity at the superfamily level in extremely large genomes.

Conclusions:

• Extremely large genomes, like those in Plethodon salamanders, can maintain high TE diversity.
• Findings challenge previous models predicting TE diversity decline with genome expansion.
• Genome size alone may not be the sole determinant of transposable element diversity.