Impact of transposable elements on genome structure and evolution in bread wheat.

Area of Science:

• Plant genomics
• Genome evolution
• Bioinformatics

Background:

• Transposable elements (TEs) are key drivers of genome evolution, particularly in large plant genomes.
• Recent bread wheat genome assembly provides a detailed view of TEs across A, B, and D subgenomes.

Purpose of the Study:

• To investigate the dynamics and evolutionary constraints of transposable elements (TEs) in the hexaploid bread wheat genome.
• To compare TE content, distribution, and evolution across the A, B, and D subgenomes.

Main Methods:

• Analysis of the most recent hexaploid bread wheat genome assembly.
• Comparative analysis of TE content and proportions across subgenomes.
• Evaluation of long terminal repeat-retrotransposon insertion times at the subfamily level.

Main Results:

• TE content is similar across A, B, and D subgenomes, with no evidence of post-polyploidization amplification bursts.
• Despite extensive TE turnover, 76% of TE families remain in similar proportions, and gene spacing is conserved.
• TE composition near genes differs from intergenic regions, with consistent enrichment/depletion patterns across subgenomes.
• Analysis of LTR-retrotransposon insertions reveals independent diploid lineage evolution and concerted proliferation in the AB tetraploid.

Conclusions:

• Unexpected preservation of TE family proportions, gene spacing, and TE enrichment patterns exists across wheat subgenomes.
• Evolutionary constraints may act on gene spacing rather than specific TE sequences.
• TE turnover significantly alters intergenic regions, yet core genomic features remain conserved.