LTR retrotransposons in fungi

Area of Science:

• Genomics
• Molecular Biology
• Evolutionary Biology

Background:

• Transposable elements (TEs) with long terminal direct repeats (LTR TEs) are mobile genetic elements found in most eukaryotic genomes.
• Their abundance and conservation offer insights into genome dynamics.
• LTR TEs are classified into Ty1/Copia and Ty3/Gypsy superfamilies.

Purpose of the Study:

• To comprehensively identify and analyze LTR-containing retrotransposons across published fungal genomes.
• To investigate the genome-ecology of these elements, focusing on abundance and expansion patterns.
• To explore the evolutionary relationships of TE protein domains.

Main Methods:

• Bioinformatic search for LTR retrotransposons in fungal genome databases.
• Identification of complete and remnant TE copies.
• Genome-ecology analysis of TE abundance and types.
• Phylogenetic analysis of TE elements and protein domains.

Main Results:

• Over 66,000 LTR TEs were identified, belonging to Ty1/Copia and Ty3/Gypsy superfamilies.
• Fungal genomes exhibit significant variability in TE content, ranging from scarce (<50) to highly expanded (>8000) elements.
• Transposon expansions typically involve increases in both copy number and element diversity.
• Ty3/Gypsy elements, particularly Chromoviridae, are the most abundant highest-copy TEs.
• Phylogenetic analyses indicate independent TE expansion events across diverse fungal lineages.
• Protease domains evolve fastest, while reverse transcriptase and RNase H evolve slower and cohesively.

Conclusions:

• Fungal genomes display dynamic LTR TE landscapes with independent expansion events.
• Ty3/Gypsy elements play a significant role in fungal genome evolution and dynamics.
• Differential evolution rates of transposon domains suggest distinct functional constraints.