GC Content Across Insect Genomes: Phylogenetic Patterns, Causes and Consequences

Area of Science:

• Genomics
• Molecular Evolution
• Bioinformatics

Background:

• Nucleotide pair proportions (A:T and G:C) vary significantly across animal species and chromosomes.
• The evolutionary drivers and implications of this genomic variation remain largely unknown.
• Large-scale genome projects offer new opportunities to study GC heterogeneity in insects.

Purpose of the Study:

• To analyze GC content variation across chromosomes, genes, and codons in 150 insect species.
• To compare GC content patterns among four major holometabolous insect orders: Coleoptera, Diptera, Hymenoptera, and Lepidoptera.
• To investigate the relationship between GC content, chromosome size, genomic regions, and codon bias.

Main Methods:

• Comparative genomic analysis of GC content in 150 insect species.
• Examination of GC distribution along chromosomes and within protein-coding genes and codons.
• Statistical analysis to identify patterns and correlations in GC content variation.

Main Results:

• Protein-coding sequences exhibit higher GC content than the genome average.
• Lepidoptera generally show higher GC content compared to Coleoptera, Diptera, and Hymenoptera.
• GC content correlates with chromosome size in Lepidoptera and increases towards subtelomeric regions in Diptera, Coleoptera, and Lepidoptera.
• Two Diptera species display extreme AT-biased genomes, yet this did not lead to divergent protein evolution.

Conclusions:

• GC content variation in insect genomes is influenced by GC-biased gene conversion, particularly strong in Lepidoptera.
• Specific insect orders and species show distinct GC content landscapes due to varying evolutionary pressures.
• Atypical AT-biased codon usage in some species does not necessarily drive significant protein sequence divergence.