Evolutionary history of the element in avian genomes.

BACKGROUND

Transposable elements (TEs) are highly abundant genomic parasites in eukaryote genomes. Although several genomes have been screened for TEs, so far very limited information is available regarding avian TEs and their evolutionary histories. Taking advantage of the rich genomic data available for birds, we characterized the evolutionary history of the element, originally described in , through the use of several bioinformatic analyses.

RESULTS

homologous sequences were found in 6 of 72 genomes analyzed: 5 species of Galliformes (, , , , ) and one Buceritiformes (). The copy number ranged from 5 to 10,158, in the genomes of and respectively. All 6 species possessed short elements, suggesting the presence of Miniature Inverted repeats Transposable Elements (MITEs), which underwent an ancient massive amplification in the and genomes. Only 4 species showed potential MITE full-length partners, although no potential coding copies were detected. Phylogenetic analysis of reconstructed coding sequences showed that homolog sequences form a new subfamily, which we termed . Inter-species and intragenomic distance analyses indicated a high identity between the consensus of and the other 5 related species, and different emergence ages of the element between the Galliformes species and , suggesting that horizontal transfer took place from Galliformes to a Buceritiformes ancestor, probably through an intermediate species.

CONCLUSIONS

Overall, our results showed that elements have amplified to high copy numbers in some avian species, and that this transposition burst probably occurred in the common ancestor of and In addition, although no coding sequences could be found currently, they probably existed, allowing an ancient massive MITE amplification in these 2 species. The other 4 species also have MITEs, suggesting that this new family is prone to give rise to such non-autonomous derivatives. Last, our results suggest that a horizontal transfer event of a element occurred between Galliformes and Buceritiformes.