Genomics GM_D0010

Title : Comparative genomics reveals a constant rate of origination and
convergent acquisition of functional retrogenes in Drosophila
Author : Yongsheng Bai, Claudio Casola, Cédric Feschotte and Esther Betrán
Year : 2007
Place of publish :
Abstract :

Background: Processed copies of genes (retrogenes) are duplicate genes that originated through
the reverse-transcription of a host transcript and insertion in the genome. This type of gene
duplication, as any other, could be a source of new genes and functions. Using whole genome
sequence data for 12 Drosophila species, we dated the origin of 94 retroposition events that gave
rise to candidate functional genes in D. melanogaster.
Results: Based on this analysis, we infer that functional retrogenes have emerged at a fairly
constant rate of 0.5 genes per million years per lineage over the last approximately 63 million years
of Drosophila evolution. The number of functional retrogenes and the rate at which they are
recruited in the D. melanogaster lineage are of the same order of magnitude as those estimated in
the human lineage, despite the higher deletion bias in the Drosophila genome. However, unlike
primates, the rate of retroposition in Drosophila seems to be fairly constant and no burst of
retroposition can be inferred from our analyses. In addition, our data also support an important
role for retrogenes as a source of lineage-specific male functions, in agreement with previous
hypotheses. Finally, we identified three cases of functional retrogenes in D. melanogaster that have
been independently retroposed and recruited in parallel as new genes in other Drosophila lineages.
Conclusion: Together, these results indicate that retroposition is a persistent mechanism and a
recurrent pathway for the emergence of new genes in Drosophila.