title: Origination of an X-linked testes chimeric gene by illegitimate recombination in Drosophila.
abstract: The formation of chimeric gene structures provides important routes by which novel proteins and functions are introduced into genomes. Signatures of these events have been identified in organisms from wide phylogenic distributions. However, the ability to characterize the early phases of these evolutionary processes has been difficult due to the ancient age of the genes or to the limitations of strictly computational approaches. While examples involving retrotransposition exist, our understanding of chimeric genes originating via illegitimate recombination is limited to speculations based on ancient genes or transfection experiments. Here we report a case of a young chimeric gene that has originated by illegitimate recombination in Drosophila. This gene was created within the last 2-3 million years, prior to the speciation of Drosophila simulans, Drosophila sechellia, and Drosophila mauritiana. The duplication, which involved the Bällchen gene on Chromosome 3R, was partial, removing substantial 3' coding sequence. Subsequent to the duplication onto the X chromosome, intergenic sequence was recruited into the protein-coding region creating a chimeric peptide with approximately 33 new amino acid residues. In addition, a novel intron-containing 5' UTR and novel 3' UTR evolved. We further found that this new X-linked gene has evolved testes-specific expression. Following speciation of the D. simulans complex, this novel gene evolved lineage-specifically with evidence for positive selection acting along the D. simulans branch.
authors.affiliation: Committee on Evolutionary Biology, University of Chicago, Chicago, Illinois, USA.
authors.forename: J Roman
authors.initials: JR
authors.lastname: Arguello
authors.forename: Ying
authors.initials: Y
authors.lastname: Chen
authors.forename: Shuang
authors.initials: S
authors.lastname: Yang
authors.forename: Wen
authors.initials: W
authors.lastname: Wang
authors.forename: Manyuan
authors.initials: M
authors.lastname: Long
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D004330:Drosophila; D019143:Evolution, Molecular; D050172:Genes, X-Linked; D008040:Genetic Linkage; D008297:Male; D050506:Mutant Chimeric Proteins / Q000235:genetics*; D010802:Phylogeny; D011995:Recombination, Genetic; D018626:Retroelements; D013737:Testis / Q000473:pathology*; D014960:X Chromosome
chemical_list: D020413:3' Untranslated Regions; D050506:Mutant Chimeric Proteins; D018626:Retroelements