Characterizing the evolution and potential function of eleven horizontally transferred genes in amphioxus.

Horizontal gene transfer (HGT) is the important driver for biological evolution. To date, most of the studies on HGT have focused on prokaryotes, and the HGTs involving eukaryotes are less investigated, especially for HGTs occurring in chordates. In this study, we firstly identify eleven horizontally transferred genes (HTGs) in cephalochordate amphioxus, including eight HTGs from eubacteria, one HTG from fungus, one HTG from virus, and one HTG from Trichoplax. Secondly, our results demonstrate that the HTGs with high GC content are more likely to be horizontally transferred into amphioxus. Thirdly, our analyses indicate that these HTGs are conserved with the donor genes in different degree and may generate some novel functions. Finally, our results suggest that these HTGs contribute to the functional optimization of the notochord during amphioxus evolution. Collectively, our work provides the evidences for the existence of HGT events in chordates and has important theoretical implications for further elucidating the mechanisms and functions of HGTs in the adaptive evolution of chordates.