Horizontal gene transfer (HGT), the transfer of genetic material between organisms other than vertical gene transfer (transfer from the parents to offspring), is an important force in speciation and genome evolution. Although numerous cases of HGT have been documented in prokaryotes and unicellular eukaryotes, a common belief is that HGT is rare in multicellular eukaryotes such as animals, let alone its effects on animal evolution.
The research team “Evolutionary Genomics of Eukaryotic Cells” led by Prof. Wen Jian-fan of Kunming institute of zoology, CAS has embarked on the investigation of heterogenous animal genes that acquired through HGT events. Through genome screening, phylogenetic and domain analyses, 14 gene families, including 92 genes, were identified in the tunicate Ciona intestinalis that are likely derived from miscellaneous photosynthetic eukaryotes, algae. Almost all of these gene families are distributed in diverse animals, suggesting that they were mostly acquired by the common ancestor of animals. The miscellaneous origins also suggest that these genes are, most probably, derived from feeding on algae, rather than a particular algal endosymbiont, which is also consistent with the words from Doolittle W.F. (1998) -- You are what you eat! In addition, most genes identified in the analyses are functionally related to molecule transport, cellular regulation and methylation signaling, suggesting that the acquisition of these genes might have facilitated the intercellular communication in the ancestral animal and further lead to multicellular formation.
To sum up, this data represent the first evidence that more anciently acquired genes might exist in animals and that ancient HGT events have played an important role in animal evolution. Moreover, these findings provide additional evidence that algal genes in aplastidic eukaryotes are not exclusively derived from historical plastids. This work has been officially published on BMC Evolutionary Biology (DOI 10.1186/1471-2148-12-83) recently.
This work was supported by grants from the National Natural Science Foundation of China and the Knowledge Innovation Program.