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Open Access Highly Accessed Research article

Ancient gene transfer from algae to animals: Mechanisms and evolutionary significance

Ting Ni12, Jipei Yue3, Guiling Sun3, Yong Zou12, Jianfan Wen1* and Jinling Huang3*

Author Affiliations

1 State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, 650223, China

2 Graduate School of the Chinese Academy of Sciences, Beijing, 100039, China

3 Department of Biology, East Carolina University, Greenville, NC, 27858, USA

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BMC Evolutionary Biology 2012, 12:83  doi:10.1186/1471-2148-12-83

Published: 12 June 2012

Abstract

Background

Horizontal gene transfer (HGT) is traditionally considered to be rare in multicellular eukaryotes such as animals. Recently, many genes of miscellaneous algal origins were discovered in choanoflagellates. Considering that choanoflagellates are the existing closest relatives of animals, we speculated that ancient HGT might have occurred in the unicellular ancestor of animals and affected the long-term evolution of animals.

Results

Through genome screening, phylogenetic and domain analyses, we identified 14 gene families, including 92 genes, in the tunicate Ciona intestinalis that are likely derived from miscellaneous photosynthetic eukaryotes. Almost all of these gene families are distributed in diverse animals, suggesting that they were mostly acquired by the common ancestor of animals. Their miscellaneous origins also suggest that these genes are not derived from a particular algal endosymbiont. In addition, most genes identified in our 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.

Conclusions

Our findings provide additional evidence that algal genes in aplastidic eukaryotes are not exclusively derived from historical plastids and thus important for interpreting the evolution of eukaryotic photosynthesis. Most importantly, our 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.

Keywords:
Gene transfer; Endosymbiosis; Plastids; Animal evolution