Takeshi Kawashima1, Shuichi Kawashima2, Chisaki Tanaka3, Miho Murai4,
Masahiko Yoneda4, Nicholas H Putnum5, Daniel S Rokhsar5, Minoru Kanehisa6,
Nori Satoh7 and Hiroshi Wada3,8
E-mail: 98champ@msg.biglobe.ne.jp
Abstract
The evolution of vertebrates was driven by a number of important events, including the development of cartilage, the immune system, and complicated craniofacial structures. Here we examine domain shuffling as an alternative mechanism for the contribution of novel genetic material required for vertebrate evolution. We mapped domain-shuffling events during the evolution of deuterostomes with a focus on how domain shuffling contributed to the evolution of vertebrate- and chordate-specific characteristics. We identified approximately 1,000 new domain pairs in the vertebrate lineage, including approximately 100 that were shared by all seven of the vertebrate species examined. Some of these pairs occur in the protein components of vertebrate-specific structures, such as cartilage and the inner ear, suggesting that domain shuffling made a marked contribution to the evolution of vertebrate-specific characteristics. The evolutionary history of the domain pairs is traceable; for example, the Xlink domain of aggrecan, one of the major components of cartilage, was originally utilized as a functional domain of a surface molecule of blood cells in protochordate ancestors, and it was recruited by the protein of the matrix component of cartilage in the vertebrate ancestor. We also identified genes that were created as a result of domain shuffling in ancestral chordates. Some of these are involved in the functions of chordate structures, such as the endostyle, Reissner's fiber of the neural tube, and the notochord. Our analyses shed new light on the evolutionary role of domain shuffling, especially in the evolution of vertebrates and chordates.
Footnotes
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- Received September 23, 2008.
- Accepted April 24, 2009.
- Copyright © 2009, Cold Spring Harbor Laboratory Press
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