Evolution of an antifreeze protein by neofunctionalization under escape from adaptive conflict

Cheng Deng, C. H.Christina Cheng, Hua Ye, Ximiao He, Liangbiao Chen

Research output: Contribution to journalArticlepeer-review


The evolutionary model escape from adaptive conflict (EAC) posits that adaptive conflict between the old and an emerging new function within a single gene could drive the fixation of gene duplication, where each duplicate can freely optimize one of the functions. Although EAC has been suggested as a common process in functional evolution, definitive cases of neofunctionalization under EAC are lacking, and the molecular mechanisms leading to functional innovation are not well-understood. We report here clear experimental evidence for EAC-driven evolution of type III antifreeze protein gene from an old sialic acid synthase (SAS) gene in an Antarctic zoarcid fish. We found that an SAS gene, having both sialic acid synthase and rudimentary ice-binding activities, became duplicated. In one duplicate, the N-terminal SAS domain was deleted and replaced with a nascent signal peptide, removing pleiotropic structural conflict between SAS and ice-binding functions and allowing rapid optimization of the C-terminal domain to become a secreted protein capable of noncolligative freezingpoint depression. This study reveals how minor functionalities in an old gene can be transformed into a distinct survival protein and provides insights into how gene duplicates facing presumed identical selection and mutation pressures at birth could take divergent evolutionary paths.

Original languageEnglish (US)
Pages (from-to)21593-21598
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number50
StatePublished - Dec 14 2010


  • Antarctic eelpouts
  • Positive selection
  • Tandem repeats
  • Thermal hysteresis

ASJC Scopus subject areas

  • General


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