Continuouscis-regulatory changes in an advantageous gene are linked with adaptive radiation in cichlid fishes

Abstract

Genes whose dysfunction do not affect normal survival is a common phenomenon. Are they only meaningless residues during evolution? Here, we identified a fish-specific new gene, which we named lg. Gene knockout resulted in no obvious phenotype in zebrafish, but lg evolves an amino acid mutation that is under positive selection in the modern haplochromine (MH) cichlid fish lineage, the well-known adaptive radiative lineage. Moreover, the cichlid fish-specific upstream region of lg can drive new eGFP expression profiles in tissues related to adaptation. Besides, this homologous region from different cichlid fishes drive different eGFP expressions which is simply due to three MH-segregated SNPs mutations that are predicted to bind a hormone related transcription factor. We thus revealed an initially redundant gene evolving new functions in an adaptive radiative lineage. This further illuminates the mechanism about the emergence of new gene function with respect to evo-devo in a broad way.