The evolution of cichlid fish egg-spots is linked with a cis-regulatory change

The origin of novel phenotypic characters is a key component in organismal diversification; yet, the mechanisms underlying the emergence of such evolutionary novelties are largely unknown. Here we examine the origin of egg-spots, an evolutionary innovation of the most species-rich group of cichlids,...

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Published in:Nature communications 2014-10, Vol.5 (1), p.5149-5149, Article 5149
Main Authors: Santos, M. Emília, Braasch, Ingo, Boileau, Nicolas, Meyer, Britta S., Sauteur, Loïc, Böhne, Astrid, Belting, Heinz-Georg, Affolter, Markus, Salzburger, Walter
Format: Article
Language:English
Subjects:
631/208/182
631/601
Animals
Base Sequence
Cichlids
Evolution, Molecular
Gene Expression Regulation
Humanities and Social Sciences
LIM Domain Proteins - genetics
Molecular Sequence Data
multidisciplinary
Ovum - metabolism
Pigmentation - genetics
Science
Science (multidisciplinary)
Zebrafish
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Summary:The origin of novel phenotypic characters is a key component in organismal diversification; yet, the mechanisms underlying the emergence of such evolutionary novelties are largely unknown. Here we examine the origin of egg-spots, an evolutionary innovation of the most species-rich group of cichlids, the haplochromines, where these conspicuous male fin colour markings are involved in mating. Applying a combination of RNAseq, comparative genomics and functional experiments, we identify two novel pigmentation genes, fhl2a and fhl2b , and show that especially the more rapidly evolving b-paralog is associated with egg-spot formation. We further find that egg-spot bearing haplochromines, but not other cichlids, feature a transposable element in the cis -regulatory region of fhl2b . Using transgenic zebrafish, we finally demonstrate that this region shows specific enhancer activities in iridophores, a type of pigment cells found in egg-spots, suggesting that a cis -regulatory change is causally linked to the gain of expression in egg-spot bearing haplochromines. The mechanisms underlying the emergence of novel morphological traits are largely unknown. Here, the authors show that cis -regulatory changes controlling the expression of the fhl2b pigmentation gene are associated with the evolution of egg-spots colour markings in the male fins of a group of cichlids.
ISSN:2041-1723
2041-1723
DOI:10.1038/ncomms6149