Abstract
BackgroundThe annual fish Nothobranchius furzeri is characterized by a natural dichromatism with yellow-tailed and red-tailed male individuals. These differences are due to different distributions of xanthophores and erythrophores in the two morphs. Previous crossing studies have showed that dichromatism in N. furzeri is inherited as a simple Mendelian trait with the yellow morph dominant over the red morph. The causative genetic variation was mapped by linkage analysis in a chromosome region containing the Mc1r locus. However, subsequent mapping showed that Mc1r is most likely not responsible for the color difference in N. furzeri. To gain further insight into the molecular basis of this phenotype, we performed RNA-seq on F2 progeny of a cross between N. furzeri male and N. kadleci female.ResultsWe identified 210 differentially-expressed genes between yellow and red fin samples. Functional annotation analysis revealed that genes with higher transcript levels in the yellow morph are enriched for the melanin synthesis pathway indicating that xanthophores are more similar to melanophores than are the erythrophores. Genes with higher expression levels in red-tails included xanthine dehydrogenase (Xdh), coding for a biosynthetic enzyme in the pteridine synthesis pathway, and genes related to muscle contraction. Comparison of DEGs obtained in this study with genes associated with pigmentation in the Midas cichlid (A. citrinellus) reveal similarities like involvement of the melanin biosynthesis pathway, the genes Ptgir, Rasef (RAS and EF-hand domain containing), as well as genes primarily expressed in muscle such as Ttn and Ttnb (titin, titin b).ConclusionsRegulation of genes in the melanin synthetic pathway is an expected finding and shows that N. furzeri is a genetically-tractable species for studying the genetic basis of natural phenotypic variations. The current list of differentially-expressed genes can be compared with the results of fine-mapping, to reveal the genetic architecture of this natural phenotype. However, an evolutionarily-conserved role of muscle-related genes in tail fin pigmentation is novel finding and interesting perspective for the future.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-754) contains supplementary material, which is available to authorized users.
Highlights
The annual fish Nothobranchius furzeri is characterized by a natural dichromatism with yellow-tailed and red-tailed male individuals
In Midas cichlids, pigmentation may change in the course of ontogeny giving rise to the gold morph, and a recent transcriptomic study identified genes regulated during this transition [2]
Tail expression profiles correspond with dichromatism To make sure that genetic mechanisms of tail pigmentation are identical in the two species, we performed a complementation test by crossing individuals of the MZM-0703 red-tailed strain of N. furzeri [22] with those of N. kadleci in both possible combinations of parents
Summary
The annual fish Nothobranchius furzeri is characterized by a natural dichromatism with yellow-tailed and red-tailed male individuals. These differences are due to different distributions of xanthophores and erythrophores in the two morphs. Previous crossing studies have showed that dichromatism in N. furzeri is inherited as a simple Mendelian trait with the yellow morph dominant over the red morph. Pigmentation has received considerable attention both in Teleost fish are characterized by the existence of further pigmentation cells in addition to melanocytes (melanophores in fish) These are xanthophores (ochre or yellow), erythrophores (red), leucophores (whitish), iridophores (metallic or iridescent) and cyanophores (blue) [13]. In Midas cichlids, pigmentation may change in the course of ontogeny giving rise to the gold morph, and a recent transcriptomic study identified genes regulated during this transition [2]
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