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Ahi EP, Lecaudey LA, Ziegelbecker A, Steiner O, Glabonjat R, Goessler W, Hois V, Wagner C, Lass A, Sefc KM. Comparative transcriptomics reveals candidate carotenoid color genes in an East African cichlid fish. BMC Genomics 2020; 21:54. [PMID: 31948394 PMCID: PMC6966818 DOI: 10.1186/s12864-020-6473-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 01/09/2020] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Carotenoids contribute significantly to animal body coloration, including the spectacular color pattern diversity among fishes. Fish, as other animals, derive carotenoids from their diet. Following uptake, transport and metabolic conversion, carotenoids allocated to body coloration are deposited in the chromatophore cells of the integument. The genes involved in these processes are largely unknown. Using RNA-Sequencing, we tested for differential gene expression between carotenoid-colored and white skin regions of a cichlid fish, Tropheus duboisi "Maswa", to identify genes associated with carotenoid-based integumentary coloration. To control for positional gene expression differences that were independent of the presence/absence of carotenoid coloration, we conducted the same analyses in a closely related population, in which both body regions are white. RESULTS A larger number of genes (n = 50) showed higher expression in the yellow compared to the white skin tissue than vice versa (n = 9). Of particular interest was the elevated expression level of bco2a in the white skin samples, as the enzyme encoded by this gene catalyzes the cleavage of carotenoids into colorless derivatives. The set of genes with higher expression levels in the yellow region included genes involved in xanthophore formation (e.g., pax7 and sox10), intracellular pigment mobilization (e.g., tubb, vim, kif5b), as well as uptake (e.g., scarb1) and storage (e.g., plin6) of carotenoids, and metabolic conversion of lipids and retinoids (e.g., dgat2, pnpla2, akr1b1, dhrs). Triglyceride concentrations were similar in the yellow and white skin regions. Extracts of integumentary carotenoids contained zeaxanthin, lutein and beta-cryptoxanthin as well as unidentified carotenoid structures. CONCLUSION Our results suggest a role of carotenoid cleavage by Bco2 in fish integumentary coloration, analogous to previous findings in birds. The elevated expression of genes in carotenoid-rich skin regions with functions in retinol and lipid metabolism supports hypotheses concerning analogies and shared mechanisms between these metabolic pathways. Overlaps in the sets of differentially expressed genes (including dgat2, bscl2, faxdc2 and retsatl) between the present study and previous, comparable studies in other fish species provide useful hints to potential carotenoid color candidate genes.
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Affiliation(s)
- Ehsan Pashay Ahi
- Institute of Biology, University of Graz, Universitätsplatz 2, A-8010, Graz, Austria
- Department of Comparative Physiology, Uppsala University, Norbyvägen 18A, SE-75 236 Uppsala, Sweden
| | - Laurène A. Lecaudey
- Institute of Biology, University of Graz, Universitätsplatz 2, A-8010, Graz, Austria
- Department of Natural History, NTNU University Museum, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
| | - Angelika Ziegelbecker
- Institute of Biology, University of Graz, Universitätsplatz 2, A-8010, Graz, Austria
| | - Oliver Steiner
- Institute of Chemistry, University of Graz, Universitätsplatz 1, A-8010, Graz, Austria
| | - Ronald Glabonjat
- Institute of Chemistry, University of Graz, Universitätsplatz 1, A-8010, Graz, Austria
| | - Walter Goessler
- Institute of Chemistry, University of Graz, Universitätsplatz 1, A-8010, Graz, Austria
| | - Victoria Hois
- Institute of Molecular Biosciences, University of Graz, Heinrichstraße 31/II, 8010, Graz, Austria
| | - Carina Wagner
- Institute of Molecular Biosciences, University of Graz, Heinrichstraße 31/II, 8010, Graz, Austria
| | - Achim Lass
- Institute of Molecular Biosciences, University of Graz, Heinrichstraße 31/II, 8010, Graz, Austria
- BioTechMed-Graz, 8010 Graz, Austria
| | - Kristina M. Sefc
- Institute of Biology, University of Graz, Universitätsplatz 2, A-8010, Graz, Austria
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Dick C, Reznick DN, Hayashi CY. Sex-biased expression between guppies varying in the presence of ornamental coloration. PeerJ 2018; 6:e5782. [PMID: 30324034 PMCID: PMC6186404 DOI: 10.7717/peerj.5782] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 09/18/2018] [Indexed: 01/21/2023] Open
Abstract
Sex-biased gene expression provides a means to achieve sexual dimorphism across a genome largely shared by both sexes. Trinidadian guppies are ideal to examine questions of sex-bias as they exhibit sexual dimorphism in ornamental coloration with male only expression. Here we use RNA-sequencing to quantify whole transcriptome gene expression differences, with a focus on differential expression of color genes between the sexes. We determine whether males express genes positively correlated with coloration at higher levels than females. We find that all the differentially expressed color genes were more highly expressed by males. Males also expressed all known black melanin synthesis genes at higher levels than females, regardless of whether the gene was significantly differentially expressed in the analysis. These differences correlated with the visual color differences between sexes at the stage sampled, as all males had ornamental black coloration apparent. We propose that sexual dimorphism in ornamental coloration is caused by male-biased expression of color genes.
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Affiliation(s)
- Cynthia Dick
- Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, Riverside, CA, United States of America
| | - David N Reznick
- Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, Riverside, CA, United States of America
| | - Cheryl Y Hayashi
- Division of Invertebrate Zoology and Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, NY, United States of America
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