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Gao J, Wang Y, Liu J, Chen F, Guo Y, Ke H, Wang X, Luo M, Fu S. Genome-wide association study reveals genomic loci of sex differentiation and gonadal development in Plectropomus leopardus. Front Genet 2023; 14:1229242. [PMID: 37645057 PMCID: PMC10461086 DOI: 10.3389/fgene.2023.1229242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 07/17/2023] [Indexed: 08/31/2023] Open
Abstract
Introduction: Plectropomus leopardus, a commercially significant marine fish, is primarily found in the Western Pacific regions and along the coast of Southeast Asia. A thorough analysis of the molecular mechanisms involved in sex differentiation is crucial for gaining a comprehensive understanding of gonadal development and improving sex control breeding. However, the relevant fundamental studies of P. leopardus are relatively lacking. Methods: In this study, a genome-wide association study (GWAS) was conducted to investigate the genetic basis mechanism of sex differentiation and gonadal developmental traits in P. leopardus utilizing about 6,850,000 high-quality single-nucleotide polymorphisms (SNPs) derived from 168 individuals (including 126 females and 42 males) by the genome-wide efficient mixed-model association (GEMMA) algorithm. Results: The results of these single-trait GWASs showed that 46 SNP loci (-log10 p > 7) significantly associated with sex differentiation, and gonadal development traits were distributed in multiple different chromosomes, which suggested the analyzed traits were all complex traits under multi-locus control. A total of 1,838 potential candidate genes were obtained by considering a less-stringent threshold (-log10 p > 6) and ±100 kb regions surrounding the significant genomic loci. Moreover, 31 candidate genes were identified through a comprehensive analysis of significant GWAS peaks, gene ontology (GO) annotations, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, including taf7, ddx6, apoeb, sgk1, a2m, usf1, hsd3b7, dll4, xbp1, tet3, esr1, and gli3. These trait-associated genes have been shown to be involved in germline development, male sex differentiation, gonad morphogenesis, hormone receptor binding, oocyte development, male gonad development, steroidogenesis, estrogen-synthetic pathway, etc. Discussion: In the present study, multiple genomic loci of P. leopardus associated with sex differentiation and gonadal development traits were identified for the first time by using GWAS, providing a valuable resource for further research on the molecular genetic mechanism and sex control in P. leopardus. Our results also can contribute to understanding the genetic basis of the sex differentiation mechanism and gonadal development process in grouper fish.
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Affiliation(s)
- Jin Gao
- Hainan Academy of Ocean and Fisheries Sciences, Haikou, China
- Hainan Tropical Ocean University Yazhou Bay Innovation Institute, Sanya, China
| | - Yongbo Wang
- Hainan Academy of Ocean and Fisheries Sciences, Haikou, China
- Hainan Tropical Ocean University Yazhou Bay Innovation Institute, Sanya, China
| | - Jinye Liu
- Hainan Academy of Ocean and Fisheries Sciences, Haikou, China
- Hainan Provincial Engineering Research Center for Tropical Sea-Farming, Haikou, China
| | - Fuxiao Chen
- Hainan Academy of Ocean and Fisheries Sciences, Haikou, China
- Hainan Tropical Ocean University Yazhou Bay Innovation Institute, Sanya, China
| | - Yilan Guo
- Hainan Academy of Ocean and Fisheries Sciences, Haikou, China
| | - Hongji Ke
- Hainan Academy of Ocean and Fisheries Sciences, Haikou, China
| | - Xulei Wang
- Hainan Academy of Ocean and Fisheries Sciences, Haikou, China
| | - Ming Luo
- Hainan Academy of Ocean and Fisheries Sciences, Haikou, China
| | - Shuyuan Fu
- Hainan Academy of Ocean and Fisheries Sciences, Haikou, China
- Hainan Tropical Ocean University Yazhou Bay Innovation Institute, Sanya, China
- Hainan Provincial Engineering Research Center for Tropical Sea-Farming, Haikou, China
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Whole-Genome Inter-Sex Variation in Russian Sturgeon ( Acipenser gueldenstaedtii). Int J Mol Sci 2022; 23:ijms23169469. [PMID: 36012734 PMCID: PMC9409348 DOI: 10.3390/ijms23169469] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2022] [Revised: 08/17/2022] [Accepted: 08/17/2022] [Indexed: 11/17/2022] Open
Abstract
The Russian sturgeon (Acipenser gueldenstaedtii, AG) is an endangered fish species increasingly raised on fish farms for black caviar. Understanding the process of sex determination in AG is, therefore, of scientific and commercial importance. AG lacks sexual dimorphism until sexual maturation and has a predominantly octoploid genome without a definite sex chromosome. A conserved short female-specific genomic sequence was recently described, leading to the development of a genetic sex marker. However, no biological function has been reported for this sequence. Thus, the mechanism of sex determination and the overall inter-sex genomic variation in AG are still unknown. To comprehensively analyze the inter-sex genomic variation and assess the overall inter-species variation between AG and A. ruthenus (AR, sterlet), a related tetraploid sturgeon species, we performed whole-genome sequencing on DNA from 10 fish-farm-raised adult AG (5 males and 5 females). We produced a partially assembled, ~2390 MBp draft genome for AG. We validated in AG the female-specific region previously described in AR. We identified ~2.8 million loci (SNP/indels) varying between the species, but only ~7400 sex-associated loci in AG. We mapped the sex-associated AG loci to the AR genome and identified 15 peaks of sex-associated variation (10 kb segments with 30 or more sex-associated variants), 1 of which matched the previously reported sex-variable region. Finally, we identified 14 known and predicted genes in proximity to these peaks. Our analysis suggests that one or more of these genes may have functional roles in sex determination and/or sexual differentiation in sturgeons. Further functional studies are required to elucidate these roles.
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Gabián M, Morán P, Saura M, Carvajal-Rodríguez A. Detecting Local Adaptation between North and South European Atlantic Salmon Populations. BIOLOGY 2022; 11:933. [PMID: 35741456 PMCID: PMC9219887 DOI: 10.3390/biology11060933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 06/09/2022] [Accepted: 06/16/2022] [Indexed: 06/15/2023]
Abstract
Pollution and other anthropogenic effects have driven a decrease in Atlantic salmon (Salmo salar) in the Iberian Peninsula. The restocking effort carried out in the 1980s, with salmon from northern latitudes with the aim of mitigating the decline of native populations, failed, probably due to the deficiency in adaptation of foreign salmon from northern Europe to the warm waters of the Iberian Peninsula. This result would imply that the Iberian populations of Atlantic salmon have experienced local adaptation in their past evolutionary history, as has been described for other populations of this species and other salmonids. Local adaptation can occur by divergent selections between environments, favoring the fixation of alleles that increase the fitness of a population in the environment it inhabits relative to other alleles favored in another population. In this work, we compared the genomes of different populations from the Iberian Peninsula (Atlantic and Cantabric basins) and Scotland in order to provide tentative evidence of candidate SNPs responsible for the adaptive differences between populations, which may explain the failures of restocking carried out during the 1980s. For this purpose, the samples were genotyped with a 220,000 high-density SNP array (Affymetrix) specific to Atlantic salmon. Our results revealed potential evidence of local adaptation for North Spanish and Scottish populations. As expected, most differences concerned the comparison of the Iberian Peninsula with Scotland, although there were also differences between Atlantic and Cantabric populations. A high proportion of the genes identified are related to development and cellular metabolism, DNA transcription and anatomical structure. A particular SNP was identified within the NADP-dependent malic enzyme-2 (mMEP-2*), previously reported by independent studies as a candidate for local adaptation in salmon from the Iberian Peninsula. Interestingly, the corresponding SNP within the mMEP-2* region was consistent with a genomic pattern of divergent selection.
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Affiliation(s)
- María Gabián
- Centro de Investigación Mariña (CIM), Departamento de Bioquímica, Genética e Inmunología, Universidade de Vigo, 36310 Vigo, Spain; (M.G.); (P.M.)
| | - Paloma Morán
- Centro de Investigación Mariña (CIM), Departamento de Bioquímica, Genética e Inmunología, Universidade de Vigo, 36310 Vigo, Spain; (M.G.); (P.M.)
| | - María Saura
- Departamento de Mejora Genética Animal, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA-CSIC), 28040 Madrid, Spain;
| | - Antonio Carvajal-Rodríguez
- Centro de Investigación Mariña (CIM), Departamento de Bioquímica, Genética e Inmunología, Universidade de Vigo, 36310 Vigo, Spain; (M.G.); (P.M.)
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Panthum T, Jaisamut K, Singchat W, Ahmad SF, Kongkaew L, Wongloet W, Dokkaew S, Kraichak E, Muangmai N, Duengkae P, Srikulnath K. Something Fishy about Siamese Fighting Fish (Betta splendens) Sex: Polygenic Sex Determination or a Newly Emerged Sex-Determining Region? Cells 2022; 11:cells11111764. [PMID: 35681459 PMCID: PMC9179492 DOI: 10.3390/cells11111764] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 05/23/2022] [Accepted: 05/25/2022] [Indexed: 12/04/2022] Open
Abstract
Fishes provide a unique and intriguing model system for studying the genomic origin and evolutionary mechanisms underlying sex determination and high sex-chromosome turnover. In this study, the mode of sex determination was investigated in Siamese fighting fish, a species of commercial importance. Genome-wide SNP analyses were performed on 75 individuals (40 males and 35 females) across commercial populations to determine candidate sex-specific/sex-linked loci. In total, 73 male-specific loci were identified and mapped to a 5.6 kb region on chromosome 9, suggesting a putative male-determining region (pMDR) containing localized dmrt1 and znrf3 functional sex developmental genes. Repeat annotations of the pMDR revealed an abundance of transposable elements, particularly Ty3/Gypsy and novel repeats. Remarkably, two out of the 73 male-specific loci were located on chromosomes 7 and 19, implying the existence of polygenic sex determination. Besides male-specific loci, five female-specific loci on chromosome 9 were also observed in certain populations, indicating the possibility of a female-determining region and the polygenic nature of sex determination. An alternative explanation is that male-specific loci derived from other chromosomes or female-specific loci in Siamese fighting fish recently emerged as new sex-determining loci during domestication and repeated hybridization.
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Affiliation(s)
- Thitipong Panthum
- Animal Genomics and Bioresource Research Unit (AGB Research Unit), Faculty of Science, Kasetsart University, Bangkok 10900, Thailand; (T.P.); (K.J.); (W.S.); (S.F.A.); (L.K.); (W.W.); (E.K.); (N.M.); (P.D.)
- Interdisciplinary Graduate Program in Bioscience, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand
- Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand
| | - Kitipong Jaisamut
- Animal Genomics and Bioresource Research Unit (AGB Research Unit), Faculty of Science, Kasetsart University, Bangkok 10900, Thailand; (T.P.); (K.J.); (W.S.); (S.F.A.); (L.K.); (W.W.); (E.K.); (N.M.); (P.D.)
- Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand
| | - Worapong Singchat
- Animal Genomics and Bioresource Research Unit (AGB Research Unit), Faculty of Science, Kasetsart University, Bangkok 10900, Thailand; (T.P.); (K.J.); (W.S.); (S.F.A.); (L.K.); (W.W.); (E.K.); (N.M.); (P.D.)
- Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand
| | - Syed Farhan Ahmad
- Animal Genomics and Bioresource Research Unit (AGB Research Unit), Faculty of Science, Kasetsart University, Bangkok 10900, Thailand; (T.P.); (K.J.); (W.S.); (S.F.A.); (L.K.); (W.W.); (E.K.); (N.M.); (P.D.)
- Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand
- The International Undergraduate Program in Bioscience and Technology, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand
| | - Lalida Kongkaew
- Animal Genomics and Bioresource Research Unit (AGB Research Unit), Faculty of Science, Kasetsart University, Bangkok 10900, Thailand; (T.P.); (K.J.); (W.S.); (S.F.A.); (L.K.); (W.W.); (E.K.); (N.M.); (P.D.)
- Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand
| | - Wongsathit Wongloet
- Animal Genomics and Bioresource Research Unit (AGB Research Unit), Faculty of Science, Kasetsart University, Bangkok 10900, Thailand; (T.P.); (K.J.); (W.S.); (S.F.A.); (L.K.); (W.W.); (E.K.); (N.M.); (P.D.)
- Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand
| | - Sahabhop Dokkaew
- Department of Aquaculture, Faculty of Fisheries, Kasetsart University, Bangkok 10900, Thailand;
| | - Ekaphan Kraichak
- Animal Genomics and Bioresource Research Unit (AGB Research Unit), Faculty of Science, Kasetsart University, Bangkok 10900, Thailand; (T.P.); (K.J.); (W.S.); (S.F.A.); (L.K.); (W.W.); (E.K.); (N.M.); (P.D.)
- Department of Botany, Kasetsart University, Bangkok 10900, Thailand
| | - Narongrit Muangmai
- Animal Genomics and Bioresource Research Unit (AGB Research Unit), Faculty of Science, Kasetsart University, Bangkok 10900, Thailand; (T.P.); (K.J.); (W.S.); (S.F.A.); (L.K.); (W.W.); (E.K.); (N.M.); (P.D.)
- Department of Fishery Biology, Faculty of Fisheries, Kasetsart University, Bangkok 10900, Thailand
| | - Prateep Duengkae
- Animal Genomics and Bioresource Research Unit (AGB Research Unit), Faculty of Science, Kasetsart University, Bangkok 10900, Thailand; (T.P.); (K.J.); (W.S.); (S.F.A.); (L.K.); (W.W.); (E.K.); (N.M.); (P.D.)
- Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand
| | - Kornsorn Srikulnath
- Animal Genomics and Bioresource Research Unit (AGB Research Unit), Faculty of Science, Kasetsart University, Bangkok 10900, Thailand; (T.P.); (K.J.); (W.S.); (S.F.A.); (L.K.); (W.W.); (E.K.); (N.M.); (P.D.)
- Interdisciplinary Graduate Program in Bioscience, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand
- Special Research Unit for Wildlife Genomics (SRUWG), Department of Forest Biology, Faculty of Forestry, Kasetsart University, Bangkok 10900, Thailand
- The International Undergraduate Program in Bioscience and Technology, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand
- Laboratory of Animal Cytogenetics and Comparative Genomics (ACCG), Department of Genetics, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand
- Center for Advanced Studies in Tropical Natural Resources, National Research University-Kasetsart University, Kasetsart University, (CASTNAR, NRU-KU, Thailand), Bangkok 10900, Thailand
- Center of Excellence on Agricultural Biotechnology (AG-BIO/PERDO-CHE), Bangkok 10900, Thailand
- Amphibian Research Center, Hiroshima University, Kagamiyama, Higashihiroshima 739-8527, Japan
- Correspondence:
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Christensen KA, Rondeau EB, Sakhrani D, Biagi CA, Johnson H, Joshi J, Flores AM, Leelakumari S, Moore R, Pandoh PK, Withler RE, Beacham TD, Leggatt RA, Tarpey CM, Seeb LW, Seeb JE, Jones SJM, Devlin RH, Koop BF. The pink salmon genome: Uncovering the genomic consequences of a two-year life cycle. PLoS One 2021; 16:e0255752. [PMID: 34919547 PMCID: PMC8682878 DOI: 10.1371/journal.pone.0255752] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 12/02/2021] [Indexed: 12/30/2022] Open
Abstract
Pink salmon (Oncorhynchus gorbuscha) adults are the smallest of the five Pacific salmon native to the western Pacific Ocean. Pink salmon are also the most abundant of these species and account for a large proportion of the commercial value of the salmon fishery worldwide. A two-year life history of pink salmon generates temporally isolated populations that spawn either in even-years or odd-years. To uncover the influence of this genetic isolation, reference genome assemblies were generated for each year-class and whole genome re-sequencing data was collected from salmon of both year-classes. The salmon were sampled from six Canadian rivers and one Japanese river. At multiple centromeres we identified peaks of Fst between year-classes that were millions of base-pairs long. The largest Fst peak was also associated with a million base-pair chromosomal polymorphism found in the odd-year genome near a centromere. These Fst peaks may be the result of a centromere drive or a combination of reduced recombination and genetic drift, and they could influence speciation. Other regions of the genome influenced by odd-year and even-year temporal isolation and tentatively under selection were mostly associated with genes related to immune function, organ development/maintenance, and behaviour.
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Affiliation(s)
- Kris A. Christensen
- West Vancouver, Fisheries and Oceans Canada, British Columbia, Canada
- Department of Biology, University of Victoria, Victoria, British Columbia, Canada
- * E-mail: (KAC); (BFK)
| | - Eric B. Rondeau
- West Vancouver, Fisheries and Oceans Canada, British Columbia, Canada
- Department of Biology, University of Victoria, Victoria, British Columbia, Canada
- Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, British Columbia, Canada
| | - Dionne Sakhrani
- West Vancouver, Fisheries and Oceans Canada, British Columbia, Canada
| | - Carlo A. Biagi
- West Vancouver, Fisheries and Oceans Canada, British Columbia, Canada
| | - Hollie Johnson
- Department of Biology, University of Victoria, Victoria, British Columbia, Canada
| | - Jay Joshi
- Department of Biology, University of Victoria, Victoria, British Columbia, Canada
| | - Anne-Marie Flores
- Department of Biology, University of Victoria, Victoria, British Columbia, Canada
| | - Sreeja Leelakumari
- Canada’s Michael Smith Genome Sciences Centre, BC Cancer, Vancouver, British Columbia, Canada
| | - Richard Moore
- Canada’s Michael Smith Genome Sciences Centre, BC Cancer, Vancouver, British Columbia, Canada
| | - Pawan K. Pandoh
- Canada’s Michael Smith Genome Sciences Centre, BC Cancer, Vancouver, British Columbia, Canada
| | - Ruth E. Withler
- Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, British Columbia, Canada
| | - Terry D. Beacham
- Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, British Columbia, Canada
| | | | - Carolyn M. Tarpey
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington, United States of America
| | - Lisa W. Seeb
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington, United States of America
| | - James E. Seeb
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington, United States of America
| | - Steven J. M. Jones
- Canada’s Michael Smith Genome Sciences Centre, BC Cancer, Vancouver, British Columbia, Canada
| | - Robert H. Devlin
- West Vancouver, Fisheries and Oceans Canada, British Columbia, Canada
| | - Ben F. Koop
- Department of Biology, University of Victoria, Victoria, British Columbia, Canada
- * E-mail: (KAC); (BFK)
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Bertho S, Herpin A, Schartl M, Guiguen Y. Lessons from an unusual vertebrate sex-determining gene. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200092. [PMID: 34247499 DOI: 10.1098/rstb.2020.0092] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
So far, very few sex-determining genes have been identified in vertebrates and most of them, the so-called 'usual suspects', evolved from genes which fulfil essential functions during sexual development and are thus already tightly linked to the process that they now govern. The single exception to this 'usual suspects' rule in vertebrates so far is the conserved salmonid sex-determining gene, sdY (sexually dimorphic on the Y chromosome), that evolved from a gene known to be involved in regulation of the immune response. It is contained in a jumping sex locus that has been transposed or translocated into different ancestral autosomes during the evolution of salmonids. This special feature of sdY, i.e. being inserted in a 'jumping sex locus', could explain how salmonid sex chromosomes remain young and undifferentiated to escape degeneration. Recent knowledge on the mechanism of action of sdY demonstrates that it triggers its sex-determining action by deregulating oestrogen synthesis that is a conserved and crucial pathway for ovarian differentiation in vertebrates. This result suggests that sdY has evolved to cope with a pre-existing sex differentiation regulatory network. Therefore, 'limited options' for the emergence of new master sex-determining genes could be more constrained by their need to tightly interact with a conserved sex differentiation regulatory network rather than by being themselves 'usual suspects', already inside this sex regulatory network. This article is part of the theme issue 'Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part I)'.
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Affiliation(s)
- Sylvain Bertho
- INRAE, LPGP, 35000 Rennes, France.,Developmental Biochemistry, Biocenter, University of Wuerzburg, 97074 Wuerzburg, Germany
| | - Amaury Herpin
- INRAE, LPGP, 35000 Rennes, France.,State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Sciences, Hunan Normal University, Changsha, 410081 Hunan, People's Republic of China
| | - Manfred Schartl
- Developmental Biochemistry, Biocenter, University of Wuerzburg, 97074 Wuerzburg, Germany.,Department of Chemistry and Biochemistry, The Xiphophorus Genetic Stock Center, Texas State University, San Marcos, TX 78666, USA
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Ayllon F, Solberg MF, Besnier F, Fjelldal PG, Hansen TJ, Wargelius A, Edvardsen RB, Glover KA. Autosomal sdY Pseudogenes Explain Discordances Between Phenotypic Sex and DNA Marker for Sex Identification in Atlantic Salmon. Front Genet 2020; 11:544207. [PMID: 33173531 PMCID: PMC7591749 DOI: 10.3389/fgene.2020.544207] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 09/17/2020] [Indexed: 11/13/2022] Open
Abstract
Despite the key role that sex-determination plays in evolutionary processes, it is still poorly understood in many species. In salmonids, which are among the best studied fishes, the master sex-determining gene sexually dimorphic on the Y-chromosome (sdY) has been identified. However, sdY displays unexplained discordance to the phenotypic sex, with a variable frequency of phenotypic females being reported as genetic males. Multiple sex determining loci in Atlantic salmon have also been reported, possibly as a result of recent transposition events in this species. We hypothesized the existence of an autosomal copy of sdY, causing apparent discordance between phenotypic and genetic sex, that is transmitted in accordance with autosomal inheritance. To test this, we developed a qPCR methodology to detect the total number of sdY copies present in the genome. Based on the observed phenotype/genotype frequencies and linkage analysis among 2,025 offspring from 64 pedigree-controlled families of accurately phenotyped Atlantic salmon, we identified both males and females carrying one or two autosomal copies of sdY in addition to the Y-specific copy present in males. Patterns across families were highly consistent with autosomal inheritance. These autosomal sdY copies appear to have lost the ability to function as a sex determining gene and were only occasionally assigned to the actual sex chromosome in any of the affected families.
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Affiliation(s)
| | | | | | | | | | | | | | - Kevin Alan Glover
- Institute of Marine Research, Bergen, Norway.,Department of Biological Sciences, University of Bergen, Bergen, Norway
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