Limits...
A novel sex-determining QTL in Nile tilapia (Oreochromis niloticus).

Palaiokostas C, Bekaert M, Khan MG, Taggart JB, Gharbi K, McAndrew BJ, Penman DJ - BMC Genomics (2015)

Bottom Line: Fish species often exhibit significant sexual dimorphism for commercially important traits.QTL analyses provided evidence for a novel genome-wide significant QTL in LG 20.Evidence was also found for another sex-determining QTL in the fifth family, in the proximal region of LG 1.

View Article: PubMed Central - PubMed

Affiliation: Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, FK9 4LA, Scotland, UK. c.palaiokostas@stir.ac.uk.

ABSTRACT

Background: Fish species often exhibit significant sexual dimorphism for commercially important traits. Accordingly, the control of phenotypic sex, and in particular the production of monosex cultures, is of particular interest to the aquaculture industry. Sex determination in the widely farmed Nile tilapia (Oreochromis niloticus) is complex, involving genomic regions on at least three chromosomes (chromosomes 1, 3 and 23) and interacting in certain cases with elevated early rearing temperature as well. Thus, sex ratios may vary substantially from 50%.

Results: This study focused on mapping sex-determining quantitative trait loci (QTL) in families with skewed sex ratios. These included four families that showed an excess of males (male ratio varied between 64% and 93%) when reared at standard temperature (28°C) and a fifth family in which an excess of males (96%) was observed when fry were reared at 36°C for ten days from first feeding. All the samples used in the current study were genotyped for two single-nucleotide polymorphisms (rs397507167 and rs397507165) located in the expected major sex-determining region in linkage group 1 (LG 1). The only misassigned individuals were phenotypic males with the expected female genotype, suggesting that those offspring had undergone sex-reversal with respect to the major sex-determining locus. We mapped SNPs identified from double digest Restriction-site Associated DNA (ddRAD) sequencing in these five families. Three genetic maps were constructed consisting of 641, 175 and 1,155 SNPs from the three largest families. QTL analyses provided evidence for a novel genome-wide significant QTL in LG 20. Evidence was also found for another sex-determining QTL in the fifth family, in the proximal region of LG 1.

Conclusions: Overall, the results from this study suggest that these previously undetected QTLs are involved in sex determination in the Nile tilapia, causing sex reversal (masculinisation) with respect to the XX genotype at the major sex-determining locus in LG 1.

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Sequencing and polymorphic marker summary. (A) Details of the number of reads before and after filters (orange disk) followed by the reconstructed number of RAD markers and polymorphic RAD markers (orange circles). (B) Genetic map reconstruction. Number of shared polymorphic markers within each family, the number of informative loci and final genetic map size.
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Fig1: Sequencing and polymorphic marker summary. (A) Details of the number of reads before and after filters (orange disk) followed by the reconstructed number of RAD markers and polymorphic RAD markers (orange circles). (B) Genetic map reconstruction. Number of shared polymorphic markers within each family, the number of informative loci and final genetic map size.

Mentions: In total, 689,324,604 raw reads (100 bases long) were produced (344,662,302 paired-end reads, EBI SRA study ERP004077). After removing low quality sequences, ambiguous barcodes and orphaned paired-end reads, 79.7% of the raw reads were retained (549,361,162 reads). In total 10,303 unique RAD-tags were retrieved (Figure 1A). The number of reads and RAD-tags for each sample are reported in Additional file 1: Table S1.Figure 1


A novel sex-determining QTL in Nile tilapia (Oreochromis niloticus).

Palaiokostas C, Bekaert M, Khan MG, Taggart JB, Gharbi K, McAndrew BJ, Penman DJ - BMC Genomics (2015)

Sequencing and polymorphic marker summary. (A) Details of the number of reads before and after filters (orange disk) followed by the reconstructed number of RAD markers and polymorphic RAD markers (orange circles). (B) Genetic map reconstruction. Number of shared polymorphic markers within each family, the number of informative loci and final genetic map size.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4358704&req=5

Fig1: Sequencing and polymorphic marker summary. (A) Details of the number of reads before and after filters (orange disk) followed by the reconstructed number of RAD markers and polymorphic RAD markers (orange circles). (B) Genetic map reconstruction. Number of shared polymorphic markers within each family, the number of informative loci and final genetic map size.
Mentions: In total, 689,324,604 raw reads (100 bases long) were produced (344,662,302 paired-end reads, EBI SRA study ERP004077). After removing low quality sequences, ambiguous barcodes and orphaned paired-end reads, 79.7% of the raw reads were retained (549,361,162 reads). In total 10,303 unique RAD-tags were retrieved (Figure 1A). The number of reads and RAD-tags for each sample are reported in Additional file 1: Table S1.Figure 1

Bottom Line: Fish species often exhibit significant sexual dimorphism for commercially important traits.QTL analyses provided evidence for a novel genome-wide significant QTL in LG 20.Evidence was also found for another sex-determining QTL in the fifth family, in the proximal region of LG 1.

View Article: PubMed Central - PubMed

Affiliation: Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, FK9 4LA, Scotland, UK. c.palaiokostas@stir.ac.uk.

ABSTRACT

Background: Fish species often exhibit significant sexual dimorphism for commercially important traits. Accordingly, the control of phenotypic sex, and in particular the production of monosex cultures, is of particular interest to the aquaculture industry. Sex determination in the widely farmed Nile tilapia (Oreochromis niloticus) is complex, involving genomic regions on at least three chromosomes (chromosomes 1, 3 and 23) and interacting in certain cases with elevated early rearing temperature as well. Thus, sex ratios may vary substantially from 50%.

Results: This study focused on mapping sex-determining quantitative trait loci (QTL) in families with skewed sex ratios. These included four families that showed an excess of males (male ratio varied between 64% and 93%) when reared at standard temperature (28°C) and a fifth family in which an excess of males (96%) was observed when fry were reared at 36°C for ten days from first feeding. All the samples used in the current study were genotyped for two single-nucleotide polymorphisms (rs397507167 and rs397507165) located in the expected major sex-determining region in linkage group 1 (LG 1). The only misassigned individuals were phenotypic males with the expected female genotype, suggesting that those offspring had undergone sex-reversal with respect to the major sex-determining locus. We mapped SNPs identified from double digest Restriction-site Associated DNA (ddRAD) sequencing in these five families. Three genetic maps were constructed consisting of 641, 175 and 1,155 SNPs from the three largest families. QTL analyses provided evidence for a novel genome-wide significant QTL in LG 20. Evidence was also found for another sex-determining QTL in the fifth family, in the proximal region of LG 1.

Conclusions: Overall, the results from this study suggest that these previously undetected QTLs are involved in sex determination in the Nile tilapia, causing sex reversal (masculinisation) with respect to the XX genotype at the major sex-determining locus in LG 1.

Show MeSH
Related in: MedlinePlus