Mapping of five candidate sex-determining loci in rainbow trout (Oncorhynchus mykiss).

Mahmoud A Alfaqih,Robert E Drew,Gary H Thorgaard,Joseph P Brunelli

doi:10.1186/1471-2156-10-2

Mahmoud A Alfaqih, Robert E Drew + Show 2 more

Open Access

https://doi.org/10.1186/1471-2156-10-2

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Abstract

BackgroundRainbow trout have an XX/XY genetic mechanism of sex determination where males are the heterogametic sex. The homology of the sex-determining gene (SDG) in medaka to Dmrt1 suggested that SDGs evolve from downstream genes by gene duplication. Orthologous sequences of the major genes of the mammalian sex determination pathway have been reported in the rainbow trout but the map position for the majority of these genes has not been assigned.ResultsFive loci of four candidate genes (Amh, Dax1, Dmrt1 and Sox6) were tested for linkage to the Y chromosome of rainbow trout. We exclude the role of all these loci as candidates for the primary SDG in this species. Sox6i and Sox6ii, duplicated copies of Sox6, mapped to homeologous linkage groups 10 and 18 respectively. Genotyping fishes of the OSU × Arlee mapping family for Sox6i and Sox6ii alleles indicated that Sox6i locus might be deleted in the Arlee lineage.ConclusionAdditional candidate genes should be tested for their linkage to the Y chromosome. Mapping data of duplicated Sox6 loci supports previously suggested homeology between linkage groups 10 and 18. Enrichment of the rainbow trout genomic map with known gene markers allows map comparisons with other salmonids. Mapping of candidate sex-determining loci is important for analyses of potential autosomal modifiers of sex-determination in rainbow trout.

Highlights

Rainbow trout have an XX/XY genetic mechanism of sex determination where males are the heterogametic sex
Linkage analysis of Amh, Dax1 and Dmrt1 Through comparison of rainbow trout Amh cDNA sequence with zebrafish (Danio rerio) orthologous genomic sequences, it was determined that the Amh gene of rainbow trout and zebrafish both have six tentative introns
Comparison of Oregon State University (OSU) and Arlee intron sequences indicated the presence of a single nucleotide polymorphism (SNP) in the 5th intron of OSU in a Tsp509I restriction site (Table 1)

Summary

Introduction

Rainbow trout have an XX/XY genetic mechanism of sex determination where males are the heterogametic sex. The homology of the sex-determining gene (SDG) in medaka to Dmrt suggested that SDGs evolve from downstream genes by gene duplication. The recent discovery that the sex-determining gene of the medaka, Dmy, is a homologue of a downstream gene of the pathway in mammalian species [4] led researchers to propose that downstream genes can be recruited to the top of the hierarchy by gene duplication [5]. This model of evolution of (page number not for citation purposes)

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