Discordance for genotypic sex in phenotypic female Atlantic salmon (Salmo salar) is related to a reduced sdY copy number

• Published in: Scientific Reports
• Main Authors: Brown, Morgan S., Evans, Brad S., Afonso, Luis O. B.
• Format: Text
• Language: English
• Published: Nature Publishing Group UK 2020
• Subjects: Article; The ''Y''; Atlantic salmon; Salmo salar
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7296011/; http://www.ncbi.nlm.nih.gov/pubmed/32541863; https://doi.org/10.1038/s41598-020-66406-x

The master sex determinant in rainbow trout (Oncorhynchus mykiss), sexually dimorphic on the Y chromosome (sdY), is strongly but not perfectly associated with male phenotype in several other species from the family Salmonidae. Currently, the cause and implications of discordance for sdY-predicted genotypic sex and phenotypic sex in these species is unclear. Using an established multiplex PCR test for exons 2 and 3 of sdY, we demonstrated that sdY-predicted genotypic sex was discordant with histologically evidenced phenotypic sex in 4% of 176 Tasmanian Atlantic salmon. All discordant individuals were phenotypic females presenting a male genotype. Using real-time qPCR assays that we developed and validated for exons 2, 3 and 4 of sdY, all genotype-phenotype discordant females were confirmed to possess sdY, albeit at a reduced number of copies when compared to phenotypic males. The real-time qPCR assays also demonstrated reduced levels of sdY in 30% of phenotypic females that the established multiplex PCR-based test indicated to be devoid of sdY. These findings suggest sdY may be reduced in copy number or mosaicked in the genomic DNA of sdY-positive phenotypic female Atlantic salmon and highlight the importance of understanding the effects of reduced sdY copies on the development of phenotypic sex.