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: Article in Journal/Newspaper
• Language: English
• Published: Springer Science and Business Media LLC 2020
• Subjects: Multidisciplinary; The ''Y''; Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1038/s41598-020-66406-x; http://www.nature.com/articles/s41598-020-66406-x.pdf; http://www.nature.com/articles/s41598-020-66406-x

Abstract 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.