School of Life and Environmental Sciences, Centre for Integrative Ecology, Deakin University Warrnambool Campus, Warrnambool, Victoria, 3280, Australia.
Breeding & Research, Tassal Operations, Hobart, Tasmania, 7000, Australia.
Sci Rep. 2020 Jun 15;10(1):9651. doi: 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.
虹鳟（Oncorhynchus mykiss）中的主要性别决定因子（sex determinant）位于 Y 染色体上，具有性别二态性（sex dimorphism），即 sdY，在鲑科（Salmonidae）的其他几个物种中也与雄性表型强烈相关，但并非完全相关。目前，这些物种中 sdY 预测的基因型性别与表型性别之间的不一致的原因和影响尚不清楚。
我们使用一种已建立的用于 sdY 外显子 2 和 3 的多重 PCR 测试，证明在 176 只塔斯马尼亚大西洋鲑鱼中，有 4%的个体的 sdY 预测的基因型性别与组织学证实的表型性别不一致。所有不一致的个体都是表型为雌性但具有雄性基因型的个体。
我们使用为 sdY 的外显子 2、3 和 4 开发并验证的实时 qPCR 检测，证实所有基因型-表型不一致的雌性个体都具有 sdY，尽管与表型雄性相比，其拷贝数减少。实时 qPCR 检测还表明，在 30%的表型雌性个体中，sdY 的水平降低，而建立的基于多重 PCR 的测试表明这些个体缺乏 sdY。
这些发现表明，sdY 的拷贝数可能减少或在 sdY 阳性的表型雌性大西洋鲑鱼的基因组 DNA 中呈镶嵌状态，并强调了了解 sdY 拷贝数减少对表型性别发育的影响的重要性。
