Artificially high temperatures during critical thermosensitive periods (TSPs) can induce the sex reversal of Nile tilapia (Oreochromis niloticus) females into pseudomales; Nile tilapia is a GSD + TE (genotypic plus temperature effects) fish species. Previous studies have shown that water temperature affects the expression levels of many genes in the gonad or brain in various teleost species. However, few studies on the effect of temperature at the whole-gonad transcriptomic level in the early stage of sex differentiation have been reported in fish species exhibiting GSD + TE. In this study, RNA-Seq was performed to characterize the transcriptomic profile and identify genes exhibiting temperature- and sex-biased expressions in the Nile tilapia gonad at 21 dpf. A total of 42 genes were found to be associated with both high-temperature treatment and sex development, as the expression levels of these genes differed in both FC (female control) vs MC (male control) and FC vs FT (high temperature–treated females in the TSP). Among these genes, the transcriptional alterations of many male sex determination and differentiation genes, such as Dmrt1, Gsdf, and the DNA damage-inducible protein GADD45 alpha, suggested that the male pathway is initiated after high-temperature treatment and that its initiation may play a role in high temperature–induced masculinization in Nile tilapia. The qRT-PCR validation results for thirteen differentially expressed genes showed that the Pearson’s correlation of the log₁₀ fold change values between the qPCR and RNA-Seq results was 0.70 (p < 0.001), indicating the accuracy and reliability of the RNA-Seq results. Our study provides insights into how high-temperature treatment induces the sex reversal of Nile tilapia females.

中文翻译：

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性别未分化的尼罗罗非鱼性腺的转录组分析和与高温诱导的男性化相关的基因分析。

在关键的热敏期（TSPs）期间人为升高的温度可以诱导尼罗罗非鱼（Oreochromis niloticus雌成假雄；尼罗罗非鱼是GSD + TE（基因型加温度效应）鱼类。先前的研究表明，水温会影响各种硬骨鱼类性腺或大脑中许多基因的表达水平。但是，关于性别分化早期阶段，在全性腺转录组水平上温度的影响的研究鲜有报道。在这项研究中，进行了RNA-Seq表征转录组特征，并鉴定了尼罗罗非鱼性腺中21 dpf表现出温度和性别偏向表达的基因。发现共有42个基因与高温治疗和性发育有关，因为这些基因的表达水平在FC（女性对照）与MC（男性对照）以及FC与FT（TSP中经过高温处理的女性）中均不同。在这些基因中，许多男性性别决定和分化基因的转录改变，例如DMRT1，GSDF和DNA损伤诱导蛋白GADD45α，建议男性途径高温处理之后开始，并且其启动可以起到在尼罗罗非鱼高温度引起的男性化作用。十三种差异表达基因的qRT-PCR验证结果表明，qPCR和RNA-Seq结果之间的log ₁₀倍变化值的Pearson相关性为0.70（p  <0.001），表明RNA-Seq结果的准确性和可靠性。我们的研究提供了有关高温治疗如何诱发尼罗罗非鱼雌性性行为的见解。