Nagasaki Field Station, Fisheries Technology Institute, Japan Fisheries Research and Education Agency, 1551-8 Taira-machi, Nagasaki, Nagasaki, 851-2213, Japan.
Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo, 108-8477, Japan.
Sci Rep. 2023 Aug 24;13(1):13867. doi: 10.1038/s41598-023-40914-y.
Tunas (genus Thunnus) are one of the most ecologically and commercially important fish worldwide. To establish a biological basis for reproduction in this globally essential species, we have recently studied crucial reproductive aspects of the Pacific bluefin tuna (T. orientalis; PBT), as a model of tuna species, based on our closed-cycle aquaculture technology. In this study, we clarified the global expression profile of the genes regulating gonadal sex differentiation in PBT, as this developmental process is vital to sexual reproduction. Based on the results of our comparative (RNA-sequencing) and temporal (qRT-PCR) transcriptome analyses using the updated genome dataset, we propose the molecular mechanisms of gonadal sex differentiation in PBT. In female gonads, foxl2 and cyp19a1a (coding aromatase) are expressed at the onset of sex differentiation. Active aromatase-mediated estrogen biosynthesis, which includes positive regulation of cyp19a1a expression by Foxl2, induces ovarian differentiation. By contrast, dmrt1 and gsdf are upregulated in differentiating male gonads lacking active estrogen synthesis. Dmrt1 and Gsdf would mainly promote testicular differentiation. Furthermore, androgen biosynthesis is upregulated in differentiating male gonad. Endogenous androgens may also be vital to testicular differentiation. This study provides the first comprehensive data clarifying the molecular basis for gonadal sex differentiation in tunas.
金枪鱼（金枪鱼属）是世界上生态和商业上最重要的鱼类之一。为了为这个全球重要物种的繁殖建立生物学基础，我们最近基于我们的循环水养殖技术，以太平洋蓝鳍金枪鱼（T. orientalis；PBT）为模型，研究了金枪鱼物种的关键繁殖方面。在这项研究中，我们阐明了调控 PBT 性腺性别分化的基因的全球表达谱，因为这个发育过程对有性生殖至关重要。基于我们使用更新的基因组数据集进行的比较（RNA-seq）和时间（qRT-PCR）转录组分析的结果，我们提出了 PBT 性腺性别分化的分子机制。在雌性性腺中，foxl2 和 cyp19a1a（编码芳香酶）在性别分化开始时表达。活性芳香酶介导的雌激素生物合成，包括 Foxl2 对 cyp19a1a 表达的正向调节，诱导卵巢分化。相比之下，在缺乏活性雌激素合成的分化雄性性腺中，dmrt1 和 gsdf 上调。Dmrt1 和 Gsdf 将主要促进睾丸分化。此外，分化的雄性性腺中雄激素生物合成上调。内源性雄激素对睾丸分化也可能至关重要。这项研究提供了第一个全面的数据，阐明了金枪鱼性腺性别分化的分子基础。
