The mechanism of osmoregulation is crucial for maintaining growth, development, and life activities in teleosts. Takifugu obscurus, the only euryhaline species in the genus Takifugu, is a proper model organism for studying the mechanism of low-salt tolerance and hypoosmotic regulation. In this study, whole-genome sequencing data were obtained from 90 pufferfish representing five species within this genus, T. rubripes, T. obscurus, T. flavidus, T. niphobles, and T. bimaculatus. Using a phylogeny, PCA, and population structure analyses, we observed similar amounts of population genetic differentiation among species. The five species are closely related to each other and have differentiated within a relatively short period, while T. bimaculatus and T. flavidus shared the most similar genetic backgrounds. We further identified hundreds of genes under selection related to hypoosmotic regulation between T. obscurus and other Takifugu species, including 16 representative genes involving ion transporters (atp1a3, atp2a2, atp2a3, slc13a1, slc5a8, slc12a2, slc12a4, slc26a2, scn1b, and kcna2/3/10), genes involved in hormone regulation (fyn, prlr, and grb2), and a gene associated with water absorption (aqp3). Our findings provide preliminary insight into the mechanism of osmoregulation and will facilitate follow-up validation of candidate genes related to osmoregulation in T. obscurus.

中文翻译：

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广盐硬骨鱼低盐耐受性和低渗调节的适应性进化，Takifugu obscurus

渗透调节机制对于维持硬骨鱼的生长、发育和生命活动至关重要。Takifugu obscurus 是Takifugu 属中唯一的广盐性物种，是研究低盐耐受性和低渗调节机制的合适模式生物。在这项研究中，从代表该属内 5 个物种的 90 条河豚中获得了全基因组测序数据，T. rubripes、T. obscurus、T. flavidus、T. niphobles 和 T. bimaculatus。使用系统发育、PCA 和种群结构分析，我们观察到物种之间相似数量的种群遗传分化。这五个物种彼此密切相关，并在相对较短的时间内分化，而 T. bimaculatus 和 T. flavidus 拥有最相似的遗传背景。我们进一步鉴定了数百个与 T. obscurus 和其他 Takifugu 物种之间的低渗调节相关的选择基因，包括 16 个涉及离子转运蛋白的代表性基因（atp1a3、atp2a2、atp2a3、slc13a1、slc5a8、slc12a2、slc12a4、slc21b2、 3/10)、参与激素调节的基因 (fyn、prlr 和 grb2)，以及与吸水相关的基因 (aqp3)。我们的研究结果提供了对渗透调节机制的初步了解，并将促进与 T. obscurus 中与渗透调节相关的候选基因的后续验证。涉及激素调节的基因（fyn、prlr 和 grb2），以及与吸水相关的基因（aqp3）。我们的研究结果提供了对渗透调节机制的初步了解，并将促进与 T. obscurus 中与渗透调节相关的候选基因的后续验证。涉及激素调节的基因（fyn、prlr 和 grb2），以及与吸水相关的基因（aqp3）。我们的研究结果提供了对渗透调节机制的初步了解，并将促进与 T. obscurus 中与渗透调节相关的候选基因的后续验证。