Department of Information Systems Creation, Faculty of Engineering, Kanagawa University, Yokohama 221-8686, Japan.
Department of Biology, Faculty of Science, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
J Theor Biol. 2018 Sep 14;453:146-155. doi: 10.1016/j.jtbi.2018.05.023. Epub 2018 May 22.
Temperature-dependent sex determination (TSD) is adopted by many animal taxa, including reptiles and fishes. In some species, the eggs develop into females under a low hatching temperature, whereas they will develop into males under a high hatching temperature (called the FM-pattern). In other species, the eggs develop into males (or females) under a low (or high) hatching temperature (MF-pattern). Still, in other species, the eggs develop into females, males, or females, respectively, when under a low, intermediate, or high hatching temperature (FMF-pattern). In this paper, we study a mechanism for realizing TSD. Specifically, we explore a hypothesis that the temperature dependence of enzymatic reaction rates causes a clear switching of sex hormone levels with gradual change of temperature. Herein, we analyze a simple hormonal-dynamics with temperature-sensitive rates of enzymatic reactions included in the sex-determining gene-protein regulatory network. We first examined the cases in which the enzymatic reactions followed Arrhenius equation. The MF-pattern appeared when the rates of aromatase production and/or estradiol production depend more strongly on temperature than do the rates of their decay. By contrast, the FM-pattern appeared when the temperature dependence is stronger for the decay rates of aromatase and/or estradiol than their production rates. However, the FMF-pattern appeared only when some enzymatic reactions follow Berthelot-Hood equation, which exhibits a stronger temperature dependence under higher temperatures than Arrhenius equation. We discuss the possible mechanisms for TSD of FMF-pattern, including alternative splicing and post-translational modification.
温度依赖型性别决定（TSD）被许多动物类群采用，包括爬行动物和鱼类。在一些物种中，当孵化温度较低时，卵发育为雌性，而当孵化温度较高时，卵发育为雄性（称为 FM 模式）。在其他物种中，当孵化温度较低或较高时，卵发育为雄性（或雌性）（MF 模式）。还有一些物种，当孵化温度较低、中等或较高时，卵分别发育为雌性、雄性或雌雄同体（FMF 模式）。在本文中，我们研究了一种实现 TSD 的机制。具体来说，我们探讨了一个假设，即酶反应速率的温度依赖性导致性激素水平随着温度的逐渐变化而发生明显的转换。在这里，我们分析了一个简单的激素动力学模型，其中包含了温度敏感的酶反应速率，这些反应速率包含在性别决定基因-蛋白调控网络中。我们首先研究了酶反应遵循阿伦尼乌斯方程的情况。当芳香酶和/或雌二醇的产生速率比其衰减速率对温度更敏感时，MF 模式出现。相比之下，当芳香酶和/或雌二醇的衰减速率对温度的依赖性比其产生速率更强时，FM 模式出现。然而，只有当一些酶反应遵循 Berthelot-Hood 方程时，FMF 模式才会出现，该方程在较高温度下表现出比阿伦尼乌斯方程更强的温度依赖性。我们讨论了 FMF 模式 TSD 的可能机制，包括选择性剪接和翻译后修饰。
