Taubenheim Jan, Kortmann Constantin, Fraune Sebastian
Zoology and Organismic Interactions, Heinrich Heine University Düsseldorf, Düsseldorf, Germany.
Front Cell Dev Biol. 2021 Jun 10;9:653792. doi: 10.3389/fcell.2021.653792. eCollection 2021.
Nuclear receptors (NRs) fulfill key roles in the coordination of postembryonal developmental transitions in animal species. They control the metamorphosis and sexual maturation in virtually all animals and by that the two main environmental-dependent developmental decision points. Sexual maturation and metamorphosis are controlled by steroid receptors and thyroid receptors, respectively in vertebrates, while both processes are orchestrated by the ecdysone receptor (EcR) in insects. The regulation of these processes depends on environmental factors like nutrition, temperature, or photoperiods and by that NRs form evolutionary conserved mediators of phenotypic plasticity. While the mechanism of action for metamorphosis and sexual maturation are well studied in model organisms, the evolution of these systems is not entirely understood and requires further investigation. We here review the current knowledge of NR involvement in metamorphosis and sexual maturation across the animal tree of life with special attention to environmental integration and evolution of the signaling mechanism. Furthermore, we compare commonalities and differences of the different signaling systems. Finally, we identify key gaps in our knowledge of NR evolution, which, if sufficiently investigated, would lead to an importantly improved understanding of the evolution of complex signaling systems, the evolution of life history decision points, and, ultimately, speciation events in the metazoan kingdom.
核受体（NRs）在动物胚胎后发育转变的协调过程中发挥着关键作用。它们控制着几乎所有动物的变态发育和性成熟，也就是控制着两个主要的依赖环境的发育决策点。在脊椎动物中，性成熟和变态发育分别由类固醇受体和甲状腺受体控制，而在昆虫中，这两个过程均由蜕皮激素受体（EcR）协调。这些过程的调节取决于营养、温度或光周期等环境因素，因此核受体形成了表型可塑性的进化保守介质。虽然在模式生物中对变态发育和性成熟的作用机制已有深入研究，但这些系统的进化尚未完全明晰，仍需进一步探究。我们在此回顾了目前关于核受体参与动物生命之树中变态发育和性成熟的知识，特别关注环境整合以及信号传导机制的进化。此外，我们比较了不同信号系统的异同。最后，我们确定了核受体进化知识中的关键空白，如果能对其进行充分研究，将有助于显著增进我们对复杂信号系统进化、生活史决策点进化以及后生动物王国物种形成事件的理解。
