Evolution of steroid hormone signaling and size determination in Cnidaria and Xenacoelomorpha

类固醇激素控制着重要的发育开关，因为它们诱导性成熟并介导许多两侧对称物种生长期的终止。它们为生长、繁殖力、发育时间和资源利用设定了至关重要的权衡，并依赖于内在遗传和外在环境信号。因此，它们是发育可塑性和适应性的关键组成部分。类固醇激素由核受体（NR）识别，核受体是一个在发育和生理学中具有各种功能的多样化受体家族。当类固醇激素和相应的NR进化是不充分的理解，但关于这个话题的信息承诺在类固醇的祖先功能及其对不同的身体计划和生活方式的贡献的见解。系统发育和生物化学预测将类固醇受体的进化追溯到刺胞动物-两侧刺胞动物的分裂，而在早期出现的两侧刺胞动物和刺胞动物的代表性物种中没有类固醇激素/ NRs在发育中的功能证据（Xenacoelomorpha，所有其他Bilateria的姐妹群），以了解他们的祖先在不断变化的环境条件下调节身体大小的功能。我将使用系统发育的方法与原位杂交配对，以确定发育和环境响应的NR。将通过细胞计量术观察环境变化后和NR诱变后的细胞变化，同时将通过色谱法和质谱法在两个种属的提取物中鉴定类固醇激素。该项目将阐明原型的分子机制和环境依赖的发展决策（表型可塑性）的所有双边的演变。

Steroid hormones control important developmental switches as they induce sexual maturity and mediate termination of the growth phase for many bilaterian species. They set crucial trade-offs for growth, fecundity, developmental time, and resource utilization and are dependent on intrinsic genetic as well as extrinsic environmental signals. Hence, they are key components for developmental plasticity and adaptation. Steroid hormones are recognized by nuclear receptors (NR), a diverse receptor family with various functions in development and physiology. When steroid hormones and the corresponding NRs evolved is insufficiently understood, but information on this topic promises insights in the ancestral function of steroids and their contribution to diverse body plans and life styles. Phylogenetic and biochemical predictions date the evolution of steroid receptors to the cnidarian-bilaterian split, without functional evidences of steroid hormones/ NRs in development in representative species in early emerging Bilateria and Cnidaria.I will study the evolution and function of steroid-binding NRs in the Cnidaria Hydra vulgaris and the Bilateria Hofstenia miamia (Xenacoelomorpha, a sister group to all other Bilateria) to understand their ancestral function in body size regulation under changing environmental conditions. I will use a phylogenetic approach paired with insitu hybridization to identify developmentally and environmentally responsive NRs. Cellular alterations upon changing environments and after mutagenesis of NRs will be observed by cytometry, while steroid hormones will be identified in extracts of the two species by chromatography and mass spectrometry. The project will elucidate the prototypic molecular mechanism and the evolution of environmental dependent developmental decisions (phenotypic plasticity) of all Bilateria.