Ruiz-Jarabo Ignacio, Martos-Sitcha J A, Barragán-Méndez C, Martínez-Rodríguez G, Mancera J M, Arjona F J
Departamento de Biología, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, Av. República Saharaui s/n, 11519, Puerto Real, Cádiz, Spain.
Instituto de Ciencias Marinas y Limnológicas, Facultad de Ciencias, Universidad Austral de Chile, Casilla 567, Valdivia, Chile.
Fish Physiol Biochem. 2018 Apr;44(2):615-628. doi: 10.1007/s10695-017-0457-x. Epub 2017 Dec 23.
In euryhaline teleosts, the hypothalamus-pituitary-thyroid and hypothalamus-pituitary-interrenal axes (HPT and HPI, respectively) are regulated in response to environmental stimuli such as salinity changes. However, the molecular players participating in this physiological process in the gilthead seabream (Sparus aurata), a species of high value for aquaculture, are still not identified and/or fully characterized in terms of gene expression regulation. In this sense, this study identifies and isolates the thyrotropin-releasing hormone (trh) mRNA sequence from S. aurata, encoding prepro-Trh, the putative factor initiating the HPT cascade. In addition, the regulation of trh expression and of key brain genes in the HPI axis, i.e., corticotrophin-releasing hormone (crh) and corticotrophin-releasing hormone-binding protein (crhbp), was studied when the osmoregulatory status of S. aurata was challenged by exposure to different salinities. The deduced amino acid structure of trh showed 65-81% identity with its teleostean orthologs. Analysis of the tissue distribution of gene expression showed that trh mRNA is, though ubiquitously expressed, mainly found in brain. Subsequently, regulation of gene expression of trh, crh, and crhbp was characterized in fish acclimated to 5-, 15-, 40-, and 55-ppt salinities. In this regard, the brain gene expression pattern of trh mRNA was similar to that found for the crh gene, showing an upregulation of gene expression in seabream acclimated to the highest salinity tested. Conversely, crhbp did not change in any of the groups tested. Our results suggest that Trh and Crh play an important role in the acclimation of S. aurata to hypersaline environments.
在广盐性硬骨鱼类中，下丘脑 - 垂体 - 甲状腺轴和下丘脑 - 垂体 - 肾间组织轴（分别为HPT和HPI）会根据盐度变化等环境刺激进行调节。然而，对于具有重要水产养殖价值的金头鲷（Sparus aurata），参与这一生理过程的分子机制，在基因表达调控方面仍未明确和/或完全表征。从这个意义上讲，本研究从金头鲷中鉴定并分离出促甲状腺激素释放激素（trh）的mRNA序列，该序列编码前体促甲状腺激素释放激素（prepro-Trh），即启动HPT级联反应的假定因子。此外，当金头鲷的渗透调节状态因暴露于不同盐度而受到挑战时，研究了trh表达以及HPI轴中关键脑基因（即促肾上腺皮质激素释放激素（crh）和促肾上腺皮质激素释放激素结合蛋白（crhbp））的调控情况。trh推导的氨基酸结构与其硬骨鱼类直系同源物具有65 - 81%的同一性。基因表达的组织分布分析表明，trh mRNA虽然在各处均有表达，但主要存在于脑中。随后，对适应5、15、40和55ppt盐度的鱼类中trh、crh和crhbp的基因表达调控进行了表征。在这方面，trh mRNA的脑基因表达模式与crh基因相似，在适应测试的最高盐度的金头鲷中显示基因表达上调。相反，crhbp在任何测试组中均未发生变化。我们的结果表明，Trh和Crh在金头鲷适应高盐环境中起重要作用。
