The Nile tilapia, Oreochromis niloticus, is an important species for global aquaculture. Recently, a single genetic line of Nile tilapia was developed using estimated breeding values (EBVs) for body weight under moderately saline water that showed significant improvement in growth performance. To explore the molecular mechanisms underlying this enhanced growth capacity, RNA-Seq was used to profile differences in gene expression in the liver and pituitary gland of high- and low-growth performance families of male Nile tilapia progeny, reared in either saline or freshwater environments. Comparisons of tissues from high- and low-EBV families, and also between fish reared in either saline or freshwater, revealed 142 and 2208 differentially expressed genes (DEGs), respectively. DEGs identified between the EBV groups comprised a number of genes involved in the regulation of growth and reproduction. We found an overexpression of hormone genes involved in growth-inhibition in the pituitary of Low-EBV tilapia including 2 somatostatin genes (GHIH), corticoliberin (CRH) and tachykinin-3-like protein. Furthermore, several genes associated with the cAMP pathway were underexpressed in low-EBV tilapia pituitary together with several early response genes.

This study provides insight into the transcriptomic factors associated with growth performance in saline-adapted Nile tilapia reared in environments with high and low salinity levels and provides valuable knowledge for the future development of selection strategies to improve growth performance in this species.

尼罗罗非鱼Oreochromis niloticus，是全球水产养殖的重要物种。最近，尼罗罗非鱼的单一遗传品系在适度咸水下使用体重的估计育种值 (EBV) 开发，显示出生长性能的显着改善。为了探索这种生长能力增强背后的分子机制，使用 RNA-Seq 分析了在盐水或淡水环境中饲养的雄性尼罗罗非鱼后代的高生长和低生长性能家族的肝脏和垂体腺中基因表达的差异. 对来自高和低 EBV 家族的组织以及在盐水或淡水中养殖的鱼的组织进行比较，分别揭示了 142 和 2208 个差异表达基因 (DEG)。在 EBV 组之间鉴定的 DEG 包含许多参与生长和繁殖调节的基因。我们发现低 EBV 罗非鱼垂体中涉及生长抑制的激素基因的过度表达，包括 2 个生长抑素基因 (GHIH)、皮质醇 (CRH) 和速激肽-3 样蛋白。此外，与 cAMP 途径相关的几个基因在低 EBV 罗非鱼垂体中与几个早期反应基因一起表达不足。

这项研究提供了与在高盐度和低盐度环境中饲养的适应盐碱的尼罗罗非鱼生长性能相关的转录组学因素的见解，并为未来发展选择策略以提高该物种的生长性能提供了宝贵的知识。