In fish breeding practices, gamete maturity of females is vital to reproductive success. For some species, it is possible to estimate the female maturation status based on abdomen observation, but quite difficult for some species which mature at big size. To screen out the potential biomarker in fish blood relating to female maturation, we employed the approach integrating the UPLC-MS/MS and RNA-seq techniques to investigate the metabolites and genes reflecting the sexual maturation and spawning of female blunt snout bream Megalobrama amblycephala. The study included four groups, 1-year-old immature female individuals, 2-year-old immature female individuals, 2-year-old sexually mature female individuals, and 2-year-old sexually mature female individuals after 24 h of successful spawning. The upregulated metabolites in mature females were involved in “steroid hormone biosynthesis,” “metabolic pathways,” “glycerophospholipid metabolism,” etc. compared with those of immature individuals. As the key intermediate of steroid hormone biosynthesis, 17α-hydroxypregnenolone exhibited the highest level in 2-year-old mature females than in the immature females. Meanwhile, the metabolites (i.e., dodecanoic acid and myristic acid) participating in fatty acid synthesis exhibited much lower levels in the females after spawning than those before spawning. In addition to the metabolites, the genes involved in ovarian steroidogenesis were significantly upregulated in the 2-year-old immature females compared to the 1-year-old immature females, indicating that the ovarian steroidogenesis plays important roles in ovarian development of M. amblycephala at the early stages. The significant upregulation of genes (i.e., itpr1, camk2, and mekk2) involved in the “GnRH signaling pathway” was observed in the mature females compared with the immature females, which indicated that the estrogen levels increased after female maturation in M. amblycephala. Moreover, many genes (e.g., gck, creb1, tf2-9, ryr2, asgr1, and creb1) regulating insulin secretion and thyroid hormone synthesis were significantly downregulated after female spawning. The dynamics of gene expression and metabolites observed in this study provide novel cues for guiding fish practical artificial reproduction.

中文翻译：

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基于代谢组学和转录组学技术筛选钝性鼻烟（Megalobrama amblycephala）卵巢成熟和产卵相关的生物标志物。

在鱼类育种实践中，雌配子的成熟对生殖成功至关重要。对于某些物种，可以通过腹部观察来估计雌性的成熟状态，但是对于某些大尺寸成熟的物种而言，这是非常困难的。筛选出在鱼血的潜在生物标志物有关雌性成熟，我们所采用的方法整合UPLC-MS / MS和RNA-SEQ技术调查代谢物和基因反射性成熟和雌性头鲂产卵团头鲂。该研究包括四组：成功产卵24小时后的1岁未成年女性个体，2岁未成年女性个体，2岁性成熟女性个体和2岁性成熟女性个体。 。与未成熟个体相比，成熟女性的代谢产物参与了“类固醇激素的生物合成”，“代谢途径”，“甘油磷脂代谢”等。作为类固醇激素生物合成的关键中间产物，17α-羟基孕烯醇酮在2岁的成年女性中比未成熟的女性表现出最高的水平。同时，参与脂肪酸合成的代谢产物（即十二烷酸和肉豆蔻酸）在产卵后的雌性中的水平要比产卵前的低得多。除了代谢物早期的M. amblycephala。与未成熟雌性相比，在成熟雌性中观察到参与“ GnRH信号传导途径”的基因（即itpr1，camk2和mekk2）显着上调，这表明雌性成熟后在雌性M. amblycephala中增加了雌激素水平。而且，许多基因（例如gck，creb1，tf2-9，ryr2，asgr1和creb1雌性产卵后，调节胰岛素分泌和甲状腺激素合成被显着下调。在这项研究中观察到的基因表达和代谢产物的动力学为指导鱼类实际的人工繁殖提供了新的线索。