Astaxanthin (Ax), the main carotenoid responsible for the distinct red flesh color in salmonids (Oncorhynchus, Salvelinus, Salmo, and Parahucho), is added to the diet of farmed fish at a substantial cost. Despite the great economical value for the salmon industry, the key molecular mechanisms involved in the regulation of muscle coloration are poorly understood. Chinook salmon (Oncorhynchus tshawytscha) represent an ideal model to study flesh coloration because they exhibit a distinct color polymorphism responsible for two color morphs, white and red flesh pigmented fish. This study was designed to identify the molecular basis for the development of red and white coloration of fish reared under the same experimental conditions and to better understand the absorption mechanism of Ax in salmonids. Pyloric caeca, liver, and muscle of both groups (n = 6 each) were selected as the most likely critical target organs to be involved respectively in the intestinal uptake, metabolism, and retention of Ax. Difference in the transcriptome profile of each tissue using next-generation sequencing technology was conducted. Ten KEGG pathways were significantly enriched for differentially expressed genes between red and white salmon pylorus tissue, while none for the transcriptome profile in the other two tissues. Differential expressed gene (DE) analyses showed that there were relatively few differences in muscle (31 DE genes, p < 0.05) and liver (43 DE genes, p < 0.05) of white and red Chinook salmon compared approximately 1125 DE genes characterized in the pylorus tissue, with several linked to Ax binding ability, absorption, and metabolism.

中文翻译：

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红色和白色奇努克鲑鱼 (Oncorhynchus tshawytscha)：肌肉、肝脏和幽门转录组谱的差异。

虾青素 (Ax) 是造成鲑鱼（Oncorhynchus、Salvelinus、Salmo 和 Parahucho）明显红色肉色的主要类胡萝卜素，以高昂的成本添加到养殖鱼类的饮食中。尽管鲑鱼产业具有巨大的经济价值，但人们对肌肉着色调节所涉及的关键分子机制知之甚少。奇努克鲑鱼 ( Oncorhynchus tshawytscha) 代表了研究肉色的理想模型，因为它们表现出独特的颜色多态性，负责两种颜色变形，白色和红色肉色鱼。本研究旨在确定在相同实验条件下饲养的鱼的红色和白色颜色发展的分子基础，并更好地了解 Ax 在鲑鱼中的吸收机制。两组的幽门盲囊、肝脏和肌肉（n = 6 个）分别被选为最可能参与肠道摄取、代谢和 Ax 滞留的关键靶器官。使用下一代测序技术对每个组织的转录组谱进行了差异化。10 条 KEGG 通路显着富集了红鲑鱼和白鲑鱼幽门组织之间的差异表达基因，而其他两种组织中的转录组谱则没有。差异表达基因 (DE) 分析表明，肌肉（31 个 DE 基因，p  < 0.05）和肝脏（43 个 DE 基因，p < 0.05) 的白色和红色奇努克鲑鱼比较了大约 1125 个在幽门组织中表征的 DE 基因，其中几个与 Ax 结合能力、吸收和代谢有关。