Li Busu, Song Kai, Meng Jie, Li Li, Zhang Guofan
Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.
University of Chinese Academy of Sciences, Beijing, China.
BMC Genomics. 2017 Sep 11;18(1):713. doi: 10.1186/s12864-017-4069-8.
The Pacific oyster Crassostrea gigas is an important marine fishery resource, which contains high levels of glycogen that contributes to the flavor and the quality of the oyster. However, little is known about the molecular and chemical mechanisms underlying glycogen content differences in Pacific oysters. Using a homogeneous cultured Pacific oyster family, we explored these regulatory networks at the level of the metabolome and the transcriptome.
Oysters with the highest and lowest natural glycogen content were selected for differential transcriptome and metabolome analysis. We identified 1888 differentially-expressed genes, seventy-five differentially-abundant metabolites, which are part of twenty-seven signaling pathways that were enriched using an integrated analysis of the interaction between the differentially-expressed genes and the differentially-abundant metabolites. Based on these results, we found that a high expression of carnitine O-palmitoyltransferase 2 (CPT2), indicative of increased fatty acid degradation, is associated with a lower glycogen content. Together, a high level of expression of phosphoenolpyruvate carboxykinase (PEPCK), and high levels of glucogenic amino acids likely underlie the increased glycogen production in high-glycogen oysters. In addition, the higher levels of the glycolytic enzymes hexokinase (HK) and pyruvate kinase (PK), as well as of the TCA cycle enzymes malate dehydrogenase (MDH) and pyruvate carboxylase (PYC), imply that there is a concomitant up-regulation of energy metabolism in high-glycogen oysters. High-glycogen oysters also appeared to have an increased ability to cope with stress, since the levels of the antioxidant glutathione peroxidase enzyme 5 (GPX5) gene were also increased.
Our results suggest that amino acids and free fatty acids are closely related to glycogen content in oysters. In addition, oysters with a high glycogen content have a greater energy production capacity and a greater ability to cope with stress. These findings will not only provide insights into the molecular mechanisms underlying oyster quality, but also promote research into the molecular breeding of oysters.
太平洋牡蛎（Crassostrea gigas）是一种重要的海洋渔业资源，其糖原含量很高，这对牡蛎的风味和品质有重要作用。然而，关于太平洋牡蛎糖原含量差异背后的分子和化学机制，我们了解得还很少。我们利用一个均匀养殖的太平洋牡蛎家系，在代谢组和转录组水平上探索了这些调控网络。
选择糖原含量自然最高和最低的牡蛎进行差异转录组和代谢组分析。我们鉴定出1888个差异表达基因、75种差异丰富的代谢物，它们是27条信号通路的一部分，通过对差异表达基因和差异丰富代谢物之间的相互作用进行综合分析得以富集。基于这些结果，我们发现肉碱O-棕榈酰转移酶2（CPT2）的高表达表明脂肪酸降解增加，这与较低的糖原含量相关。此外，磷酸烯醇式丙酮酸羧激酶（PEPCK）的高水平表达以及生糖氨基酸的高水平可能是高糖原牡蛎中糖原产量增加的基础。此外，糖酵解酶己糖激酶（HK）和丙酮酸激酶（PK）以及三羧酸循环酶苹果酸脱氢酶（MDH）和丙酮酸羧化酶（PYC）的较高水平表明，高糖原牡蛎中能量代谢同时上调。高糖原牡蛎似乎应对压力的能力也有所增强，因为抗氧化谷胱甘肽过氧化物酶5（GPX5）基因的水平也有所增加。
我们的结果表明，氨基酸和游离脂肪酸与牡蛎中的糖原含量密切相关。此外，糖原含量高的牡蛎具有更大的能量产生能力和更强的应对压力的能力。这些发现不仅将为牡蛎品质的分子机制提供见解，还将促进牡蛎分子育种的研究。
