YANG Zhi, ZHANG Yuan-Yue, WANG Jian-Xin, LIAO Zhi, HU Qun-Ju, YANG Qiao-Mei, ZHANG Xiao-Lin, FAN Mei-Hua
The ocean plays a critical role in the global carbon cycle, and base on the "dual carbon" goals, ocean carbon sinks have received widespread attention. Shellfish aquaculture is one of the most important sources of carbon sinks in fisheries, which has an important impact on the offshore carbon cycle. As global temperature rises and ocean acidification intensifies, the capacity of the ocean to absorb CO2 will change. However, the effects of high temperature on the physiology and transcriptome related to carbon metabolism in Mytilus coruscus are not clear enough. This study investigated the effects of high temperatures on the total carbon content, carbon metabolism, antioxidant-related enzyme activities, and the transcriptome of Mytilus coruscus. The results showed that high temperature significantly inhibited the activities of hexokinase and pyruvate kinase, increased carbonic anhydrase activity (P＜0.05), decreased the ATP content of digestive glands (P＜0.05), and affected glycolysis and the tricarboxylic acid cycle, leading to a significant decrease in the mussel’s ability to sequester carbon. High temperature resulted in significant (P<0.05) increases in the levels of reactive oxygen species and malondialdehyde, and enhanced the activities of superoxide dismutase and catalase. Observations by transmission electron microscopy showed that high temperatures damaged the subcellular structure of the digestive gland in Mytilus coruscus, resulting in the shrinkage of the nucleolus, swelling of the endoplasmic reticulum, and a significant reduction in the mitochondrial cristae. Comparative transcriptomic analysis showed that the upregulated DEGs were mainly enriched in protein processing in the endoplasmic reticulum, antigen processing and presentation, and MAPK signaling pathway. The downregulated DEGs were mainly enriched in necroptosis, DNA replication, and the NF-kappa B signaling pathway. In antioxidant-related DEGs, the upregulated DEGs include vitamin K epoxide reductase, peroxidases, heat shock protein 105 kD, heat shock protein 70 kD, and superoxide dismutase; The downregulated DEGs mainly included NADPH oxidase, glutathione reductase, cytochrome b-245, cytochrome P450, and quinone reductase. The upregulated genes enriched in the carbon metabolism pathway included chitinase, phosphatidylinositol 4, 5-bisphosphate 3-kinase, phosphoenolpyruvate carboxykinase, galactokinase, and inositol trisphosphate 3-kinase. The downregulated genes included aldose-1-epimerase, carbonic anhydrase, galactose mutarotase, acyl-CoA synthetase, alcohol dehydrogenase, and hexokinase. In conclusion, high temperature has an inhibitory effect on the activities of enzymes and the expression of genes related to carbon metabolism in Mytilus coruscus. The results of this study are intended to provide a scientific basis for the healthy development of mussel aquaculture and the assessment of carbon sinks.
