Gill and brain transcriptomic analysis of mandarin fish(Siniperca chuatsi)reveals hypoxia-induced mitochondrial dysfunction and modulation of metabolism.

The oxygen content in the fish ponds is facing greater challenges than before in the aquaculture of mandarin fish (Siniperca chuatsi) due to the change of climate and eutrophication. Until now, little is known about the molecular mechanisms underlying the harmful effects of hypoxia on this species. In this work, we built transcriptomes for the mandarin fish that were exposed to decreased oxygen concentration at two times points (24 h and 96 h). The respiratory metabolism activities of pyruvate kinase (PK), hexokinase (HK), lactate dehydrogenase (LDH), succinate dehydrogenase (SDH) and malate dehydrogenase (MDH) had different significantly changes during hypoxic treatment. Histological observation of the gill and brain also revealed some damages by hypoxia. A total of 196,355 transcripts were involved in the Gene Ontology analysis, and the numbers of differentially expressed genes (DEGs) in the brain and the gill between the control and experiment groups are 141 and 552 respectively involved in the different hypoxic stress time. The DEGs were then analyzed using KEGG enrichment analysis. The results showed significant differences in the expression of some genes involved in ribosome pathways,biosynthesis of amino acids, hippo signaling pathway, and pentose phosphate pathway,glycolysis/gluconeogenesis pathway and the TCA cycle. The huge number of transcriptome sequences collected in this study has enhanced the mandarin fish gene resources, and the identified DEGs and related pathway analysis give essential information for understanding biological responses to hypoxia.