Effects of dissolved oxygen on gill tissue of juvenile Eleutheronema tetradactylum based on transcriptome sequencing

【Objective】Transcriptome sequencing-based analysis of the effects of dissolved oxygen on gill tissues of juvenile Eleutheronema tetradactylum was conducted to investigate the adaptive mechanisms of E. tetradactylum in response to hypoxia stress. To provide a reference basis for research on the resistance of E. tetradactylum. 【Method】Juvenile E. tetradactylum were used as experimental materials， and three dissolved oxygen content treatments were set up， normoxic group （CG） 6.33±0.15 mg/L， moderately hypoxic group （OC4） 3.99±0.18 mg/L， and severely hypoxic group （OC2） 2.05±0.15 mg/L. The treatments were carried out for 29 h， and gill tissues were collected for transcriptome sequencing. Differentially expressed genes （DEGs） from different comparison groups were screened using DEGseq， GO functional annotation analysis was performed using GOseq， and KEGG signaling pathway enrichment analysis was performed using KOBAS， trends of DEGs were analyzed by STEM. 【Result】The OC4 vs CG comparison group had 86 DEGs， of which 28 were up-regulated and 58 were down-regulated； the OC2 vs CG comparison group had 2018 DEGs， of which 740 were up-regulated and 1278 were down-regulated； and the OC4 vs OC2 comparison group had 171 DEGs， of which 68 were up-regulated and 103 were down-regulated. The results of GO functional annotation analysis showed that DEGs were mainly involved in functional terms such as metabolic processes， organic matter biosynthesis， cellular redox homeostasis， intracellular， chromatin， ribosomal structural components and catalytic activity. KEGG signaling pathway enrichment analysis showed that DEGs were mainly enriched in signaling pathways such as proteasome， DNA replication， fatty acid degradation， pentose phosphate pathway， oxidative phosphorylation， glutathione metabolism， lysine degradation， and ribosome biogenesis； among them， genes such as pac1， lsm7， mcm6， mcm2 and mdm2 were enriched in signaling pathways such as proteasome， spliceosome， DNA replication and cell cycle， they were related to protein synthesis in gill tissues of juvenile E. tetradactylum， and the expression of which showed a decreasing trend with the decrease of dissolved oxygen content； shmt2， hsd17b10， sucla2 and glo1 genes were enriched in pentose phosphate pathway， which were related to energy metabolism in gill tissues of juvenile E. tetradactylum. 【Conclusion】Both protein synthesis capacity and energy metabolism activity of gill tissues of juvenile E. tetradactylum decrease with decreasing dissolved oxygen content， decrease of dissolved oxygen content significantly affects signaling pathways such as cell cycle， DNA replication， fatty acid degradation and sugar metabolism.