Brain Transcriptome Analysis Reveals Metabolic Changes Adapting to Hyperhaline or Hypohaline Environments in Spotted Scat(Scatophagus argus)

The fish brain is crucial for adjusting to environmental changes.Metabolic changes play a vital role in the adaptation to salinity change in aquatic animals.However,few studies have evaluated the responses of the fish brain to salinity changes.To evaluate the response to various salinities,spotted scat(Scatophagus argus)was cultured in water with salinity levels of 5(low salinity:LS),25(control group:Ctrl),and 35(high salinity group:HS)for 22 days.The brain transcriptome was analyzed.In total,1698 differentially expressed genes(DEGs)were identified between the HS and Ctrl groups,and 841 DEGs were identified between the LS and Ctrl groups.KEGG analysis showed that the DEGs in the HS vs.Ctrl comparison were involved in steroid biosynthesis,terpenoid backbone biosynthesis,fatty acid biosynthesis,ascorbate and aldarate metabolism,other types of O-glycan biosynthesis,and fatty acid metabolism.Glyoxylate and dicarboxylate metabolism,one carbon pool by folate,steroid biosynthesis,and cysteine and methionine metabolism were significantly enriched in the LS vs.Ctrl comparison.Additionally,the genes related to metabolism(acc,fas,hmgcr,hmgcs1,mvd,soat1,nsdhl,sqle,cel,fdft1,dnmt3a and mtr)were significantly up-regulated in the HS vs.Ctrl comparison.The genes related to metabolism(lipa,sqle,acc,fas,bhmt,mpst,dnmt3a,mtr,hao2,LOC111225351 and hmgcs1)were significantly up-regulated,while hmgcr and soat1 were significantly down-regulated in the LS vs.Ctrl compparison.These results suggest that salinity stress affects signaling pathways and genes’expressions involved in metabolic processes in the brain,and the differences in metabolism play an important role in adaptation to hyperhaline or hypohaline environments in spotted scat.This research provides a comprehensive overview of transcriptional changes in the brain under hyperhaline or hypohaline conditions,which is helpful to understand the mechanisms underlying salinity adaptation in euryhaline fishes.