Transcriptome analysis of stinging catfish (Heteropneustes fossilis) kidney reveals its role during adaptation to hypertonic environment

The stinging catfish (Heteropneustes fossilis) can easily adapt to anisotonic environment up to a level of 6 ppt. The teleost kidney is an essential osmoregulatory organ and plays an important role in maintaining the immune system. To investigate the stress responses and mechanisms of salinity tolerance in stinging catfish, we sampled the kidney tissues from control and environmental hypertonically treated (100 mM NaCl solution) stinging catfish and performed transcriptome analysis by high throughput sequencing. The raw data generated was filtered and assembled for de novo transcriptome assembly. The final contig assembly produced a total of 89,813 unigene transcripts with an average transcript length of 901 bp and a GC content of 47.28%. A total of 45,855 unigenes showed significant similarity to known sequences of Swiss-Prot and Ref-Seq databases with BLAST search. Comparative transcriptomic analysis showed that a total of 1660 genes were differentially expressed (693 were upregulated and 967 DEGs downregulated) in the kidney of NaCl-treated fish compared to the control. Functional and enrichment analysis of the DEGs demonstrated that several GO pathway terms were significantly over-represented, such as 'inflammatory response', 'neutrophil chemotaxis' and 'GPCR signaling pathway' in the biological process category, 'cytoplasm' and 'integral component of membrane' in the cellular component category, 'metal ion binding', 'DNA binding' and 'chemokine activity' in the molecular function category. Moreover, pathways such as 'cytokine-cytokine receptor interaction', 'chemokine signaling pathway' and 'metabolic pathways' were over-represented. The present study establishes that tolerance to hypertonic environmental stress requires the activation of numerous molecular processes involved in maintaining the physiological mechanisms in air-breathing stinging catfish.Keywords: Heteropneustes fossilis, High throughput sequencing, Transcriptome, Hypersalinity, Osmoregulation, Environmental stressProject type: Research and development