Differential expression of miRNAs and mRNAs in the livers of largemouth bass Micropterus salmoides under heat stress

Global warming threatens freshwater ecosystems and compromises fish survival. To elucidate the role of miRNAs in the livers of heat stressed largemouth bass, juvenile fish was subject to heat stress under 37 C-degrees. Both mRNA-seq and miRNA-seq were conducted on the liver tissues under control and heat stress conditions. Differential gene expression analysis and enrichment analysis were performed on mRNA and miRNA expression profiles. A total of 406 differentially expressed genes (DEGs) were discovered, of which 212 were up-regulated and 194 were down-regulated. Most of the DEGs were significantly implicated in the regulation of "protein processing in endoplasmic reticulum", "proteasome", "steroid biosynthesis", and "ornithine decarboxylase inhibitor activity" pathways. In addition, 47 differentially expressed miRNAs (DEMs) were identified in largemouth bass livers under heat stress, including 21 up-regulated and 25 down-regulated miRNAs. A negatively regulated miRNA-mRNA network including 12 miRNAs and 19 mRNAs was constructed with DEMs involved in "protein degradation", "calcium ion regulation", "cell apoptosis", and "lipid metabolism". Moreover, this study indicated novel-miR-144 activated the IRE1 signaling pathway by targeting txndc5 to induce liver apoptosis in largemouth bass under heat stress. This study revealed the involvement of miRNA regulation in largemouth bass in response to heat stress.