Abstract:A rapid reduction in the dissolved oxygen concentration of water is an important factor contributing to disease in shrimps. In this study, we examined differential gene expression in the shrimp Palaemon carincauda under conditions of hypoxic stress. We obtained 10.62 Gb of high-quality sequencing data, from which 155113 transcripts and 118953 unigenes were assembled. Among the unigenes, 37580 were annotated and 33659 were found to be homologous to genes in the Nr protein database. We also annotated 11275 unigenes using the KEGG database, which were further classified into 223 metabolic pathways. We detected 1392 genes that were differentially expressed in shrimps exposed to hypoxic stress, among which 311 and 1081 were up- and down-regulated, respectively, and 784 were annotated. The enrichment of differentially expressed genes in antioxidant activity, cell connection, protein-binding transcription factor activity, multicellular biological processes, replication, and reproductive processes indicated that exposure to hypoxia activated a series of physiological responses in shrimps associated with adaptation to low levels of dissolved oxygen. Among the genes up-regulated under hypoxic stress was hypoxic induction factor 1 (HIF1), which is comprised the two subunits HIF1α and HIF1β. RT-PCR analysis revealed that during the latter stages of hypoxic stress, there was a notable up-regulated expression of HIF1α and HIF1β in the hepatopancreas and gills of P. carincauda. These observations indicated that P. carincauda cells induced hypoxic induction factor production in a hypoxic environment, thereby inducing an increase in blood oxygen supply. We also detected an enrichment of differentially expressed genes in the glycolysis/glucose generation pathway, arginine and proline metabolism, and pyruvate metabolism in response to hypoxic stress, which indicated an upregulation of anaerobic metabolic processes such as glycolysis, and increased metabolism of certain carbohydrates and amino acids. In addition, we detected numerous differentially expressed genes associated with the pathways involving lysozymes, phagocytosis, peroxisomes, and endocytosis in P. carincauda exposed to hypoxia, thereby indicating that HIFs might reduce mitochondrial oxygen consumption by inhibiting mitochondrial biosynthesis and activating mitochondrial autophagy.
