Transcriptome analysis reveals hub genes in the hepatopancreas of Exopalaemon carinicauda in response to hypoxia and reoxygenation

Hypoxia is a common stressor in shrimp, but the molecular mechanisms underlying the adaptation of the ridgetail white prawn, Exopalaemon carinicauda, to hypoxia and reoxygenation remain poorly understood. In the present study, ridgetail white prawns were exposed to gradual changes in hypoxia for 6 h via oxygen consumption in a static respiration chamber and then rapidly aerated to allow reoxygenation for 8 h. The dissolved oxygen concentration after 6 h of hypoxia was 1.04 mg/L, and the survival rate of the shrimp was 47%. A transcriptomic analysis of hepatopancreas tissues after 0 (control), 3 (hypoxic starting point), and 6 (hypoxic lethal half point) h of exposure to hypoxia and after 1 and 8 h of reoxygenation was conducted using the Illumina HiSeq(TM) 4000 high-throughput sequencing platform. A total of 93,227 genes were obtained, and 4315 of these genes were identified as differentially expressed genes (DEGs) that respond to hypoxia and reoxygenation. A KEGG pathway enrichment analysis suggested that all identified DEGs were mostly enriched in ribosome biogenesis in eukaryotes, apoptosis, the longevity regulating pathway, the MAPK signaling pathway, and protein processing in the endoplasmic reticulum. In addition, 20,203 genes with RPKM values >= 1 were parsed into 20 modules through a weighted gene coexpression network (WGCNA), and three of these modules were related to hypoxia and reoxygenation. GO and KEGG enrichment analyses of these three modules were then performed, and three hub genes were identified based on their connectivity: RREB1 (Ras-responsive element-binding protein 1-like), UBE1 (ubiquitin-activating enzyme E1), and an unknown gene. This study might help further elucidate the hypoxia tolerance mechanism of E. carinicauda