Comparative transcriptome profiling and functional analysis in the blood of tiger puffer (Takifugu rubripes) in response to acute hypoxia

Abstract

Dissolved oxygen (DO) is an essential ecological factor encountered by fish and other aquatic animals, and hypoxia can adversely affect the physiology, biochemistry and behavior of aquatic animals. Blood is an essential tissue for oxygen transportation and plays a key role in maintaining homeostasis and adapting the organism to hypoxia. However, studies focusing on the molecular regulatory mechanisms of blood under hypoxia are scant. Therefore, to explore the hypoxia adaptive mechanisms in the blood, we used RNA-Seq technology to investigate the transcriptome changes in the blood of Takifugu rubripes under acute hypoxia. In our study, 20 fish were selected and divided into four groups, including a control group (PPM5.4) and three experimental groups (PPM4, PPM2 and PPM0). In addition to GO and KEGG enrichment analysis, we further used GSEA enrichment analysis to screen the pathways mediated in T. rubripes under hypoxia. Results revealed that hypoxia had a greater effect on blood than other tissues, and T. rubripes could inhibit cell proliferation and down-regulated immune-related pathways (including IL-17 signaling pathway, C-type lectin receptor signaling pathway, B cell receptor signaling pathway and Toll-like receptor signaling pathway). However, the blood of T. rubripes could positively modulate the genes expression involved in energy regulation, angiogenesis and oxidative stress to resist hypoxic damage. Furthermore, T. rubripes could also up-regulate apoptosis and JAK−STAT signaling pathway to conduct self-protection in response to hypoxia. In conclusion, all these results indicated that immune processes, energy metabolism, angiogenesis and oxidative stress were significantly altered in the blood of acute hypoxic T. rubripes, which contributed to maintain cellular energy balance and oxygen supply during hypoxic conditions. The key regulatory genes and pathways identified in this study not only reveal the mechanism of hypoxia tolerance in T. rubripes, but also provide a theoretical basis for breeding hypoxia-tolerant T. rubripes and other fish.