Elucidating the Molecular Network Underpinning Hypoxia Adaptation in the Liver of Silver Carp (Hypophthalmichthys molitrix) via Transcriptome Analysis

The fish liver serves as a crucial metabolic organ, integral to detoxification, nutrient storage, and energy regulation, thereby playing a pivotal role in enabling organisms to adapt to environmental fluctuations. The silver carp (Hypophthalmichthys molitrix), an important species in Chinese freshwater aquaculture, demonstrates limited tolerance to hypoxic conditions. Nevertheless, the alterations in gene expression patterns within the liver of silver carp under hypoxic stress are not yet fully elucidated. In this study, we exposed silver carp to hypoxic conditions using a natural oxygen depletion method and utilized RNA sequencing to investigate transcriptional regulation in the liver across varying levels of hypoxic stress. We identified a total of 628 differentially expressed genes (DEGs), with 42 being common across all stress conditions. These DEGs were classified into four groups based on their expression trends and subjected to GO enrichment analysis, which revealed significant enrichment in terms associated with the endoplasmic reticulum, cell proliferation, myofibrils, and sterol metabolic processes. The KEGG enrichment analysis identified nine pathways that were consistently and significantly enriched across all stress levels, six of which encompass the maintenance of cellular homeostasis, metabolic regulation, and immune modulation. The elucidation of the molecular network associated with hypoxia adaptation in the liver of silver carp presented in this study provides crucial theoretical insights into the mechanisms underlying hypoxia tolerance in fish.