Effect of ammonia stress on transcriptome and endoplasmic reticulum stress pathway for common carp (Cyprinus carpio) hepatopancreas

Ammonia is the mainly environmental pollutant in the field of aquaculture in association with negative impact on the healthy cultivation of common carp. Gene expression profiles in the hepatopancreas of common carp treated with ammonia stress using an RNA-seq technique, and 22,431,825 and 23,592,342 clean reads from the control and treatment groups by a 96-h ammonia challenge (0.85 mg/L unionized ammonia, NH3) are obtained. Total amount of 3367 unigenes are identified as differentially expressed genes (DEGs) related to ammonia stress. The 1724 DEGs are down-regulated and 1643 DEGs are upregulated. The metabolic pathways of these DEGs are classified into 49 different terms by KEGG pathway analysis. Protein processing in the endoplasmic reticulum (ko04141) pathway is a significantly enriched pathway of DEGs. Many DEGs are enriched in the endoplasmic reticulum stress (ERS) pathway and unfolded protein response (UPR) signal pathway in the ko04141 pathway. ERS and UPR pathway are involved in the response of hepatopancreas cells by ammonia stress. The RT-PCR and transcriptomic results indicate that PERK- eIF2α and IRE1-xbp1 pathways take participate in the response to ERS in hepatopancreas cells induced by ammonia stress. The TUNEL assays results confirmed that ammonia stress induced apoptosis in hepatopancreatic cells. Furthermore, apoptosis of hepatopancreas cells under ammonia-stress is definitely induced by ERS through the PERK-eIF2α-CHOP and IRE1-XBP1-CHOP signaling pathways.