Shrimp Shapes a Nitrite Tolerance Trait via Regulating Autophagy and Apoptosis

Nitrite is a significant toxic substance that causes acute toxicity in aquatic animals. However, the molecular mechanisms underlying nitrite tolerance remain largely unidentified. Here, we investigated the physiological and transcriptomic profiles of nitrite-sensitive and nitrite-tolerant families of the white shrimp Penaeus vannamei under nitrite stress. Exposure to a lethal concentration of nitrite for 72 h caused higher mortality, higher nitrite accumulation, and more severe physiological damage in both the hemolymph and hepatopancreas of nitrite-sensitive families than in nitrite-tolerant families. This damage manifested as hepatic tubular deformation, hepatocyte necrosis, decreased hemocyte counts, lowered phagocytic activity in hemocytes, elevated production of reactive oxygen species (ROS), and decreased AKP enzyme activity. Furthermore, transcriptomic analysis revealed an upregulation in protein processing in the endoplasmic reticulum (ER) in the nitrite-tolerant families, triggering apoptosis- and autophagy-related pathways in the hemocytes and hepatopancreas upon nitrite exposure. Additionally, TUNEL staining and transmission electron microscopy (TEM) experiments revealed that the tolerant families may mitigate nitrite toxicity by modulating autophagy and apoptosis. Collectively, our results provide a valuable foundation for exploring the molecular mechanisms underlying nitrite tolerance in shrimp, which could facilitate the targeted breeding of shrimp germplasm with enhanced nitrite tolerance in aquaculture.