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.

Background: As a globally significant aquaculture species, elucidating the molecular mechanisms underlying the regulation of the Pacific White Shrimp (Litopenaeus vannamei) growth holds substantial scientific and industrial value. This study systematically investigates the role of the LvChia2 gene in governing growth and development through a cross-tissue metabolic network approach. Methods: RNA knockdown (RNAi)-mediated knockdown of LvChia2 significantly impaired growth performance and triggered a tissue-specific metabolic compensation mechanism. Results: This mechanism was characterized by reduced crude lipid content in muscle and adaptive modulation of lipase (LPS) activities in hepatopancreatic and intestinal tissues, suggesting inter-tissue metabolic coordination. Transcriptomic profiling identified 610 differentially expressed genes (DEGs), forming a three-dimensional regulatory network encompassing “energy metabolism, molt regulation, and nutrient utilization.” Key mechanistic insights revealed the following: (1) Enhanced mitochondrial energy transduction through the upregulation of ATP synthase subunits and NADH dehydrogenase (ND-SGDH). (2) The disruption of ecdysteroid signaling pathways via suppression of Krueppel homolog 1 (Kr-h1). (3) The coordinated regulation of nitrogen metabolism through the downregulation of glutamine synthetase and secretory phospholipase A2. These molecular adaptations, coupled with tissue-specific oxidative stress responses, reflect an integrated physiological strategy for environmental adaptation. Conclusions: Notably, this study provides the first evidence in crustaceans of chitinase-mediated growth regulation through cross-tissue metabolic interactions and identifies six core functional genes (ATP5L, ATP5G, ND-SGDH, Kr-h1, GS, sPLA2) as potential targets for molecular breeding. A novel “gut-hepatopancreas axis” energy compensation mechanism is proposed, offering insights into resource allocation during metabolic stress. These findings advance our understanding of crustacean growth regulation and establish a theoretical foundation for precision aquaculture strategies, including genome editing and multi-trait genomic selection.

Nitrite is a key environmental challenge in intensive shrimp aquaculture, adversely affecting physiological regulation and survival. Although tolerant Penaeus vannamei families have been established by selective breeding, the basis of family-level variation in tolerance has yet to be clarified. In this study, nitrite-tolerant and nitrite-sensitive families were compared using survival analysis, transcriptomics, targeted qPCR validation, physiological assays, and RNA interference of representative transport-related genes. Under nitrite exposure, the tolerant family exhibited significantly higher survival and a distinct gill transcriptional response, characterized by stronger induction of acid–base and ion-transport genes, including carbonic anhydrase 2 (CA2), the Na⁺/K⁺-ATPase subunits ATP1A and ATP1B, as well as several V-type H⁺-ATPase-related genes. These transcriptional changes were accompanied by elevated ATP content and Na⁺/K⁺-ATPase activity, improved hemolymph pH stability, and reduced nitrite accumulation in both gill and hemolymph. RNAi-mediated knockdown of CA2 or ATP1B attenuated the nitrite-induced transport response, decreased ATP content and NKA activity, exacerbated hemolymph acidification, promoted internal nitrite accumulation, and ultimately reduced shrimp survival under nitrite stress. Family-based validation further showed that the tolerant family displayed higher survival than the sensitive family in the dsEGFP group, whereas this advantage was markedly reduced after CA2 or ATP1B knockdown under nitrite stress. These findings highlight that strengthened branchial ion transport and acid–base regulation represent key physiological mechanisms underlying nitrite tolerance in resistant shrimp families.