Dietary lipid sources modulate low-salinity adaptation in Scylla paramamosain via integrated multi-omics and AQP1/AQP7 regulation
摘要
Understanding the mechanisms of salinity adaptation is crucial for developing resilient aquaculture practices, especially under fluctuating or low-salinity conditions. This study integrated growth performance, physiological metabolism, transcriptomics, proteomics, and in vivo knockdown to investigate low-salinity adaptation in mud crabs under two salinity conditions (25‰ and 6‰) and three dietary lipid sources (fish oil, FO; krill oil, KO; safflower oil, SO). The results indicate that low-salinity adaptation is driven by energy-dependent osmoregulatory reprogramming through the coupling of lipid-energy metabolism and ion–water regulation. Low-salinity-induced structural and functional remodeling of osmoregulatory organs, promoted triglyceride mobilization by suppressing acc and fas while activating cpt1 and hsl, and enhanced mitochondrial β-oxidation and respiratory energy production to support osmoregulation. Under low-salinity conditions, crabs fed the FO and KO diet showed stronger lipid catabolism, mitochondrial activity, and osmoregulatory responses than those fed the SO diet. Multi-omics analysis further suggested that FO mainly supported membrane repair, and KO enhanced antioxidant and anti-apoptotic capacity, whereas SO caused broad inhibition of basic cellular processes. The proximal tubule bicarbonate reclamation pathway and aquaporins emerged as central components of the adaptive response. Two aquaporin genes, AQP1 and AQP7, were cloned and characterized for the first time in mud crab. Subcellular localization in HEK293T cells showed hypoosmotic stimulation-induced redistribution of AQP1 and AQP7 toward the plasma membrane, indicating their potential membrane relocalization under osmotic challenge. Functional knockdown of AQP1 or AQP7 under low salinity disrupted osmoregulation and impaired lipid catabolism and mitochondrial energy production, as reflected by reduced CPT1 and respiratory chain gene expression. These findings suggest that AQP1 and AQP7 contribute to the coordination of osmotic regulation, lipid metabolism, and energy homeostasis, providing new insights into nutritional regulation of low-salinity adaptation in mud crab.