Molecular drivers and physiological consequences of saline-alkaline stress resilience in the large-scale loach...

The development of saline-alkaline tolerant fish species has received extensive attention as a strategy for expanding aquaculture into inland saline-alkaline waters to optimize land use efficiency. Paramisgurnus dabryanus presented remarkable tolerance to the extreme environments. However, the physiological and molecular underpinnings of this exceptional tolerance remain largely unclear. In this study, we investigated the saline and alkaline lethal concentrations of this species. The LC₅₀ for salinity and alkalinity in P. dabryanus were 13.2 ‰ and 126.64 mmol/L respectively, suggesting relatively high tolerance to the saline-alkaline stress compared to other freshwater fishes. We also performed transcriptomic and physiological analysis to understand the stress response mechanisms. we identified distinct stress response strategies to saline-alkaline stress and their interactive effects. In total, we identified 525 saline responsive genes, 860 alkaline responsive genes and 813 saline and alkaline interactive genes. Salinity stress primarily disrupted ion transport and steroid hormone biosynthesis, while alkalinity stress induced comprehensive oxidative stress responses. Crucially, we observed interactive effects between saline-alkaline stress, with combined exposure amplifying specific gene expression patterns (particularly in antioxidant-related genes and steroid metabolism). Physiological assessments further confirmed the interactive effects on ion homeostasis and antioxidant responses. Additionally, we also identified saline and alkaline responsive genes governing physiological changes to the combined saline-alkaline stress. These findings not only elucidate the molecular basis of dual-stress adaptation in aquatic species but also demonstrate the potential of P. dabryanus for commercial aquaculture in saline-alkaline waters.