Integrated transcriptome and metabolome reveal nano-selenium-mediated low temperature tolerance in lettuce (Lactuca...

Low temperature stress is a major abiotic constraint on agricultural productivity, especially in temperature-sensitive crops like lettuce. Nano-selenium has demonstrated considerable potential in improving plant stress resilience. In this study, lettuce plants exposed to low-temperature stress were treated with five concentrations (N1: 1 mg L^-1; N2: 3 mg L^-1; N3: 9 mg L^-1; N4: 27 mg L^-1) of nano-selenium. The optimal concentration of nano-selenium was determined to be N3 (9 mg L^-1). Integrated transcriptomic and metabolomic analyses revealed that nano-selenium application significantly enhanced photosynthetic efficiency, antioxidant defenses, and metabolic adaptation under cold stress. A total of 25,593 differentially expressed genes (DEGs) and 20 key metabolites were identified. Enriched metabolic pathways included arginine and proline metabolism, amino sugar and nucleotide sugar metabolism, and glycerophospholipid metabolism. Under low-temperature conditions, nano-selenium treatment markedly improved cold tolerance by modulating proline metabolism-promoting its biosynthesis while inhibiting its catabolism-resulting in substantial proline accumulation. Furthermore, nano-selenhanced cellular structural integrity through two distinct mechanisms: (1) reinforcing cell wall architecture via enhanced amino sugar metabolism, thereby mitigating low-temperature-induced membrane damage; and (2) optimizing glycerophospholipid composition, particularly by regulating phosphatidylcholine and phosphatidylethanolamine biosynthesis through key enzyme modulation, which helped maintain membrane fluidity and stability under cold stress. These findings advance our understanding of nano-selenium-mediated stress tolerance and underscore its potential application in sustainable agriculture.