Stress response and tolerance to perfluorooctane sulfonate (PFOS) in lettuce (Lactuca sativa)

Comprehensive understanding of stress response and tolerance to perfluorooctane sulfonate (PFOS) in plants at physiological, biochemical and molecular levels is scarce. Here, lettuce was cultivated in hydroponic media, to investigate the cross-talk among reactive oxygen species (ROS) production, oxidative damage, antioxidative defense and metabolic regulation in different parts of plants. Under exposure to 5 and 50 μg/L PFOS for 10 days, 8.8 and 82.5 ng/g dry weight (dw) PFOS were accumulated in leaves, respectively, and 150.9 and 1445.6 ng/g dw in roots, respectively·H₂O₂ was the dominant ROS in roots, while H₂O₂ and •O₂^- were detected in leaves. Impaired permeability of plasma membrane (58.7-88.7%, p < 0.05) and reduction in chlorophyll a (41.4-55.6%, p < 0.01) and b (38.4-41.3%, p < 0.01) were observed in leaves. The concentration of soluble proteins was elevated by 93.2-127.4% in roots (p < 0.05). Non-enzymatic antioxidants (glutathione, phenolics and carotenoids) were regulated to scavenge ROS in leaves, beside additional enzymatic antioxidants (ascorbate peroxidase, peroxidase, catalase and glutathione peroxidase) were activated in roots. Metabolomics revealed that some metabolites in primary (amino acids and carbohydrates) and secondary ((poly)phenols, terpenoids and benzylisoquinolines) metabolism were regulated, in accordance with the ROS scavenging process in plants. Our results demonstrated stress response and tolerance to PFOS were different in lettuce leaves and roots, and multiple defensive mechanisms in roots rendered high tolerance to PFOS.