Trade-off strategies for driving the toxicity and metabolic remodeling of copper oxide nanoparticles and copper ions in Ipomoea aquatica.

The ecological safety of copper oxide nanoparticles (CuO NPs) in the environment determines the advancement of nano-agriculture owing to breakthroughs in nanotechnology; however, the release of Cu is an uncontrollable factor. Currently, the trade-off mechanisms of CuO NPs and Cu dominating the potential hazards of plant-nano systems remain unclear. This study proposed the trade-off strategy for reconstructing physiological responses and metabolic profiles and deciphered the differential regulation of dominant CuO NPs and Cu in plants. The results showed that 100 and 500 mg/kg CuO NPs promoted root fresh weight but reduced shoot fresh weight, while 1000 mg/kg Cu demonstrated the strongest inhibition on both roots and shoots. The net photosynthetic perturbation in photosynthetic disorders is accompanied by superoxide anion and hydrogen peroxide accumulation, which are severe under 1000 mg/kg CuO NPs and Cu stress. Metabolomics revealed that CuO NPs significantly altered coumaric acid and derivatives, for example, down-regulating coumaroyl hexoside (isomers of 690 and 691) by 40.79 %. Additionally, Cu treatment severely interfered with the dominant metabolic response, activating plant hormone signal transduction and α-linolenic acid metabolism. The trade-off strategies of galactose metabolism, amino sugar and nucleotide sugar metabolism, pantothenate and coenzyme A (CoA) biosynthesis, and β-alanine metabolism as differential metabolism were confirmed by comparing the CuO NPs and Cu exposure. Protein secondary structure analysis revealed specific regulation of protein conformation upon exposure to CuO NPs and Cu. These findings provide new insights into differential metabolism and environmental effects in plant-nano systems.