Phytodegradation of neonicotinoids in Cyperus papyrus from enzymatic and transcriptomic perspectives

Neonicotinoids are widely used but environmentally hazardous insecticides. Constructed wetlands offer potential for neonicotinoid removal, but the corresponding metabolic pathways and mechanisms in wetland plants are incompletely understood. This study investigated the fate of six neonicotinoids and their metabolites in Cyperus papyrus, a common wetland plant, and the underlying metabolic mechanisms through enzymatic and transcriptomic analyses. Neonicotinoids were absorbed by roots and translocated upward, causing high levels in shoots. Concentrations of neonicotinoids and their metabolites declined to their minimum at day 28 of exposure. Nitro reduction, hydroxylation, and demethylation were the major metabolic reactions with which C. papyrus responded to neonicotinoids. These reactions may be mediated by cytochrome P450 enzyme, aldehyde oxidase, glutathione-disulfide reductase, and glucuronate reductase. The toxicity of neonicotinoids in C. papyrus was evaluated according to the peroxidase and catalase enzymatic activities. Transcriptomic analysis revealed that differentially expressed genes (DEGs) mainly encoded proteins related to immune processes and cell growth regulation. Co-expression correlation analysis of DEGs revealed that the genes encoding P450s, peroxidase and glutathione S-transferase were the key functional genes. This study elucidates the stress response and degradation mechanism of neonicotinoids in wetland plants, providing new insights into the phytoremediation of organic contaminants in constructed wetlands.