Photoaging Exacerbates Nanoplastic Phytotoxicity and Differentially Activates Defense Mechanisms in Wild versus Cultivated Maize

The environmental aging of plastics into nanoplastics (NPs) poses an emerging threat to global food security. However, how photoaging modulates phytotoxicity in crops relative to their wild ancestors remains unknown. Here, we addressed this gap by comparing the phytotoxicity of pristine and photoaged polystyrene nanoplastics (nPS and nAPS) in cultivated maize ( Zea mays ) and its wild progenitor ( Z. mays ssp. Mexicana), by elucidating the underlying metabolic and molecular mechanisms. We found that photoaging functions as a toxicity multiplier, inducing significantly greater oxidative damage and growth inhibition compared with the pristine nPS. This detrimental effect was markedly amplified in cultivated maize. Multiomics analysis identified the suppression of flavonoid and carbohydrate metabolism as the core mechanism for the increased susceptibility of cultivated maize. Specifically, in cultivated maize, nAPS exposure significantly down-regulated key metabolites (e.g., apigenin, chlorogenic acid, α,α-trehalose) and their biosynthetic genes (e.g., CYP73A, CYP75B1, and CHI ) compared to pristine nPS treatment. In contrast, wild maize demonstrated greater resilience, characterized by higher basal transcriptional levels and a strong coordinated upregulation of gene expression in these defense pathways. Our findings reveal that domesticated crops are more vulnerable to photoaged nanoplastics, making the reintroduction of tolerance traits from wild relatives essential for breeding plastic pollution-resilient crops and securing food security.