Contrasting Impacts on Plant Endogenous Metabolic Pathways from Trace Organic Contaminants Relevant to Recycled Water

Plant uptake and metabolism of contaminants from recycled water raise concerns regarding exposure through crops but may also cause plant endogenous metabolic network perturbation. In this work, we investigated impacts on endogenous metabolic pathways of Brassicaceae model plant Arabidopsis thaliana following hydroponic exposure for 48 h to anticorrosive benzotriazole (BT) or antimicrobial benzoisothiazolinone (BIT) at 200 μg/L and 2 mg/L, trace organic contaminants relevant to recycled water. We observed ∼99.9% uptake of both compounds and 13–25% lower plant biomass in exposed plants compared to no-exposure control plants. Despite the similar uptake and effect on biomass, plant metabolomics revealed that BT exposure significantly impacted the tryptophan metabolism through downregulation of indole metabolites and upregulation of kynurenic acid, indicating altered tryptophan utilization. Conversely, BIT exposure impacted antioxidant defense and oxidative stress signaling pathways through downregulation of flavonoids and upregulation of jasmonic acid. Even within shared impacted pathways such as phenylpropanoid biosynthesis, BT exposure shifted the main pathway toward benzoic acid derivatives, whereas BIT exposure shifted the pathway toward antioxidant defense-related compounds (e.g., flavonoids, sinapic acid). These findings demonstrate that structurally similar contaminants can cause distinct pathway-level metabolic shifts, highlighting the importance of evaluating biological impacts of specific trace organic contaminant uptake in crops relevant to recycled water irrigation.