Toxicological effects of active and inert ingredients of imazethapyr formulation Verosil® against Scenedesmus vacuolatus (Chlorophyta)

Transcriptomic and metabolomic analysis provides insight into imazethapyr toxicity to non-target plants

Imazethapyr is a widely used imidazolinone herbicide worldwide, and its potential adverse effects on non-target plants have raised concerns. Understanding the mechanisms of imazethapyr phytotoxicity is crucial for its agro-ecological risk assessment. Here, the comprehensive molecular responses and metabolic alterations of Arabidopsis in response to imazethapyr were investigated. Our results showed that root exposure to imazethapyr inhibited shoot growth, reduced chlorophyll contents, induced photoinhibition and decreased photosynthetic activity. By non-target metabolomic analysis, we identified 75 metabolites that were significantly changed after imazethapyr exposure, and they are mainly enriched in carbohydrate, lipid and amino acid metabolism. Transcriptomic analysis confirmed that imazethapyr significantly downregulated the genes involved in photosynthetic electron transport and the carbon cycle. In detail, 48 genes in the photosynthetic lightreaction and 11 genes in Calvin cycle were downregulated. Additionally, the downregulation of genes related to electron transport in mitochondria provides strong evidence for imazethapyr inhibiting photosynthetic carbon fixation and cellular energy metabolism as one of mechanisms of toxicity. These results revealed the molecular and metabolic basis of imazethapyr toxicity on non-target plants, contributing to environmental risk assessment and mitigate negative impact of imazethapyr residues in agricultural soils.