Commercial nano-enabled fertilizer: unveiling its mechanisms of toxicity in non-target soil invertebrate species using a high-throughput transcriptomics approach

Abstract

Nanoagrochemicals have the potential to increase agricultural productivity while being more environmentally friendly than conventional agrochemicals. However, given their infancy, concerns regarding their risks to human health and the environment remain largely unexplored. New approach methodologies (NAMs), such as omics, are in high demand, allowing them to move beyond standard hazards and providing insights into their mechanism of chemical toxicity. The toxicity of WELGRO®, a commercial nanoagrochemical, was studied in the non-target soil invertebrate Enchytraeus crypticus (Oligochaeta), but its mechanisms are unknown. The aim of the present study was to investigate the mechanisms underlying the toxicity of WELGRO®, which was based on high-throughput transcriptomic analysis (4 × 44 K microarray), using differentially expressed genes (DEGs). The animals were exposed in natural soil LUFA 2.2 for 2 and 21 days, to control (un-spiked soil) plus 100–1000 mg WELGRO® kg⁻¹, the lower dose corresponding to realistic topsoil concentrations, based on the recommended application rates. Results showed that gene transcription was time-dependent. The impacts after immediate exposure (2 d) were the highest at the lowest concentration, whereas the opposite occurred for longer exposure times (21 d) at the highest concentration. The main findings showed that regardless of the exposure period, ABC transporters were shut down, leading to the accumulation of waste products and further endoplasmic reticulum (ER) stress as a possible cause of toxicity. DNA damage also appeared to have been part of the impact. Immediate exposure (2 days) affected neurotoxicity-related pathways, although it probably was a transient/reverted impact, as this effect was no longer observed after 21 days. Indications are that WELGRO® is probably taken up (at the cellular level) via clathrin-mediated endocytosis—a nano-related pathway. This study provides novel insights into the mechanisms of toxicity of a commercially available nanoagrochemical based on a realistic exposure scenario for a non-target species. Our findings support the principle that risk assessment of nanoagrochemicals should consider the nanospecific features of such products.