Nano enabled fertilizer commercial product – unveiling the mechanisms of toxicity in non-target soil invertebrate species – a high-throughput transcriptomics approach

Abstract

Nanoagrochemicals have the potential to increase agricultural productivity while being more environmentally friendly, compared to conventional agrochemicals. However, and given its early days, concerns regarding their risks to human health and environment remain to be investigated. New Approach Methodologies (NAMs) are on high demand, e.g. omics, allowing to move beyond standard hazards, providing insights into the mechanism of toxicity of chemicals. The toxicity of WELGRO®, a commercial nanoagrochemical, was studied in the non-target soil invertebrate Enchytraeus crypticus (Oligochaeta) but the mechanisms are unknown. The aim of the present study was to investigate the underlying mechanisms that lead to the toxicity of WELGRO®, this based on high-throughput transcriptomic analysis (4x44K microarray), measuring the Differentially Expressed Genes (DEGs). The animals were exposed in the natural soil LUFA 2.2, for 2 and 21 days, to control (un-spiked soil) plus 100-1000 mg WELGRO®/kg, the lower dose corresponding to realistic topsoil concentrations, based on the recommended application rates. Results showed that gene transcription was clearly time dependent. The impacts after immediate exposure (2d) were highest at lowest concentration while the opposite occurred for the longer exposure time (21d), at highest concentration. The main findings showed that, regardless of the exposure period, ABC transporters were shut down, leading to accumulation of waste products and further endoplasmic reticulum (ER) stress as a possible cause of toxicity. DNA damage seems to also occur as part of the impact. Immediate exposure (2 days) affected neurotoxicity related pathways, although probably a transient/ reverted impact, as this was no longer observed after 21 days. Indications are that WELGRO® is probably up-taken (at cellular level) by clathrin-mediated endocytosis – a nano-related pathway. This study provides the first 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 nano-specific features of those products.