Distinct physiological and molecular responses in Arabidopsis thaliana exposed to aluminum oxide nanoparticles and ionic aluminum.

Nano-aluminium oxide (nAlO) is one of the most widely used nanomaterials. However, nAlO toxicity mechanisms and potential beneficial effects on terrestrial plant physiology remain poorly understood. Such knowledge is essential for the development of robust nAlO risk assessment. In this study, we studied the influence of a 10-d exposure to a total selected concentration of 98 μM nAlO or to the equivalent molar concentration of ionic Al (AlCl) (196 μM) on the model plant Arabidopsis thaliana on the physiology (e.g., growth and photosynthesis, membrane damage) and the transcriptome using a high throughput state-of-the-art technology, RNA-seq. We found no evidence of nAlO toxicity on photosynthesis, growth and lipid peroxidation. Rather the nAlO treatment stimulated root weight and length by 48% and 39%, respectively as well as photosynthesis opening up the door to the use of nAlO in biotechnology and nano agriculture. Transcriptomic analyses indicate that the beneficial effect of nAlO was related to an increase in the transcription of several genes involved in root growth as well as in root nutrient uptake (e.g., up-regulation of the root hair-specific gene family and root development genes, POLARIS protein). By contrast, the ionic Al treatment decreased shoot and root weight of Arabidopsis thaliana by 57.01% and 45.15%, respectively. This toxic effect was coupled to a range of response at the gene transcription level including increase transcription of antioxidant-related genes and transcription of genes involved in plant defense response to pathogens. This work provides an integrated understanding at the molecular and physiological level of the effects of nAlO and ionic Al in Arabidopsis.