Phytotoxicity of Metal- Based Nanoparticles in Crops and Their Impact on Global Food Production and Security.

Widespread use of metal-based nanoparticles (NPs) such as oxides of silver (Ag), titanium (Ti), zinc (Zn), and rare earth elements (REE) including cerium (Ce) and Indium (In) in the environment has raised some serious concerns about their adverse effects on the agriculture, environmental and human health. In this study, the effects of these NPs exposure on several plants including arabidopsis, rice and soybean were investigated at the physiological, biochemical, and molecular levels. Our results demonstrate that most of these NPs induce severe oxidative stress and causes significant membrane damage. The levels of malondialdehyde (MDA), an important indicator for membrane damage, and antioxidant enzymes such as SOD, CAT, APX, PPO and POD that scavenge ROS under stress conditions were also significantly higher compared the untreated plants. We also evaluated the effect of Ag and Ce NPs exposure on N fixation and nutrient displacement in soybean. To our surprise, even a very low level of Ag NPs exposure severely reduced the nodule formation in roots, N fixation, and plant growth. Exposure of plants to Ag and other metal oxides NPs also inhibited Fe and other nutrient element uptake in plants. Additionally, we explored the role of glutathione (GSH) in ameliorating the NP-induced stress in plants. Transgenic Arabidopsis and Crambe abyssinica plants overexpessing gamma-glutamylecysteine synthase (γ-ECS) produce several-fold higher levels of GSH. Transgenic lines, when exposed to Ag NPs, showed enhanced tolerance to NPs toxicity as these line grew better and had higher biomass, root length, transpiration rate compared to control plants. Our results showed that metal-based NPs could cause significant toxicity in crops and can affect crop yield and manipulation of GSH homeostasis can reduce the nanotoxicity in crop plants. These studies will be help in understanding the fate, transport, and toxicity of NPs in the agricultural crops and to further develop strategies for mitigating the toxicity of these NPs in food crops.