A potential involvement of plant systemic response in initiating genotoxicity of Ag-nanoparticles in Arabidopsis thaliana

Recent Advances in Metal-Based Nanoparticle-Mediated Biological Effects in Arabidopsis thaliana: A Mini Review

The widespread application of metal-based nanoparticles (MNPs) has prompted great interest in nano-biosafety. Consequently, as more and more MNPs are released into the environment and eventually sink into the soil, plants, as an essential component of the ecosystem, are at greater risk of exposure and response to these MNPs. Therefore, to understand the potential impact of nanoparticles on the environment, their effects should be thoroughly investigated. Arabidopsis (Arabidopsis thaliana L.) is an ideal model plant for studying the impact of environmental stress on plants’ growth and development because the ways in which Arabidopsis adapt to these stresses resemble those of many plants, and therefore, conclusions obtained from these scientific studies have often been used as the universal reference for other plants. This study reviewed the main findings of present-day interactions between MNPs and Arabidopsis thaliana from plant internalization to phytotoxic effects to reveal the mechanisms by which nanomaterials affect plant growth and development. We also analyzed the remaining unsolved problems in this field and provide a perspective for future research directions.

Cross-examination of engineered nanomaterials in crop production: Application and related implications

The review presents the current knowledge on the development and implementation of nanotechnology in crop production, giving particular attention to potential opportunities and challenges of the use of nano-sensors, nano-pesticides, and nano-fertilizers. Due to the size-dependent properties, e.g. high reactivity, targeted and controlled delivery of active ingredients, engineered nanomaterials (ENMs) are expected to be more efficient agrochemicals than conventional agents. Growing production and usage of ENMs result in the spread of ENMs in the environment. Because plants constitute an important component of the agri-ecosystem, they are subjected to the ENMs activity. A number of studies have confirmed the uptake and translocation of ENMs by plants as well as their positive/negative effects on plants. Here, these endpoints are briefly summarized to show the diversity of plant responses to ENMs. The review includes a detailed molecular analysis of ENMs-plant interactions. The transcriptomics, proteomics and metabolomics tools have been very recently employed to explore ENMs-induced effects in planta. The omics approach allows a comprehensive understanding of the specific machinery of ENMs occurring at the molecular level. The summary of data will be valuable in defining future studies on the ENMs-plant system, which is crucial for developing a suitable strategy for the ENMs usage.

Can the properties of engineered nanoparticles be indicative of their functions and effects in plants?

The extensive applicability of engineered nanoparticles (ENPs) in various fields such as environment, agriculture, medicine or biotechnology has mostly been attributed to their better physicochemical properties as compared with conventional bulk materials. However, functions and biological effects of ENPs change across different scenarios which impede the progress in their risk assessment and safety management. This review thus intends to figure out whether properties of ENPs can be indicators of their behavior through summarizing and analyzing the available literature and knowledge. The studies have indicated that size, shape, solubility, specific surface area, surface charge and surface reactivity constitute a more accurate measure of ENPs functions and toxic effects in addition to mass concentration. Effects of ENPs are also highly dependent on dose metrics, species and strains of organisms, environmental conditions, exposure route and duration. Searching correlations between properties and functions or biological effects may serve as an effective way in understanding positive and negative impacts of ENPs. This will ensure safe design and sustainable future use of ENPs.

Nitric oxide is involved in nano-titanium dioxide-induced activation of antioxidant defense system and accumulation of osmolytes under water-deficit stress in Vicia faba L

Nano-titanium dioxide (nTiO₂) has been reported to improve tolerance of plants against different environmental stresses by modulating various physiological and biochemical processes. Nitric oxide (NO) has been shown to act as an important stress signaling molecule during plant responses to abiotic stresses. The present work was planned to investigate the involvement of endogenous NO in nTiO₂-induced activation of defense system of fava bean (Vicia faba L.) plants under water-deficit stress (WDS) conditions. Water-suffered plants showed increased concentration of hydrogen peroxide (H₂O₂) and superoxide (O₂^-) content coupled with increased electrolyte leakage and lipid peroxidation which adversely affected nitrate reductase (NR) activity, chlorophyll content and growth of the plants. However, application of 15 mg L^-1 nTiO₂ to stressed plants significantly induced NR activity and synthesis of NO which elevated enzymatic and non-enzymatic defense system of the stressed plants and suppressed the generation of H₂O₂ and O₂^- content, leakage of electrolytes, and lipid peroxidation. Application of nTiO₂, in association with NO, also enhanced the accumulation of osmolytes (proline and glycine betaine) that assisted the stressed plants in osmotic adjustment as witnessed by improved hydration level of the plants. Involvement of NO in nTiO₂-induced activation of defense system was confirmed with NO scavenger cPTIO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide] which caused recurrence of WDS.

Silver nanoparticles regulate Arabidopsis root growth by concentration-dependent modification of reactive oxygen species accumulation and cell division

Silver nanoparticles (AgNPs) are widely used in industry, increasing their potential level in the environment. Plant root, the key organ absorbing water and nutrients, are directly exposed to the soil. Little is known about AgNP-mediated effects on plant root growth. Here, we show that AgNPs are absorbed by root and mostly localized in cell wall and intercellular spaces, which affect root growth in a dose-dependent manner. Increased root elongation was observed when Arabidopsis was exposed to an AgNP concentration of 50 mg L^-1, while decreased elongation was observed at concentrations of equal to or more than 100 mg L^-1. Similarly, there was an increase in the number of cells in the root apical meristem and also in cell-cycle related gene expression (CYCB1;1) at 50 mg L^-1 AgNP, while both cell number and gene expression declined at concentrations equal to or more than 100 mg L^-1. This indicates that AgNPs regulate root growth by affecting cell division. Reactive oxygen species (ROS) related genes were deferentially expressed after 50 mg L^-1 AgNP treatment. Further studies showed that AgNPs induce ROS accumulation in root tips in a dose-dependent manner. KI treatment, which scavenges H₂O₂, partially rescued AgNP-inhibited root growth. The application 50 mg L^-1 AgNPs also rescued the root length phenotype of upb1-1, a mutant with slightly higher ROS levels and longer root length. Our results revealed that ROS mediate the dose-dependent effects of AgNPs on root growth. These findings provide new insights into mechanisms underlying how AgNPs regulate root growth in Arabidopsis.

Synergistic Effect of Zinc Oxide Nanoparticles and Heat Stress on the Alleviation of Transcriptional Gene Silencing in Arabidopsis thaliana

Phytotoxicity is an inevitable consideration in evaluating the potential ecological effects of nanoparticles (NPs). Natural ecosystems are complex and accompanied by many other environmental factors. Thus understanding the impact of NPs on plant response to other environmental stresses is crucial to assess the comprehensive toxicity of NPs in ecosystem. In the present study, Arabidopsis thaliana seedlings were cultured in medium containing zinc oxide NPs (ZnO-NPs) then subjected to heat stress at 37°C. Alleviation of transcriptional gene silencing (TGS) in aerial leafy tissues was assessed as an epi-genotoxic endpoint. Results showed that 1 µg/mL ZnO-NPs alone can not alleviate GUS gene (β-glucuronidase) which silenced by TGS (TGS-GUS), but it significantly enhanced heat stress-induced alleviation of TGS-GUS, suggesting an synergistic effect of ZnO-NPs and heat stress on genomic instability. Further study showed that the initiation of synergistic effect could be regulated by plant developmental stage, heat duration and temperature, and heat shock related genes might be involved in.