The Transcriptomic Response of Arabidopsis thaliana to Zinc Oxide: A Comparison of the Impact of Nanoparticle, Bulk, and Ionic Zinc

Insights into the ameliorative effect of ZnONPs on arsenic toxicity in soybean mediated by hormonal regulation, transporter modulation, and stress responsive genes

Arsenic (As) contamination of agricultural soils poses a serious threat to crop productivity and food safety. Zinc oxide nanoparticles (ZnONPs) have emerged as a potential amendment for mitigating the adverse effects of As stress in plants. Soybean crop is mostly grown on marginalized land and is known for high accumulation of As in roots than others tissue. Therefore, this study aimed to elucidate the underlying mechanisms of ZnONPs in ameliorating arsenic toxicity in soybean. Our results demonstrated that ZnOB significantly improved the growth performance of soybean plants exposed to arsenic. This improvement was accompanied by a decrease (55%) in As accumulation and an increase in photosynthetic efficiency. ZnOB also modulated hormonal balance, with a significant increase in auxin (149%), abscisic acid (118%), gibberellin (160%) and jasmonic acid content (92%) under As(V) stress assuring that ZnONPs may enhance root growth and development by regulating hormonal signaling. We then conducted a transcriptomic analysis to understand further the molecular mechanisms underlying the NPs-induced As(V) tolerance. This analysis identified genes differentially expressed in response to ZnONPs supplementation, including those involved in auxin, abscisic acid, gibberellin, and jasmonic acid biosynthesis and signaling pathways. Weighted gene co-expression network analysis identified 37 potential hub genes encoding stress responders, transporters, and signal transducers across six modules potentially facilitated the efflux of arsenic from cells, reducing its toxicity. Our study provides valuable insights into the molecular mechanisms associated with metalloid tolerance in soybean and offers new avenues for improving As tolerance in contaminated soils.

Unveiling key mechanisms: Transcriptomic meta-analysis of diverse nanomaterial applications addressing biotic and abiotic stresses in Arabidopsis Thaliana

The potential applications of nanomaterials in agriculture for alleviating diverse biotic and abiotic stresses have garnered significant attention. The reported mechanisms encompass promoting plant growth and development, alleviating oxidative stress, inducing defense responses, modulating plant-microbe interactions, and more. However, individual studies may not fully uncover the common pathways or distinguish the effects of different nanostructures. We examined Arabidopsis thaliana transcriptomes exposed to biotic, abiotic, and metal or carbon-based nanomaterials, utilizing 24 microarray chipsets and 17 RNA-seq sets. The results showed that: 1) from the perspective of different nanostructures, all metal nanomaterials relieved biotic/abiotic stresses via boosting metal homeostasis, particularly zinc and iron. Carbon nanomaterials induce hormone-related immune responses in the presence of both biotic and abiotic stressors. 2) Considering the distinct features of various nanostructures, metal nanomaterials displayed unique characteristics in seed priming for combating abiotic stresses. In contrast, carbon nanomaterials exhibited attractive features in alleviating water deprivation and acting as signaling amplifiers during biotic stress. 3) For shared pathway analysis, response to hypoxia emerges as the predominant and widely shared regulatory mechanism governing diverse stress responses, including those induced by nanomaterials. By deciphering shared and specific pathways and responses, this research opens new avenues for precision nano-agriculture, offering innovative strategies to optimize plant resilience, improve stress management, and advance sustainable crop production practices.

Analysis of multiple biomarkers revealed the size matters of Cu particles for barley response under foliar exposure

The impact of particle size of engineered nanoparticles (ENPs) on plant response has marginally been investigated under the foliar application so far. Concerning the significance of particle diameter for their properties and interaction with plants, the effect of size should be considered in the analysis of the effect of micronutrient-based ENPs on plants. It is of particular importance for ENPs containing Cu due to plants needing a relatively low amount of this element, thus there is a risk of overdosing during application as a fertilizer or pesticide. Here, we examined the biochemical and transcriptional response of barley (Hordeum vulgare L.) to Cu nanoparticles (nano-Cu) with different diameters (25 nm, 50 nm, 70 nm), microparticles (micro-Cu), and chelated Cu (EDTA-Cu). The plants suffering from Cu deficiency were foliar sprayed with Cu compounds at 1000 mg/L during the tillering stage. 1- and 7-day plants were analyzed in terms of biomass, Cu content, the activity of enzymes involved with antioxidant response, the content of low molecular weight compounds, and the expression of genes regulated metal homeostasis, aquaporins, and defense. The results showed that the Cu leaf level was differentiated over time and after 7 days it was higher under exposure to the smallest nano-Cu than other particulate Cu. Regardless of the duration of exposure, the Cu content was highest in plants treated with Cu-EDTA. The cluster analysis of all markers revealed a clear distinct response to the smallest nano-Cu and other particulate and ionic treatments. The bigger nano-Cu, depending on the markers, caused the medium effects between the nano-Cu 25 nm and micro-Cu and Cu-EDTA. The found size thresholds at the nanoscale will be useful for the fabrication of safe-by-design agrochemicals to provide crop security and attenuate environmental impact.

Unveiling the silver lining: examining the effects of biogenic silver nanoparticles on the growth dynamics of in vitro olive shoots

The current study aimed to evaluate the effects of biogenic silver nanoparticles (AgNPs) on growth behavior and leaf anatomy of in vitro growing shoots of 'Picual' and 'Dolce' olive cultivars. Biosynthesis of AgNPs was carried out using the cell-free filtrate of Fusarium oxysporum. The dimension and shape of the synthesized AgNPs have been analyzed using spectroscopy and topography analysis tools, confirming that the biosynthesis of AgNPs is a crystalline nanostructure with an average particle size of 37 nm. The shoots of the selected olive cultivars were cultured on Rugini olive medium-supplemented AgNPs at 0, 10, 20, and 30mg L- 1. The effect of genotypes on shoot multiplication was significant, 'Picual' recorded higher values of shoot growth parameters compared with 'Dolce' cultivar. Adding AgNPs to the culture medium significantly affected the growth of in vitro olive shoots. AgNPs at 20 and 30mg L- 1 produced higher values of the number of shoots, shoot length, and leaf number of Picual cv. compared with the control treatments, but the higher AgNPs concentration harmed the growth parameters of Dolce cv. and recorded lower growth values compared with the lower concentration (10mg L- 1). AgNPs had a significant effect on leaf morphology and their anatomical structure. The current results showed that the stimulatory effect of AgNPs on shoot growth of in vitro olive shoots is highly dependent on plant genotype and nanoparticle concentration.

Integrative chemical, physiological, and metabolomics analyses reveal nanospecific phytotoxicity of metal nanoparticles

The increasing application of metal nanoparticles (NPs) via agrochemicals and sewage sludge results in non-negligible phytotoxicological risks. Herein, the potential phytotoxicity of ZnO and CuO NPs on wheat was determined using integrative chemical, physiological, and metabolomics analyses, in comparison to Zn2+ and Cu2+. It was found that ZnO or CuO NPs had a stronger inhibitory effect on wheat growth than Zn2+ or Cu2+. After exposure to ZnO or CuO NPs, wheat seedlings accumulated significantly higher levels of Zn or Cu than the corresponding Zn2+ or Cu2+ treatments, indicating the active uptake of NPs via wheat root. TEM analysis further confirmed the intake of NPs. Moreover, ZnO or CuO NPs exposure altered micronutrients (Fe, Mn, Cu, and Zn) accumulation in the tissues and decreased the activities of antioxidant enzymes. The metabolomics analysis identified 312, 357, 145, and 188 significantly changed metabolites (SCMs) in wheat root exposed to ZnO NPs, CuO NPs, Zn2+, and Cu2+, respectively. Most SCMs were nano-specific to ZnO (80%) and CuO NPs (58%), suggesting greater metabolic reprogramming by NPs than metal ions. Overall, nanospecific toxicity dominated the phytotoxicity of ZnO and CuO NPs, and our results provide a molecular perspective on the phytotoxicity of metal oxide NPs.

Zinc and nano zinc mediated alleviation of heavy metals and metalloids in plants: an overview

Heavy metals and metalloids (HMs) contamination in the environment has heightened recently due to increasing global concern for food safety and human livability. Zinc (Zn2+ ) is an important nutrient required for the normal development of plants. It is an essential cofactor for the vital enzymes involved in various biological mechanisms of plants. Interestingly, Zn2+ has an additional role in the detoxification of HMs in plants due to its unique biochemical-mediating role in several soil and plant processes. During any exposure to high levels of HMs, the application of Zn2+ would confer greater plant resilience by decreasing oxidative stress, maintaining uptake of nutrients, photosynthesis productivity and optimising osmolytes concentration. Zn2+ also has an important role in ameliorating HMs toxicity by regulating metal uptake through the expression of certain metal transporter genes, targeted chelation and translocation from roots to shoots. This review examined the vital roles of Zn2+ and nano Zn in plants and described their involvement in alleviating HMs toxicity in plants. Moving forward, a broad understanding of uptake, transport, signalling and tolerance mechanisms of Zn2+ /zinc and its nanoparticles in alleviating HMs toxicity of plants will be the first step towards a wider incorporation of Zn2+ into agricultural practices.

Siddique K, Li B. Nanobiotechnology to advance stress resilience in plants: Current opportunities and challenges

A sustainable and resilient crop production system is essential to meet the global food demands. Traditional chemical-based farming practices have become ineffective due to increased population pressures and extreme climate variations. Recently, nanobiotechnology is considered to be a promising approach for sustainable crop production by improving the targeted nutrient delivery, pest management efficacy, genome editing efficiency, and smart plant sensor implications. This review provides deeper mechanistic insights into the potential applications of engineered nanomaterials for improved crop stress resilience and productivity. We also have discussed the technology readiness level of nano-based strategies to provide a clear picture of our current perspectives of the field. Current challenges and implications in the way of upscaling nanobiotechnology in the crop production are discussed along with the regulatory requirements to mitigate associated risks and facilitate public acceptability in order to develop research objectives that facilitate a sustainable nano-enabled Agri-tech revolution. Conclusively, this review not only highlights the importance of nano-enabled approaches in improving crop health, but also demonstrated their roles to counter global food security concerns.

Nanoparticles as novel elicitors in plant tissue culture applications: Current status and future outlook

Plant tissue culture is the primary, fundamental, and applied aspect of plant biology. It is an indispensable and valuable technique for investigating morphogenesis, embryogenesis, clonal propagation, crop improvements, generation of pathogen-free plants, gene transfer and expression, and the production of secondary metabolites. The extensive use of various nanoparticles (NPs) in fields such as cosmetics, energy, medicine, pharmaceuticals, electronics, agriculture, and biotechnology have demonstrated positive impacts in microbial decontamination, callus differentiation, organogenesis, somatic variations, biotransformation, cryopreservation, and enhanced synthesis of bioactive compounds. This review summarizes the current state of knowledge with regard to the use of nanoparticles in plant tissue culture, with a particular focus on the beneficial outcomes. The positive (beneficial) and negative (toxic) effects of engineered NPs in tissue culture medium, delivery of transgenes, NPs toxicity concerns, safety issues, and potential hazards arising from utilization of nanomaterials in agriculture through plant tissue culture are discussed in detail, along with the future prospects for these applications. In addition, the potential use of novel nanomaterials such as graphene, graphite, dendrimers, quantum dots, and carbon nanotubes as well as unique metal or metalloid NPs are proposed. Further, the potential mechanisms underlying NPs elicitation of tissue culture response in different applications are critically evaluated. The potential of these approaches in plant nanobiotechnology is only now becoming understood and it is clear that the role of these strategies in sustainably increasing crop production to combat global food security and safety in a changing climate will be significant.

Engineered nanoparticles in plant growth: Phytotoxicity concerns and the strategies for their attenuation

In the agricultural sector, the use of engineered nanoparticles (ENPs) has been acclaimed as the next big thing for sustaining and increasing crop productivity. A vast amount of literature is available regarding the growth-promoting attributes of different ENPs. In this context, it has been emphasized that the ENPs can bolster vegetative growth, leaf development, and seed setting and also help in mitigating the effects of abiotic and biotic stresses. At the same time, there have been a lot of speculations and concerns regarding the phytotoxicity of ENPs off-late. In this connection, many research articles have presented the negative effects of ENPs on plant systems. These studies have highlighted that almost all the ENPs impart a certain degree of phytotoxicity in terms of reduction in growth, biomass, impairment of photosynthesis, oxidative status of plant cells, etc. Mostly, the ENPs based on metal or metal oxides (Cd, Cr, Pb, Ag, Ce, etc.) and nonmetals (C) that are introduced into the environment are known to incite inhibitory effects. However, the phytotoxicity of ENPs are known to be determined mostly by the chemical nature of the element, size, surface charge, coating molecules, and abiotic factors like pH and light. This review article, therefore, elucidates the phytotoxic properties of different ENPs and the plant responses induced at the molecular level subjected to nanoparticle exposure. Moreover, the article highlights the probable strategies that may be adopted for the suppression of the phytotoxicity of ENPs to ensure the safe and sustainable application of ENPs in crop fields.

Nanomaterials biotransformation: In planta mechanisms of action

Research on engineered nanomaterials (ENMs) exposure has continued to expand rapidly, with a focus on uncovering the underlying mechanisms. The EU largely limits the number and the type of organisms that can be used for experimental testing through the 3R normative. There are different routes through which ENMs can enter the soil-plant system: this includes the agricultural application of sewage sludges, and the distribution of nano-enabled agrochemicals. However, a thorough understanding of the physiological and molecular implications of ENMs dispersion and chronic low-dose exposure remains elusive, thus requiring new evidence and a more mechanistic overview of pathways and major effectors involved in plants. Plants can offer a reliable alternative to conventional model systems to elucidate the concept of ENM biotransformation within tissues and organs, as a crucial step in understanding the mechanisms of ENM-organism interaction. To facilitate the understanding of the physico-chemical forms involved in plant response, synchrotron-based techniques have added new potential perspectives in studying the interactions between ENMs and biota. These techniques are providing new insights on the interactions between ENMs and biomolecules. The present review discusses the principal outcomes for ENMs after intake by plants, including possible routes of biotransformation which make their final fate less uncertain, and therefore require further investigation.

Cell damage repair mechanism in a desert green algae Chlorella sp. against UV-B radiation

The protective ozone layer is continually depleting owing to an increase in the levels of solar UV-B radiation, which has harmful effects on organisms. Algae in desert soil can resist UV-B radiation, but most research on the radiation resistance of desert algae has focused on cyanobacteria. In this study, we found that desert green algae, Chlorella sp., could maintain high photosynthetic activity under UV-B stress. To examine the tolerance mechanism of the desert green algae photosystem, we observed the physiological and transcriptome-level responses of Chlorella sp. to high doses of UV-B radiation. The results showed that the reactive oxygen species (ROS) content first increased and then decreased, while the malondialdehyde (MDA) content revealed no notable lipid peroxidation during the UV-B exposure period. These results suggested that Chlorella sp. may have strong system characteristics for scavenging ROS. The antioxidant enzyme system showed efficient alternate coordination, which exhibited a protective effect against enhanced UV-B radiation. DNA damage and the chlorophyll and soluble protein contents had no significant changes in the early irradiation stage; UV-B radiation did not induce extracellular polysaccharides (EPS) synthesis. Transcriptomic data revealed that a strong photosynthetic system, efficient DNA repair, and changes in the expression of genes encoding ribosomal protein (which aid in protein synthesis and improve resistance) are responsible for the high UV-B tolerance characteristics of Chlorella sp. In contrast, EPS synthesis was not the main pathway for UV-B resistance. Our results revealed the potential cell damage repair mechanisms within Chlorella sp. that were associated with high intensity UV-B stress, thereby providing insights into the underlying regulatory adaptations of desert green algae.

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.

Comparative physiological and metabolomic analyses reveal that Fe3O4 and ZnO nanoparticles alleviate Cd toxicity in tobacco

BACKGROUND

Heavy metals repress tobacco growth and quality, and engineered nanomaterials have been used for sustainable agriculture. However, the underlying mechanism of nanoparticle-mediated cadmium (Cd) toxicity in tobacco remains elusive.

RESULTS

Herein, we investigated the effects of Fe3O4 and ZnO nanoparticles (NPs) on Cd stress in tobacco cultivar 'Yunyan 87' (Nicotiana tabacum). Cd severely repressed tobacco growth, whereas foliar spraying with Fe3O4 and ZnO NPs promoted plant growth, as indicated by enhancing plant height, root length, shoot and root fresh weight under Cd toxicity. Moreover, Fe3O4 and ZnO NPs increased, including Zn, K and Mn contents, in the roots and/or leaves and facilitated seedling growth under Cd stress. Metabolomics analysis showed that 150 and 76 metabolites were differentially accumulated in roots and leaves under Cd stress, respectively. These metabolites were significantly enriched in the biosynthesis of amino acids, nicotinate and nicotinamide metabolism, arginine and proline metabolism, and flavone and flavonol biosynthesis. Interestingly, Fe3O4 and ZnO NPs restored 50% and 47% in the roots, while they restored 70% and 63% in the leaves to normal levels, thereby facilitating plant growth. Correlation analysis further indicated that these metabolites, including proline, 6-hydroxynicotinic acid, farrerol and quercetin-3-O-sophoroside, were significantly correlated with plant growth.

CONCLUSIONS

These results collectively indicate that metal nanoparticles can serve as plant growth regulators and provide insights into using them for improving crops in heavy metal-contaminated areas.

Application of zinc oxide nanoparticles to promote remediation of nickel by Sorghum bicolor: metal ecotoxic potency and plant response

Nickel (Ni) is one of the most toxic metals in human health. Its bioaccumulation in gluten-free crops limits the progressing demand of safe foods for allergic people to gluten. Nanoparticles have shown promising results in enhancing the crop yield and reducing the risk of heavy metal uptake. However, their nanotoxicity has been raised environmental concerns. This study investigated the environmental behavior of Ni (II) with the co-presence of Zinc Oxide Nanoparticles (ZnO-NPs) in sorghum bicolor. The plants were exposed to different treatments of Ni, ZnO-NPs, or their coexistence. The uptake experiments were carried out within nine treatments consisting of 1 or 5 ppm Ni alone or in coexistence with 50 or 100 ppm ZnO-NPs. The physiological impacts on plants as potential fingerprints for nanotoxicity were recorded and assessed in a phenotypic spectrum. The total Ni or Zn contents were quantified using atomic absorption. NPs significantly altered the bioavailability of Ni. The results revealed that at 5 ppm Ni contamination, 50 and 100 ZnO-NPs significantly reduced the Ni uptake by ∼43% and 47%, respectively. Further, the results showed at 50 ppm NPs, the phytotoxicity effects of both Ni and NPs may reduce, leading to higher plant dry biomass yield.Novelty statement Characterization of zinc oxide nanotoxicity threshold by developing a phenotypic spectrum. Also, the study revealed the phytoremediation potential of ZnO nanoparticle in mitigating the nickel uptake in a gluten-free crop (sorghum bicolor).

A New Look at the Effects of Engineered ZnO and TiO2 Nanoparticles: Evidence from Transcriptomics Studies

Titanium dioxide (TiO2) and zinc oxide (ZnO) nanoparticles (NPs) have attracted a great deal of attention due to their excellent electrical, optical, whitening, UV-adsorbing and bactericidal properties. The extensive production and utilization of these NPs increases their chances of being released into the environment and conferring unintended biological effects upon exposure. With the increasingly prevalent use of the omics technique, new data are burgeoning which provide a global view on the overall changes induced by exposures to NPs. In this review, we provide an account of the biological effects of ZnO and TiO2 NPs arising from transcriptomics in in vivo and in vitro studies. In addition to studies on humans and mice, we also describe findings on ecotoxicology-related species, such as Danio rerio (zebrafish), Caenorhabditis elegans (nematode) or Arabidopsis thaliana (thale cress). Based on evidence from transcriptomics studies, we discuss particle-induced biological effects, including cytotoxicity, developmental alterations and immune responses, that are dependent on both material-intrinsic and acquired/transformed properties. This review seeks to provide a holistic insight into the global changes induced by ZnO and TiO2 NPs pertinent to human and ecotoxicology.

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.

Omics technologies used in pesticide residue detection and mitigation in crop

In agriculture, the convenience and efficacy of chemical pesticides have become inevitable to manage cultivated crop production. Here, we review the worldwide use of pesticides based on their categories, mode of actions and toxicity. Excessive use of pesticides may lead to hazardous pesticide residues in crops, causing adverse effects on human health and the environment. A wide range of high-tech-analytical methods are available to analyse pesticide residues. However, they are mostly time-consuming and inconvenient for on-site detection, calling for the development of biosensors that detect cellular changes in crops. Such new detection methods that combine biological and physicochemical knowledge may overcome the shortage in current farming to develop sustainable systems that support environmental and human health. This review also comprehensively compiles domestic pesticide residues removal tips from vegetables and fruits. Synthetic pesticide alternatives such as biopesticide and nanopesticide are greener to the environment. However, its safety assessment for large-scale application needs careful evaluation. Lastly, we strongly call for reversions of pesticide application trends based on the changing climate, which is lacking in the current scenario.

Uptake, translocation, weathering and speciation of gold nanoparticles in potato, radish, carrot and lettuce crops

Extensive use of nanomaterials in agriculture will inevitably lead to their release to the environment in significant loads. Thus, understanding the fate of nanoparticles in the soil-plant environment, and potential presence and consequent implication of nanoparticles in food and feed products, is required. We study plant uptake of gold nanoparticles from soil, and their distribution, translocation and speciation (in terms of particle size change and release of ionic Au) in the different plant tissues of four important crops (potato, radish, carrot and lettuce). Our new analytical protocol and experiments show the feasibility of determining the presence, concentration and distribution of nanoparticles in different plant parts, which differ from plant to plant. Critically, we identify the evident capacity of plants to break down (or substantially change the properties of) nanoparticles in the rhizosphere prior to uptake, as well as the evident capacity of plants to reorganize ionic metals as nanoparticles in their tissues. This could lead to nanoparticle exposure through consumption of crops.

Silver nanoparticles and Chlorella treatments induced glucosinolates and kaempferol key biosynthetic genes in Eruca sativa

Background

Microalgae and nanoparticles are currently considered promising tools for numerous agricultural and biotechnological applications. The green microalga Chlorella sp. MF1 and its biosynthesized silver nanoparticles (AgNPs) were used in this study as biofortification agents to enhance glucosinolate and kaempferol levels in Eruca sativa. UV–visible spectroscopy, XRD, FTIR and TEM were comprehensively used for characterizing Chlorella-based AgNPs.

Results

The biosynthesized AgNPs were found to be spherical in shape, with size ranging from 1.45 to 5.08 nm. According to FTIR measurements, silver ions were reduced to AgNPs by functional groups such as amide, hydroxyl and carboxylate. Different experimental treatments were conducted, including either soaking seeds of E. sativa or foliar spray with various concentrations of Chlorella suspension (1, 2, 3 and 4 g L−1) and AgNPs (5, 10, 20 and 40 mg L−1). Expression levels of five key genes in the biosynthetic pathway of glucosinolates (MAM1, SUR1, MYB34 and MYB51) and kaempferol (CHS) were assessed using qRT-PCR. The results indicated an upregulation in the gene expression levels in all treatments compared to control, recording the highest level at 40 mg L−1 AgNPs and 4 g L−1Chlorella suspension. In addition, high glucosinolates and kaempferol content was detected in plants whose leaves were sprayed with AgNPs and Chlorella suspension (40 mg L−1 and 4 g L−1) based on HPLC analysis. Sequence analysis of amplified CHS fragments from E. sativa plants treated with AgNPs (40 mg L−1) showed high sequence similarity to A. thaliana CHS gene. However, there were several CHS regions with sequence polymorphism (SNPs and Indels) in foliar sprayed plants.

Conclusions

Results of this study evidenced that the application of AgNPs and Chlorella suspension increased glucosinolates and kaempferol content in E. sativa through upregulation of key genes in their biosynthetic pathway.

Gold Nanoparticles-Induced Modifications in Cell Wall Composition in Barley Roots

The increased use of nanoparticles (NP) in different industries inevitably results in their release into the environment. In such conditions, plants come into direct contact with NP. Knowledge about the uptake of NP by plants and their effect on different developmental processes is still insufficient. Our studies concerned analyses of the changes in the chemical components of the cell walls of Hordeum vulgare L. roots that were grown in the presence of gold nanoparticles (AuNP). The analyses were performed using the immunohistological method and fluorescence microscopy. The obtained results indicate that AuNP with different surface charges affects the presence and distribution of selected pectic and arabinogalactan protein (AGP) epitopes in the walls of root cells.

Involvement of glucosinolates in the resistance to zinc oxide nanoparticle-induced toxicity and growth inhibition in Arabidopsis

Zinc oxide nanoparticles (ZnO NPs) are widely used to manufacture textile fibers, synthetic rubber, and paint. However, crop yields and quality are threatened by the increased use of metallic NPs in industry, which has resulted in their accumulation in agricultural land. Many studies have shown that plants defend against biotic and abiotic stresses through the activities of metabolites and hormones. However, whether glucosinolates (GSs) are involved in plant responses to ZnO NP-related stress remains unknown. In this study, wild-type (WT) and GS mutant (myb28/29 and cyp79B2/B3) Arabidopsis plants were subjected to ZnO NP stress to address this question. Our results showed that exposure to ZnO NPs promoted GS accumulation and induced the relative messenger RNA (mRNA) expression levels of GS biosynthesis-related genes. Moreover, ZnO NP treatment adversely affected root length, the number of lateral roots, chlorophyll contents, and plant biomass. Importantly, our results showed that root growth, chlorophyll contents, and plant biomass were all decreased in the GS mutants compared with those in WT plants. Overall, our results showed that WT plants tolerated ZnO NP-induced stress more efficiently than the GS mutants, suggesting that GSs are involved in plant resistance to ZnO NP-induced toxicity.

Nanoimpact in Plants: Lessons from the Transcriptome

Transcriptomics studies are available to evaluate the potential toxicity of nanomaterials in plants, and many highlight their effect on stress-responsive genes. However, a comparative analysis of overall expression changes suggests a low impact on the transcriptome. Environmental challenges like pathogens, saline, or drought stress induce stronger transcriptional responses than nanoparticles. Clearly, plants did not have the chance to evolve specific gene regulation in response to novel nanomaterials; but they use common regulatory circuits with other stress responses. A shared effect with abiotic stress is the inhibition of genes for root development and pathogen response. Other works are reviewed here, which also converge on these results.

Positive effects of metallic nanoparticles on plants: Overview of involved mechanisms

Engineered nanoparticles (NPs) are considered as potential agents for agriculture as fertilizers, growth enhancers and pesticides. Therefore, understanding the mechanisms that are responsible for their effects is important. Various studies demonstrated that the application of nontoxic concentrations can promote seed germination, enhance plant growth and increase the yield. Moreover, NPs can be used to protect plants from environmental impacts such as salt or drought stress and diminish accumulation and toxicity of heavy metals. NPs can serve as a source of micronutrients (e.g. ZnO, iron- and manganese-based NPs), thus increasing fitness and helps plants to cope with stress conditions. TiO₂ and iron-based NPs are able to delay senescence and speed-up cell division via changes in phytohormonal levels. The application of some NPs can promote the activity of enzymes such as amylase, nitrate reductase, phosphatase, phytase and carbonic anhydrases, which are involved in metabolism and nutrient acquisition. E.g. ZnO and TiO₂ NPs can stimulate chlorophyll biosynthesis and photosynthetic activity. Iron-based and CeO₂ NPs enhance stomata opening resulting in better gas exchange and CO₂ assimilation rate. NPs can also modulate oxidative stress by the stimulation of the antioxidant enzymes such peroxidases and superoxide dismutase. However, the knowledge about the fate, transformation, and accumulation of NPs in the environment and organisms is needed prior to their use in agriculture to avoid negative environmental impacts. Higher or lower toxicity of various NPs was established for microorganisms, plants or animals. In this overview, we focused on the possible mechanisms of Ag, ZnO, TiO₂, Fe-based, CeO₂, Al₂O₃, and manganese-based NPs responsible for their positive effects on plants.

Comparative Analysis of Proteins Regulated during Cadmium Sulfide Quantum Dots Response in Arabidopsis thaliana Wild Type and Tolerant Mutants

In previous work, two independent Arabidopsis thaliana Ac/Ds transposon insertional mutant lines, atnp01 and atnp02, were identified that showed a higher level of tolerance than the wild type (wt) line to cadmium sulfide quantum dots (CdS QDs). The tolerance response was characterized at physiological, genetic and transcriptomic levels. In this work, a comparative analysis was performed on protein extracts from plantlets of the two mutants and of wt, each treated with 80 mg L-1 CdS QDs. A comparative protein analysis was performed by 2D-PAGE, and proteins were characterized by MALDI-TOF/TOF mass spectrometry. Of 250 proteins identified from all three lines, 98 showed significant changes in relative abundance between control and CdS QD-treated plantlets. The wt, atnp01, and atnp02 control-treated pairs respectively showed 61, 31, and 31 proteins with differential expression. The two mutants had a different response to treatment in terms of type and quantity of up- and downregulated proteins. This difference became more striking when compared to wt. A network analysis of the proteins differentially expressed in atnp01 and atnp02 included several of those encoded by putative genes accommodating the transposons, which were responsible for regulation of some proteins identified in this study. These included nifu-like protein 3 (Nfu3), involved in chloroplast assembly, elongator complex 3 (Elo3), involved in transcriptional elongation, magnesium-chelate subunit-2 (Chli2), involved in chlorophyll biosynthesis, and protein phosphatase 2C (PP2C) which mediates abiotic stress response.

Cadmium, nickel, copper, and zinc influence on microfilament organization in Arabidopsis root cells

The plant cytoskeleton orchestrates such fundamental processes in cells as division, growth and development, polymer cross-linking, membrane anchorage, etc. Here, we describe the influence of Cd²⁺ , Ni²⁺ , Zn²⁺ , and Cu²⁺ on root development and vital organization of actin filaments into different cells of Arabidopsis thaliana line expressing GFP-FABD2. CdSO₄ , NiSO₄ , CuSO₄ , and ZnSO₄ were used in concentrations of 5-20 µM in this study. It was found that Cd, Ni, and Cu cause dose-dependent primary root growth inhibition and alteration of the root morphology, whereas Zn slightly stimulates root growth and does not affect the morphology of Arabidopsis roots. This growth inhibition/stimulation correlated with the various sensitivities of microfilaments to Cd, Ni, Cu, and Zn action. It was established that Cd, Ni, and Cu affected predominantly the actin filaments of meristematic cells. Cells of transition and elongation zones demonstrated strong actin filament sensitivity to Cd and Cu. Microfilaments of elongating root cells were more sensitive to Ni and Cu. Although Cd, Ni, and Cu stimulated root hair growth after long-term treatment, actin filaments were destroyed after 1 h exposure with these metals. Zn did not disrupt native actin filament organization in root cells. Thus, our investigation shows that microfilaments act as sensitive cellular targets for Cd, Ni, and Cu. More data on effects on native actin filaments organization would contribute to a better understanding of plant tolerance mechanisms to the action of these metals.

Additive interactions of nanoparticulate ZnO with copper, manganese and iron in Pisum sativum L., a hydroponic study

Widespread occurrence of ZnO nanoparticles in environment follows the growing number of applications either in technology or agriculture. The impact of five forms of nanoparticulate ZnO on copper, manganese and iron uptake by Pisum sativum L. cultivated in Hoagland solutions was investigated. Plants were collected after twelve days of zinc administration. Effect of bulk ZnO has also been studied. Initial zinc concentration was 100 mg L^-1. Nanoparticles were characterized by the Transmission Electron Microscopy, Dynamic Light Scattering and Zeta potential measurements. Metal contents were analyzed using the Atomic Absorption Spectrometry with flame atomization for samples digested in a microwave closed system. Analysis of variance indicated that zinc species at either molecular or nanoscale levels altered Cu, Mn and Fe uptake and their further transport in pea plants. In particular, significant reduction of Mn and Fe combined with the Cu increase was observed. Additive interactions originated by nanoparticles affect the heavy metals uptake and indicate pollutants migration pathways in plants. Unfortunately, regulations for the plant cultivation were formulated when anthropogenic nanoparticles were not in common use. They underestimate complexity of metals interactions in either plant or habitat. Our results indicate that these additive interactions cannot be neglected and deserve further investigations.

Nanotechnology in agriculture: Current status, challenges and future opportunities

Nanotechnology has shown promising potential to promote sustainable agriculture. This article reviews the recent developments on applications of nanotechnology in agriculture including crop production and protection with emphasis on nanofertilizers, nanopesticides, nanobiosensors and nano-enabled remediation strategies for contaminated soils. Nanomaterials play an important role regarding the fate, mobility and toxicity of soil pollutants and are essential part of different biotic and abiotic remediation strategies. Efficiency and fate of nanomaterials is strongly dictated by their properties and interactions with soil constituents which is also critically discussed in this review. Investigations into the remediation applications and fate of nanoparticles in soil remain scarce and are mostly limited to laboratory studies. Once entered in the soil system, nanomaterials may affect the soil quality and plant growth which is discussed in context of their effects on nutrient release in target soils, soil biota, soil organic matter and plant morphological and physiological responses. The mechanisms involved in uptake and translocation of nanomaterials within plants and associated defense mechanisms have also been discussed. Future research directions have been identified to promote the research into sustainable development of nano-enabled agriculture.

Elucidating Toxicodynamic Differences at the Molecular Scale between ZnO Nanoparticles and ZnCl2 in Enchytraeus crypticus via Nontargeted Metabolomics

Much effort has been devoted to clarifying the comparative toxicity of ZnO nanoparticles (NPs) and Zn ions; however, little is known about their toxicodynamic processes at the metabolic level. Here, we investigated the acute (2d) and chronic (7d) effects to a soil species, Enchytraeus crypticus, of two sublethal doses of ZnO-NPs and ZnCl₂ (10 and 30 mg/L Zn) using ultrahigh performance liquid chromatography-quadrupole-time-of-flight/mass spectrometry-based metabolomics. The metabolomics analysis identified 99, 128, 121, and 183 significantly changed metabolites (SCMs) in E. crypticus exposed to ZnO-NPs for 2d, ZnCl₂ for 2d, ZnO-NPs for 7d, and ZnCl₂ for 7d, respectively, suggesting that ZnCl₂ induced stronger metabolic reprogramming than ZnO-NPs, and a longer exposure time caused greater metabolite changes. Among the SCMs, 67 were shared by ZnO-NPs and ZnCl₂ after 2d and 84 after 7d. These metabolites were mainly related to oxidative stress and antioxidant defense, membrane disturbance, and energy expenditure. The targeted analysis on physiological and biochemical responses further proved the metabolic observations. Nevertheless, 32 (33%) and 37 (31%) SCMs were found only in ZnO-NP treatments after 2 and 7d, respectively, suggesting that the toxicity of ZnO-NPs cannot be solely attributed to the released Zn ions. Metabolic pathway analysis revealed significant perturbations of galactose metabolism, amino sugar and nucleotide sugar metabolism, and glycerophospholipid metabolism in all test groups. Based on involvement frequency, glucose-1-phosphate, glycerol 3-phosphate, and phosphorylcholine could serve as universal biomarkers for exposure to different Zn forms. Four pathways perturbed by ZnO-NPs were nanospecific upon acute exposure and three upon chronic exposure. Our findings demonstrated that metabolomics is an effective tool for understanding the molecular toxicity mechanism and highlighted that time-series measurements are essential for discovering and comparing modes of action of metal ions and NPs.

Nickel Toxicity Targets Cell Wall-Related Processes and PIN2-Mediated Auxin Transport to Inhibit Root Elongation and Gravitropic Responses in Arabidopsis

Contamination of soils with heavy metals, such as nickel (Ni), is a major environmental concern due to increasing pollution from industrial activities, burning of fossil fuels, incorrect disposal of sewage sludge, excessive manure application and the use of fertilizers and pesticides in agriculture. Excess Ni induces leaf chlorosis and inhibits plant growth, but the mechanisms underlying growth inhibition remain largely unknown. A detailed analysis of root development in Arabidopsis thaliana in the presence of Ni revealed that this heavy metal induces gravitropic defects and locally inhibits root growth by suppressing cell elongation without significantly disrupting the integrity of the stem cell niche. The analysis of auxin-responsive reporters revealed that excess Ni inhibits shootward auxin distribution. Furthermore, we found that PIN2 is very sensitive to Ni, as the presence of this heavy metal rapidly reduced PIN2 levels in roots. A transcriptome analysis also showed that Ni affects the expression of many genes associated with plant cell walls and that Ni-induced transcriptional changes are largely independent of iron (Fe). In addition, we raised evidence that excess Ni increases the accumulation of reactive oxygen species and disturbs the integrity and orientation of microtubules. Together, our results highlight which processes are primarily targeted by Ni to alter root growth and development.

Metatranscriptomic Insights Into the Response of River Biofilm Communities to Ionic and Nano-Zinc Oxide Exposures

Manufactured Zn oxide nanoparticle (ZnO-NP) are extensively used world-wide in personal care and industrial products and are important contaminants of aquatic environments. To understand the overall impact of ZnO-NP contamination on aquatic ecosystems, investigation of their toxicity on aquatic biofilms is of particular consequence, given biofilms are known sinks for NP contaminants. In order to assess alterations in the functional activity of river microbial biofilm communities as a result of environmentally-relevant ZnO-NP exposure, biofilms were exposed to ionic zinc salt or ZnOPs that were uncoated (hydrophilic), coated with silane (hydrophobic) or stearic acid (lipophilic), at a total concentration of 188 μg l^-1 Zn. ICP-MS analyses of biofilms indicated ZnO-NP concentrated in the biofilms, with hydrophilic, hydrophobic, and lipophilic treatments reaching 0.310, 0.250, and 0.220 μg Zn cm^-2 of biofilm, respectively, while scanning transmission X-ray microspectroscopy (STXM) analyses of biofilms confirmed that Zn was extensively- and differentially-sorbed to biofilm material. Microbial community composition, based on taxonomic affiliation of mRNA sequences and enumeration of protozoa and micrometazoa, was not affected by these treatments, and the total transcriptional response of biofilms to all experimental exposures was not indicative of a global toxic-response, as cellular processes involved in general cell maintenance and housekeeping were abundantly transcribed. Transcripts related to major biological processes, including photosynthesis, energy metabolism, nitrogen metabolism, lipid metabolism, membrane transport, antibiotic resistance and xenobiotic degradation, were differentially expressed in Zn-exposures relative to controls. Notably, transcripts involved in nitrogen fixation and photosynthesis were decreased in abundance in response to Zn-exposure, while transcripts related to lipid degradation and motility-chemotaxis were increased, suggesting a potential role of Zn in biofilm dissolution. ZnO-NP and ionic Zn exposures elicited generally overlapping transcriptional responses, however hydrophilic and hydrophobic ZnO-NPs induced a more distinct effect than that of lipophilic ZnO-NPs, which had an effect similar to that of low ionic Zn exposure. While the physical coating of ZnO-NP may not induce specific toxicity observable at a community level, alteration of ecologically important processes of photosynthesis and nitrogen cycling are an important potential consequence of exposure to ionic Zn and Zn oxides.

Common Gene Expression Patterns in Environmental Model Organisms Exposed to Engineered Nanomaterials: A Meta-Analysis

The use of omics is gaining importance in the field of nanoecotoxicology; an increasing number of studies are aiming to investigate the effects and modes of action of engineered nanomaterials (ENMs) in this way. However, a systematic synthesis of the outcome of such studies regarding common responses and toxicity pathways is currently lacking. We developed an R-scripted computational pipeline to perform reanalysis and functional analysis of relevant transcriptomic data sets using a common approach, independent from the ENM type, and across different organisms, including Arabidopsis thaliana, Caenorhabditis elegans, and Danio rerio. Using the pipeline that can semiautomatically process data from different microarray technologies, we were able to determine the most common molecular mechanisms of nanotoxicity across extremely variable data sets. As expected, we found known mechanisms, such as interference with energy generation, oxidative stress, disruption of DNA synthesis, and activation of DNA-repair but also discovered that some less-described molecular responses to ENMs, such as DNA/RNA methylation, protein folding, and interference with neurological functions, are present across the different studies. Results were visualized in radar charts to assess toxicological response patterns allowing the comparison of different organisms and ENM types. This can be helpful to retrieve ENM-related hazard information and thus fill knowledge gaps in a comprehensive way in regard to the molecular underpinnings and mechanistic understanding of nanotoxicity.

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.

Molecular mechanisms underlying zinc oxide nanoparticle induced insulin resistance in mice

Zinc oxide nanoparticles (ZnO NPs) represent an important class of commercially applied materials. Recently, adverse effects of ZnO NPs were found in humans and animals following ingestion, although the effects on endocrine system disease remain unclear. In this study, ZnO NPs were orally administered to mice, and at doses of 25 mg/kg bw (body weight) ZnO NPs and above, plasma glucose increased significantly. The genome-wide effects of ZnO NPs were then investigated using RNA-sequencing technology. In the cluster analysis, the most significantly enriched Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways concerned membranes and their close association with endoplasmic reticulum (ER) stress and reactive oxygen species (ROS) generation. Biochemical and gene and protein expression analyses revealed that ZnO NPs activated a xenobiotic biodegradation response and increased the expression of cytochrome P450 (CYP) enzymes in mice livers, leading to ER stress. The ER stress increased ROS generation. The high levels of ROS activated the MAPK and NF-κB pathways and induced an inflammation response, resulting in the phosphorylation of insulin receptor substrate 1. Thus, the insulin resistance that developed was the primary mechanism for the increase in the plasma glucose of mice treated orally with ZnO NPs.

Quantitative Proteomic Analysis to Understand the Mechanisms of Zinc Oxide Nanoparticle Toxicity to Daphnia pulex (Crustacea: Daphniidae): Comparing with Bulk Zinc Oxide and Zinc Salt

The widespread use of zinc oxide nanoparticles (ZnO NPs) has resulted in their release to the environment. There has been concern about the ecotoxicity of ZnO NPs, but little is known about their toxic mechanisms. In the present study, we conducted acute toxicity tests to show that ZnO NPs are more toxic to the freshwater crustacean Daphnia pulex compared to bulk ZnO or ZnSO₄·7H₂O. To provide an integrated and quantitative insights into the toxicity of ZnO NPs, we conducted isobaric tags for relative and absolute quantitation (iTRAQ) proteomic analysis, which detected 262, 331, and 360 differentially expressed proteins (DEPs) in D. pulex exposed to ZnO NPs, bulk ZnO, and ZnSO₄·7H₂O, respectively. Among the DEPs, 224 were shared among the three treatments. These proteins were related to energy metabolism, oxidative stress, and endoplasmic reticulum stress. The three forms of Zn all caused D. pulex to downregulate Chitinase expression, disrupt Ca²⁺ homeostasis, and reduce expression of digestive enzymes. Nevertheless, 29 proteins were expressed only in the ZnO NP treatment. In particular, histone (H3) and ribosomal proteins (L13) were obviously influenced under ZnO NP treatment. However, increased expression levels of h3 and l13 genes were not induced only in ZnO NP treatment, they were sensitive to Zn ions under the same exposure concentration. These results indicate that the three zinc substances have a similar mode of action and that released zinc ions are the main contributor to ZnO NP toxicity to D. pulex under a low concentration. Further investigation is needed to clarify whether a small proportion of DEPs or higher bioavailability cause ZnO NPs to be more toxic compared to bulk ZnO or ionic zinc.

Comparative Physiological and Transcriptomic Analyses Reveal the Toxic Effects of ZnO Nanoparticles on Plant Growth

Zinc oxide (ZnO) nanoparticles (nZnO) are among the most commonly used nanoparticles (NPs), and they have been shown to have harmful effects on plants. However, the molecular mechanisms underlying nZnO tolerance and root sensing of NP stresses have not been elucidated. Here, we compared the differential toxic effects of nZnO and Zn²⁺ toxicity on plants during exposure and recovery using a combination of transcriptomic and physiological analyses. Although both nZnO and Zn²⁺ inhibited primary root (PR) growth, nZnO had a stronger inhibitory effect on the growth of elongation zones, whereas Zn²⁺ toxicity had a stronger toxic effect on meristem cells. Timely recovery from stresses is critical for plant survival. Despite the stronger inhibitory effect of nZnO on PR growth, nZnO-exposed plants recovered from stress more rapidly than Zn²⁺-exposed plants upon transfer to normal conditions, and transcriptome data supported these results. In contrast to Zn²⁺ toxicity, nZnO induced endocytosis and caused microfilament rearrangement in the epidermal cells of elongation zones, thereby repressing PR growth. nZnO also repressed PR growth by disrupting cell wall organization and structure through both physical interactions and transcriptional regulation. The present study provides new insight into the comprehensive understanding and re-evaluation of NP toxicity in plants.

Separation and size characterization of zinc oxide nanoparticles in environmental waters using asymmetrical flow field-flow fractionation

There are few studies on separation and size characterization of zinc oxide nanoparticles (ZnO-NPs), which have wide applications in several science and technology areas, in the environment. In this work, we report a method for the separation and size characterization of ZnO-NPs by asymmetrical flow field-flow fractionation (AF4) coupled to UV-vis detector. Experimental conditions such as composition of the carrier solution, focus time, crossflow, detector flow rate and injection volume were systematically studied in terms of NPs separation, recovery, and repeatability. Size characterization was achieved using polystyrene nanoparticles as a size standard and a mixture of < 35 nm (NP-A) and < 100 nm (NP-B) ZnO-NPs were separated and size characterized posterior preconcentration using ultracentrifugation. The method was also employed to characterize the size of homemade ZnO-NPs, and the results were in concordance with dynamic light scattering (DLS) analysis and thus, the method can be used as an alternate method. Upon application on environmental water samples, the two ZnO-NPs, NP-A and NP-B, have been separated and size characterized. The estimated hydrodynamic sizes of the NP-A and NP-B were found to be in the range of 83-97 nm and 188-202 nm, respectively, with good precision (RSD, <11%), suggesting that the current method can satisfactorily separate and generate information about sizes of the NPs in samples with a complex matrix. Therefore, the developed technique can be used as a baseline to investigate size related environmental processes of the NPs in environmental water samples.

Metabolism of the anthelmintic drug fenbendazole in Arabidopsis thaliana and its effect on transcriptome and proteome

Fenbendazole, a broad spectrum anthelmintic used especially in veterinary medicine, may impact non-target organisms in the environment. Nevertheless, information about the effects of fenbendazole in plants is limited. We investigated the biotransformation of fenbendazole and the effect of fenbendazole and its metabolites on gene expression in the model plant Arabidopsis thaliana. High-sensitive UHPLC coupled with tandem mass spectrometry, RNA-microarray analysis together with qPCR verification and nanoLC-MS proteome analysis were used in this study. Twelve fenbendazole metabolites were identified in the roots and leaves of A. thaliana plants. Hydroxylation, S-oxidation and glycosylation represent the main fenbendazole biotransformation pathways. Exposure of A. thaliana plants to 5 μM fenbendazole for 24 and 72 h significantly affected gene and protein expression. The changes in transcriptome were more pronounced in the leaves than in roots, protein expression was more greatly affected in the roots at a shorter period of exposure (24 h) and in leaf rosettes over a longer period (72 h). Up-regulated (>2-fold change, p < 0.1) proteins are involved in various biological processes (electron transport, energy generating pathways, signal transduction, transport), and in response to stresses (e.g. catalase, superoxide dismutase, cytochromes P450, UDP-glycosyltransferases). Some of the proteins which were up-regulated after fenbendazole-exposure probably participate in fenbendazole biotransformation (e.g. cytochromes P450, UDP-glucosyltransferases). Finally, fenbendazole in plants significantly affects many physiological and metabolic processes and thus the contamination of ecosystems by manure containing this anthelmintic should be restricted.

Transcriptomic response of Arabidopsis thaliana roots to naproxen and praziquantel

Exposition to pharmaceutical compounds released to the environment is considered as a potential risk for various organisms. We exposed Arabidopsis thaliana plants to naproxen (NAP) and praziquantel (PZQ) in 5 µM concentration for 2 days and recorded transcriptomic response in their roots with the aim to estimate ecotoxicity and to identify gene candidates potentially involved in metabolism of both compounds. Nonsteroidal anti-inflammatory drug NAP up-regulated 105 and down-regulated 29 genes (p-value ≤ 0.1, fold change ≥ 2), while anthelmintic PZQ up-regulated 389 and down-regulated 353 genes with more rigorous p-value ≤ 0.001 (fold change ≥ 2). High number of up-regulated genes coding for heat shock proteins and other genes involved in response to biotic and abiotic stresses as well as down-regulation of genes involved in processes such as cell proliferation, transcription and water transport indicates serious negative effect of PZQ. NAP up-regulated mostly genes involved in various biological processes and signal transduction and down-regulated mainly genes involved in signal transduction and electron transport or energy pathways. Further, two cytochrome P450s (demethylation) and one methyltransferase (methylation of carboxyl group) were identified as candidates for phase I and several glutathione- and glycosyltransferases (conjugation) for phase II of NAP metabolism. Cytochrome P450s, glutathione and glycosyltransferases seem to play role also in metabolism of PZQ. Up-regulation of several ABC and MATE transporters by NAP and PZQ indicated their role in transport of both compounds.

Comparative study of the phytotoxicity of ZnO nanoparticles and Zn accumulation in nine crops grown in a calcareous soil and an acidic soil

The increasing use of zinc oxide nanoparticles (ZnO NPs) in agriculture and consumer products has created the need to evaluate their impact on crops. Nine crops were investigated: wheat, maize, radish, bean, lettuce, tomato, pea, cucumber, and beet. The toxic effects of ZnO NPs on seed germination, plant growth, and biochemical parameters, including photosynthetic pigments, protein and malondialdehyde (MDA) content, reactive oxygen species (ROS), enzymes of the antioxidant defence system, as well as the Zn translocation in the plants were investigated using pots containing non-contaminated or ZnO NP-contaminated soil at concentrations of 20, 225, 450, and 900 mg Zn kg^-1. Two soils with different physicochemical properties, namely a calcareous soil and an acidic soil, were used. The total and available Zn in the soils were correlated with the Zn in the plants (roots and shoots) and the observed effects. In the calcareous soil, the available Zn was very low and the phytotoxicity was limited to a slight reduction in the biomass for wheat, cucumber, and beet at the highest concentration. Only beet showed an increase in photosynthetic pigments. The parameters related to oxidative stress were affected to different degrees depending on the crop, with the exceptions of maize, lettuce, pea, and beet. In the acidic soil, the available Zn was high, and the germination of bean, tomato, lettuce, and beet, and the growth of most of the crops were seriously affected. The calculated EC50 values (growth) in the acidic soil ranged from 110 to 520 mg Zn kg^-1. The photosynthetic pigments and most of the markers of oxidative stress were negatively affected in maize, wheat, bean, and pea. However, these changes were not always associated with a decrease in plant weight. In summary, soil pH and plant species are key factors affecting the Zn availability and phytotoxicity of ZnO NPs.

Synthesis and characterization of isotopically-labeled silver, copper and zinc oxide nanoparticles for tracing studies in plants

In parallel to technological advances and ever-increasing use of nanoparticles in industry, agriculture and consumer products, the potential ecotoxicity of nanoparticles and their potential accumulation in ecosystems is of increasing concern. Because scientific reports raise a concern regarding nanoparticle toxicity to plants, understanding of their bioaccumulation has become critical and demands more research. Here, the synthesis of isotopically-labeled nanoparticles of silver, copper and zinc oxide is reported; it is demonstrated that while maintaining the basic properties of the same unlabeled ("regular") nanoparticles, labeled nanoparticles enable more sensitive tracing of nanoparticles within plants that have background elemental levels. This technique is particularly useful for working with elements that are present in high abundance in natural environments. As a benchmark, labeled and unlabeled metal nanoparticles (Ag-NP, Cu-NP, ZnO-NP) were synthesized and compared, and then exposed in a series of growth experiments to Arabidopsis thaliana; the NPs were traced in different parts of the plant. All of the synthesized nanoparticles were characterized by TEM, EDS, DLS, ζ-potential and single particle ICP-MS, which provided essential information regarding size, composition, morphology and surface charge of nanoparticles, as well as their stability in suspensions. Tracing studies with A. thaliana showed uptake/retention of nanoparticles that is more significant in roots than in shoots. Single particle ICP-MS, and scanning electron micrographs and EDS of plant roots showed presence of Ag-NPs in particular, localized areas, whereas copper and zinc were found to be distributed over the root tissues, but not as nanoparticles. Thus, nanoparticles in any natural matrix can be replaced easily by their labeled counterparts to trace the accumulation or retention of NPs. Isotopically-labeled nanoparticles enable acquisition of specific results, even if there are some concentrations of the same elements that originate from other (natural or anthropogenic) sources.

Plant Response to Metal-Containing Engineered Nanomaterials: An Omics-Based Perspective

The increasing use of engineered nanomaterials (ENMs) raises questions regarding their environmental impact. Improving the level of understanding of the genetic and molecular basis of the response to ENM exposure in biota is necessary to accurately assess the true risk to sensitive receptors. The aim of this Review is to compare the plant response to several metal-based ENMs widely used, such as quantum dots, metal oxides, and silver nanoparticles (NPs), integrating available "omics" data (transcriptomics, miRNAs, and proteomics). Although there is evidence that ENMs can release their metal components into the environment, the mechanistic basis of both ENM toxicity and tolerance is often distinct from that of metal ions and bulk materials. We show that the mechanisms of plant defense against ENM stress include the modification of root architecture, involvement of specific phytohormone signaling pathways, and activation of antioxidant mechanisms. A critical meta-analysis allowed us to identify relevant genes, miRNAs, and proteins involved in the response to ENMs and will further allow a mechanistic understanding of plant-ENM interactions.

Uptake of Engineered Nanoparticles by Food Crops: Characterization, Mechanisms, and Implications

With the rapidly increasing demand for and use of engineered nanoparticles (NPs) in agriculture and related sectors, concerns over the risks to agricultural systems and to crop safety have been the focus of a number of investigations. Significant evidence exists for NP accumulation in soils, including potential particle transformation in the rhizosphere and within terrestrial plants, resulting in subsequent uptake by plants that can yield physiological deficits and molecular alterations that directly undermine crop quality and food safety. In this review, we document in vitro and in vivo characterization of NPs in both growth media and biological matrices; discuss NP uptake patterns, biotransformation, and the underlying mechanisms of nanotoxicity; and summarize the environmental implications of the presence of NPs in agricultural ecosystems. A clear understanding of nano-impacts, including the advantages and disadvantages, on crop plants will help to optimize the safe and sustainable application of nanotechnology in agriculture for the purposes of enhanced yield production, disease suppression, and food quality.

Uptake and transformations of engineered nanomaterials: Critical responses observed in terrestrial plants and the model plant Arabidopsis thaliana

With the applications of engineered nanomaterials (ENMs) continually expanding and production quickly growing, residues of ENMs will end up in the environment at levels that may be harmful to non-target organisms. Many of the tunable properties that have made them desirable, such as type, size, charge, or coating, also contribute to the current difficulties in understanding the fate of ENMs in the environment. This review article focuses on studies that investigate plant-ENM interactions, including techniques used to study these interactions and documented plant responses due to the phytotoxic effects of ENMs. The many variables which can be altered for an experiment, such as type, size, and concentration of ENMs, make it difficult to formulate generalizations about the uptake mechanism involved, or to make an inference on the subcellular localization and distribution of the internalized ENMs in plant tissue. In order to avoid these challenges, studies can utilize a model organism such as Arabidopsis thaliana, and a combination of analytical techniques that can reveal complementary information in order to assess how the different experimental conditions influence the uptake and phytotoxicity of ENMs. This review presents recent studies regarding plant-ENM interactions employing Arabidopsis to demonstrate how the use of this model plant can advance our understanding of plant-ENM interactions and guide additional studies using other plant species. Overarching results suggest that more sensitive tests and consistency in experimental designs are needed to fully assess and understand the phytotoxic effects of ENMs in the environment.

Transcriptomic Response of Arabidopsis thaliana Exposed to CuO Nanoparticles, Bulk Material, and Ionic Copper

Engineered nanoparticles (ENPs) exhibit unique properties advantageous in a number of applications, but they also represent potential health and environmental risks. In this study, we investigated the phytotoxic mechanism of CuO ENPs using transcriptomic analysis and compared this response with the response to CuO bulk particles and ionic Cu²⁺. Ionic Cu²⁺ at the concentration of 0.16 mg L^-1 changed transcription of 2692 genes (p value of <0.001, fold change of ≥2) after 7 days of exposure, whereas CuO ENPs and bulk particles (both in the concentration of 10 mg L^-1) altered the expression of 922 and 482 genes in Arabidopsis thaliana roots, respectively. The similarity between transcription profiles of plants exposed to ENPs and ionic Cu²⁺ indicated that the main factor in phytotoxicity was the release of Cu²⁺ ions from CuO ENPs after 7 days of exposure. The effect of Cu²⁺ ions was evident in all treatments, as indicated by the down-regulation of genes involved in metal homeostasis and transport and the up-regulation of oxidative stress response genes. ENPs were more soluble than bulk particles, resulting in the up-regulation of metallochaperone-like genes or the down-regulation of aquaporins and metal transmembrane transporters that was also characteristic for ionic Cu²⁺ exposure.

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

Nano-aluminium oxide (nAl₂O₃) is one of the most widely used nanomaterials. However, nAl₂O₃ toxicity mechanisms and potential beneficial effects on terrestrial plant physiology remain poorly understood. Such knowledge is essential for the development of robust nAl₂O₃ risk assessment. In this study, we studied the influence of a 10-d exposure to a total selected concentration of 98 μM nAl₂O₃ or to the equivalent molar concentration of ionic Al (AlCl₃) (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 nAl₂O₃ toxicity on photosynthesis, growth and lipid peroxidation. Rather the nAl₂O₃ treatment stimulated root weight and length by 48% and 39%, respectively as well as photosynthesis opening up the door to the use of nAl₂O₃ in biotechnology and nano agriculture. Transcriptomic analyses indicate that the beneficial effect of nAl₂O₃ 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 nAl₂O₃ and ionic Al in Arabidopsis.

ZnO nanoparticle effects on hormonal pools in Arabidopsis thaliana

At present, nanoparticles have been more and more used in a wide range of areas. However, very little is known about the mechanisms of their impact on plants, as both positive and negative effects have been reported. As plant interactions with the environment are mediated by plant hormones, complex phytohormone analysis has been performed in order to characterize the effect of ZnO nanoparticles (mean size 30nm, concentration range 0.16-100mgL^-1) on Arabidopsis thaliana plants. Taking into account that plant hormones exhibit high tissue-specificity as well as an intensive cross-talk in the regulation of growth and development as well as defense, plant responses were followed by determination of the content of five main phytohormones (cytokinins, auxins, abscisic acid, salicylic acid and jasmonic acid) in apices, leaves and roots. Increasing nanoparticle concentration was associated with gradually suppressed biosynthesis of the growth promoting hormones cytokinins and auxins in shoot apical meristems (apices). In contrast, cis-zeatin, a cytokinin associated with stress responses, was elevated by 280% and 590% upon exposure to nanoparticle concentrations 20 and 100mgL^-1, respectively, in roots. Higher ZnO nanoparticle doses resulted in up-regulation of the stress hormone abscisic acid, mainly in apices and leaves. In case of salicylic acid, stimulation was found in leaves and roots. The other stress hormone jasmonic acid (as well as its active metabolite jasmonate isoleucine) was suppressed at the presence of nanoparticles. The earliest response to nanoparticles, associated with down-regulation of growth as well as of cytokinins and auxins, was observed in apices. At higher dose, up-regulation of abscisic acid, was detected. This increase, together with elevation of the other stress hormone - salicylic acid, indicates that plants sense nanoparticles as severe stress. Gradual accumulation of cis-zeatin in roots may contribute to relatively higher stress resistance of this tissue.

Thorium impact on tobacco root transcriptome

Thorium is natural actinide metal with potential use in nuclear energetics. Contamination by thorium, originated from mining activities or spills, represents environmental risk due to its radioactivity and chemical toxicity. A promising approach for cleaning of contaminated areas is phytoremediation, which need to be based, however, on detail understanding of the thorium effects on plants. In this study we investigated transcriptomic response of tobacco roots exposed to 200μM thorium for one week. Thorium application resulted in up-regulation of 152 and down-regulation of 100 genes (p-value <0.01, fold change ≥2). The stimulated genes were involved in components of jasmonic acid and salicylic acid signaling pathways and various abiotic (e.g. oxidative stress) and biotic stress (e.g. pathogens, wounding) responsive genes. Further, up-regulation of phosphate starvation genes and down-regulation of genes involved in phytic acid biosynthesis indicated that thorium disturbed phosphate uptake or signaling. Also expression of iron responsive genes was influenced. Negative regulation of several aquaporins indicated disturbance of water homeostasis. Genes potentially involved in thorium transport could be zinc-induced facilitator ZIF2, plant cadmium resistance PCR2, and ABC transporter ABCG40. This study provides the first insight at the processes in plants exposed to thorium.