Nanomaterial sulfonated graphene oxide advances the tolerance against nitrate and ammonium toxicity by regulating chloroplastic redox balance, photochemistry of photosystems and antioxidant capacity in Triticum aestivum

Genome-Wide Identification and Characterization of Ammonium Transporter (AMT) Genes in Chlamydomonas reinhardtii

Ammonium transporters (AMTs) are vital plasma membrane proteins facilitating NH4+ uptake and transport, crucial for plant growth. The identification of favorable AMT genes is the main goal of improving ammonium-tolerant algas. However, there have been no reports on the systematic identification and expression analysis of Chlamydomonas reinhardtii (C. reinhardtii) AMT genes. This study comprehensively identified eight CrAMT genes, distributed across eight chromosomes, all containing more than 10 transmembrane structures. Phylogenetic analysis revealed that all CrAMTs belonged to the AMT1 subfamily. The conserved motifs and domains of CrAMTs were similar to those of the AMT1 members of OsAMTs and AtAMTs. Notably, the gene fragments of CrAMTs are longer and contain more introns compared to those of AtAMTs and OsAMTs. And the promoter regions of CrAMTs are enriched with cis-elements associated with plant hormones and light response. Under NH4+ treatment, CrAMT1;1 and CrAMT1;3 were significantly upregulated, while CrAMT1;2, CrAMT1;4, and CrAMT1;6 saw a notable decrease. CrAMT1;7 and CrAMT1;8 also experienced a decline, albeit less pronounced. Transgenic algas with overexpressed CrAMT1;7 did not show a significant difference in growth compared to CC-125, while transgenic algas with CrAMT1;7 knockdown exhibited growth inhibition. Transgenic algas with overexpressed or knocked-down CrAMT1;8 displayed reduced growth compared to CC-125, which also resulted in the suppression of other CrAMT genes. None of the transgenic algas showed better growth than CC-125 at high ammonium levels. In summary, our study has unveiled the potential role of CrAMT genes in high-ammonium environments and can serve as a foundational research platform for investigating ammonium-tolerant algal species.

Selenium nanomaterials alleviate Brassica chinensis L cadmium stress: Reducing accumulation, regulating microorganisms and activating glutathione metabolism

Agricultural heavy metal contamination can cause significant crop damage, highlighting the urgent need to mitigate its negative effects. Under Cd2+ stress, selenium nanomaterials (Se NMs, 2 mg kg-1) can significantly improve Brassica chinensis L. root growth and vigor, enhance photosynthesis (31.4%), and increase biomass. Se NMs treatment also reduces Brassica chinensis L root and shoot Cd concentration by 67.2 and 72.9%, respectively. This reduction is mainly due to the gene expression of Cd2+ absorption (BcITR1 and BcHMA2) which was down-regulated 51.9 and 67.0% by Se NMs, respectively. Meanwhile, Se NMs can increase the abundance of Cd-resistant microorganisms (Gemmatimonas, RB41, Haliangium, Gaiella, and Steroidobacter) in rhizosphere soil while also reducing Cd migration from soil to plants. Additionally, Se NMs also contribute to reducing ROS accumulation by improving the oxidation-reduction process between GSH and GSSG through enhancing γ-ECS (15.6%), GPx (50.2%) and GR (97.3%) activity. Remarkably, crop Se content can reach 50.8 μg/100 g, which fully meets the standards of Se-rich vegetables. These findings demonstrate the potential of Se NMs in relieving heavy metal stress, while simultaneously increasing crop Se content, making it a promising technology for sustainable agricultural production.

Toxicity of bisphenol A (BPA) and its analogues BPF and BPS on the free-floating macrophyte Salvinia biloba

Evidence linking the toxicity of bisphenol A (BPA) to environmental and public-health issues has led to restrictions on its use. This compound has been gradually replaced with analogues proposed as a safer alternative, normally bisphenol F (BPF) and bisphenol S (BPS), but these substitutes are structurally almost identical to BPA, suggesting they may pose similar risks. The effects of BPA and these analogues were compared for antioxidant activity, lipid peroxidation, free-radical generation, photosynthetic pigments, and chlorophyll fluorescence in Salvinia biloba Raddi (S. biloba) plants exposed to environmentally relevant and sublethal concentrations (1, 10, 50, 100 and 150 μM). Bisphenol exposure promoted alterations in most of the physiological parameters investigated, with BPS toxicity differing slightly from that of the analogues. Furthermore, S. biloba removed similar levels of BPA and BPF from aqueous solutions with ≈70% removed at the 150 μM concentration, while BPS was less effectively removed, with only 23% removed at 150 μM. These findings show that high concentrations of bisphenols (10≥) are toxic to S. biloba, and even typical environmental levels (≤1 μM) can induce metabolic changes in plants, bringing to light that both BPA and its substitutes BPF and BPS pose risks to aquatic ecosystems.

Nanoparticles regulate redox metabolism in plants during abiotic stress within hormetic boundaries

Abiotic stress management remains under scrutiny because of the unpredictable nature of climate, which undergoes abrupt alterations. Population pressure, loss of cultivable lands, environmental pollution and other anthropogenic disturbances add to the problem and grossly hinder ongoing management strategies. This has driven increasing effort to find better performing, eco-friendly and reliable alternatives that can contribute to sustainable agricultural practices to manage abiotic stress. Nanotechnology and its implementation in agriculture have emerged as a promising option to cater to the problem of abiotic stress. Induction of reactive oxygen species (ROS) is an inevitable phenomenon linked to stress. Nanoparticles (NPs) perform dual actions in regulating ROS biology. The bidirectional roles of NPs in modulating ROS generation and/or ROS detoxification is tightly coupled within the hormetic boundaries. Nonetheless, how these NPs control the ROS metabolism within hormetic limits demands extensive investigation. This review focuses on the details of ROS metabolism under normal versus stressed conditions. It shall elaborate on the types, modes and process of uptake and translocation of NPs. The molecular dissection of the role of NPs in controlling transcriptomic expressions and modulating molecular crosstalks with other growth regulators, ions, reactive nitrogen species and other signalling molecules shall also be detailed. Throughout, this review aims to summarise the potential roles and regulation of NPs and consider how they can be used for green synthesis within a sustainable agricultural industry.

Graphene-Cu Nanocomposites Induce Tolerance against Fusarium oxysporum, Increase Antioxidant Activity, and Decrease Stress in Tomato Plants

The tomato crop is susceptible to various types of stress, both biotic and abiotic, which affect the morphology, physiology, biochemistry, and genetic regulation of plants. Among the biotic factors, is the phytopathogen Fusarium oxysporum f. sp. lycopersici (Fol), which can cause losses of up to 100%. Graphene-Cu nanocomposites have emerged as a potential alternative for pathogen control, thanks to their antimicrobial activity and their ability to induce the activation of the antioxidant defense system in plants. In the present study, the effect of the Graphene-Cu nanocomposites and the functionalization of graphene in the tomato crop inoculated with Fol was evaluated, analyzing their impacts on the antioxidant defense system, the foliar water potential (Ψ_h), and the efficiency of photosystem II (PSII). The results demonstrated multiple positive effects; in particular, the Graphene-Cu nanocomposite managed to delay the incidence of the "vascular wilt" disease and reduce the severity by 29.0%. This translated into an increase in the content of photosynthetic pigments and an increase in fruit production compared with Fol. In addition, the antioxidant system of the plants was improved, increasing the content of glutathione, flavonoids, and anthocyanins, and the activity of the GPX, PAL, and CAT enzymes. Regarding the impact on the water potential and the efficiency of the PSII, the plants inoculated with Fol and treated with the Graphene-Cu nanocomposite responded better to biotic stress compared with Fol, reducing water potential by up to 31.7% and Fv/Fm levels by 32.0%.

Fe2O3-modified graphene oxide mitigates nanoplastic toxicity via regulating gas exchange, photosynthesis, and antioxidant system in Triticum aestivum

The ever-increasing plastic pollution in soil and water resources raises concerns about its effects on terrestrial plants and agroecosystems. Although there are many reports about the contamination with nanoplastics on plants, the presence of magneto-assisted nanomaterials enabling the removal of their adverse impacts still remains unclear. Therefore, the purpose of the current study is to evaluate the potential of nanomaterial Fe₂O₃-modified graphene oxide (FGO, 50-250 mg L^-1) to eliminate the adverse effects of nanoplastics in plants. Wheat plants exposed to polystyrene nanoplastics concentrations (PS, 10, 50 and 100 mg L^-1) showed decreased growth, water content and loss of photosynthetic efficiency. PS toxicity negatively altered gas exchange, antenna structure and electron transport in photosystems. Although the antioxidant system was partially activated (only superoxide dismutase (SOD), NADPH oxidase (NOX) and glutathione reductase (GR)) in plants treated with PS, it failed to prevent PS-triggered oxidative damage, as showing lipid peroxidation and hydrogen peroxide (H₂O₂) levels. FGOs eliminated the adverse impacts of PS pollution on growth, water status, gas exchange and oxidative stress markers. In addition, FGOs preserve the biochemical reactions of photosynthesis by actively increasing chlorophyll fluorescence parameters in the stressed-wheat leaves. The activities of all enzymatic antioxidants increased, and the H₂O₂ and TBARS contents decreased. GSH-mediated detoxifying antioxidants such as glutathione S-transferase (GST) and glutathione peroxidase (GPX) were stimulated by FGOs against PS pollution. FGOs also triggered the enzymes and non-enzymes related to the Asada-Halliwell cycle and protected the regeneration of ascorbate (AsA) and glutathione (GSH). Our findings indicated that FGO had the potential to mitigate nanoplastic-induced damage in wheat by regulating water relations, protecting photosynthesis reactions and providing efficient ROS scavenging with high antioxidant capacity. This is the first report on removing PS-induced damage by FGO applications in wheat leaves.

Advances in Biologically Applicable Graphene-Based 2D Nanomaterials

Climate change and increasing contamination of the environment, due to anthropogenic activities, are accompanied with a growing negative impact on human life. Nowadays, humanity is threatened by the increasing incidence of difficult-to-treat cancer and various infectious diseases caused by resistant pathogens, but, on the other hand, ensuring sufficient safe food for balanced human nutrition is threatened by a growing infestation of agriculturally important plants, by various pathogens or by the deteriorating condition of agricultural land. One way to deal with all these undesirable facts is to try to develop technologies and sophisticated materials that could help overcome these negative effects/gloomy prospects. One possibility is to try to use nanotechnology and, within this broad field, to focus also on the study of two-dimensional carbon-based nanomaterials, which have excellent prospects to be used in various economic sectors. In this brief up-to-date overview, attention is paid to recent applications of graphene-based nanomaterials, i.e., graphene, graphene quantum dots, graphene oxide, graphene oxide quantum dots, and reduced graphene oxide. These materials and their various modifications and combinations with other compounds are discussed, regarding their biomedical and agro-ecological applications, i.e., as materials investigated for their antineoplastic and anti-invasive effects, for their effects against various plant pathogens, and as carriers of bioactive agents (drugs, pesticides, fertilizers) as well as materials suitable to be used in theranostics. The negative effects of graphene-based nanomaterials on living organisms, including their mode of action, are analyzed as well.

The Effects of Graphene-Family Nanomaterials on Plant Growth: A Review

Numerous reports of graphene-family nanomaterials (GFNs) promoting plant growth have opened up a wide range of promising potential applications in agroforestry. However, several toxicity studies have raised growing concerns about the biosafety of GFNs. Although these studies have provided clues about the role of GFNs from different perspectives (such as plant physiology, biochemistry, cytology, and molecular biology), the mechanisms by which GFNs affect plant growth remain poorly understood. In particular, a systematic collection of data regarding differentially expressed genes in response to GFN treatment has not been conducted. We summarize here the fate and biological effects of GFNs in plants. We propose that soil environments may be conducive to the positive effects of GFNs but may be detrimental to the absorption of GFNs. Alterations in plant physiology, biochemistry, cytological structure, and gene expression in response to GFN treatment are discussed. Coincidentally, many changes from the morphological to biochemical scales, which are caused by GFNs treatment, such as affecting root growth, disrupting cell membrane structure, and altering antioxidant systems and hormone concentrations, can all be mapped to gene expression level. This review provides a comprehensive understanding of the effects of GFNs on plant growth to promote their safe and efficient use.