Hydrogen peroxide metabolism and functions in plants

The overexpression of E. coli formaldehyde metabolism genes in Arabidopsis conferred varying degrees of resistance to oxidative stress induced by small organic compounds

Small organic compounds (SOCs) are widespread environmental pollutants that pose a significant threat to ecosystem health and human well-being. In this study, the FrmA gene from Escherichia coli was overexpressed alone or in combination with FrmB in Arabidopsis thaliana and their resistance to multiple SOCs was investigated. The transgenic plants exhibited varying degrees of increased tolerance to methanol, formic acid, toluene, and phenol, extending beyond the known role of FrmA in formaldehyde metabolism. Biochemical and histochemical analyses showed reduced oxidative damage, especially in the FrmA/BOE lines, as evidenced by lower malondialdehyde (MDA), H2O2 and O2•- levels, indicating improved scavenging of reactive oxygen species (ROS). SOC treatment led to significantly higher levels of glutathione (GSH) and, to a lesser extent, ascorbic acid (AsA) in the transgenic plants than in the wild-types. After methanol exposure, GSH levels increased by 95 % and 72 % in the FrmA/BOE and FrmAOE plants, respectively, while showing no significant increase in the wild-type plants. The transgenic plants also maintained higher GSH:GSSG and AsA:DHA ratios, exhibited upregulated glutathione reductase (GR) and dehydroascorbate reductase (DHAR) activities, and correspondingly increased gene expression. In addition, the photosynthetic parameters of the transgenic plants were less affected by SOC stress, which represents a significant photosynthetic advantage. These results emphasize the potential of genetically engineered plants for phytoremediation and crop improvement, as they exhibit increased tolerance to multiple hazardous SOCs. This research lays the foundation for sustainable approaches to combat pollution and improve plant resilience in the face of escalating environmental problems.

Volatile organic compounds from Irpex lacteus inhibit pathogenic fungi and enhance plant resistance to Botrytis cinerea in tomato

Biocontrol fungi may exert antagonistic effects by emitting volatile organic compounds (VOCs), thus identifying fungal VOCs is crucial for understanding biocontrol mechanisms and developing novel biofungicides. In this study, we examined the antagonistic effect of Irpex lacteus LL210 against three major fungal pathogens: Botrytis cinerea (tomato gray mold), Fusarium oxysporum (cucumber wilt), and Alternaria alternata (pepper leaf spots) using in vitro assays. The results of both the dual-culture and dual-petri-dish methods showed that I. lacteus LL210 strongly inhibited the growth of B. cinerea, likely through the release of volatile compounds. SPME-GC-MS analysis of I. lacteus LL210 identified 770 volatile compounds, of which 26 key volatiles were screened on the basis of their relative odor activity values, peak areas and concentrations. Further evaluation using the dual-petri-dish method showed that compounds such as 2-Octen-1-ol, (E)-; Benzeneacetaldehyde; (E)-2-Octenal; Hexanal; (E)-2-Butenal; 5-Heptenal, 2,6-dimethyl-; 1-Octanol; 2,3-dihydro-Benzofuran; Diallyl Sulfur compounds exhibited significant inhibition of B. cinerea, suggesting their potential utility in the development of novel fungicides. We also tested their effects on plant growth and physiology and found that 1-octanol had minimal deleterious effects on tomato plants, as evidenced by growth and oxidative stress markers. This study systematically deciphered the VOCs profile of I. lacteus LL210, revealing critical mechanisms of pathogen inhibition through both direct inhibitory effects of VOCs and plant-mediated enhanced defense. These findings have driven the development of potential biocontrol agents based on VOCs, thereby providing sustainable solutions for crop disease management.

The ZjMYB44-ZjPOD51 module enhances jujube defense response against phytoplasma by upregulating lignin biosynthesis

Lignin is a major component of the plant cell wall and has a conserved basic defense function in higher plants, helping the plants cope with pathogen infection. However, the regulatory mechanism of lignin biosynthesis in plants under phytoplasma stress remains unclear. In this study, we reported that peroxidase 51 (ZjPOD51), which is involved in lignin monomer polymerization, was induced by phytoplasma infection and that overexpression of ZjPOD51 in phytoplasma-infected jujube seedlings and Arabidopsis plants significantly increased their defense response against phytoplasma. Yeast one-hybrid (Y1H) and luciferase (LUC) assays showed that ZjPOD51 transcription was directly upregulated by ZjMYB44. Genetic validation demonstrated that ZjMYB44 expression was also induced by phytoplasma infection and contributed to lignin accumulation, which consequently enhanced phytoplasma defense in a ZjPOD51-dependent manner. These results demonstrated that the ZjMYB44-ZjPOD51 module enhanced the jujube defense response against phytoplasma by upregulating lignin biosynthesis. Overall, our study first elucidates how plants regulate lignin to enhance their defense response against phytoplasma and provides clues for jujube resistance breeding.

Sexual reproduction in land plants: an evolutionary perspective

KEY MESSAGE

We link key aspects of land plant reproductive evolution and detail how successive molecular changes leading to novel tissues and organs require co-evolution of communication systems between tissues. The transition of water-dependent reproduction of algae to mechanisms with very limited water dependence in many land plant lineages allowed plants to colonize diverse terrestrial environments, leading to the vast variety of extant plant species. The emergence of modified cell types, novel tissues, and organs enabled this transition; their origin is associated with the co-evolution of novel or adapted molecular communication systems and gene regulatory networks. In the light of an increasing number of genome sequences in combination with the establishment of novel genetic model organisms from diverse green plant lineages, our knowledge and understanding about the origin and evolution of individual traits that arose in a concerted way increases steadily. For example, novel members of gene families in signaling pathways emerged for communication between gametes and gametophytes with additional tissues surrounding the gametes. Here, we provide a comprehensive overview on the origin and evolution of reproductive novelties such as pollen grains, immobile sperms, ovules and seeds, carpels, gamete/gametophytic communication systems, double fertilization, and the molecular mechanisms that have arisen anew or have been co-opted during evolution, including but not limited to the incorporation of phytohormones, reactive oxygen species and redox signaling as well as small RNAs in regulatory modules that contributed to the evolution of land plant sexual reproduction.

Graphene Oxide Nanosheets for Delivery of RNAi and Plant Immune Stimulation for Sustained Protection against Plant Viruses

Given the dearth of effective antiviral drugs, the exogenous delivery of dsRNA for RNAi against plant viral diseases holds great promise. Here, we present an effective delivery approach of dsRNA utilizing graphene oxide nanosheets (GONs) on mature plant leaves via a spray. Our method achieves rapid and sustained gene knockdown, reducing the level of the target gene to 46% by day 2, and continuously releases dsRNA for at least 6 days. The coupling of GONs with specific fragments of coat protein and replicase gene dsRNA exhibited a superior antiviral effect compared to specific fragments of RNA-dependent replicase and movement protein. The coupling of GONs with the specific fragment of the replicase gene even has 87.2% protection against TMV. Moreover, the nanocomplex GONs@dsRNA can also stimulate plant immunity through bursts of reactive oxygen species without harming growth. Overall, our findings present a robust and convenient tool for plant virus control.

Mutually reinforcing and transpiration-dependent propagation of H2O2 and variation potential in plants revealed by fiber organic electrochemical transistors

Plants use hydrogen peroxide (H2O2) and variation potential (VP) waves as well as chemical transport by transpiration-driven xylem flow to facilitate cell signaling, cell-to-cell communication, and adaptation to environmental stresses. The underlying mechanisms and complex interplay among H2O2, VP, and transpiration are not clearly understood because of the lack of bioengineering tools for continuous in planta monitoring of the dynamic biological processes. Here, we tackle the challenge by developing microfiber-shaped organic electrochemical transistors (fOECTs) that can be threaded into the plants. The sensorized microfiber revealed that both H2O2 and VP waves propagate faster toward the leaves than toward the roots because of the directional long-distance transport of H2O2 in the xylem. In addition, the revealed interplays among VP, H2O2, and xylem flow strongly suggest a transpiration- and intensity-dependent H2O2-VP mutual-reinforcing propagation mechanism. The microfiber electronics offer a versatile platform for the in situ study of dynamic physiological processes in plants with high temporospatial resolution.

Nectar peroxide: assessing variation among plant species, microbial tolerance, and effects on microbial community assembly

Nectar contains antimicrobial constituents including hydrogen peroxide, yet it is unclear how widespread nectar hydrogen peroxide might be among plant species or how effective it is against common nectar microbes. Here, we surveyed 45 flowering plant species across 23 families and reviewed the literature to assess the field-realistic range of nectar hydrogen peroxide (Aim 1). We experimentally explored whether plant defense hormones increase nectar hydrogen peroxide (Aim 2). Further, we tested the hypotheses that variation in microbial tolerance to peroxide is predicted by the microbe isolation environment (Aim 3); increasing hydrogen peroxide in flowers alters microbial abundance and community assembly (Aim 4), and that the microbial community context affects microbial tolerance to peroxide (Aim 5). Peroxide in sampled plants ranged from undetectable to c3000 μM, with 50% of species containing less than 100 μM. Plant defensive hormones did not affect hydrogen peroxide in floral nectar, but enzymatically upregulated hydrogen peroxide significantly reduced microbial growth. Together, our results suggest that nectar peroxide is a common but not pervasive antimicrobial defense among nectar-producing plants. Microbes vary in tolerance and detoxification ability, and co-growth can facilitate the survival and growth of less tolerant species, suggesting a key role for community dynamics in the microbial colonization of nectar.

Recent progress in nanomaterial-based electrochemical biosensors for hydrogen peroxide detection & their biological applications

The electrochemical biosensor has brought a paradigm shift in the field of sensing due to its fast response and easy operability. The performance of electrochemical sensors can be modified by coupling them with various metal oxides, nanomaterials, and nanocomposites. Hydrogen peroxide is a short-lived reactive oxygen species that plays a crucial role in various physiological and biological processes. Therefore, its monitoring is of paramount importance. With this, the research fraternity has developed various nanomaterial-based superlative sensors that have enhanced the sensing performance towards H2O2 in terms of sensitivity, detection limit, and linear range. The integration of nanocomposite materials has allowed for the synergistic combination of different components, leading to improved sensor stability, selectivity, and detection limits. The precious metal alloys, metal oxides, semiconductor nanomaterials, carbon cloth, multi-walled carbon nanotubes, graphene oxide, and nanoparticles demonstrate effective catalytic performance for detecting H2O2 electrochemically. These advanced materials possess extraordinary properties and structures, rendering them highly advantageous for diverse applications. These biosensors aid in monitoring H2O2 levels secreted by MCF-7, HeLa cells, NIH-3T3, and A549 cells in real-time. Further, this type of biosensor identified alterations in H2O2 levels in the lungs, bronchoalveolar lavage fluid (BALF) of mice with pulmonary fibrosis, activated hepatic stellate cells, and the livers of mice with liver fibrosis. The current review highlights the recent advancements in compositions, morphology, limit of detection, sensitivity, biological applications, etc. properties of the electrochemical biosensors for H2O2 detection.

Extracellular ATP receptors P2Ks are involved in regulating local and systemic stomatal responses to local environmental stimuli

Extracellular ATP (exATP) and its receptors play important roles in the regulation of the responses of plants to environmental stimulation. The lectin receptor kinases I.9 (P2K1) and I.5 (P2K2) are known as the receptors of exATP in Arabidopsis thaliana. The change of stomata aperture can show adaptive relationships to the environmental conditions surrounding the plant. However, when plants are exposed to local environmental stimuli, whether the exATP level has the systemic characteristic change and regulates stomata aperture by binding its receptors is still poorly studied. The present work showed that local environmental stimuli (including wounding, high light stress, dark-to-light transition and heat stress) in Arabidopsis thaliana triggered an increase of exATP level not only in the local leaf but also in the systemic leaves. By using p2k1 single-mutant, p2k2 single-mutant, and p2k1/p2k2 double-mutant plants, it was found that the local environmental stimuli-induced stomatal response was weakened or attenuated not only in the local leaf but also in systemic leaves in P2Ks mutants. These results indicate that exATP/P2Ks are involved in regulating local and systemic stomatal responses to local environmental stimuli.

Machine learning modeling and response surface methodology driven antioxidant and anticancer activities of chitosan nanoparticle-mediated extracts of Bacopa monnieri

This study investigates the potential of chitosan nanoparticles (CNPs) in enhancing the bioavailability and efficacy of Bacopa monnieri extracts, known for their neuroprotective, antioxidant, and anticancer properties. Different concentrations of CNPs were added to the culture medium for in vitro shoot regeneration. Antioxidant activity (DPPH free radical scavenging and H2O2 removal assays) and cytotoxicity assay (LDH release and XTT viability) were performed. The results demonstrated the highest DPPH radical scavenging activity of 95.60 % at 125 μg/mL CNPs from methanol extract. Whereas, H2O2 scavenging activity increased with higher extract concentrations, and the maximum was recorded from methanol extract when used at 1000 μg/mL. Cytotoxicity assays revealed a dose-dependent increase in LDH activity and XTT reduction, and water-based extracts demonstrated the strongest cytotoxic effects. IC50 analysis indicated that CNP-enriched methanol and water extracts were significantly more cytotoxic to HeLa cells as compared to ethanol extracts. Response surface regression analysis and ML models confirmed the reliability of the experimental data, with the multilayer perceptron (MLP) model exhibiting the best predictive accuracy, followed by the random forest (RF) model. It can be concluded that CNP enrichment significantly improved the antioxidant and anticancer properties of B. monnieri extracts, highlighting the potential of CNP-based formulations for future studies.

Combination of magnesium and iron nanoparticles with biochar mitigated salt toxicity and altered antioxidant activity and essential oil production of chamomile

This research was conducted in a greenhouse to examine the effects of solid biochar (25 g kg-1 soil), and biochar-based nanoparticles of magnesium (BNP-MgO), iron (BNP-Fe3O4), and magnesium + iron (BNP-MgO + BNP-Fe3O4) in comparison with control (soil) on German chamomile (Matricaria chamomilla L.) under salinity levels (0.9, 6, and 12 dS m-1 as non-saline treatment and moderate and high salinities, respectively). Salinity increased sodium uptake, generation of reactive oxygen species and enzymatic and non-enzymatic antioxidant activities, leading to a reduction in leaf nutrients and pigments, and organs masses. High salinity significantly decreased the essential oil percentage and yield. However, solid and especially enriched biochars with BNP-MgO, BNP-Fe3O4, and their combined form reduced hydrogen peroxide and consequently enzymatic and non-enzymatic antioxidant activities under saline conditions. The BNP-MgO was the best treatment for enhancing leaf pigments, and the BNP-Fe3O4 was generally the best choice for improving organs masses and essential oil percentage and yield of chamomile under salinity. Therefore, solid and especially enriched biochars, due to their excellent physicochemical properties, were suggested as the suitable soil amendments to mitigate salt toxicity and improve the growth and essential oil production of medicinal plants in the greenhouse and field cultivations.

Plasma-activated water promotes and finely tunes arbuscular mycorrhizal symbiosis in Lotus japonicus

BACKGROUND

Plasma-activated water (PAW) is a recently developed cutting-edge technology that is increasingly gaining interest for its applications in medicine, food industry and agriculture. In plant biology, PAW has been shown to enhance seed germination, plant growth, and plant resilience against biotic and abiotic stresses. Despite increasing knowledge of the beneficial effects exerted by PAW on plants, little information is currently available about how this emerging technology may affect mutualistic plant-microbe interactions in the rhizosphere.

RESULTS

In this work we investigated the impact of irrigation with PAW, generated by a plasma torch, on arbuscular mycorrhizal (AM) symbiosis. Roots of the model legume Lotus japonicus expressing the bioluminescent Ca2+ reporter aequorin responded to treatment with PAW 5' (obtained by 5 min water exposure to plasma) with the immediate induction of cytosolic and nuclear Ca2+ signals, indicating that Ca2+-mediated signalling is one of the earliest cellular responses to PAW. The long-lasting elevations in intracellular Ca2+ levels were not found to alter cell viability. Quantitative analyses of AM fungal accommodation in the host plant roots along with phosphate accumulation in leaves, as well as chemical analysis of N, C, S in shoots, showed that treatments with PAW play a modulatory role on plant AM symbiotic performance, in a manner dependent on the time interval of water exposure to the plasma and on the duration of plant treatment with PAW. In particular, irrigation with PAW 5' increased fungal colonization after 4 weeks, leading to a significant increase in leaf phosphate content after 7 weeks.

CONCLUSIONS

Our findings reveal that PAW enhances AM symbiosis by facilitating early fungal accommodation in roots and subsequently increasing phosphate content in leaves at later stages. A better understanding of the mechanisms underlying the effects of PAW on the plant microbiome may drive research towards a fine-tuning of this novel green technology to maximize its beneficial effects in the context of a more sustainable agriculture.

The effect of H2O2 on elongation growth and oxidative stress in maize coleoptile cells treated with auxin and fusicoccin

The aim of this study was to evaluate the impact of hydrogen peroxide (H2O2) on the elongation growth of maize coleoptile cells induced by auxin (IAA) and fusicoccin (FC) according to the "acid growth theory". The key component of this process is PM H+-ATPase activity and the resulting proton extrusion. In order to complete this objective, measurements of coleoptile growth were made, pump activity was analyzed through changes in environmental pH and cell membrane potential, and the impact on oxidative stress in response to H2O2 was determined. It was found that although hydrogen peroxide restricts acid growth induced by both IAA and FC to a similar level, the PM H+-ATPase activity is inhibited differently. These findings indicate that in the presence of H2O2, the previously described wall-stiffening process might be the primary limiting factor in the elongation growth of maize coleoptile cells.

Redox signalling in the nucleus: shaping the epigenetic code

This article comments on:

De Smet B, Yang X, Plskova Z, Castell C, Fernández-Fernández A, Dard A, Masood J, Mhamdi A, Huang J, Vertommen D, Chan KX, Pyr dit Ruys S, Messens J, Kerchev PI, Van Breusegem F. 2025. The nuclear sulfenome of Arabidopsis: spotlight on histone acetyltransferase GCN5 regulation through functional thiols. Journal of Experimental Botany 76, 1569–1584. https://doi.org/10.1093/jxb/erae514

Rapid detection and imaging of methylglyoxal in plant tissues by the near-infrared fluorescent probe SWJT-2

Methylglyoxal (MG) can be produced via various pathways in plants. MG is toxic for plant cells at high levels, however it acts as a signaling molecule at low levels, just as H2O2 in plants. Therefore, MG detection is very important for investigating its roles in plant cells, especially in plants under environmental stresses. The near-infrared fluorescent probe SWJT-2 is a novel probe with high sensitivity for the rapid detection of MG in human HeLa cells, but at present it is not clear whether the probe can be used to determine MG levels in plant tissues. In this present research, we tried to apply the probe in plant research. Our results showed that 40 min treatment of SWJT-2 (80 μM) can be applied to the detection and imaging of MG levels in tobacco (Nicotiana benthamiana) tissues.

Overexpression of the patatin-related phospholipase A gene, PgpPLAIIIβ, in ginseng adventitious roots reduces lignin and ginsenoside content while increasing fatty acid content

The patatin-related phospholipase AIII (pPLAIII) gene family plays a crucial role in regulating cell elongation, cell wall composition, and lipid metabolism in plants, making it a promising target for agricultural and commercial innovations. This study provides a comprehensive functional analysis of PgpPLAIIIβ in Panax ginseng, a medicinal plant of substantial economic importance. Overexpression of PgpPLAIIIβ led to significant morphological changes, including shorter, thicker roots, and an 8% reduction in lignin content, while cellulose levels remained unaffected. The reduced lignification was attributed to the downregulation of key lignin biosynthetic genes and decreased hydrogen peroxide accumulation. A yeast two-hybrid assay identified a CCCH-type zinc finger protein as a potential PgpPLAIIIβ interactor, pointing to a mechanism that may underlie the changes in root structure and lignin deposition. Metabolite analysis revealed a 7.6% increase in total free fatty acid content, with notable increases in palmitic and linoleic acids, alongside a 28% reduction in ginsenoside levels, linked to the downregulation of triterpenoid biosynthetic genes. These findings demonstrate that PgpPLAIIIβ is a key regulator of root architecture, lignin composition, and secondary metabolite balance in ginseng. The metabolic engineering of PgpPLAIIIβ could be a powerful strategy to improve root traits, optimize lignin deposition, and enhance metabolite profiles, ultimately boosting the commercial and medicinal value of ginseng.

An integrative overview of cold response and regulatory pathways in horticultural crops

Global climate change challenges agricultural production, as extreme temperature fluctuations negatively affect crop growth and yield. Low temperature (LT) stress impedes photosynthesis, disrupts metabolic processes, and compromises the integrity of cell membranes, ultimately resulting in diminished yield and quality. Notably, many tropical or subtropical horticultural plants are particularly susceptible to LT stress. To address these challenges, it is imperative to understand the mechanisms underlying cold tolerance in horticultural crops. This review summarizes recent advances in the physiological and molecular mechanisms that enable horticultural crops to withstand LT stress, emphasizing discrepancies between horticultural crops and model systems. These mechanisms include C-repeat binding factor-dependent transcriptional regulation, post-translational modifications, epigenetic control, and metabolic regulation. Reactive oxygen species, plant hormones, and light signaling pathways are integrated into the cold response network. Furthermore, technical advances for improving cold tolerance are highlighted, including genetic improvement, the application of light-emitting diodes, the utility of novel plant growth regulators, and grafting. Finally, prospective directions for fundamental research and practical applications to boost cold tolerance are discussed.

Polyploidization leads to salt stress resilience via ethylene signaling in citrus plants

Polyploidization is a common occurrence in the evolutionary history of flowering plants, significantly contributing to their adaptability and diversity. However, the molecular mechanisms behind these adaptive advantages are not well understood. Through comprehensive phenotyping of diploid and tetraploid clones from Citrus and Poncirus genera, we discovered that genome doubling significantly enhances salt stress resilience. Epigenetic and transcriptomic analyses revealed that increased ethylene production in the roots of tetraploid plants was associated with hypomethylation and enhanced chromatin accessibility of the ACO1 gene. This increased ethylene production activates the transcription of reactive oxygen species scavenging genes and stress-related hormone biosynthesis genes. Consequently, tetraploid plants exhibited superior root functionality under salt stress, maintaining improved cytosolic K+/Na+ homeostasis. To genetically validate the link between salt stress resilience and ACO1 expression, we generated overexpression and knockout lines, confirming the central role of ACO1 expression regulation following genome doubling in salt stress resilience. Our work elucidates the molecular mechanisms underlying the role of genome doubling in stress resilience. We also highlight the importance of chromatin dynamics in fine-tuning ethylene gene expression and activating salt stress resilience pathways, offering valuable insights into plant adaptation and crop genome evolution.

CmTGA8-CmAPX1/CmGSTU25 regulatory model involved in trehalose induced cold tolerance in oriental melon seedlings

Plants have developed complex regulatory networks to adapt to various stresses, including cold stress. Trehalose (Tre), known as the "sugar of life," plays a crucial role in enhancing cold tolerance by triggering antioxidation. However, the underlying regulatory mechanisms remain unclear. This study examines the transcription factor gene CmTGA8, which is induced by Tre under normal and cold conditions in melon seedlings (Cucumis melo L.), through transcriptome analysis and RT-qPCR. Reverse genetic analyses showed that silencing CmTGA8 reduced ascorbate peroxidase (APX) and glutathione S-transferase (GST) activities, suppressed CmAPX1 and CmGSTU25 expression, and increased cold susceptibility in melon seedlings. Our previous reports illustrated that Tre treatment significantly induced the expression of respiratory burst oxidase homologues (CmRBOHD) gene, encoding NADPH oxidases responsible for generating apoplastic H2O2. Silencing CmRBOHD markedly inhibited CmTGA8, CmAPX1, and CmGSTU25 expression and reduced cold tolerance. Moreover, H2O2 treatment upregulated CmTGA8 expression, while the NADPH oxidase inhibitor diphenyleneiodonium (DPI) treatment downregulated it. Additionally, CmTGA8 physically interacted with CmAPX1 and CmGSTU25 to promote their expression. Silencing CmGSTU25 decreased GST activity and ferric reducing ability of plasma (FRAP), further increasing cold sensitivity. These findings identify a novel regulatory hierarchy of the H2O2-CmTGA8-CmAPX1/CmGSTU25 cascade in the Tre-mediated cold response pathway in melon seedlings.

Effects of reactive oxygen species on fruit ripening and postharvest fruit quality

Reactive oxygen species (ROS) serve as important signaling molecule, involved in numerous biological processes, particularly in the physiological changes associated with fruit ripening and postharvest handing. This review explores ROS key role in plant fruit ripening and postharvest quality. The mechanism of ROS production and degradation in maintaining ROS homeostasis are analyzed in detail. Fruit ripening is a complex and highly coordinated process involving physiological and biochemical changes. Studies have observed that the content of ROS, mainly hydrogen peroxide (H2O2), dynamically changes in various types of fruits during ripening. Furthermore, ROS have significant effects on fruit softening, color change, and other ripening processes. In addition, in the postharvest stage, the abnormal accumulation of ROS isclosely related to the decline in fruit quality and the occurrence of decay browning, which seriously affects the market value and shelf life of fruit. Overall, this review demonstrates the crucial role of ROS in regulating the ripening process and postharvest quality of fruit.

Apoplastic pH is a chemical switch for extracellular H2O2 signaling in abscisic acid-mediated inhibition of cotyledon greening

The apoplastic pH (pHApo) in plants is susceptible to environmental stimuli. However, the biological implications of pHApo variation have remained largely unknown. The universal stress phytohormone abscisic acid (ABA) as well as the major environmental stimuli drought and salinity were selected as representative cases to investigate how changes in pHApo relate to plant behaviors in Arabidopsis. Variations in pHApo negatively regulated the cotyledon greening inhibition to the universal stress hormone ABA or environmental stimuli through the action of extracellular hydrogen peroxide (eH2O2). Further studies revealed that an increase in pHApo diminishes the chemical reactivity of eH2O2, effectively functioning as an 'off' switch for its action in oxidizing thiols of plasma membrane proteins. Consequently, this suppresses the eH2O2-mediated cotyledon greening inhibition to environmental stimuli and ABA, alongside inhibiting the eH2O2-mediated intracellular Ca2+ signaling. Conversely, a decrease in pHApo serves as an 'on' switch for the action of eH2O2. In summary, the pHApo is a crucial messenger and chemical switch for eH2O2 in signal transduction, notwithstanding the apparent simplicity of the underlying mechanism. Our findings provide a novel fundamental biological insight into the significance of pH.

The synergistic impact of Spirulina and Sulfate reducing bacteria on lettuce growth in Cadmium contaminated soil

Cadmium (Cd) contamination is a critical environmental issue, adversely affecting plant growth and agricultural productivity. While numerous studies have explored the role of various bacteria in mitigating heavy metal toxicity, the specific impacts of sulfate-reducing bacteria ( Desulfovibrio desulfuricans, SRB) and the cyanobacterium Spirulina (Arthrospira platensis, SP), both individually and in combination, on Cd-contaminated plants remain underexplored. This study investigates the effects of SRB and SP on lettuce plants exposed to Cd contamination, aiming to enhance our understanding of their potential in alleviating Cd toxicity and promoting plant health. Results revealed that Cd contamination significantly reduced root growth in all treatments except for the combined application of SRB and SP. This combination also led to a marked decrease in leaf Cd content and improved leaf area, particularly under Cd stress. Furthermore, SP and SRB together increased the relative water content in contaminated soils, and SRB alone induced hydrogen peroxide production in non-contaminated soils. The co-application of SRB and SP significantly boosted catalase and superoxide dismutase activities, enhancing photosynthetic capacity and overall plant growth under Cd stress. These findings underscore the promising potential of using SRB and SP synergistically to mitigate Cd-induced challenges in lettuce cultivation, offering a viable strategy to improve crop productivity in contaminated environments.

Ca2+-dependent H2O2 response in roots and leaves of barley - a transcriptomic investigation

BACKGROUND

Ca2+ and H2O2 are second messengers that regulate a wide range of cellular events in response to different environmental and developmental cues. In plants, stress-induced H2O2 has been shown to initiate characteristic Ca2+ signatures; however, a clear picture of the molecular connection between H2O2-induced Ca2+ signals and H2O2-induced cellular responses is missing, particularly in cereal crops such as barley. Here, we employed RNA-seq analyses to identify transcriptome changes in roots and leaves of barley after H2O2 treatment under conditions that inhibited the formation of cytosolic Ca2+ transients. To that end, plasma membrane Ca2+ channels were blocked by LaCl3 application prior to stimulation of barley tissues with H2O2.

RESULTS

We examined the expression patterns of 4246 genes that had previously been shown to be differentially expressed upon H2O2 application. Here, we further compared their expression between H2O2 and LaCl3 + H2O2 treatment. Genes showing expression patterns different to the previous study were considered to be Ca2+-dependent H2O2-responsive genes. These genes, numbering 331 in leaves and 1320 in roots, could be classified in five and four clusters, respectively. Expression patterns of several genes from each cluster were confirmed by RT-qPCR. We furthermore performed a network analysis to identify potential regulatory paths from known Ca2+-related genes to the newly identified Ca2+-dependent H2O2 responsive genes, using the recently described Stress Knowledge Map. This analysis indicated several transcription factors as key points of the responses mediated by the cross-talk between H2O2 and Ca2+.

CONCLUSION

Our study indicates that about 70% of the H2O2-responsive genes in barley roots require a transient increase in cytosolic Ca2+ concentrations for alteration in their transcript abundance, whereas in leaves, the Ca2+ dependency was much lower at about 33%. Targeted gene analysis and pathway modeling identified not only known components of the Ca2+ signaling cascade in plants but also genes that are not yet connected to stimuli-associated signaling. Potential key transcription factors identified in this study can be further analyzed in barley and other crops to ultimately disentangle the underlying mechanisms of H2O2-associated signal transduction mechanisms. This could aid breeding for improved stress resistance to optimize performance and productivity under increasing climate challenges.

Deciphering Antioxidant Responses in Tomato Autografts

Grafting is a horticultural technique that involves a healing process that requires grafted plants to develop physiological responses to overcome oxidative stress. In this study, oxidative damage, total antioxidant capacity and antioxidant enzymatic activities were analysed in functional and non-functional tomato autografts for eight days after grafting, considering scion and rootstock tissues separately. The results showed that oxidative damage, measured as lipid peroxidation, was controlled, especially in functional grafts. Scion tissues showed significant increases in total antioxidant capacity and activities of key antioxidant enzymes, including superoxide dismutase and catalase. Non-functional grafts showed elevated levels of class III peroxidase, potentially related to defensive suberisation and lignification. Principal component analysis revealed that antioxidant activities correlated dynamically with grafting stages, highlighting their critical role in stress mitigation. These results suggest that an efficient and asymmetric antioxidant response is essential for successful graft healing in tomato plants. Furthermore, different patterns in non-functional grafts underline the importance of redox balance in determining graft success.

Biomass-based carbon dot-modified cerium oxide nanoparticles (BCDs@CeO2) efficiently promote Myriophyllum aquaticum to remove NH4+-N and TP in eutrophic water

Aquatic plants are widely used for eutrophication remediation. However, strong abiotic plant stress often limits their remediation efficiency. This study proposed biomass-based carbon dot-modified cerium oxide nanoparticles (BCDs@CeO2) with good biocompatibility to mitigate abiotic plant stress. The BCDs@CeO2 pretreated Myriophyllum aquaticum exhibited enhanced removal rates of NH4+-N and TP, with the 10 mg/L BCDs@CeO2 treatment showing increases of 39.23 % and 29.11 %, respectively, compared to the pure water-precultured plant system (p < 0.05). Plant physiological changes and transcriptomic analysis revealed that BCDs@CeO2 treatment upregulated glycolysis/gluconeogenesis and α-linolenic acid metabolism pathways in rhizomes, inducing increased ATP synthase and antioxidant enzyme (Peroxidase, Catalase, and Superoxide Dismutase) activities, and enhancing amino acid metabolism, which further boosted Glutamine Synthetase activity and promoted NH4+-N and TP absorption and utilization. ICP-MS and microscopic analysis confirmed the uptake and migration of BCDs@CeO2 in plants. In summary, this study provides an effective strategy to enhance eutrophication phytoremediation.

Mitochondrial AOX1a and an H2O2 feed-forward signalling loop regulate flooding tolerance in rice

Flooding is a widespread natural disaster that causes tremendous yield losses of global food production. Rice is the only cereal capable of growing in aquatic environments. Direct seeding by which seedlings grow underwater is an important cultivation method for reducing rice production cost. Hypoxic germination tolerance and root growth in waterlogged soil are key traits for rice adaptability to flooded environments. Alternative oxidase (AOX) is a non-ATP-producing terminal oxidase in the plant mitochondrial electron transport chain, but its role in hypoxia tolerance had been unclear. We have discovered that AOX1a is necessary and sufficient to promote germination/coleoptile elongation and root development in rice under flooding/hypoxia. Hypoxia enhances endogenous H2O2 accumulation, and H2O2 in turn activates an ensemble of regulatory genes including AOX1a to facilitate the conversion of deleterious reactive oxygen species to H2O2 in rice under hypoxia. We show that AOX1a and H2O2 act interdependently to coordinate three key downstream events, that is, glycolysis/fermentation for minimal ATP production, root aerenchyma development and lateral root emergence under hypoxia. Moreover, we reveal that ectopic AOX1a expression promotes vigorous root and plant growth, and increases grain yield under regular irrigation conditions. Our discoveries provide new insights into a unique sensor-second messenger pair in which AOX1a acts as the sensor perceiving low oxygen tension, while H2O2 accumulation serves as the second messenger triggering downstream root development in rice against hypoxia stress. This work also reveals AOX1a genetic manipulation and H2O2 pretreatment as potential targets for improving flooding tolerance in rice and other crops.

Zinc oxide seed priming enhances drought tolerance in wheat seedlings by improving antioxidant activity and osmoprotection

Drought can affect all growth stages and has a significant effect on seed germination, which affects all physiological and metabolic germination processes. It also leads to dehydration, which increases the oxidation of lipids and membranes and disrupts the functioning of biomolecules in plants. Zinc is an essential element for several enzymes involved in metabolism, cell elongation, preservation of the strength and integrity of cell membranes, seed development, and resistance to environmental stress. A pot experiment was conducted to determine how ZnO seed priming, either in the form of ZnO NPs (nanopriming) or ZnO bulk priming (60 mg L- 1), counteracts the negative impacts of drought at different levels (80% and 60% FC) on wheat (Triticum aestivum L.) seedlings at the seedling stage. A recent experiment revealed that seed priming agents significantly mitigate the negative effects of drought stress, especially at 60% FC, by positively influencing various parameters of wheat seedlings. Notably, the POD activity increased by 91.8% and 289.9% for the shoots, 218.6% and 261.6% for the roots, the phenolic content increased by 194.4% for the shoots and 1139.6% for the roots, the H2O2 scavenging percentage increased by 124.9% and 135.4% for the shoots and 147.6% for the roots, and the lipid peroxidation inhibition percentage increased by 320.6% and 433% for the shoots. Moreover, the utilization of seed priming agents had a profound effect on free amino acids (393.8%, 502.8% for roots) and soluble carbohydrates (183.4% for roots) compared with those in stressed seedlings without priming. Experimental and computational methods (time-dependent density functional theory (TD-DFT)) were employed to perform IR and XRD analyses of the isolated molecules of the ZnO NPs/Iso. In conclusion, the application of ZnO NPs or bulk ZnO was found to create effective mechanical and physiological barriers, as confirmed by the analysis of antioxidant enzyme activities, nonenzymatic components, free radical scavenging, and osmoprotectant constituents.

Enzyme Biosensor Based on 3D-Printed Flow-Through Reactor Modified with Thiacalixarene-Functionalized Oligo (Lactic Acids)

Electrochemical enzyme biosensors are extensively utilized in clinical analysis and environmental monitoring, yet achieving effective enzyme immobilization while maintaining high activity remains a challenge. In this work, we developed a flow-through enzyme biosensor system using a 3D-printed flow-through electrochemical cell fabricated from commercially available poly (lactic acid). After modification with thiacalixarene-functionalized oligo (lactic acids) (OLAs), the material enabled efficient immobilization of uricase on the inner surface of a replaceable reactor of the cell. Swelling and hydrolytic stability of OLAs in cone, partial cone, and 1,3-alternate conformations were studied, with 1,3-alernate conformation demonstrating superior stability and enzyme immobilization performance. The use of OLAs enhanced immobilization efficiency by over 30% and protected the reactor from swelling, hydrolytic degradation, and enzyme loss. The biosensor was validated for amperometric uric acid determination, with a screen-printed carbon electrode modified with carbon black and Prussian Blue. This modification reduced the cathodic potential for uric acid detection to -0.05 V. The biosensor exhibited a linear detection range of 10 nM to 30 μM with a detection limit of 7 nM, and it performed effectively in artificial urine and synthetic blood plasma. The novel cell design, featuring easy assembly and low-cost replaceable parts, makes this biosensor a promising candidate for routine clinical analysis and other practical applications.

Insights of cellular and molecular changes in sugarcane response to oxidative signaling

MAIN CONCLUSION

Significant changes in the proteome highlight essential metabolic adaptations for development and oxidative signaling induced by the treatment of young sugarcane plants with hydrogen peroxide. These adaptations suggest that hydrogen peroxide acts not only as a stressor but primarily as a signaling molecule, triggering specific metabolic pathways that regulate growth and plant resilience. Sugarcane is a crucial crop for sugar and ethanol production, often influenced by environmental signals. Hydrogen peroxide (H2O2) is increasingly recognized as an important signaling molecule that regulates plant development and adaptation. In this study, two-month-old sugarcane plants were treated with varying concentrations of H2O2 to investigate how this molecule acts as a signal at the cellular, biochemical, and proteomic levels. Antioxidant enzyme activity exhibited fluctuations, suggesting a dynamic response to oxidative signaling. Lipid peroxidation, observed through TBARs and scanning electron microscopy, highlighted early membrane modifications. Proteomic analysis (ProteomeXchange PXD048142) identified 2,699 proteins, with 155 showing significant expression changes in response to H2O2 signaling. Bioinformatics, including Principal Component Analysis, revealed distinct proteomic profiles in roots and leaves, indicating tissue-specific metabolic reprogramming. Functional annotation through Gene Ontology and KEGG pathway enrichment showed that oxidative signaling led to the repression of photosynthesis-related pathways in leaves, while promoting pathways related to protein processing, glycolysis, and carbon metabolism in roots. Additionally, bioinformatic tools identified proteins involved in amino acid metabolism, the TCA cycle, and carbohydrate metabolism as critical components of sugarcane's adaptive signaling response. The data suggest that sugarcane plants responded to oxidative signals by adjusting their metabolic networks, promoting sustained development and potential pathways for targeted plant breeding.

The AP2/ERF Transcription Factor ERF56 Negatively Regulating Nitrate-Dependent Plant Growth in Arabidopsis

ERF56, a member of the APETALA2/ETHYLENE-RESPONSIVE FACTOR (AP2/ERF) transcription factor (TF) family, was reported to be an early nitrate-responsive TF in Arabidopsis. But the function of ERF56 in nitrate signaling remains not entirely clear. This study aimed to investigate the role of ERF56 in nitrate-dependent plant growth and nitrate signaling. We confirmed with reverse transcription quantitative PCR (RT-qPCR) that the transcription of ERF56 is quickly induced by nitrate. ERF56 overexpressors displayed decreased nitrate-dependent plant growth, while erf56 mutants exhibited increased plant growth. Confocal imaging demonstrated that ERF56 is localized into nuclei. Assays with the glucuronidase (GUS) reporter showed that ERF56 is mainly expressed at the region of maturation of roots and in anthers. The dual-luciferase assay manifested that the transcription of ERF56 is not directly regulated by NIN-LIKE PROTEIN 7 (NLP7). The transcriptome analysis identified 1038 candidate genes regulated by ERF56 directly. A gene ontology (GO) over-representation analysis showed that ERF56 is involved in the processes of water transport, inorganic molecule transmembrane transport, secondary metabolite biosynthesis, and cell wall organization. We revealed that ERF56 represses nitrate-dependent growth through regulating the processes of inorganic molecule transmembrane transport, the secondary metabolite biosynthesis, and cell wall organization.

The MADS-box gene XAANTAL1 participates in Arabidopsis thaliana primary root growth and columella stem cell patterns in response to ROS, via direct regulation of PEROXIDASE 28 and RETINOBLASTOMA-RELATED genes

The balance between cell growth, proliferation, and differentiation emerges from gene regulatory networks coupled to various signal transduction pathways, including reactive oxygen species (ROS) and transcription factors (TFs), enabling developmental responses to environmental cues. The primary root of Arabidopsis thaliana has become a valuable system for unravelling such networks. Recently, the role of TFs that mediate ROS inhibition of primary root growth has begun to be characterized. This study demonstrates that the MADS-box TF gene XAANTAL1 (XAL1) is an essential regulator of hydrogen peroxide (H2O2) in primary root growth and root stem cell niche identity. Interestingly, our findings indicated that XAL1 acts as a positive regulator of H2O2 concentration in the root meristem by directly regulating genes involved in oxidative stress response, such as PEROXIDASE 28 (PER28). Moreover, we found that XAL1 is necessary for the H2O2-induced inhibition of primary root growth through the negative regulation of peroxidase and catalase activities. Furthermore, XAL1, in conjunction with RETINOBLASTOMA-RELATED (RBR), is essential for positively regulating the differentiation of columella stem cells and for participating in primary root growth inhibition in response to oxidative stress induced by H2O2 treatment.

ERD14 regulation by the HY5- or HY5-MED2 module mediates the cold signal transduction of asparagus bean

Cold stress affects the growth, development, and yield of asparagus bean (Vigna unguiculata subsp. sesquipedalis). Mediator (MED) complex subunits regulate the cold tolerance of asparagus bean, but the underlying regulatory mechanisms remain unclear. Here, VunMED2 positively responds to cold stress of asparagus beans. Under cold acclimation and freezing treatment, the survival rate, ROS scavenging activity, and expression levels of VunMED2 were increased in VunMED2 transgenic plants. Natural variation in the promoter of VunMED2 in two different cold-tolerant asparagus beans was observed. Under cold stress, the expression of the GUS reporter gene was higher in cold-tolerant plants than in cold-sensitive plants, and the expression of the GUS reporter gene was tissue-specific. VunHY5 positively influenced the expression of VunMED2 by binding to the E-box motif, and the transcriptional activation of the promoter was stronger in the cold-tolerant variety than in cold-sensitive plants. VunHY5 overexpression improved plant freezing resistance by increasing the antioxidant capacity and expression of dehydrin genes. VunHY5 and VunMED2 play a synergistic role in binding to the G-box/ABRE motif and transcriptionally activating the expression of VunERD14. VunERD14 complemented the med2 mutant, which could positively respond to plant freezing resistance by reducing membrane lipid peroxidation and improving the antioxidant capacity. Therefore, the VunHY5-VunERD14 module and the VunHY5-VunMED2-VunERD14 positive cascade effect are involved in the cold signal transduction in asparagus bean. Our findings have implications for the breeding of asparagus bean varieties with improved cold tolerance.

OsBRW1, a novel blast-resistant gene, coded a NBS-LRR protein to interact with OsSRFP1 to balance rice growth and resistance

It is urgent to mine novel blast-resistant genes in rice and develop new rice varieties with pyramiding blast-resistant genes. In this study, a new blast-resistant gene, OsBRW1, was screened from a set of rice near-isogenic lines (NILs) with different blast-resistant ability. Under the infection of Magnaporthe oryzae (M. oryzae), OsBRW1 in the resistant NIL Pi-4b was highly induced than that in the susceptible NIL Pi-1 and their parent line CO39, and the blast-resistant ability of OsBRW1 was further confirmed by using CRISPR/Cas9 knockout and over-expression methods. The protein encoded by OsBRW1 was a typical NBS-LRR with NB-ARC domain and localized in both cytoplasm and nucleus, and the transient expression of OsBRW1 was capable of triggering hypersensitive response in tobacco leaves. Protein interaction experiments showed that OsBRW1 protein directly interacted with OsSRFP1. At the early infection stage of M. oryzae, OsBRW1 gene induced OsSRFP1 to highly expression level and accumulated H2O2, up-regulated the defence responsive signalling transduction genes and the pathogenesis-related genes and increased JA and SA content in the resistant NIL Pi-4b. By contrary, lower content of endogenous JA and SA in osbrw1 mutants was found at the same stage. After that, OsSRFP1 was down-regulated to constitution abundance to balance the growth of the resistant NIL Pi-4b. In summary, OsBRW1 solicited OsSRFP1 to resist the infection of blast fungus in rice by inducing the synergism of induced systemic resistance (ISR) and system acquired resistance (SAR) and to balance the growth of rice plants.

The promotive and repressive effects of exogenous H2O2 on Arabidopsis seed germination and seedling establishment depend on application dose

Hydrogen peroxide (H2O2) displays significant and dual effects on seed germination and seedling development, depending on the application dosage. However, the definition of H2O2 thresholds and the mechanisms underlying the dual actions in Arabidopsis seed germination and seedling development are not yet clear. Here, we analyzed the Arabidopsis seed germination profiles in response to different concentrations of exogenous H2O2 and found that 2 mM functions as the key threshold, above this threshold, both seed germination and seedling establishment were gradually inhibited. By RNA-seq analysis and function verification, we identified pathways of abscisic acid (ABA) signalling, seed post-ripening, energy metabolism, ROS homeostasis, and cell wall loosening play positive roles in seed germination and seedling establishment downstream of the H2O2 signalling. Further physio-chemical approaches revealed that exogenous H2O2 affected the accumulation and distribution of O2 •- and H2O2 in embryonic tissues by regulating the tissue-specific expression of SDH2-3, RHD2, and PRXs. Collectively, we found that germination rate and aerial growth were positively correlated with endogenous H2O2 content and root length was positively correlated with O2 •- accumulation, demonstrating that different ROS signals played specific functions in different tissues and development processes. On the other hand, excessive H2O2 (10 mM) represses these two processes for radicle cell damage caused by oxidation stress. Finally, we put forward the mechanism model of the dual effects of exogenous H2O2 on seed germination and seedling establishment.

Proline and ROS: A Unified Mechanism in Plant Development and Stress Response?

The proteinogenic amino acid proline plays crucial roles in both plant development and stress responses, far exceeding its role in protein synthesis. However, the molecular mechanisms and the relative importance of these additional functions of proline remain under study. It is well documented that both stress responses and developmental processes are associated with proline accumulation. Under stress conditions, proline is believed to confer stress tolerance, while under physiological conditions, it assists in developmental processes, particularly during the reproductive phase. Due to proline's properties as a compatible osmolyte and potential reactive oxygen species (ROS) scavenger, most of its beneficial effects have historically been attributed to the physicochemical consequences of its accumulation in plants. However, emerging evidence points to proline metabolism as the primary driver of these beneficial effects. Recent reports have shown that proline metabolism, in addition to supporting reproductive development, can modulate root meristem size by controlling ROS accumulation and distribution in the root meristem. The dynamic interplay between proline and ROS highlights a sophisticated regulatory network essential for plant resilience and survival. This fine-tuning mechanism, enabled by the pro-oxidant and antioxidant properties of compartmentalized proline metabolism, can modulate redox balance and ROS homeostasis, potentially explaining many of the multiple roles attributed to proline. This review uniquely integrates recent findings on the dual role of proline in both ROS scavenging and signaling, provides an updated overview of the most recent research published to date, and proposes a unified mechanism that could account for many of the multiple roles assigned to proline in plant development and stress defense. By focusing on the interplay between proline and ROS, we aim to provide a comprehensive understanding of this proposed mechanism and highlight the potential applications in improving crop resilience to environmental stress. Additionally, we address current gaps in understanding and suggest future research directions to further elucidate the complex roles of proline in plant biology.

Aquaporin CmPIP2;3 links H2O2 signal and antioxidation to modulate trehalose-induced cold tolerance in melon seedlings

Cold stress severely restricts the growth and development of cold-sensitive crops. Trehalose (Tre), known as the "sugar of life", plays key roles in regulating plant cold tolerance by triggering antioxidation. However, the relevant regulatory mechanism remains unclear. Here, we confirmed that Tre triggers apoplastic hydrogen peroxide (H2O2) production and thus plays key roles in improving the cold tolerance of melon (Cucumis melo var. makuwa Makino) seedlings. Moreover, Tre treatment can promote the transport of apoplastic H2O2 to the cytoplasm. This physiological process may depend on aquaporins. Further studies showed that a Tre-responsive plasma membrane intrinsic protein 2;3 (CmPIP2;3) had strong H2O2 transport function and that silencing CmPIP2;3 significantly weakened apoplastic H2O2 transport and reduced the cold tolerance of melon seedlings. Yeast library and protein-DNA interaction technology were then used to screen 2 Tre-responsive transcription factors, abscisic acid-responsive element (ABRE)-binding factor 2 (CmABF2) and ABRE-binding factor 3 (CmABF3), which can bind to the ABRE motif of the CmPIP2;3 promoter and activate its expression. Silencing of CmABF2 and CmABF3 further dramatically increased the ratio of apoplastic H2O2/cytoplasm H2O2 and reduced the cold tolerance of melon seedlings. This study uncovered that Tre treatment induces CmABF2/3 to positively regulate CmPIP2;3 expression. CmPIP2;3 subsequently enhances the cold tolerance of melon seedlings by promoting the transport of apoplastic H2O2 into the cytoplasm for conducting redox signals and stimulating downstream antioxidation.

ROS, an Important Plant Growth Regulator in Root Growth and Development: Functional Genes and Mechanism

Roots are fundamental to the growth, development, and survival of plants. Beyond anchoring the plant, roots absorb water and nutrients, supporting the plant's ability to grow and function normally. Root systems, originating from the apical meristem, exhibit significant diversity depending on the plant species. ROS are byproducts of aerobic metabolism, present in both above- and below-ground plant tissues. While ROS were once considered merely harmful byproducts of oxygen metabolism, they are now recognized as critical signaling molecules that regulate plant growth and development. Under stress conditions, plants produce elevated levels of ROS, which can inhibit growth. However, moderate ROS levels act as signals that integrate various regulatory pathways, contributing to normal plant development. However, there is still a lack of comprehensive and systematic research on how ROS precisely regulate root growth and development. This review provides an overview of ROS production pathways and their regulatory mechanisms in plants, with a particular focus on their influence on root development.

Ecotoxicological effects of paracetamol on the biochemical and molecular responses of spinach (Spinacia oleracea L.)

The widespread use of pharmaceuticals, including paracetamol, has raised concerns about their impact on the environment and non-target species. The aim of this study was to investigate the biochemical and molecular responses of Spinacia oleracea (spinach) to high paracetamol concentrations in order to understand the plant's stress responses and underlying mechanisms. Under controlled conditions, spinach plants were exposed to different paracetamol concentrations (0, 50, 100, and 200 mg/L). The study evaluated the impact of paracetamol exposure on biochemical parameters such as oxidative stress markers (H2O2, MDA), activities of antioxidant enzymes (APX, CAT, GPOD, SOD), levels of non-enzymatic components (phenolics and flavonoids), and phytohormones (ABA, SA, and IAA). Furthermore, the study assessed molecular impacts by analyzing stress-related genetic variation and alterations in the gene expression of the antioxidant enzymes. Results showed that paracetamol exposure significantly increased oxidative stress in spinach, which was evident through the elevated H2O2 and MDA levels. However, the antioxidant defense mechanisms were activated to counteract this effect, as evidenced by increased activity of antioxidant enzymes and higher phenolics and flavonoid levels. Moreover, induction in the phytohormone levels indicated a stress response in paracetamol-treated plants compared to control plants. RAPD analysis revealed polymorphism indicating the DNA damage, and the Real-time qRT-PCR method showed significant upregulation of stress-responsive genes, highlighting the severe impact of paracetamol at the molecular level. The study concludes that high paracetamol concentrations pose a significant threat to spinach growth by affecting both biochemical and molecular processes. These findings underscore the need for strict environmental management practices to mitigate the possible impact of continuous release, accumulation, and long-term exposure of pharmaceutical contaminants to the environment and implement policies to reduce pharmaceutical pollutants to preserve ecological health and biodiversity.

Superoxide dismutase positively regulates Cu/Zn toxicity tolerance in Sorghum bicolor by interacting with Cu chaperone for superoxide dismutase

Heavy metal stress threatens plant growth and productivity. In this study, we investigated the effects of CuSO4 and ZnSO4 toxicity on sorghum seedlings, focusing on their impact on biomass, germination rates, growth parameters, antioxidant enzyme activities, gene expression profiles, and stress resistance mechanisms. As a result, eight sorghum superoxide dismutase (SOD) genes were identified, and their evolutionary relationships with cis-acting regulatory elements and their expressional patterns were evaluated. Integrating transcriptomic data revealed a key SOD member SbCSD1 that might contribute to plant abiotic stress resistance. Furthermore, SbCSD1 overexpression enhanced plant tolerance to CuSO4 and ZnSO4 stress by regulating SOD activity and interacting with copper chaperone for superoxide dismutase 1 (CCS1) in the plant nucleus and cytoplasm. Meanwhile, silencing CCS1 in SbCSD1-overexpressing plants revealed that SbCSD1 and CCS1 synergistically contribute to Cu stress tolerance. By integrating transcriptomic and genetic data, herein we provide novel insights into the orchestration of plant responses to heavy-metal stress in sorghum by SOD.

A sensitive and reliable method for the quantitative determination of hydrogen peroxide produced by microalgae cells

One of the reactive forms of oxygen is hydrogen peroxide (H2O2), which has been investigated as a key component of growth processes and stress responses. Different methods for the determination of H2O2 production by animal and bacterial cells exist; however, its detection in algal cell cultures is more complicated due to the presence of photosynthetic pigments in the cells and the complex structure of cell walls. Considering these issues, a reliable, quick, and simple method for H2O2 detection is needed in phycological research. The aim of this methodological study was to optimize an Amplex UltraRed method for the fluorometric detection of H2O2 produced by microalgae cells, using a wild-type strain of Chlamydomonas reinhardtii as a model. The results showed that (i) potassium phosphate is the most suitable reaction buffer for this method, (ii) a 560 nm wavelength variant is the most appropriate as the excitation wavelength for fluorescence spectra measurement, (iii) a 50:50 ratio for the reaction mixture to sample was the most suitable, (iv) the fluorescence signal was significantly influenced by the density of the microalgae biomass, and (v) sample fortification with H2O2 allowed for an increase of the method's reliability and repeatability. The proposed protocol of the Amplex UltraRed method for the fluorometric detection of H2O2 produced by microalgae cells can yield a sensitive and accurate determination of the content of the test compound, minimizing measurement errors, eliminating chlorophyll autofluorescence problem, and compensating for the matrix effect. This method can be applied to the study of other microalgae species.

A gene cluster for polyamine transport and modification improves salt tolerance in tomato

Polyamines act as protective compounds directly protecting plants from stress-related damage, while also acting as signaling molecules to participate in serious abiotic stresses. However, the molecular mechanisms underlying these effects are poorly understood. Here, we utilized metabolome genome-wide association study to investigate the polyamine content of wild and cultivated tomato accessions, and we discovered a new gene cluster that drove polyamine content during tomato domestication. The gene cluster contains two polyphenol oxidases (SlPPOE and SlPPOF), two BAHD acyltransferases (SlAT4 and SlAT5), a coumaroyl-CoA ligase (Sl4CL6), and a polyamine uptake transporter (SlPUT3). SlPUT3 mediates polyamine uptake and transport, while the five other genes are involved in polyamine modification. Further salt tolerance assays demonstrated that SlPPOE, SlPPOF, and SlAT5 overexpression lines showed greater phenolamide accumulation and salt tolerance as compared with wild-type (WT). Meanwhile, the exogenous application of Spm to SlPUT3-OE lines displayed salt tolerance compared with WT, while having the opposite effect in slput3 lines, confirms that the polyamine and phenolamide can play a protective role by alleviating cell damage. SlPUT3 interacted with SlPIP2;4, a H2O2 transport protein, to maintain H2O2 homeostasis. Polyamine-derived H2O2 linked Spm to stress responses, suggesting that Spm signaling activates stress response pathways. Collectively, our finding reveals that the H2O2-polyamine-phenolamide module coordinately enhanced tomato salt stress tolerance and provide a foundation for tomato stress-resistance breeding.

Cyclophosphamide-Induced Infertility and the Impact of Antioxidants

An important drawback of anticancer chemotherapy is the harm it causes to healthy cells. Cyclophosphamide (CP) is a widely used chemotherapeutic alkylating agent that is regularly used in cancer treatment. However, it can cause severe side effects, including genotoxicity, due to its ability to damage DNA. This toxicity is thought to be associated with oxidative stress induced by an excessive amount of reactive oxygen species (ROS). Therefore, there is a specific focus on the potential effects of anticancer treatments on fertility. Due to the increasing life expectancy of cancer patients, those desiring parenthood may face the negative impacts of therapies. Utilizing substances with antioxidant and cytoprotective characteristics to protect the reproductive system from harmful consequences during chemotherapy would be highly beneficial. This review introduces the physiological and pathological roles of ROS in the reproductive systems of both males and females, then we address the adverse effects of CP administration on infertility and discuss how antioxidants can reverse these effects.

Integrative transcriptomic analysis reveals the molecular responses of tobacco to magnesium deficiency

Introduction

Magnesium (Mg) is a crucial macronutrient for plants. Understanding the molecular responses of plants to different levels of Mg supply is important for improving cultivation practices and breeding new varieties with efficient Mg utilization.

Methods

In this study, we conducted a comprehensive transcriptome analysis on tobacco (Nicotiana tabacum L.) seedling leaves to investigate changes in gene expression in response to different levels of Mg supply, including Mg-deficient, 1/4-normal Mg, normal Mg, and 4×-normal Mg, with a particular focus on Mg deficiency at 5, 15 and 25 days after treatment (DAT), respectively.

Results

A total of 11,267 differentially expressed genes (DEGs) were identified in the Mg-deficient, 1/4-normal Mg, and/or 4×-normal Mg seedlings compared to the normal Mg seedlings. The global gene expression profiles revealed potential mechanisms involved in the response to Mg deficiency in tobacco leaves, including down-regulation of genes-two DEGs encoding mitochondria-localized NtMGT7 and NtMGT9 homologs, and one DEG encoding a tonoplast-localized NtMHX1 homolog-associated with Mg trafficking from the cytosol to mitochondria and vacuoles, decreased expression of genes linked to photosynthesis and carbon fixation at later stages, and up-regulation of genes related to antioxidant defenses, such as NtPODs, NtPrxs, and NtGSTs.

Discussion

Our findings provide new insights into the molecular mechanisms underlying how tobacco responds to Mg deficiency.

Photorespiratory Metabolism and Its Regulatory Links to Plant Defence Against Pathogens

When plants face biotic stress, the induction of defence responses imposes a massive demand for carbon and energy resources, which could decrease the reserves allocated towards growth. These growth-defence trade-offs have important implications for plant fitness and productivity and influence the outcome of plant-pathogen interactions. Biotic stress strongly affects plant cells' primary metabolism, including photosynthesis and respiration, the main source of energy and carbon skeletons for plant growth, development, and defence. Although the nature of photosynthetic limitations imposed by pathogens is variable, infection often increases photorespiratory pressure, generating conditions that promote ribulose-1,5-bisphosphate oxygenation, leading to a metabolic shift from assimilation to photorespiration. Photorespiration, the significant metabolic flux following photosynthesis, protects the photosynthetic apparatus from photoinhibition. However, recent studies reveal that its role is far beyond photoprotection. The intermediates of the photorespiratory cycle regulate photosynthesis, and photorespiration interacts with the metabolic pathways of nitrogen and sulphur, shaping the primary metabolism for stress responses. This work aims to present recent insights into the integration of photorespiration within the network of primary metabolism under biotic stress. It also explores the potential implications of regulating photosynthetic-photorespiratory metabolism for plant defence against bacterial and fungal pathogens.

Transcriptome analysis to identify genes related to programmed cell death resulted from manipulating of BnaFAH ortholog by CRISPR/Cas9 in Brassica napus

Fumarylacetoacetate hydrolase (FAH) catalyzes the final step of the tyrosine degradation pathway. In this study, we isolated and characterized two homologous BnaFAH genes in Brassica napus L. variant Westar, and then used CRISPR/Cas9-mediated targeted mutagenesis to generate a series of transgene-free mutant lines either with single or double-null bnafah alleles. Among these mutant lines, the aacc (bnafah) double-null mutant line, rather than the aaCC (bnaa06fah) mutant line, exhibited programmed cell death (PCD) under short days (SD). Histochemical staining and content measurement confirmed that the accumulation of reactive oxygen species (ROS) in bnafah was significantly higher than that in bnaa06fah. To further elucidate the mechanism of PCD, we performed transcriptomic analyses of bnaa06fah and bnafah at different SD stages. A heatmap cluster of differentially expressed genes (DEGs) revealed that PCD may be related to various redox regulatory genes involved in antioxidant activity, ROS-responsive regulation and calcium signaling. Combined with the results of previous studies, our work revealed that the expression levels of BnaC04CAT2, BnaA09/C09SAL1, BnaA08/C08ACO2, BnaA07/C06ERO1, BnaA08ACA1, BnaC04BIK1, BnaA09CRK36 and BnaA03CPK4 were significantly different and that these genes might be candidate hub genes for PCD. Together, our results underscore the ability of different PCD phenotypes to alter BnaFAH orthologs through gene editing and further elucidated the molecular mechanisms of oxidative stress-induced PCD in plants.

Tetranychus ludeni (Acari: Tetranychidae) infestation triggers a spatiotemporal redox response dependent on soybean genotypes

MAIN CONCLUSION

The redox homeostasis and photosynthetic pigments changes vary with Tetranychus ludeni infestation, with longer-cycle genotypes showing greater tolerance and efficiency in antioxidant defense. Infestations of Tetranychus ludeni Zacher (Tetranychidae) have been frequently observed in soybean plants. In this context, understanding the oscillation of redox homeostasis is crucial for detecting and assessing the stress levels caused in the plants by these organisms. The impacts of these infestations on redox metabolism and photosynthetic pigments are currently unknown. Therefore, we examined the hypothesis that T. ludeni infestations in soybean plants can influence redox homeostasis and photosynthetic pigments in a spatiotemporal manner, varying between different infestation times, modules and genotypes. For this purpose, soybean plants of the genotypes Monsoy, maturity group 5.7, and Brasmax, maturity group 6.3, grown in a controlled environment, were exposed to infestation and evaluated at two periods: 14 and 24 days. A variation in the distribution of T. ludeni within the infested plants over time increased the activity of ascorbate peroxidase and catalase, especially in Monsoy, reducing the content of hydrogen peroxide and superoxide, which prevented lipid peroxidation in the apical region in both genotypes. In the basal region, low chlorophyll indices corroborated by the yellow coloration of trifoliate leaves, high levels of membrane stability loss, and accumulation of hydrogen peroxide and superoxide characterized senescent trifoliate leaves in Brasmax, 24 days post infestation. Thus, the infestation of T. ludeni has a complex and significant impact on the redox metabolism of soybean plants, especially in shorter-cycle genotypes such as Brasmax. Furthermore, the oscillation of homeostasis can be considered as a good biochemical marker for selecting more suitable genotypes that are less sensitive and prone to infestations.

Phytotoxicity of Prussian blue nanoparticles to rice and the related defence mechanisms: In vivo observations and physiological and biochemical analysis

While the nanotoxic effects on plants have been extensively studied, the underlying mechanisms of plant defense responses and resistance to nanostress remain insufficiently understood. Particularly, Prussian blue nanoparticles (PB NPs) have been extensively used in pigments, pharmaceuticals, electrocatalysis, biosensors and energy storage. However, the impact of PB NPs on plants' health and growth are largely unknown. Herein, the phytotoxicity of PB NPs to rice and trace the uptake, accumulation and biotransformation of PB NPs was explored, along with the underlying defence mechanisms. The results showed that PB NPs (≥50 mg L-1) significantly inhibited the growth of rice seedling up to 16.16%, 27.80%, and 29.37% in plant height, shoot biomass and root biomass, respectively. The X-ray spectroscopic studies and in vivo elemental and particle-imaging demonstrated that PB NPs were transported through the cortex via xylem from root to shoot. However, most of the PB NPs and their transformation products were retained in the root, where they were blocked owing to root cell wall (RCW) remodeling, and 81.4%-83.4% of Fe accumulated in the RCW compared to 66.6% in the control. Specifically, PB NPs stimulated pectin methylesterase activity by promoting hydrogen peroxide production to participate in RCW remodeling. More interestingly, Si was specifically regulated to covalently bind to hemicellulose to form the Si-hemicellulose complex that strongly bound with PB NPs during RCW remodeling, resulting in the strong defense against PB NPs. These findings provide new insights into the phytotoxicity of artificial NPs and the defense mechanisms of plants.

Cucumber Green Mottle Mosaic Virus Coat Protein Hijacks Mitochondrial ATPδ to Promote Viral Infection

The production and scavenging of reactive oxygen species (ROS) are critical for plants to adapt to biotic and abiotic stresses. In this study, we investigated the interaction between the coat protein (CP) of cucumber green mottle mosaic virus (CGMMV) and ATP synthase subunit δ (ATPδ) in mitochondria. Silencing of ATPδ by tobacco rattle virus-based virus-induced gene silencing impeded CGMMV accumulation in Nicotiana benthamiana leaves. Both the overexpression of ATPδ in transgenic plants and transient expression promoted CGMMV infection. Nitro blue tetrazolium (NBT) and 3,3'-diaminobenzidine (DAB) staining revealed that ATPδ inhibited O2 - production but not H2O2 production. The treatment of CGMMV-infected leaves with the ROS inhibitor diphenylene iodonium (DPI) induced a ROS burst that inhibited CGMMV infection. Reverse transcription-quantitative PCR and superoxide dismutase (SOD) activity assays showed that ATPδ, CGMMV infection, and CP expression specifically induced NbFeSOD3/4 expression and SOD activity, and silencing NbFeSOD3/4 inhibited CGMMV infection. We speculate that CGMMV CP interacts with ATPδ and hijacks it, thereby enhancing O2 - quenching by upregulating NbFeSOD expression and, in turn, SOD activity.