Reactive oxygen species function as signaling molecules in controlling plant development and hormonal responses

N-terminal acetylation orchestrates glycolate-mediated ROS homeostasis to promote rice thermoresponsive growth

Climate warming poses a significant threat to global crop production and food security. However, our understanding of the molecular mechanisms governing thermoresponsive development in crops remains limited. Here we report that the auxiliary subunit of N-terminal acetyltransferase A (NatA) in rice OsNAA15 is a prerequisite for rice thermoresponsive growth. OsNAA15 produces two isoforms OsNAA15.1 and OsNAA15.2, via temperature-dependent alternative splicing. Among the two, OsNAA15.1 is more likely to form a stable and functional NatA complex with the potential catalytic subunit OsNAA10, leading to a thermoresponsive N-terminal acetylome. Intriguingly, while OsNAA15.1 promotes plant growth under elevated temperatures, OsNAA15.2 exhibits an inhibitory effect. We identified two glycolate oxidases (GLO1/5) as major substrates from the thermoresponsive acetylome. These enzymes are involved in hydrogen peroxide (H2O2) biosynthesis via glycolate oxidation. N-terminally acetylated GLO1/5 undergo their degradation through the ubiquitin-proteasome system. This leads to reduced reactive oxygen species (ROS) production, thereby promoting plant growth, particularly under high ambient temperatures. Conclusively, our findings highlight the pivotal role of N-terminal acetylation in orchestrating the glycolate-mediated ROS homeostasis to facilitate thermoresponsive growth in rice.

Abnormal Degraded Tapetum 1 (ADT1) is required for tapetal cell death and pollen development in rice

The timely degradation of tapetum, the innermost somatic anther cell layer in flowering plants, is critical for pollen development. Although several genes involved in tapetum development have been characterized, the molecular mechanisms underlying tapetum degeneration remain elusive. Here, we showed that mutation in Abnormal Degraded Tapetum 1 (ADT1) resulted in overaccumulation of Reactive Oxygen Species (ROS) and abnormal anther development, causing earlier tapetum Programmed Cell Death (PCD) and pollen abortion. ADT1 encodes a nuclear membrane localized protein, which is strongly expressed in the developing microspores and tapetal cells during early anther development. Moreover, ADT1 could interact with metallothionein MT2b, which was related to ROS scavenging and cell death regulation. These findings indicate that ADT1 is required for proper timing of tapetum PCD by regulating ROS homeostasis, expanding our understanding of the regulatory network of male reproductive development in rice.

Enhancing tomato fruit antioxidant potential through hydrogen nanobubble irrigation

Eating fruits and vegetables loaded with natural antioxidants can boost human health considerably and help fight off diseases linked to oxidative stress. Hydrogen has unique antioxidant effects. However, its low-solubility and fast-diffusion has limited its applications in agriculture. Integration of hydrogen with nanobubble technology could address such problems. However, the physiological adaptation and response mechanism of crops to hydrogen nanobubbles is still poorly understood. Antioxidant concentrations of lycopene, ascorbic acid, flavonoids, and resveratrol in hydrogen nanobubble water drip-irrigated tomato fruits increased by 16.3-264.8% and 2.2-19.8%, respectively, compared to underground water and oxygen nanobubble water. Transcriptomic and metabolomic analyses were combined to investigate the regulatory mechanisms that differed from the controls. Comprehensive multi-omics analysis revealed differences in the abundances of genes responsible for hormonal control, hydrogenase genes, and necessary synthetic metabolites of antioxidants, which helped to clarify the observed improvements in antioxidants. This is the first case of hydrogen nanobubble water irrigation increasing numerous natural antioxidant parts in fruits. Considering the characteristics of hydrogen and the application of the nanobubble technology in agriculture, the findings of the present study could facilitate the understanding of the potential effects of hydrogen on biological processes and the mechanisms of action on plant growth and development.

Co-exposure to tire wear particles and nickel inhibits mung bean yield by reducing nutrient uptake

Soil and terrestrial contamination with microplastics and nanoplastics has been discussed extensively, while tire wear particles (TWPs) have been largely overlooked. We investigated the root-surface interactions and growth response of mung bean (Vigna radiata L.) plants exposed to tire wear particles (TWPs) (0.05, 0.1, and 0.25% w/w) and nickel sulfate (50 and 100 mg kg-1 NiSO4) alone and in co-exposure scenarios for the full life cycle (105 days) under soil conditions. The results show that TWPs adhered to the root surface and reduced the water and nutrient uptake by the plant, particularly at higher concentrations of TWPs (0.25% w/w), without any observed organic contaminant accumulation in the root tissue. TWPs alone at 0.01, 0.1, and 0.25% (w/w) decreased mung bean yield by 11, 28, and 52%, respectively. Co-exposure to TWPs at 0.01, 0.1 and 0.25% w/w with 100 mg kg-1 NiSO4 decreased yield by 73, 79 and 88%, respectively. However, co-exposure to TWPs at 0.01 and 0.1% w/w with 50 mg kg-1 NiSO4 enhanced the yield by 32% and 7%, respectively. These changes in yield and nutritional aspects appear to be linked to Ni's regulatory influence on mineral homeostasis. Moreover, exposure to NiSO4 at 100 mg kg-1 increased Ni uptake in the root, shoot, and grain by 9, 26, and 20-fold, respectively as compared to the unamended control; this corresponded to increased antioxidant enzyme activity (10-127%) as compared to the control. TWPs caused blockages, significantly reducing plant yield and altering nutrient dynamics, highlighting emerging risks to plant health.

Analysis of Quantitative Phytochemical Content and Antioxidant Activity of Leaf, Stem, and Bark of Gymnosporia senegalensis (Lam.) Loes

To the best of our knowledge, there was no prior report providing valuable preliminary data through a demonstration of the quantitative phytochemical and antioxidant activity of Gymnosporia senegalensis. The total contents of phenols, flavonoid, flavanol, tannin, and saponin were evaluated from different fractions extracted from the leaf, stem, and bark of G. senegalensis by using standards such as gallic acid, quercetin, rutin, tannic acid, and saponin quillaja. The antioxidant potential was measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydrogen peroxide scavenging (H2O2), superoxide anion radical scavenging, metal chelating ferrous ion, ferric reducing antioxidant power (FRAP), and total antioxidant capacity (TAC). Data were subjected to half-inhibitory concentration (IC50) and one-way analysis of variance (ANOVA) at p < 0.05 as a significant value. The total phenol content was found to be highest in the chloroform extract of stem at 97.7 ± 0.02 mg GAE/g. The total flavonoid and flavonol contents in the aqueous extract were 97.1 ± 0.03 mg QE/g and 96.7 ± 0.07 mg RE/g, respectively. The total tannin content in the ethyl acetate extract of leaf was 97.5 ± 0.01 mg TAE/g, and the total saponin content in the methanol extract of stem was 79.1 ± 0.06 mg SQE/g. The antioxidant analysis indicated that IC50 and percentage (%) inhibition were dose-dependent and showed the highest antioxidant activity (40.9 ± 0.9 µg/mL) in methanol extract of leaf for DPPH, (88.8 ± 1.12 µg/mL) in the chloroform extract of stem for H2O2, (43.9 ± 0.15 µg/mL) in the aqueous extract of bark for superoxide anion radical scavenging activity, (26.9 ± 0.11 µg/mL) in the chloroform extract of leaf for the metal chelating ferrous ion activity, (7.55 ± 0.10 mg/mL) in the benzene extract of leaf for FRAP, and (2.97 ± 0.01 mg/mL) in the methanol extract of bark for TAC. These results show that G. senegalensis has great potential in antioxidant activities. The isolation and characterization of specific bioactive compounds and the in vivo applicability of such activity await further extensive studies for drug discovery and development.

Flavonols improve thermotolerance in tomato pollen during germination and tube elongation by maintaining ROS homeostasis

Elevated temperatures impair pollen performance and reproductive success, resulting in lower crop yields. The Solanum lycopersicum anthocyanin reduced ( are ) mutant has a FLAVANONE 3 HYDROXYLASE ( F3H ) gene mutation resulting in impaired synthesis of flavonol antioxidants. The are mutant has reduced pollen performance and seed set relative to the VF36 parental line, which is accentuated at elevated temperatures. Transformation of are with the wild-type F3H gene, or chemical complementation with flavonols, prevented temperature-dependent ROS accumulation in pollen and reversed are's reduced viability, germination, and tube elongation to VF36 levels. VF36 transformed with an F3H overexpression construct prevented temperature driven ROS increases and impaired pollen performance, revealing thermotolerance results from elevated flavonol synthesis. Although stigmas of are had reduced flavonols and elevated ROS, the growth of are pollen tubes were similarly impaired in both are and VF36 pistils. RNA-Seq was performed at optimal and stress temperatures in are , VF36, and the VF36 F3H overexpression line at multiple timepoints across pollen tube elongation. Differentially expressed gene numbers increased with duration of elevated temperature in all genotypes, with the largest number in are . These findings suggest potential agricultural interventions to combat the negative effects of heat-induced ROS in pollen that leads to reproductive failure.

One sentence summary

Flavonol antioxidants reduce the negative impacts of elevated temperatures on pollen performance by reducing levels of heat induced reactive oxygen species and modulation of heat-induced changes in the pollen transcriptome.

Reactive oxygen species are signaling molecules that modulate plant reproduction

Reactive oxygen species (ROS) can serve as signaling molecules that are essential for plant growth and development but abiotic stress can lead to ROS increases to supraoptimal levels resulting in cellular damage. To ensure efficient ROS signaling, cells have machinery to locally synthesize ROS to initiate cellular responses and to scavenge ROS to prevent it from reaching damaging levels. This review summarizes experimental evidence revealing the role of ROS during multiple stages of plant reproduction. Localized ROS synthesis controls the formation of pollen grains, pollen-stigma interactions, pollen tube growth, ovule development, and fertilization. Plants utilize ROS-producing enzymes such as respiratory burst oxidase homologs and organelle metabolic pathways to generate ROS, while the presence of scavenging mechanisms, including synthesis of antioxidant proteins and small molecules, serves to prevent its escalation to harmful levels. In this review, we summarized the function of ROS and its synthesis and scavenging mechanisms in all reproductive stages from gametophyte development until completion of fertilization. Additionally, we further address the impact of elevated temperatures induced ROS on impairing these reproductive processes and of flavonol antioxidants in maintaining ROS homeostasis to minimize temperature stress to combat the impact of global climate change on agriculture.

High night temperature stress on rice (Oryza sativa) - insights from phenomics to physiology. A review

Rice (Oryza sativa ) faces challenges to yield and quality due to urbanisation, deforestation and climate change, which has exacerbated high night temperature (HNT). This review explores the impacts of HNT on the physiological, molecular and agronomic aspects of rice growth. Rise in minimum temperature threatens a potential 41% reduction in rice yield by 2100. HNT disrupts rice growth stages, causing reduced seed germination, biomass, spikelet sterility and poor grain development. Recent findings indicate a 4.4% yield decline for every 1°C increase beyond 27°C, with japonica ecotypes exhibiting higher sensitivity than indica. We examine the relationships between elevated CO2 , nitrogen regimes and HNT, showing that the complexity of balancing positive CO2 effects on biomass with HNT challenges. Nitrogen enrichment proves crucial during the vegetative stage but causes disruption to reproductive stages, affecting grain yield and starch synthesis. Additionally, we elucidate the impact of HNT on plant respiration, emphasising mitochondrial respiration, photorespiration and antioxidant responses. Genomic techniques, including CRISPR-Cas9, offer potential for manipulating genes for HNT tolerance. Plant hormones and carbohydrate enzymatic activities are explored, revealing their intricate roles in spikelet fertility, grain size and starch metabolism under HNT. Gaps in understanding genetic factors influencing heat tolerance and potential trade-offs associated with hormone applications remain. The importance of interdisciplinary collaboration is needed to provide a holistic approach. Research priorities include the study of regulatory mechanisms, post-anthesis effects, cumulative HNT exposure and the interaction between climate variability and HNT impact to provide a research direction to enhance rice resilience in a changing climate.

Physiological and biochemical responses of Leersia hexandra Swartz to nickel stress: Insights into antioxidant defense mechanisms and metal detoxification strategies

Phytoremediation is widely considered as a cost-effective method for managing heavy metal soil pollution. Leersia hexandra Swartz shows a promising potential for the remediation of heavy metals pollution, including chromium (Cr), copper (Cu), and nickel (Ni). It is vital to understand the physiological and biochemical responses of L. hexandra to Ni stress to elucidate the mechanisms underlying Ni tolerance and accumulation. Here, we examined the metabolic and transcriptomic responses of L. hexandra exposed to 40 mg/L Ni for 24 h and 14 d. After 24-h Ni stress, gene expression of glutathione metabolic cycle (GSTF1, GSTU1 and MDAR4) and superoxide dismutase (SODCC2) was significantly increased in plant leaves. Furthermore, after 14-d Ni stress, the ascorbate peroxidase (APX7), superoxide dismutase (SODCP and SOD1), and catalase (CAT) gene expression was significantly upregulated, but that of glutathione metabolic cycle (EMB2360, GSTU1, GSTU6, GSH2, GPX6, and MDAR2) was downregulated. After 24-h Ni stress, the differentially expressed metabolites (DEMs) were mainly flavonoids (45%) and flavones (20%). However, after 14-d Ni stress, the DEMs were mainly carbohydrates and their derivatives (34%), amino acids and derivatives (15%), and organic acids and derivatives (8%). Results suggest that L. hexandra adopt distinct time-dependent antioxidant and metal detoxification strategies likely associated with intracellular reduction-oxidation balance. Novel insights into the molecular mechanisms responsible for Ni tolerance in plants are presented.

Feedback regulation of the isoprenoid pathway by SsdTPS overexpression has the potential to enhance plant tolerance to drought stress

In order to maintain the dynamic physiological balance, plants are compelled to adjust their energy metabolism and signal transduction to cope with the abiotic stresses caused by complex and changeable environments. The diterpenoid natural compound and secondary metabolites, sclareol, derived from Salvia sclarea, has gained significant attention owing to its economic value as a spice material and diverse physiological activities. Here, we focused on the roles and regulatory mechanisms of the sclareol diterpene synthase gene SsdTPS in the resistance of S. sclarea to abiotic stresses. Our results suggested that abiotic stresses could induce the response and upregulation of SsdTPS expression and isoprenoid pathway in S. sclarea. Ectopic expression of SsdTPS conferred drought tolerance in transgenic Arabidopsis, compared with wild-type. Overexpression of SsdTPS enhanced the transcription of ABA signal transduction synthetic regulators and induced the positive feedback upregulating key regulatory genes in the MEP pathway, thereby promoting the increase of ABA content and improving drought tolerance in transgenic plants. In addition, SsdTPS-overexpressed transgenic Arabidopsis improved the responses of stomatal regulatory genes and ROS scavenging enzyme activities and gene expression to drought stress. This promoted the stomatal closure and ROS reduction, thus enhancing water retention capacity and reducing oxidative stress damage. These findings unveil the potentially positive role of SsdTPS in orchestrating multiple regulatory mechanisms and maintaining homeostasis for improved abiotic stress resistance in S. sclarea, providing a novel insight into strategies for promoting drought resistance and cultivating highly tolerant plants.

Signalling responses in the bark and foliage of canker-susceptible and -resistant cypress clones inoculated with Seiridium cardinale

The necrotrophic fungus Seiridium cardinale is the main responsible for Cypress Canker Disease (CCD), a pandemic affecting many Cupressaceae worldwide. The present study aims to elucidate the signalling of the early responses in the bark and foliage of CCD-susceptible and -resistant C. sempervirens clones to S. cardinale inoculation (SI and RI, respectively). In the bark of SI, a peaking production of ethylene (Et) and jasmonic acid (JA) occurred at 3 and 4 days post inoculation (dpi), respectively, suggesting an attempted plant response to the pathogen. A response that, however, was ineffective, as confirmed by the severe accumulation of malondialdehyde by-products at 13 dpi (i.e., lipid peroxidation). Differently, Et emission peaked in RI bark at 3 and 13 dpi, whereas abscisic acid (ABA) accumulated at 1, 4 and 13 dpi, resulting in a lower MDA accumulation (and unchanged levels of antioxidant capacity). In the foliage of SI, Et was produced at 1 and 9 dpi, whereas JA and salicylic acid (SA) accumulated at 1 and 3 dpi. Conversely, an increase of ABA and SA occurred at 1 dpi in the RI foliage. This outcome indicates that some of the observed metabolic alterations, mainly occurring as local defence mechanisms, might be able to gradually shift to a systemic resistance, although an accumulation of MDA was observed in both SI and RI foliage (but with an increased antioxidant capacity reported only in the resistant clone). We believe that the results reported here will be useful for the selection of clones able to limit the spread and damage of CCD.

Sugarcane mosaic virus employs 6K2 protein to impair ScPIP2;4 transport of H2O2 to facilitate virus infection

Sugarcane mosaic virus (SCMV), one of the main pathogens causing sugarcane mosaic disease, is widespread in sugarcane (Saccharum spp. hybrid) planting areas and causes heavy yield losses. RESPIRATORY BURST OXIDASE HOMOLOG (RBOH) NADPH oxidases and plasma membrane intrinsic proteins (PIPs) have been associated with the response to SCMV infection. However, the underlying mechanism is barely known. In the present study, we demonstrated that SCMV infection upregulates the expression of ScRBOHs and the accumulation of hydrogen peroxide (H2O2), which inhibits SCMV replication. All eight sugarcane PIPs (ScPIPs) interacted with SCMV-encoded protein 6K2, whereby two PIP2s (ScPIP2;1 and ScPIP2;4) were verified as capable of H2O2 transport. Furthermore, we revealed that SCMV-6K2 interacts with ScPIP2;4 via transmembrane domain 5 to interfere with the oligomerization of ScPIP2;4, subsequently impairing ScPIP2;4 transport of H2O2. This study highlights a mechanism adopted by SCMV to employ 6K2 to counteract the host resistance mediated by H2O2 to facilitate virus infection and provides potential molecular targets for engineering sugarcane resistance against SCMV.

From Nature to Lab: A Review of Secondary Metabolite Biosynthetic Pathways, Environmental Influences, and In Vitro Approaches

Secondary metabolites are gaining an increasing importance in various industries, such as pharmaceuticals, dyes, and food, as is the need for reliable and efficient methods of procuring these compounds. To develop sustainable and cost-effective approaches, a comprehensive understanding of the biosynthetic pathways and the factors influencing secondary metabolite production is essential. These compounds are a unique type of natural product which recognizes the oxidative damage caused by stresses, thereby activating the defence mechanism in plants. Various methods have been developed to enhance the production of secondary metabolites in plants. The elicitor-induced in vitro culture technique is considered an efficient tool for studying and improving the production of secondary metabolites in plants. In the present review, we have documented various biosynthetic pathways and the role of secondary metabolites under diverse environmental stresses. Furthermore, a practical strategy for obtaining consistent and abundant secondary metabolite production via various elicitation agents used in culturing techniques is also mentioned. By elucidating the intricate interplay of regulatory factors, this review paves the way for future advancements in sustainable and efficient production methods for high-value secondary metabolites.

Abscisic acid increases hydrogen peroxide in mitochondria to facilitate stomatal closure

Abscisic acid (ABA) drives stomatal closure to minimize water loss due to transpiration in response to drought. We examined the subcellular location of ABA-increased accumulation of reactive oxygen species (ROS) in guard cells, which drive stomatal closure, in Arabidopsis (Arabidopsis thaliana). ABA-dependent increases in fluorescence of the generic ROS sensor, dichlorofluorescein (DCF), were observed in mitochondria, chloroplasts, cytosol, and nuclei. The ABA response in all these locations was lost in an ABA-insensitive quintuple receptor mutant. The ABA-increased fluorescence in mitochondria of both DCF- and an H2O2-selective probe, Peroxy Orange 1, colocalized with Mitotracker Red. ABA treatment of guard cells transformed with the genetically encoded H2O2 reporter targeted to the cytoplasm (roGFP2-Orp1), or mitochondria (mt-roGFP2-Orp1), revealed H2O2 increases. Consistent with mitochondrial ROS changes functioning in stomatal closure, we found that guard cells of a mutant with mitochondrial defects, ABA overly sensitive 6 (abo6), have elevated ABA-induced ROS in mitochondria and enhanced stomatal closure. These effects were phenocopied with rotenone, which increased mitochondrial ROS. In contrast, the mitochondrially targeted antioxidant, MitoQ, dampened ABA effects on mitochondrial ROS accumulation and stomatal closure in Col-0 and reversed the guard cell closure phenotype of the abo6 mutant. ABA-induced ROS accumulation in guard cell mitochondria was lost in mutants in genes encoding respiratory burst oxidase homolog (RBOH) enzymes and reduced by treatment with the RBOH inhibitor, VAS2870, consistent with RBOH machinery acting in ABA-increased ROS in guard cell mitochondria. These results demonstrate that ABA elevates H2O2 accumulation in guard cell mitochondria to promote stomatal closure.

Flavonols modulate plant development, signaling, and stress responses

Flavonols are plant-specialized metabolites with important functions in plant growth and development. Isolation and characterization of mutants with reduced flavonol levels, especially the transparent testa mutants in Arabidopsis thaliana, have contributed to our understanding of the flavonol biosynthetic pathway. These mutants have also uncovered the roles of flavonols in controlling development in above- and below-ground tissues, notably in the regulation of root architecture, guard cell signaling, and pollen development. In this review, we present recent progress made towards a mechanistic understanding of flavonol function in plant growth and development. Specifically, we highlight findings that flavonols act as reactive oxygen species (ROS) scavengers and inhibitors of auxin transport in diverse tissues and cell types to modulate plant growth and development and responses to abiotic stresses.

Current understanding, challenges and perspective on portable systems applied to plant monitoring and precision agriculture

The devastating effects of global climate change on crop production and exponential population growth pose a major challenge to agricultural yields. To cope with this problem, crop performance monitoring is becoming increasingly necessary. In this scenario, the use of sensors and biosensors capable of detecting changes in plant fitness and predicting the evolution of their morphology and physiology has proven to be a useful strategy to increase crop yields. Flexible sensors and nanomaterials have inspired the emerging fields of wearable and on-plant portable devices that provide continuous and accurate long-term sensing of morphological, physiological, biochemical, and environmental parameters. This review provides an overview of novel plant sensing technologies by discussing wearable and integrated devices proposed for engineering plant and monitoring its morphological traits and physiological processes, as well as plant-environment interactions. For each application scenario, the state-of-the-art sensing solutions are grouped according to the plant organ on which they have been installed highlighting their main technological advantages and features. Finally, future opportunities, challenges and perspectives are discussed. We anticipate that the application of this technology in agriculture will provide more accurate measurements for farmers and plant scientists with the ability to track crop performance in real time. All of this information will be essential to enable rapid optimization of plants development through tailored treatments that improve overall plant health even under stressful conditions, with the ultimate goal of increasing crop productivity in a more sustainable manner.

Natural Compounds and Products from an Anti-Aging Perspective

Aging is a very complex process that is accompanied by a degenerative impairment in many of the major functions of the human body over time. This inevitable process is influenced by hereditary factors, lifestyle, and environmental influences such as xenobiotic pollution, infectious agents, UV radiation, diet-borne toxins, and so on. Many external and internal signs and symptoms are related with the aging process and senescence, including skin dryness and wrinkles, atherosclerosis, diabetes, neurodegenerative disorders, cancer, etc. Oxidative stress, a consequence of the imbalance between pro- and antioxidants, is one of the main provoking factors causing aging-related damages and concerns, due to the generation of highly reactive byproducts such as reactive oxygen and nitrogen species during the metabolism, which result in cellular damage and apoptosis. Antioxidants can prevent these processes and extend healthy longevity due to the ability to inhibit the formation of free radicals or interrupt their propagation, thereby lowering the level of oxidative stress. This review focuses on supporting the antioxidant system of the organism by balancing the diet through the consumption of the necessary amount of natural ingredients, including vitamins, minerals, polyunsaturated fatty acids (PUFA), essential amino acids, probiotics, plants’ fibers, nutritional supplements, polyphenols, some phytoextracts, and drinking water.