Reactive oxygen species in plant development

Discovery of new 1,2,3,4-tetrahydro-β-carboline derivatives decorated with 3-N-substituted propionyl moiety flexibly bridged-chain as reactive oxygen species inducer for efficient antibacterial treatment

The widespread prevalence of bacterial plant diseases imposes a severe constraint on global food production and crop security. To address the growing challenge of bacterial resistance, there is an urgent demand to develop novel agrochemicals that combine high efficacy with low toxicity. In this study, a natural product modification strategy was employed to design new bactericidal candidates with an innovative cation mechanism. Tryptamine was employed as a precursor to synthesize 1,2,3,4-tetrahydro-β-carboline (THC) intermediates via the Pictet-Spengler reaction. Subsequent acylation enabled the introduction of 3-N-substituted propionyl group as flexible bridge chain through an aza-Michael reaction. The resulting racemic THC derivatives were then evaluated for their antimicrobial activity. Notably, molecule B3 demonstrated exceptional inhibitory effects against Xanthomonas oryzae pv. oryzae (Xoo, EC50 = 1.32 μg/mL) and Xanthomonas axonopodis pv. citri (Xac, EC50 = 2.80 μg/mL), significantly outperforming commercial agents such as bismerthiazol (BT; EC50 = 40.3 μg/mL for Xoo and 89.6 μg/mL for Xac) and thiodiazole copper (TC; EC50 = 58.2 μg/mL for Xoo and 37.3 μg/mL for Xac). Moreover, molecule B3 exhibited considerably higher activity than its parent molecule B (EC50 = 7.27 μg/mL for Xoo and 4.89 μg/mL for Xac). In vivo assays at 200 μg/mL, B3 provided protective effects of 53.87 % against Xoo and 91.2 % against Xac, exceeding those of TC. Mechanistic investigations revealed that molecule B3 disrupted the intracellular redox balance, and result in the accumulation of reactive oxygen species (ROS) and subsequent induction of apoptosis. These findings not only identify B3 as a promising ROS inducer for bactericide development but also offer novel insights into the role of ROS in combating bacterial diseases.

Rooted in Communication: Exploring Auxin-Salicylic Acid Nexus in Root Growth and Development

Plant hormones are pivotal in orchestrating diverse aspects of growth and developmental processes. Among various phytohormones, auxin and salicylic acid (SA) stand out as important regulators, often exerting opposing effects on overall plant growth. Essentially, research has indicated that auxin and SA-mediated pathways exhibit mutual antagonism during pathogen challenge. Additionally, in recent years, significant advancements have been made in uncovering the molecular intricacies that govern the action and interplay between these two phytohormones during various essential growth-related processes. In this discussion, we briefly delve into the genetic and molecular mechanisms involved in auxin and SA antagonism. We then analyse in detail how this dialogue impacts critical aspects of root development, with an emphasis on the transcriptional and protein regulatory networks. Finally, we propose the potential of exploring their interaction in various other aspects of below ground root growth processes. Understanding this relationship could provide valuable insights for optimizing and enhancing crop growth and yields.

The burning glass effect of water droplets triggers a high light-induced calcium response in the chloroplast stroma

Plants rely on water and light for photosynthesis, but water droplets on leaves can focus light into high-intensity spots, risking photodamage. Excessive light can impair growth or induce cell death, making it essential for plants to detect and respond to light fluctuations. While Ca2+ signaling has been linked to high light (HL) acclimation, the subcellular dynamics remain unclear. Here, we investigate Ca2+ responses to HL exposure in Arabidopsis thaliana. Using a glass bead to simulate light-focusing by water droplets, a biphasic increase of Ca2+ concentration was detected in the chloroplast stroma by the genetically encoded calcium indicator YC3.6 and confirmed using a newly established stroma-localized R-GECO1 (NTRC-R-GECO1). The stromal response was largely independent of light wavelength and unaffected in phot1 phot2 and cry1 cry2 mutants. Chemical inhibition of photosynthetic electron transport, microscopy-based Fv/Fm experiments, and measurement of the reactive oxygen species (ROS)-redox balance with roGFP-based reporters and Singlet Oxygen Sensor Green (SOSG) chemical dye suggested that photodamage and singlet oxygen contribute to the stromal Ca2+ response. While blue and white light also triggered a Ca2+ response in the cytosol and nucleus, pharmacological inhibition with cyclopiazonic acid (CPA) and loss-of-function mutants of the Ca2+ transporters BIVALENT CATION TRANSPORTER 2 (BICAT2) and endoplasmic reticulum (ER)-type Ca2+-ATPase (ECA) suggested that the HL response depends on a Ca2+ exchange between the ER and chloroplast stroma. The response was primarily light dependent but accelerated by increasing external temperature. This study implicates a novel Ca2+-mediated acclimation mechanism to HL stress, a process of growing relevance in the context of climate change.

Cytosolic glyceraldehyde-3-phosphate dehydrogenase regulates plant stem cell maintenance under oxidative stress

KEY MESSAGE

GAPDH regulates plant stem cell maintenance. WUSCHEL (WUS) and WUSCHEL-RELATED HOMEOBOX (WOX) family proteins are vital for maintaining the homeostasis of stem cells, which is necessary for the continuous growth and the development of plants. Plants frequently encounter environmental stress that can lead to an increase in reactive oxygen species, such as hydrogen peroxide (H2O2). However, the exact ways in which plant stem cells sense and respond to H2O2 signals remain unclear. This research indicates that cytosolic glyceraldehyde-3-phosphate dehydrogenase (GAPDH) helps regulate stem cell maintenance in Arabidopsis in response to H2O2. Hydrogen peroxide causes the relocation of two cytosolic GAPDH proteins, GAPC1 and GAPC2, from the cytoplasm to the nucleus. These isoforms interact with WUS/WOX proteins and modulate the expression of the WUS/WOX gene by binding to its promoter. When the expression of GAPC1 and GAPC2 is decreased, stem cell homeostasis and overall plant growth become more sensitive to H2O2. Thus, cytosolic GAPDH may serve as a sensor for H2O2, influencing the maintenance of plant stem cells under oxidative stress.

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.

Hormesis effect of cadmium on pakchoi growth: Unraveling the ROS-mediated IAA-sugar metabolism from multi-omics perspective

Previous research on cadmium (Cd) focused on toxicity, neglecting hormesis and its mechanisms. In this study, pakchoi seedlings exposed to varying soil Cd concentrations (CK, 5, 10, 20, 40 mg/kg) showed an inverted U-shaped growth trend (hormesis characteristics): As Cd concentration increases, biomass exhibited hormesis character (Cd5) and then disappear (Cd40). ROS levels rose in both Cd treatments, with Cd5 being intermediate between CK and Cd40. But Cd5 preserved cellular structure, unlike damaged Cd40, hinting ROS in Cd5 acted as signaling regulators. To clarify ROS controlled subsequent metabolic processes, a multi-omics study was conducted. The results revealed 143 DEGs and 793 DEMs across all Cd treatment. KEGG indicated among all Cd treatments, the functional differences encompass: "plant hormone signal transduction" and "starch and sucrose metabolism". Through further analysis, we found that under the influence of ROS, the expression of IAA synthesis and signaling-related genes was significantly up-regulated, especially under Cd5 treatment. This further facilitated the accumulation of reducing sugars, which provided more energy for plant growth. Our research results demonstrated the signaling pathway involving ROS-IAA-Sugar metabolism, thereby providing a novel theoretical basis for cultivating more heavy metal hyperaccumulator crops and achieving phytoremediation of contaminated soils.

Charged Water Microdroplets Enable Dissociation of Surrounding Dioxygen

The cleavage of dioxygen (O2) into its atomic constituents typically requires harsh conditions and metal catalysts. We present a remarkable discovery demonstrating that dioxygen can be activated, dissociated, and subsequently transformed into the ozone anion (O3-) without any catalyst at the air-water interface in charged microdroplet sprays. Using online mass spectrometry, we directly detected the dioxygen splitting products O3- and H2O·O3- in microdroplets. The high electric field at the air-water interface, along with microlightning between oppositely charged water microdroplets, induces an electrical discharge responsible for the O-O bond cleavage, leading to the formation of reactive oxygen species (ROS). Isotope labeling experiments further reveal that various ROS, i.e., ·OH, CO3-, and HCO4-, can be generated through the reaction of dioxygen splitting products with water or CO2. This study introduces a sustainable pathway for molecular oxygen utilization and offers new insights into ROS generation in microdroplets.

Plant chloroplast stress response: insights from mass spectrometry metabolites analysis

Plant chloroplasts produce excess reactive oxygen species (ROS) during photosynthesis, particularly under biotic and abiotic stress conditions. These adverse environmental stresses lead to significant alterations in various cellular components, especially within the chloroplast, which serves as a key stress-sensor organelle. The stress response of chloroplasts can trigger plastid-to-nucleus retrograde signaling and enhance the biosynthesis of biologically active compounds and phytohormones, which are mechanisms that aid plants in acclimating to environmental stress. While ROS act as signaling molecules to help re-adjust cellular metabolic homeostasis, they also risk damaging chloroplasts' structural and functional integrity. Recent research on stress-induced plant metabolism has provided new insights into the chloroplast's stress response. In particular, advancements in mass spectrometry (MS) techniques have expanded our understanding of how oxidative stress affects plants through metabolomics analyses of metabolites involved in this process. Here, we emphasize the MS-based profiling of lipids, apocarotenoids, and phytohormones linked to ROS-triggered processes in plants. Moreover, we discuss the plants' metabolic responses to abiotic stress. Finally, we outline future directions for chloroplast stress research. We advocate for integrating MS-based metabolomics with biochemical and molecular genetic approaches to discover new signaling molecules and identify interconnected signaling components that function across multiple chloroplast signaling pathways.

AuNPs/GO/Pt microneedle electrochemical sensor for in situ monitoring of hydrogen peroxide in tomato stems in response to wounding stimulation

Hydrogen peroxide (H2O2) is a critical signaling molecule with significant roles in various physiological processes in plants. Understanding its regulation through in situ monitoring could offer deeper insights into plant responses and stress mechanisms. In this study, we developed a microneedle electrochemical sensor to monitor H2O2 in situ, offering deeper insights into plant stress responses. The sensor features a platinum wire (100 µm diameter) modified with graphene oxide (GO) and gold nanoparticles (AuNPs) as the working electrode, an Ag/AgCl wire (100 µm diameter) as the reference electrode, and an untreated platinum wire (100 µm diameter) as the counter electrode. This innovative design enhances sensitivity and selectivity through the high catalytic activity of AuNPs, increased surface area from GO, and the superior conductivity of platinum. Operating at a low potential of -0.2 V to minimize interference, the sensor detects H2O2 concentrations from 10 to 1000 µM with high accuracy. In situ monitoring of H2O2 dynamics in tomato stems under the wounding stimulation reveals that H2O2 concentration increases as the sensor approaches the wound site, indicating localized production and transport of H2O2. This approach not only improves H2O2 monitoring in plant systems but also paves the way for exploring its generation, transport, and elimination mechanisms.

Hydrogen gas enhances Arabidopsis salt tolerance by modulating hydrogen peroxide-mediated redox and ion homeostasis

Hydrogen gas (H2) plays a crucial role in mitigating salt stress in plants, but the underlying mechanisms is largely unknown. Herein, we employed the pharmacological, molecular, and genetic approaches to investigate the positive roles of hydrogen peroxide (H2O2) in endogenous H2-induced salt tolerance of Arabidopsis thaliana. H2-induecd salt tolerance of CrHYD1 (hydrogenase 1 gene from Chlamydomonas reinhardtii) transgenic Arabidopsis was blocked by H2O2 scavenger or NADPH oxidase inhibitor. When RESPIRATORY BURST OXIDASE HOMOLOG (RBOH) genes (AtrbohD or AtrbohF) were mutated, salt sensitivity of CrHYD1/atrboh (especially CrHYD1/atrbohD) hybrids was increased, but diminished by exogenous H2O2 administration. Salt-stimulated endogenous H2 enrichment consequently resulted in the rapid reactive oxygen species (ROS) accumulation under early salt stress, and the expression of AtrbohD (especially) and AtrbohF in CrHYD1 plants was higher than those in the wild-type (WT), suggesting that endogenous H2 could induce Atrboh-dependent ROS burst to respond salt stress. Further, H2-induced less 3,3'-diaminobenzidine (DAB) and nitro blue tetrazolium (NBT) stain in CrHYD1 plants was reversed under salt stress when either H2O2 was removed or Atrbohs were mutated, which could be explained by higher H2O2 and thiobarbituric acid reactive substances (TBARS) levels, as well as lower antioxidant enzyme activity. Additionally, H2-induced Na+ discharge and K+ accumulation in CrHYD1 plants under salt stress were blocked by either H2O2 removal or Atrboh knockout, which was validated by higher Na+/K+ ratios and lower ion transport-related gene expression. Our findings not only elucidate that endogenous H2 enhanced Arabidopsis salt tolerance by reestablishing H2O2-dependent ion and redox homeostasis, but provide new insights into the mechanisms of plant salinity responses.

Silicon application improves tomato yield and nutritional quality

BACKGROUND

Silicon (Si) is a beneficial nutrient well-known for its functions in enhancing plant resistance to abiotic and biotic stresses. How Si application affects tomato yield and quality and underlying physiological mechanisms remain largely unclear.

RESULTS

Our pot experiment showed that Si application (45 kg ha⁻¹ Na₂SiO₃) significantly promoted accumulation of nitrogen, phosphorus, potassium, and Si in the shoot of soil-cultured tomato in the greenhouse. Such improved mineral nutrition favored Si-applied plant performance in terms of plant height, stem diameter, single fruit weight, and yield, as indicated by significant increases of 11.34%, 53.57%, 62.12%, and 33.81%, respectively, when compared to the control (0 kg ha⁻¹ Na₂SiO₃). Higher catalase and superoxide dismutase activities in contrast to lower concentrations of hydrogen peroxide and malondialdehyde in the fruit suggested that Si application facilitated plant health. Importantly, Si upregulated expression of phytoene synthase and carotenoid isomerase and enhanced corresponding enzyme activities, resulting in higher lycopene concentrations in the fruit. Si also stimulated expression of vitamin C synthesis genes (GDP-D-mannose-3', 5'-isomerase, GDP-L-galactose phosphorylase, dehydroascorb-ate reductase, and monodehydroascorbate reductase) for higher levels of vitamin C accumulation.

CONCLUSION

Si promoted tomato health, yield, and nutritional quality at the physiological and molecular level, favoring quality fruit production towards sustainable agricultural development.

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.

Integrated effects of microbial culture and nitrogen application on phytoremediation, physiology and growth of maize in glyphosate-contaminated soil

Glyphosate can disrupt the food chain and harm non-target organisms, highlighting the need to remediate contaminated soils. This study sought to determine the efficacy of co-applying mixed microbial culture (MMC) and two different levels of nitrogen (50% and 100%) in glyphosate-contaminated soil (800 mg/kg) and to assess their role in maize (Zea mays L.) growth and physiology and glyphosate uptake by plants and removal from soil. The results showed that glyphosate posed significant phytotoxicity to maize plants by causing up to 43.7-91.5%, 8.60-54.3%, and 13.2-51.6% reduction in nutrient uptake, physiological, and growth attributes of maize plants in glyphosate-contaminated soil, respectively. The co-application of MMC and the recommended dose of 100% nitrogen significantly improved the agronomic (24.6-55.0%), nutrient uptake (37.4-90.0%), and physiological (16.9-54.0%) attributes of maize plants as compared to unamended contaminated controls. Although the individual application of MMC or N was effective in improving glyphosate removal from the soil, their co-application further enhanced this effect by removing glyphosate 85.8% higher than the respective control. This research strategy contributes to sustainable development goal 2 (zero-hunger) and 15 (life on land) by enhancing food production, remediating contaminated soil, and restoring the ecosystem.

ELONGATED HYPOCOTYL 5 promotes root growth by maintaining redox homeostasis and repressing oxidative stress response

Oxidative stress is a major threat to plant growth and survival. To understand how plants cope with oxidative stress, we carried out a genetic screen for Arabidopsis (Arabidopsis thaliana) mutants with altered response to hydrogen peroxide (H2O2) in root growth. Herein, we report the characterization of one of the hypersensitive mutants obtained. This mutant had slightly shorter roots in normal growth medium, and this phenotype became more pronounced in H2O2-containing medium. Through genome-wide resequencing and complementation experiments, we identified the gene with the causal mutation as ELONGATED HYPOCOTYL 5 (HY5). Histochemical staining revealed that the apical meristem of hy5 roots had an elevated level of H2O2 but a lower level of superoxide. In further experiments, we showed that genes involved in redox homeostasis and oxidative response were altered in hy5 roots and that MYB DOMAIN PROTEIN 30 (MYB30), GLUTATHIONE S-TRANSFERASE PHI 2 (GSTF2), and GLUTATHIONE S-TRANSFERASE TAU 19 (GSTU19) are directly repressed by HY5. Interestingly, overexpression of MYB30, a master regulator of the oxidative stress response, exacerbated the root growth defect in hy5, whereas knocking it down by RNAi largely rescued the mutant's hypersensitivity to H2O2 without affecting the content of reactive oxygen species (ROS). Intriguingly, knocking down GSTF2 also rescued the H2O2 hypersensitivity and ROS homeostasis defects in hy5 roots. In addition to H2O2, we showed that hy5 was also hypersensitive to high salinity, Cd, and salicylic acid. Based on these results, we conclude that HY5 plays a positive role in root growth mainly under abiotic stress by modulating both redox homeostasis and oxidative stress response.

Crosstalk Between Abiotic and Biotic Stresses Responses and the Role of Chloroplast Retrograde Signaling in the Cross-Tolerance Phenomena in Plants

In the natural environment, plants are simultaneously exposed to multivariable abiotic and biotic stresses. Typical abiotic stresses are changes in temperature, light intensity and quality, water stress (drought, flood), microelements availability, salinity, air pollutants, and others. Biotic stresses are caused by other organisms, such as pathogenic bacteria and viruses or parasites. This review presents the current state-of-the-art knowledge on programmed cell death in the cross-tolerance phenomena and its conditional molecular and physiological regulators, which simultaneously regulate plant acclimation, defense, and developmental responses. It highlights the role of the absorbed energy in excess and its dissipation as heat in the induction of the chloroplast retrograde phytohormonal, electrical, and reactive oxygen species signaling. It also discusses how systemic- and network-acquired acclimation and acquired systemic resistance are mutually regulated and demonstrates the role of non-photochemical quenching and the dissipation of absorbed energy in excess as heat in the cross-tolerance phenomenon. Finally, new evidence that plants evolved one molecular system to regulate cell death, acclimation, and cross-tolerance are presented and discussed.

Melatonin Enhances Maize Germination, Growth, and Salt Tolerance by Regulating Reactive Oxygen Species Accumulation and Antioxidant Systems

Melatonin (MT) is a crucial hormone that controls and positively regulates plant growth under abiotic stress, but the biochemical and physiological processes of the combination of melatonin seed initiation and exogenous spray treatments and their effects on maize germination and seedling salt tolerance are not well understood. Consequently, in this research, we utilized the maize cultivars Zhengdan 958 (ZD958) and Demeiya 1 (DMY1), which are extensively marketed in northeastern China's high-latitude cold regions, to reveal the modulating effects of melatonin on maize salinity tolerance by determining the impacts of varying concentrations of melatonin on maize seedling growth characteristics, osmoregulation, antioxidant systems, and gene expression. The findings revealed that salt stress (100 mM NaCl) significantly inhibited maize seed germination and seedling development, which resulted in significant increases in the H2O2 and O2- content and decreases in the antioxidant enzyme activity and photosynthetic pigment content in maize seedlings. However, exogenous melatonin considerably reduced the development inhibition caused by salt stress in maize seedlings. Moreover, exogenous melatonin alleviated NaCl-induced membrane damage and oxidative stress, and reduced Na+ content and excessively large quantities of reactive oxygen species (ROS). In addition, exogenous melatonin increased antioxidant enzyme activity and the expression of the antioxidant enzyme genes ZmSOD4, ZmCAT2, and ZmAPX2. This study demonstrates the potential role of combined melatonin seed initiation and foliar spray treatments in mitigating the detrimental effects of salt stress on maize growth, giving a theoretical foundation to future research on the possible advantages of exogenous regulating chemicals in attaining sustainable production in salt-alkaline soils.

Dual Regulation of Ionic Effect on Zostera marina L. Seed Germination and Leaf Differentiation in Low-Salinity Conditions

Low-salinity conditions are generally used in land-based cultivation to promote the germination and growth of Zostera marina L. and to improve the restoration effect of seagrass beds. Different salinity conditions lead to morphological and physiological differences. To investigate the impacts of salinity and osmotic pressure on the germination and early development of Zostera marina seeds, this study utilized seawater with different salinity conditions and PEG-6000 solutions to simulate various non-ionic osmotic pressures and examine the germination, cotyledon growth, and leaf differentiation over 28 days, as well as determine the biochemical traits on days 1, 3, 5, and 7. The results show that the cumulative germination rate in LS-0 was 91.6%, but it was not significantly affected by the PEG solutions. The different salinities (5, 10, and 15) had no significant effect on the germination rate, which ranged from 76.4% to 78.8%: low salinity and low osmotic pressure stimulated the germination by accelerating the water uptake through increased osmotic pressure differences. The leaf differentiation was regulated by the osmotic pressure and salinity. In LS-10, the most used condition, the leaf differentiation rate was 35.2%, while PEG-10 displayed 6.4%. The total soluble sugar and soluble protein in the seeds decreased. Antioxidant enzyme activities were activated under low-salinity conditions, which supported germination within a tolerable oxidative stress range.

How the Ectopic Expression of the Barley F-Box Gene HvFBX158 Enhances Drought Resistance in Arabidopsis thaliana

In this study, the drought-responsive gene HvFBX158 from barley was transferred to Arabidopsis thaliana, and overexpression lines were obtained. The phenotypic characteristics of the transgenic plants, along with physiological indicators and transcription level changes of stress-related genes, were determined under drought treatment. Under drought stress, transgenic plants overexpressing HvFBX158 exhibited enhanced drought tolerance and longer root lengths compared to wild-type plants. Additionally, malondialdehyde and hydrogen peroxide contents were significantly lower in transgenic lines, while superoxide dismutase activity was elevated. Quantitative RT-PCR showed that the expression levels of drought and stress response genes, including AtP5CS, AtDREB2A, AtGSH1, AtHSP17.8, and AtSOD, were significantly upregulated. Transcriptome analysis further confirmed that HvFBX158 regulated multiple stress tolerance pathways. In summary, the overexpression of the HvFBX158 gene enhanced drought tolerance in Arabidopsis thaliana by regulating multiple stress response pathways. This study provides a practical basis for improving drought-resistant barley varieties and lays a foundation for subsequent research on F-box family genes for stress resistance in barley.

Maize unstable factor for orange1 encodes a nuclear protein that affects redox accumulation during kernel development

The basal endosperm transfer layer (BETL) of the maize (Zea mays L.) kernel is composed of transfer cells for nutrient transport to nourish the developing kernel. To understand the spatiotemporal processes required for BETL development, we characterized 2 unstable factor for orange1 (Zmufo1) mutant alleles. The BETL defects in these mutants were associated with high levels of reactive oxygen species, oxidative DNA damage, and cell death. Interestingly, antioxidant supplementation in in vitro cultured kernels alleviated the cellular defects in mutants. Transcriptome analysis of the loss-of-function Zmufo1 allele showed differential expression of tricarboxylic acid cycle, redox homeostasis, and BETL-related genes. The basal endosperms of the mutant alleles had high levels of acetyl-CoA and elevated histone acetyltransferase activity. The BETL cell nuclei showed reduced electron-dense regions, indicating sparse heterochromatin distribution in the mutants compared with wild-type. Zmufo1 overexpression further reduced histone methylation marks in the enhancer and gene body regions of the pericarp color1 (Zmp1) reporter gene. Zmufo1 encodes an intrinsically disordered nuclear protein with very low sequence similarity to known proteins. Yeast two-hybrid and luciferase complementation assays established that ZmUFO1 interacts with proteins that play a role in chromatin remodeling, nuclear transport, and transcriptional regulation. This study establishes the critical function of Zmufo1 during basal endosperm development in maize kernels.

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.

Glycomolecules: from "sweet immunity" to "sweet biostimulation"?

Climate changes and environmental contaminants are daunting challenges that require an urgent change from current agricultural practices to sustainable agriculture. Biostimulants are natural solutions that adhere to the principles of organic farming and are believed to have low impacts on the environment and human health. Further, they may contribute to reducing the use of chemical inputs while maintaining productivity in adverse environments. Biostimulants are generally defined as formulated substances and microorganisms showing benefits for plant growth, yield, rhizosphere function, nutrient-use efficiency, quality of harvested products, or abiotic stress tolerance. These biosolutions are categorized in different subclasses. Several of them are enriched in glycomolecules and their oligomers. However, very few studies have considered them as active molecules in biostimulation and as a subclass on their own. Herein, we describe the structure and the functions of complex polysaccharides, glycoproteins, and glycolipids in relation to plant defense or biostimulation. We also discuss the parallels between sugar-enhanced plant defense and biostimulation with glycomolecules and introduce the concept of sweet biostimulation or glycostimulation.

Comprehensive evaluation of freezing tolerance in prickly ash and its correlation with ecological and geographical origin factors

Low temperatures are a key factor affecting the growth, development, and geographical distribution of prickly ash. This study investigated the impact of ecological and geographical factors on the freezing tolerance of prickly ash germplasm. Thirty-seven germplasm samples from 18 different origins were collected, and their freezing tolerance was comprehensively evaluated. The correlation between freezing tolerance and the ecological and geographical factors of their origins was also analyzed. Significant differences in freezing tolerance were observed among germplasm from different origins. The semi-lethal temperature of the germplasm ranged from - 12.37 to 1.08 °C. As temperatures decreased, the relative conductivity (REC) and catalase (CAT) activity of the germplasm gradually increased, while soluble sugar (SS), soluble protein (SP), free proline (Pro), and Peroxidase (POD) activities decreased and then increased. Superoxide dismutase (SOD) activity initially increased and then decreased. A comprehensive evaluation of freezing tolerance was conducted using a logistic equation, membership function, and cluster analysis. Germplasm from Tongchuan and Hancheng (Shaanxi Province, China), Asakura (Japan), and Yuncheng (Shanxi Province, China) exhibited the highest freezing tolerance, whereas those from Rongchang (Chongqing Municipality, China), Qujing (Yunnan Province, China), and Honghe (Yunnan Province, China) had the lowest. The correlation analysis revealed a significant positive correlation between freezing tolerance and latitude, and a significant negative correlation with the temperature of origin. Germplasm from higher latitudes showed higher SS content, SOD and CAT activities, stronger antioxidant enzyme activity, and better freezing tolerance compared to those from lower latitudes. REC was lower in germplasm originating from low-temperature areas than in those from high-temperature areas. Additionally, SP, Pro content, SOD, and POD activities were higher, indicating effective scavenging of active oxygen free radicals. No significant correlation was found between altitude and longitude of origin and freezing tolerance. However, at similar latitudes, prickly ash from higher altitudes displayed higher antioxidant enzyme activity and stronger freezing tolerance compared to those from lower altitudes. These findings provide a scientific basis for breeding prickly ash cultivars suited to different ecological regions.

The oilseed rape R2R3-type BnaMYB78 transcription factor regulates leaf senescence by modulating PCD and chlorophyll degradation

Leaf senescence is the final stage of plant growth and development, characterized by chlorophyll degradation, organelle disintegration, and nutrient redistribution and utilization. This stage involves a complex and precise regulatory network, and the underlying mechanisms are not fully understood. Oilseed rape (Brassica napus L.) is one of the most important oil crops in China and globally. Therefore, mining and studying the key factors modulating leaf senescence and abscission in oilseed rape is of great importance to improve its yielding and nutrient use efficiency. In this study, we report that BnaMYB78 positively regulates leaf senescence in oilseed rape. As a transcriptional activator located in the nucleus, BnaMYB78 can bind to the SMRE7 (A/G)CC(T/A)AA(C/T) cis-element in vitro and positively regulate the expression of BnaPBS3, BnaMC9, and BnaNYC1 in oilseed rape. Overexpression of BnaMYB78 leads to chlorophyll degradation and premature leaf senescence in both Arabidopsis thaliana and oilseed rape. During this process, the expression of several genes associated with salicylic acid (SA) synthesis, chlorophyll metabolism, and senescence-associated genes (SAGs) was upregulated, including BnaPPH, BnaSAG14, BnaMC9, BnaPBS3, BnaNYC1, and BnaICS1, which facilitate the progression of programmed cell death (PCD). Further analyses demonstrated that BnaMYB78 activates the promoter activities of BnaMC9, BnaPBS3, and BnaNYC1 in a dual-luciferase reporter assay. Electrophoretic mobility shift assays (EMSAs) and chromatin immunoprecipitation coupled with quantitative PCR (ChIP-qPCR) assays revealed that BnaMYB78 directly binds to the promoter regions of these downstream target genes. In summary, our data demonstrate that BnaMYB78 modulates cell death and leaf senescence.

Microbe-Friendly Plants Enable Beneficial Interactions with Soil Rhizosphere Bacteria by Lowering Their Defense Responses

The use of plant growth-promoting rhizobacteria presents a promising addition to conventional mineral fertilizer use and an alternative strategy for sustainable agricultural crop production. However, genotypic variations in the plant host may result in variability of the beneficial effects from these plant-microbe interactions. This study examined growth promotion effects of commercial vegetable crop cultivars of tomato, cucumber and broccoli following application with five rhizosphere bacteria. Biochemical assays revealed that the bacterial strains used possess several nutrient acquisition traits that benefit plants, including nitrogen fixation, phosphate solubilization, biofilm formation, and indole-3-acetic acid (IAA) production. However, different host cultivars displayed genotype-specific responses from the inoculations, resulting in significant (p < 0.05) plant growth promotion in some cultivars but insignificant (p > 0.05) or no growth promotion in others. Gene expression profiling in tomato cultivars revealed that these cultivar-specific phenotypes are reflected in differential expressions of defense and nutrient acquisition genes, suggesting that plants can be categorized into "microbe-friendly" cultivars (with little or no defense responses against beneficial microbes) and "microbe-hostile" cultivars (with strong defense responses). These results validate the notion that "microbe-friendly" (positive interaction with rhizosphere microbes) should be considered an important trait in breeding programs when developing new cultivars which could result in improved crop yields.

Effects of Different LED Spectra on the Antioxidant Capacity and Nitrogen Metabolism of Chinese Cabbage (Brassica rapa L. ssp. Pekinensis)

Light quality optimization is a cost-effective method for increasing leafy vegetable quality in plant factories. Light-emitting diodes (LEDs) that enable the precise modulation of light quality were used in this study to examine the effects of red-blue (RB), red-blue-green (RBG), red-blue-purple (RBP), and red-blue-far-red (RBF) lights on the growth, antioxidant capacity, and nitrogen metabolism of Chinese cabbage leaves, while white light served as the control (CK). Results showed that the chlorophyll, carotenoid, vitamin C, amino acid, total flavonoid, and antioxidant levels of Chinese cabbage were all significantly increased under RBP combined light treatment. Meanwhile, RBG combined light treatment significantly increased the levels of amino acids but decreased the nitrite content of Chinese cabbage. In addition, RBF combined light treatment remarkably increased the amino acid levels but decreased the antioxidant capacity of Chinese cabbage. In conclusion, the addition of purple light to red-blue light was effective in improving the nutritional value and antioxidant capacity of Chinese cabbage. This light condition can be used as a model for a supplemental lighting strategy for leafy vegetables in plant factory production.

Redox regulation of meristem quiescence: outside/in

Quiescence is an essential property of meristematic cells, which restrains the cell cycle while retaining the capacity to divide. This crucial process not only facilitates life-long tissue homeostasis and regenerative capacity but also provides protection against adverse environmental conditions, enabling cells to conserve the proliferative potency while minimizing DNA damage. As a survival attribute, quiescence is inherently regulated by the products of aerobic life, in particular reactive oxygen species (ROS) and the redox (reduction/oxidation) mechanisms that plant have evolved to channel these into pervasive signals. Adaptive responses allow quiescent cells to compensate for reduced oxygen tension (hypoxia) in a reversible manner, while the regulated production of the superoxide anion (O2·-) facilitates cell division and the maintenance of stem cells. Here we discuss the role of ROS and redox reactions in the control of the quiescent state in plant meristems, and how this process is integrated with cellular energy and hormone biochemistry. We consider the pathways that sense and transmit redox signals with a focus on the central significance of redox regulation in the mitochondria and nucleus, which is a major regulator of quiescence in meristems. We discuss recent studies that suggest that ROS are a critical component of the feedback loops that control stem cell identity and fate, and suggest that the ROS/hypoxia interface is an important 'outside/in' positional cue for plant cells, particularly in meristems.

AT-hook motif nuclear localized transcription factors function redundantly in promoting root growth through modulation of redox homeostasis

Maintaining an optimal redox status is essential for plant growth and development, particularly when the plants are under stress. AT-hook motif nuclear localized (AHL) proteins are evolutionarily conserved transcription factors in plants. Much of our understanding about this gene family has been derived from studies on clade A members. To elucidate the functions of clade B genes, we first analyzed their spatial expression patterns using transgenic plants expressing a nuclear localized GFP under the control of their promoter sequences. AHL1, 2, 6, 7, and 10 were further functionally characterized owing to their high expression in the root apical meristem. Through mutant analyses and transgenic studies, we showed that these genes have the ability to promote root growth. Using yeast one-hybrid and dual luciferase assays, we demonstrated that AHL1, 2, 6, 7, and 10 are transcription regulators and this activity is required for their roles in root growth. Although mutants for these genes did not showed obvious defects in root growth, transgenic plants expressing their fusion proteins with the SRDX repressor motif exhibited a short-root phenotype. Through transcriptome analysis, histochemical staining and molecular genetics experiments, we found that AHL10 maintains redox homeostasis via direct regulation of glutathione transferase (GST) genes. When the transcript level of GSTF2, a top-ranked target of AHL10, was reduced by RNAi, the short-root phenotype in the AHL10-SRDX expressing plant was largely rescued. These results together suggest that AHL genes function redundantly in promoting root growth through direct regulation of redox homeostasis.

GLUTAMYL-tRNA SYNTHETASE 1 deficiency confers thermosensitive male sterility in rice by affecting reactive oxygen species homeostasis

Temperature is one of the key environmental factors influencing crop fertility and yield. Understanding how plants sense and respond to temperature changes is, therefore, crucial for improving agricultural production. In this study, we characterized a temperature-sensitive male sterile mutant in rice (Oryza sativa), glutamyl-tRNA synthetase 1-2 (ers1-2), that shows reduced fertility at high temperatures and restored fertility at low temperatures. Mutation of ERS1 resulted in severely delayed pollen development and meiotic progression at high temperatures, eventually leading to male sterility. Moreover, meiosis-specific events, including synapsis and crossover formation, were also delayed in ers1-2 compared with the wild type. However, these defects were all mitigated by growing ers1-2 at low temperatures. Transcriptome analysis and measurement of ascorbate, glutathione, and hydrogen peroxide (H2O2) contents revealed that the delayed meiotic progression and male sterility in ers1-2 were strongly associated with changes in reactive oxygen species (ROS) homeostasis. At high temperatures, ers1-2 exhibited decreased accumulation of ROS scavengers and overaccumulation of ROS. In contrast, at low temperatures, the antioxidant system of ROS was more active, and ROS contents were lower. These data suggest that ROS homeostasis in ers1-2 is disrupted at high temperatures but restored at low temperatures. We speculate that ERS1 dysfunction leads to changes in ROS homeostasis under different conditions, resulting in delayed or rescued meiotic progression and thermosensitive male fertility. ers1-2 may hold great potential as a thermosensitive material for crop heterosis breeding.

Chloroplast thiol redox dynamics through the lens of genetically encoded biosensors

Chloroplasts fix carbon by using light energy and have evolved a complex redox network that supports plastid functions by (i) protecting against reactive oxygen species and (ii) metabolic regulation in response to environmental conditions. In thioredoxin- and glutathione/glutaredoxin-dependent redox cascades, protein cysteinyl redox steady states are set by varying oxidation and reduction rates. The specificity and interplay of these different redox-active proteins are still under investigation, for example to understand how plants cope with adverse environmental conditions by acclimation. Genetically encoded biosensors with distinct specificity can be targeted to subcellular compartments such as the chloroplast stroma, enabling in vivo real-time measurements of physiological parameters at different scales. These data have provided unique insights into dynamic behaviours of physiological parameters and redox-responsive proteins at several levels of the known redox cascades. This review summarizes current applications of different biosensor types as well as the dynamics of distinct protein cysteinyl redox steady states, with an emphasis on light responses.

GhJUB1_3-At positively regulate drought and salt stress tolerance under control of GhHB7, GhRAP2-3 and GhRAV1 in Cotton

Climate change severely affects crop production. Cotton is one of the primary fiber crops in the world and its production is susceptible to various environmental stresses, especially drought and salinity. Development of stress tolerant genotypes is the only way to escape from these environmental constraints. We identified sixteen homologs of the Arabidopsis JUB1 gene in cotton. Expression of GhJUB1_3-At was significantly induced in the temporal expression analysis of GhJUB1 genes in the roots of drought tolerant (H177) and susceptible (S9612) cotton genotypes under drought. The silencing of the GhJUB1_3-At gene alone and together with its paralogue GhJUB1_3-Dt reduced the drought tolerance in cotton plants. The transgenic lines exhibited tolerance to the drought and salt stress as compared to the wildtype (WT). The chlorophyll and relative water contents of wildtype decreased under drought as compared to the transgenic lines. The transgenic lines showed decreased H2O2 and increased proline levels under drought and salt stress, as compared to the WT, indicating that the transgenic lines have drought and salt stress tolerance. The expression analysis of the transgenic lines and WT revealed that GAI was upregulated in the transgenic lines in normal conditions as compared to the WT. Under drought and salt treatment, RAB18 and RD29A were strongly upregulated in the transgenic lines as compared to the WT. Conclusively, GhJUB1_3-At is not an auto activator and it is regulated by the crosstalk of GhHB7, GhRAP2-3 and GhRAV1. GhRAV1, a negative regulator of abiotic stress tolerance and positive regulator of leaf senescence, suppresses the expression of GhJUB1_3-At under severe circumstances leading to plant death.

Priming of Exogenous Salicylic Acid under Field Conditions Enhances Crop Yield through Resistance to Magnaporthe oryzae by Modulating Phytohormones and Antioxidant Enzymes

This study explores the impact of exogenous salicylic acid (SA) alongside conventional treatment by farmers providing positive (Mancozeb 80 % WP) and negative (water) controls on rice plants (Oryza sativa L.), focusing on antioxidant enzyme activities, phytohormone levels, disease resistance, and yield components under greenhouse and field conditions. In greenhouse assays, SA application significantly enhanced the activities of peroxidase (POX), polyphenol oxidase (PPO), catalase (CAT), and superoxide dismutase (SOD) within 12-24 h post-inoculation (hpi) with Magnaporthe oryzae. Additionally, SA-treated plants showed higher levels of endogenous SA and indole-3-acetic acid (IAA) within 24 hpi compared to the controls. In terms of disease resistance, SA-treated plants exhibited a reduced severity of rice blast under greenhouse conditions, with a significant decrease in disease symptoms compared to negative control treatment. The field study was extended over three consecutive crop seasons during 2021-2023, further examining the efficacy of SA in regular agricultural practice settings. The SA treatment consistently led to a reduction in rice blast disease severity across all three seasons. Yield-related parameters such as plant height, the number of tillers and panicles per hill, grains per panicle, and 1000-grain weight all showed improvements under SA treatment compared to both positive and negative control treatments. Specifically, SA-treated plants yielded higher grain outputs in all three crop seasons, underscoring the potential of SA as a growth enhancer and as a protective agent against rice blast disease under both controlled and field conditions. These findings state the broad-spectrum benefits of SA application in rice cultivation, highlighting its role not only in bolstering plant defense mechanisms and growth under greenhouse conditions but also in enhancing yield and disease resistance in field settings across multiple crop cycles. This research presents valuable insights into the practical applications of SA in improving rice plant resilience and productivity, offering a promising approach for sustainable agriculture practices.

Quantitative Proteomics Analysis of ABA- and GA3-Treated Malbec Berries Reveals Insights into H2O2 Scavenging and Anthocyanin Dynamics

Abscisic acid (ABA) and gibberellic acid (GA3) are regulators of fruit color and sugar levels, and the application of these hormones is a common practice in commercial vineyards dedicated to the production of table grapes. However, the effects of exogenous ABA and GA3 on wine cultivars remain unclear. We investigated the impact of ABA and GA3 application on Malbec grapevine berries across three developmental stages. We found similar patterns of berry total anthocyanin accumulation induced by both treatments, closely associated with berry H2O2 levels. Quantitative proteomics from berry skins revealed that ABA and GA3 positively modulated antioxidant defense proteins, mitigating H2O2. Consequently, proteins involved in phenylpropanoid biosynthesis were downregulated, leading to decreased anthocyanin content at the almost ripe stage, particularly petunidin-3-G and peonidin-3-G. Additionally, we noted increased levels of the non-anthocyanins E-viniferin and quercetin in the treated berries, which may enhance H2O2 scavenging at the almost ripe stage. Using a linear mixed-effects model, we found statistical significance for fixed effects including the berry H2O2 and sugar contents, demonstrating their roles in anthocyanin accumulation. In conclusion, our findings suggest a common molecular mechanism by which ABA and GA3 influence berry H2O2 content, ultimately impacting anthocyanin dynamics during ripening.

Redox regulation of gene expression: proteomics reveals multiple previously undescribed redox-sensitive cysteines in transcription complexes and chromatin modifiers

Redox signalling is crucial for regulating plant development and adaptation to environmental changes. Proteins with redox-sensitive cysteines can sense oxidative stress and modulate their functions. Recent proteomics efforts have comprehensively mapped the proteins targeted by oxidative modifications. The nucleus, the epicentre of transcriptional reprogramming, contains a large number of proteins that control gene expression. Specific redox-sensitive transcription factors have long been recognized as key players in decoding redox signals in the nucleus and thus in regulating transcriptional responses. Consequently, the redox regulation of the nuclear transcription machinery and its cofactors has received less attention. In this review, we screened proteomic datasets for redox-sensitive cysteines on proteins of the core transcription complexes and chromatin modifiers in Arabidopsis thaliana. Our analysis indicates that redox regulation affects every step of gene transcription, from initiation to elongation and termination. We report previously undescribed redox-sensitive subunits in transcription complexes and discuss the emerging challenges in unravelling the landscape of redox-regulated processes involved in nuclear gene transcription.

Surviving the stress: Understanding the molecular basis of plant adaptations and uncovering the role of mycorrhizal association in plant abiotic stresses

Environmental stresses severely impair plant growth, resulting in significant crop yield and quality loss. Among various abiotic factors, salt and drought stresses are one of the major factors that affect the nutrients and water uptake by the plants, hence ultimately various physiological aspects of the plants that compromises crop yield. Continuous efforts have been made to investigate, dissect and improve plant adaptations at the molecular level in response to drought and salinity stresses. In this context, the plant beneficial microbiome presents in the rhizosphere, endosphere, and phyllosphere, also referred as second genomes of the plant is well known for its roles in plant adaptations. Exploration of beneficial interaction of fungi with host plants known as mycorrhizal association is one such special interaction that can facilitates the host plants adaptations. Mycorrhiza assist in alleviating the salinity and drought stresses of plants via redistributing the ion imbalance through translocation to different parts of the plants, as well as triggering oxidative machinery. Mycorrhiza association also regulates the level of various plant growth regulators, osmolytes and assists in acquiring minerals that are helpful in plant's adaptation against extreme environmental stresses. The current review examines the role of various plant growth regulators and plants' antioxidative systems, followed by mycorrhizal association during drought and salt stresses.

Molecular Identification of the Glutaredoxin 5 Gene That Plays Important Roles in Antioxidant Defense in Arma chinensis (Fallou)

Glutaredoxin (Grx) is a group of redox enzymes that control reactive oxygen species (ROS), traditionally defined as redox regulators. Recent research suggested that members of the Grx family may be involved in more biological processes than previously thought. Therefore, we cloned the AcGrx5 gene and identified its role in A. chinensis diapause. Sequence analysis revealed the ORF of AcGrx5 was 432 bp, encoding 143 amino acids, which was consistent with the homologous sequence of Halyomorpha halys. RT-qPCR results showed that AcGrx5 expression was the highest in the head, and compared with non-diapause conditions, diapause conditions significantly increased the expression of AcGrx5 in the developmental stages. Further, we found that 15 °C low-temperature stress significantly induced AcGrx5 expression, and the expression of antioxidant enzyme genes AcTrx2 and AcTrx-like were significantly increased after AcGrx5 knockdown. Following AcGrx5 silencing, there was a considerable rise in the levels of VC content, CAT activity, and hydrogen peroxide content, indicating that A. chinensis was exposed to high levels of reactive oxygen species. These results suggested that the AcGrx5 gene may play a key role in antioxidant defense.

Exogenous Sodium Nitroprusside Affects the Redox System of Wheat Roots Differentially Regulating the Activity of Antioxidant Enzymes under Short-Time Osmotic Stress

Nitric oxide (NO) is a multifunctional signalling molecule involved in the regulation of plant ontogenesis and adaptation to different adverse environmental factors, in particular to osmotic stress. Understanding NO-induced plant protection is important for the improvement of plant stress tolerance and crop productivity under global climate changes. The root system is crucial for plant survival in a changeable environment. Damages that it experiences under water deficit conditions during the initial developmental periods seriously affect the viability of the plants. This work was devoted to the comparative analysis of the pretreatment of wheat seedlings through the root system with NO donor sodium nitroprusside (SNP) for 24 h on various parameters of redox homeostasis under exposure to osmotic stress (PEG 6000, 12%) over 0.5-24 h. The active and exhausted solutions of SNP, termed as (SNP/+NO) and (SNP/-NO), respectively, were used in this work at a concentration of 2 × 10-4 M. Using biochemistry and light microscopy methods, it has been revealed that osmotic stress caused oxidative damages and the disruption of membrane cell structures in wheat roots. PEG exposure increased the production of superoxide (O2•-), hydrogen peroxide (H2O2), malondialdehyde (MDA), and the levels of electrolyte leakage (EL) and lipid peroxidation (LPO). Stress treatment enhanced the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), the excretion of proline, and the rate of cell death and inhibited their division. Pretreatment with (SNP/+NO) decreased PEG-induced root damages by differently regulating the antioxidant enzymes under stress conditions. Thus, (SNP/+NO) pretreatment led to SOD, APX, and CAT inhibition during the first 4 h of stress and stimulated their activity after 24 h of PEG exposure when compared to SNP-untreated or (SNP/-NO)-pretreated and stress-subjected plants. Osmotic stress triggered the intense excretion of proline by roots into the external medium. Pretreatment with (SNP/+NO) in contrast with (SNP/-NO) additionally increased stress-induced proline excretion. Our results indicate that NO is able to mitigate the destructive effects of osmotic stress on the roots of wheat seedlings. However, the mechanisms of NO protective action may be different at certain periods of stress exposure.

Exploring the effects of red light night break on the defence mechanisms of tomato against fungal pathogen Botrytis cinerea

Plant infections caused by fungi lead to significant crop losses worldwide every year. This study aims to better understand the plant defence mechanisms regulated by red light, in particular, the effects of red light at night when most phytopathogens are highly infectious. Our results showed that superoxide production significantly increased immediately after red light exposure and, together with hydrogen peroxide levels, was highest at dawn after 30 min of nocturnal red-light treatment. In parallel, red-light-induced expression and increased the activities of several antioxidant enzymes. The nocturnal red light did not affect salicylic acid but increased jasmonic acid levels immediately after illumination, whereas abscisic acid levels increased 3 h after nocturnal red-light exposure at dawn. Based on the RNAseq data, red light immediately increased the transcription of several chloroplastic chlorophyll a-b binding protein and circadian rhythm-related genes, such as Constans 1, CONSTANS interacting protein 1 and zinc finger protein CONSTANS-LIKE 10. In addition, the levels of several transcription factors were also increased after red light exposure, such as the DOF zinc finger protein and a MYB transcription factor involved in the regulation of circadian rhythms and defence responses in tomato. In addition to identifying these key transcription factors in tomato, the application of red light at night for one week not only reactivated key antioxidant enzymes at the gene and enzyme activity level at dawn but also contributed to a more efficient and successful defence against Botrytis cinerea infection.

CRWN nuclear lamina components maintain the H3K27me3 landscape and promote successful reproduction in Arabidopsis

Arabidopsis lamin analogs CROWDED NUCLEIs (CRWNs) are necessary to maintain nuclear structure, genome function, and proper plant growth. However, whether and how CRWNs impact reproduction and genome-wide epigenetic modifications is unknown. Here, we investigate the role of CRWNs during the development of gametophytes, seeds, and endosperm, using genomic and epigenomic profiling methods. We observed defects in crwn mutant seeds including seed abortion and reduced germination rate. Quadruple crwn null genotypes were rarely transmitted through gametophytes. Because defects in seeds often stem from abnormal endosperm development, we focused on crwn1 crwn2 (crwn1/2) endosperm. These mutant seeds exhibited enlarged chalazal endosperm cysts and increased expression of stress-related genes and the MADS-box transcription factor PHERES1 and its targets. Previously, it was shown that PHERES1 expression is regulated by H3K27me3 and that CRWN1 interacts with the PRC2 interactor PWO1. Thus, we tested whether crwn1/2 alters H3K27me3 patterns. We observed a mild loss of H3K27me3 at several hundred loci, which differed between endosperm and leaves. These data indicate that CRWNs are necessary to maintain the H3K27me3 landscape, with tissue-specific chromatin and transcriptional consequences.

The genetic orchestra of salicylic acid in plant resilience to climate change induced abiotic stress: critical review

Climate change, driven by human activities and natural processes, has led to critical alterations in varying patterns during cropping seasons and is a vital threat to global food security. The climate change impose several abiotic stresses on crop production systems. These abiotic stresses include extreme temperatures, drought, and salinity, which expose agricultural fields to more vulnerable conditions and lead to substantial crop yield and quality losses. Plant hormones, especially salicylic acid (SA), has crucial roles for plant resiliency under unfavorable environments. This review explores the genetics and molecular mechanisms underlying SA's role in mitigating abiotic stress-induced damage in plants. It also explores the SA biosynthesis pathways, and highlights the regulation of their products under several abiotic stresses. Various roles and possible modes of action of SA in mitigating abiotic stresses are discussed, along with unraveling the genetic mechanisms and genes involved in responses under stress conditions. Additionally, this review investigates molecular pathways and mechanisms through which SA exerts its protective effects, such as redox signaling, cross-talks with other plant hormones, and mitogen-activated protein kinase pathways. Moreover, the review discusses potentials of using genetic engineering approaches, such as CRISPR technology, for deciphering the roles of SA in enhancing plant resilience to climate change related abiotic stresses. This comprehensive analysis bridges the gap between genetics of SA role in response to climate change related stressors. Overall goal is to highlight SA's significance in safeguarding plants and by offering insights of SA hormone for sustainable agriculture under challenging environmental conditions.

The miR6445-NAC029 module regulates drought tolerance by regulating the expression of glutathione S-transferase U23 and reactive oxygen species scavenging in Populus

MicroRNAs are essential in plant development and stress resistance, but their specific roles in drought stress require further investigation. Here, we have uncovered that a Populus-specific microRNAs (miRNA), miR6445, targeting NAC (NAM, ATAF, and CUC) family genes, is involved in regulating drought tolerance of poplar. The expression level of miR6445 was significantly upregulated under drought stress; concomitantly, seven targeted NAC genes showed significant downregulation. Silencing the expression of miR6445 by short tandem target mimic technology significantly decreased the drought tolerance in poplar. Furthermore, 5' RACE experiments confirmed that miR6445 directly targeted NAC029. The overexpression lines of PtrNAC029 (OE-NAC029) showed increased sensitivity to drought compared with knockout lines (Crispr-NAC029), consistent with the drought-sensitive phenotype observed in miR6445-silenced strains. PtrNAC029 was further verified to directly bind to the promoters of glutathione S-transferase U23 (GSTU23) and inhibit its expression. Both Crispr-NAC029 and PtrGSTU23 overexpressing plants showed higher levels of PtrGSTU23 transcript and GST activity while accumulating less reactive oxygen species (ROS). Moreover, poplars overexpressing GSTU23 demonstrated enhanced drought tolerance. Taken together, our research reveals the crucial role of the miR6445-NAC029-GSTU23 module in enhancing poplar drought tolerance by regulating ROS homeostasis. This finding provides new molecular targets for improving the drought resistance of trees.

Superoxide Dismutase Premodulates Oxidative Stress in Plastids for Protection of Tobacco Plants from Cold Damage Ultrastructure Damage

ROS-dependent induction of oxidative damage can be used as a trigger initiating genetically determined non-specific protection in plant cells and tissues. Plants are potentially able to withstand various specific (toxic, osmotic) factors of abiotic effects, but do not have sufficient or specific sensitivity to form an adequate effective response. In this work, we demonstrate one of the possible approaches for successful cold acclimation through the formation of effective protection of photosynthetic structures due to the insertion of the heterologous FeSOD gene into the tobacco genome under the control of the constitutive promoter and equipped with a signal sequence targeting the protein to plastid. The increased enzymatic activity of superoxide dismutase in the plastid compartment of transgenic tobacco plants enables them to tolerate the oxidative factor of environmental stresses scavenging ROS. On the other hand, the cost of such resistance is quite high and, when grown under normal conditions, disturbs the arrangement of the intrachloroplastic subdomains leading to the modification of stromal thylakoids, probably significantly affecting the photosynthesis processes that regulate the efficiency of photosystem II. This is partially compensated for by the fact that, at the same time, under normal conditions, the production of peroxide induces the activation of ROS detoxification enzymes. However, a violation of a number of processes, such as the metabolism of accumulation, and utilization and transportation of sugars and starch, is significantly altered, which leads to a shift in metabolic chains. The expected step for further improvement of the applied technology could be both the use of inducible promoters in the expression cassette, and the addition of other genes encoding for hydrogen peroxide-scavenging enzymes in the genetic construct that are downstream in the metabolic chain.

A multilevel investigation to reveal the regulatory mechanism of lignin accumulation in juice sac granulation of pomelo

Granulation of juice sacs is a physiological disorder, which affects pomelo fruit quality. Here, the transcriptome and ubiquitinome of the granulated juice sacs were analyzed in Guanxi pomelo. We found that lignin accumulation in the granulated juice sacs was regulated at transcription and protein modification levels. In transcriptome data, we found that the genes in lignin biosynthesis pathway and antioxidant enzyme system of the granulated juice sacs were significantly upregulated. However, in ubiquitinome data, we found that ubiquitinated antioxidant enzymes increased in abundance but the enzyme activities decreased after the modification, which gave rise to reactive oxygen species (ROS) contents in granulated juice sacs. This finding suggests that ubiquitination level of the antioxidant enzymes is negatively correlated with the enzyme activities. Increased H2O2 is considered to be a signaling molecule to activate the key gene expressions in lignin biosynthesis pathway, which leads to the lignification in granulated juice sacs of pomelo. This regulatory mechanism in juice sac granulation of pomelo was further confirmed through the verification experiment using tissue culture by adding H2O2 or dimethylthiourea (DMTU). Our findings suggest that scavenging H2O2 and other ROS are important for reducing lignin accumulation, alleviating juice sac granulation and improving pomelo fruit quality.

Temperature-sensitive splicing defects in Arabidopsis mitochondria caused by mutations in the ROOT PRIMORDIUM DEFECTIVE 1 gene

Group II introns in plant organelles have lost splicing autonomy and require the assistance of nuclear-encoded trans-factors whose roles remain to be elucidated. These factors can be mono- or poly-specific with respect to the number of introns whose splicing they facilitate. Poly-acting splicing factors are often essential and their genetic identification may benefit from the use of conditional mutations. Temperature-sensitive (TS) mutations in the ROOT PRIMORDIUM DEFECTIVE 1 (RPD1) gene were initially selected for their inhibitory effect on root formation in Arabidopsis. Further analysis revealed that RPD1 encodes a mitochondria-targeted RNA-binding protein family member, suggesting a role in mitochondrial gene expression and making its role in root formation enigmatic. We analysed the function of RPD1 and found that it is required for the removal of 9 mitochondrial group II introns and that the identified TS mutations affect the splicing function of RPD1. These results support that the inhibition of adventitious root formation at non-permissive temperature results from a reduction in RPD1 activity and thus mitochondrial activity. We further show that RPD1 physically associates in vivo with the introns whose splicing it facilitates. Preliminary mapping indicates that RPD1 may not bind to the same regions within all of its intron targets, suggesting potential variability in its influence on splicing activation.

Physiological function and regulation of ascorbate peroxidase isoforms

Ascorbate peroxidase (APX) reduces H2O2 to H2O by utilizing ascorbate as a specific electron donor and constitutes the ascorbate-glutathione cycle in organelles of plants including chloroplasts, cytosol, mitochondria, and peroxisomes. It has been almost 40 years since APX was discovered as an important plant-specific H2O2-scavenging enzyme, during which time many research groups have conducted molecular physiological analyses. It is now clear that APX isoforms function not only just as antioxidant enzymes but also as important factors in intracellular redox regulation through the metabolism of reactive oxygen species. The function of APX isoforms is regulated at multiple steps, from the transcriptional level to post-translational modifications of enzymes, thereby allowing them to respond flexibly to ever-changing environmental factors and physiological phenomena such as cell growth and signal transduction. In this review, we summarize the physiological functions and regulation mechanisms of expression of each APX isoform.

ZmmiR398b negatively regulates maize resistance to sugarcane mosaic virus infection by targeting ZmCSD2/4/9

MicroRNAs (miRNAs) are widely involved in various biological processes of plants and contribute to plant resistance against various pathogens. In this study, upon sugarcane mosaic virus (SCMV) infection, the accumulation of maize (Zea mays) miR398b (ZmmiR398b) was significantly reduced in resistant inbred line Chang7-2, while it was increased in susceptible inbred line Mo17. Degradome sequencing analysis coupled with transient co-expression assays revealed that ZmmiR398b can target Cu/Zn-superoxidase dismutase2 (ZmCSD2), ZmCSD4, and ZmCSD9 in vivo, of which the expression levels were all upregulated by SCMV infection in Chang7-2 and Mo17. Moreover, overexpressing ZmmiR398b (OE398b) exhibited increased susceptibility to SCMV infection, probably by increasing reactive oxygen species (ROS) accumulation, which were consistent with ZmCSD2/4/9-silenced maize plants. By contrast, silencing ZmmiR398b (STTM398b) through short tandem target mimic (STTM) technology enhanced maize resistance to SCMV infection and decreased ROS levels. Interestingly, copper (Cu)-gradient hydroponic experiments demonstrated that Cu deficiency promoted SCMV infection while Cu sufficiency inhibited SCMV infection by regulating accumulations of ZmmiR398b and ZmCSD2/4/9 in maize. These results revealed that manipulating the ZmmiR398b-ZmCSD2/4/9-ROS module provides a prospective strategy for developing SCMV-tolerant maize varieties.

A calmodulin-like protein PvCML9 negatively regulates salt tolerance

Calmodulin-like proteins (CMLs) are unique Ca2+ sensors and play crucial roles in response to abiotic stress in plants. A salt-repressed PvCML9 from halophyte seashore paspalum (Paspalum vaginatum O. Swartz) was identified. PvCML9 was localized in the cytoplasm and nucleus and highly expressed in roots and stems. Overexpression of PvCML9 led to reduced salt tolerance in rice and seashore paspalum, whereas downregulating expression of PvCML9 showed increased salt tolerance in seashore paspalum as compared with the wild type (WT), indicating that PvCML9 regulated salt tolerance negatively. Na+ and K+ homeostasis was altered by PvCML9 expression. Lower level of Na+/K+ ratio in roots and shoots was maintained in PvCML9-RNAi lines compared with WT under salt stress, but higher level in overexpression lines. Moreover, higher levels of SOD and CAT activities and proline accumulation were observed in PvCML9-RNAi lines compared with WT under salt stress, but lower levels in overexpression lines, which altered ROS homeostasis. Based on the above data, mutation of its homolog gene OsCML9 in rice by CRISPR/Cas9 was performed. The mutant had enhanced salt tolerance without affecting rice growth and development, suggesting that OsCML9 gene is an ideal target gene to generate salt tolerant cultivars by genome editing in the future.

Genome-wide identification and analysis of ascorbate peroxidase (APX) gene family in hemp (Cannabis sativa L.) under various abiotic stresses

Ascorbate peroxidase (APX) plays a critical role in molecular mechanisms such as plant development and defense against abiotic stresses. As an important economic crop, hemp (Cannabis sativa L.) is vulnerable to adverse environmental conditions, such as drought, cold, salt, and oxidative stress, which lead to a decline in yield and quality. Although APX genes have been characterized in a variety of plants, members of the APX gene family in hemp have not been completely identified. In this study, we (1) identified eight members of the CsAPX gene family in hemp and mapped their locations on the chromosomes using bioinformatics analysis; (2) examined the physicochemical characteristics of the proteins encoded by these CsAPX gene family members; (3) investigated their intraspecific collinearity, gene structure, conserved domains, conserved motifs, and cis-acting elements; (4) constructed a phylogenetic tree and analyzed interspecific collinearity; and (5) ascertained expression differences in leaf tissue subjected to cold, drought, salt, and oxidative stresses using quantitative real-time-PCR (qRT-PCR). Under all four stresses, CsAPX6, CsAPX7, and CsAPX8 consistently exhibited significant upregulation, whereas CsAPX2 displayed notably higher expression levels under drought stress than under the other stresses. Taken together, the results of this study provide basic genomic information on the expression of the APX gene family and pave the way for studying the role of APX genes in abiotic stress.

Enhancing Escherichia coli Inactivation: Synergistic Mechanism of Ultraviolet Light and High-Voltage Electric Field

This study investigated the bactericidal effects of ultraviolet (UV) radiation, a high-voltage electric field (HVEF), and their combination on Escherichia coli. The results indicated that UV and combined disinfection were more effective with longer exposure, leading to significant reductions in microbial activity. Specifically, the single UV disinfection alone reduced activity by 3.3 log after 5 min, while combined disinfection achieved a 4.2 log reduction. In contrast, short-term HVEF treatment did not exhibit significant bactericidal effects, only achieving a reduction of 0.17 log in 5 min. Furthermore, prolonged exposure to both UV disinfection and an HVEF was found to damage cell membranes, ultimately causing cell death, while shorter durations did not. Despite rapid cell count decreases, flow cytometry did not detect apoptotic or necrotic cells, likely due to rapid cell rupture. This study suggests that combining UV radiation and an HVEF could be a promising approach for inhibiting bacterial reproduction, with HVEF enhancing UV effects. These findings provide insights for using combined HVEF and UV disinfection in food safety and preservation.

Exploring Natural Variations in Arabidopsis thaliana: Plant Adaptability to Salt Stress

The increase in soil salinization represents a current challenge for plant productivity, as most plants, including crops, are mainly salt-sensitive species. The identification of molecular traits underpinning salt tolerance represents a primary goal for breeding programs. In this scenario, the study of intraspecific variability represents a valid tool for investigating natural genetic resources evolved by plants in different environmental conditions. As a model system, Arabidopsis thaliana, including over 750 natural accessions, represents a species extensively studied at phenotypic, metabolic, and genomic levels under different environmental conditions. Two haplogroups showing opposite root architecture (shallow or deep roots) in response to auxin flux perturbation were identified and associated with EXO70A3 locus variations. Here, we studied the influence of these genetic backgrounds on plant salt tolerance. Eight accessions belonging to the two haplogroups were tested for salt sensitivity by exposing them to moderate (75 mM NaCl) or severe (150 mM NaCl) salt stress. Salt-tolerant accessions were found in both haplogroups, and all of them showed efficient ROS-scavenging ability. Even if an exclusive relation between salt tolerance and haplogroup membership was not observed, the modulation of root system architecture might also contribute to salt tolerance.

Genome-wide association study reveals the genetic basis for petal-size formation in rapeseed (Brassica napus) and CRISPR-Cas9-mediated mutagenesis of BnFHY3 for petal-size reduction

Petals in rapeseed (Brassica napus) serve multiple functions, including protection of reproductive organs, nutrient acquisition, and attraction of pollinators. However, they also cluster densely at the top, forming a thick layer that absorbs and reflects a considerable amount of photosynthetically active radiation. Breeding genotypes with large, small, or even petal-less varieties, requires knowledge of primary genes for allelic selection and manipulation. However, our current understanding of petal-size regulation is limited, and the lack of markers and pre-breeding materials hinders targeted petal-size breeding. Here, we conducted a genome-wide association study on petal size using 295 diverse accessions. We identified 20 significant single nucleotide polymorphisms and 236 genes associated with petal-size variation. Through a cross-analysis of genomic and transcriptomic data, we focused on 14 specific genes, from which molecular markers for diverging petal-size features can be developed. Leveraging CRISPR-Cas9 technology, we successfully generated a quadruple mutant of Far-Red Elongated Hypocotyl 3 (q-bnfhy3), which exhibited smaller petals compared to the wild type. Our study provides insights into the genetic basis of petal-size regulation in rapeseed and offers abundant potential molecular markers for breeding. The q-bnfhy3 mutant unveiled a novel role of FHY3 orthologues in regulating petal size in addition to previously reported functions.