Exogenous Nitric Oxide Treatment Research Articles

Exogenous Nitric Oxide Induces Pathogenicity of Alternaria alternata on Huangguan Pear Fruit by Regulating Reactive Oxygen Species Metabolism and Cell Wall Modification.

Black spot caused by Alternaria alternata is one of the most common postharvest diseases in fruit and vegetables. A comprehensive investigation into its pathogenicity mechanism is imperative in order to propose a targeted and effective control strategy. The effect of nitric oxide (NO) on the pathogenicity of A. alternata and its underlying mechanism was studied. The results showed that treatment with 0.5 mM L-1 of sodium nitroprusside (SNP) (NO donor) increased the lesion diameter of A. alternata in vivo and in vitro, which was 22.8% and 13.2% higher than that of the control, respectively. Exogenous NO treatment also induced endogenous NO accumulation by activating nitric oxide synthase (NOS). In addition, NO triggered an increase in reactive oxygen species (ROS) levels. NO enhanced activities and gene expression levels of NADPH oxidase (NOX), superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione peroxidase (GPX), and glutathione reductase (GR). Moreover, NO stimulated cell wall degrading enzymes by activating the corresponding gene expression in vivo and in vitro. These results suggested that exogenous NO promoted the pathogenicity of A. alternata by inducing ROS accumulation and activating antioxidants and cell wall degrading enzymes. The present results could establish a theoretical foundation for the targeted control of the black spot disease in pear fruit.

Nitric oxide-mediated regulation of Aspergillus flavus asexual development by targeting TCA cycle and mitochondrial function

Nitric oxide (NO) is a signaling molecule with diverse roles in various organisms. However, its role in the opportunistic pathogen Aspergillus flavus remains unclear. This study investigates the potential of NO, mediated by metabolites from A. oryzae (AO), as an antifungal strategy against A. flavus. We demonstrated that AO metabolites effectively suppressed A. flavus asexual development, a critical stage in its lifecycle. Transcriptomic analysis revealed that AO metabolites induced NO synthesis genes, leading to increased intracellular NO levels. Reducing intracellular NO content rescued A. flavus spores from germination inhibition caused by AO metabolites. Furthermore, exogenous NO treatment and dysfunction of flavohemoglobin Fhb1, a key NO detoxification enzyme, significantly impaired A. flavus asexual development. RNA-sequencing and metabolomic analyses revealed significant metabolic disruptions within tricarboxylic acid (TCA) cycle upon AO treatment. NO treatment significantly reduced mitochondrial membrane potential (Δψm) and ATP generation. Additionally, aberrant metabolic flux within the TCA cycle was observed upon NO treatment. Further analysis revealed that NO induced S-nitrosylation of five key TCA cycle enzymes. Genetic analysis demonstrated that the S-nitrosylated Aconitase Acon and one subunit of succinate dehydrogenase Sdh2 played crucial roles in A. flavus development by regulating ATP production. This study highlights the potential of NO as a novel antifungal strategy to control A. flavus by compromising its mitochondrial function and energy metabolism.

Characterization of leucine aminopeptidase (LAP) activity in sweet pepper fruits during ripening and its inhibition by nitration and reducing events

Key messagePepper fruits contain two leucine aminopeptidase (LAP) genes which are differentially modulated during ripening and by nitric oxide. The LAP activity increases during ripening but is negatively modulated by nitration.Leucine aminopeptidase (LAP) is an essential metalloenzyme that cleaves N-terminal leucine residues from proteins but also metabolizes dipeptides and tripeptides. LAPs play a fundamental role in cell protein turnover and participate in physiological processes such as defense mechanisms against biotic and abiotic stresses, but little is known about their involvement in fruit physiology. This study aims to identify and characterize genes encoding LAP and evaluate their role during the ripening of pepper (Capsicum annuum L.) fruits and under a nitric oxide (NO)-enriched environment. Using a data-mining approach of the pepper plant genome and fruit transcriptome (RNA-seq), two LAP genes, designated CaLAP1 and CaLAP2, were identified. The time course expression analysis of these genes during different fruit ripening stages showed that whereas CaLAP1 decreased, CaLAP2 was upregulated. However, under an exogenous NO treatment of fruits, both genes were downregulated. On the contrary, it was shown that during fruit ripening LAP activity increased by 81%. An in vitro assay of the LAP activity in the presence of different modulating compounds including peroxynitrite (ONOO−), NO donors (S-nitrosoglutathione and nitrosocyteine), reducing agents such as reduced glutathione (GSH), l-cysteine (l-Cys), and cyanide triggered a differential response. Thus, peroxynitrite and reducing compounds provoked around 50% inhibition of the LAP activity in green immature fruits, whereas cyanide upregulated it 1.5 folds. To our knowledge, this is the first characterization of LAP in pepper fruits as well as of its regulation by diverse modulating compounds. Based on the capacity of LAP to metabolize dipeptides and tripeptides, it could be hypothesized that the LAP might be involved in the GSH recycling during the ripening process.

NADP-Dependent Malic Enzyme Genes in Sweet Pepper Fruits: Involvement in Ripening and Modulation by Nitric Oxide (NO).

NADPH is an indispensable cofactor in a wide range of physiological processes that is generated by a family of NADPH dehydrogenases, of which the NADP-dependent malic enzyme (NADP-ME) is a member. Pepper (Capsicum annuum L.) fruit is a horticultural product consumed worldwide that has great nutritional and economic relevance. Besides the phenotypical changes that pepper fruit undergoes during ripening, there are many associated modifications at transcriptomic, proteome, biochemical and metabolic levels. Nitric oxide (NO) is a recognized signal molecule with regulatory functions in diverse plant processes. To our knowledge, there is very scarce information about the number of genes encoding for NADP-ME in pepper plants and their expression during the ripening of sweet pepper fruit. Using a data mining approach to evaluate the pepper plant genome and fruit transcriptome (RNA-seq), five NADP-ME genes were identified, and four of them, namely CaNADP-ME2 to CaNADP-ME5, were expressed in fruit. The time course expression analysis of these genes during different fruit ripening stages, including green immature (G), breaking point (BP) and red ripe (R), showed that they were differentially modulated. Thus, while CaNADP-ME3 and CaNADP-ME5 were upregulated, CaNADP-ME2 and CaNADP-ME4 were downregulated. Exogenous NO treatment of fruit triggered the downregulation of CaNADP-ME4. We obtained a 50-75% ammonium-sulfate-enriched protein fraction containing CaNADP-ME enzyme activity, and this was assayed via non-denaturing polyacrylamide gel electrophoresis (PAGE). The results allow us to identify four isozymes designated from CaNADP-ME I to CaNADP-ME IV. Taken together, the data provide new pieces of information on the CaNADP-ME system with the identification of five CaNADP-ME genes and how the four genes expressed in pepper fruits are modulated during ripening and exogenous NO gas treatment.

Role of Exogenous Nitric Oxide in Protecting Plants against Abiotic Stresses

The continuously changing environment has led to devastating effects on the normal growth and development of plants. This necessitates the understanding of different components that can be involved in alleviating these effects. In the last two decades, nitric oxide (NO) has been largely focused on as a molecule whose endogenous production and exogenous supply lead to several molecular and physiological changes in plants under stressed conditions. Although its role as a signaling molecule in endogenous production has been largely discussed, its function in dealing with contemporary abiotic stress conditions on exogenous supply remains comparatively less explored. There is growing evidence that NO plays a critical role in many physiological processes; however, there is debate about the exact mechanism(s) through which NO lessens abiotic stress on external supply. In this review, we discuss the studies that were focused on observing the effect of exogenous NO on different abiotic stresses including heavy metal stress, element deficiency or toxicity stress, salt stress, drought stress, ultraviolet radiation stress, waterlogging stress, and chilling stress. Though the positive effects of endogenous NO have been discussed in brief in different sections, the focus of the review is to discuss the effects of exogenous NO on plant grown under abiotic stresses. Deciphering the underlying mechanism of exogenous NO treatment may open up new ideas that can suggest the successful application of NO in agricultural regions to reduce the damaging influences of different abiotic stresses.

MP20-18 EXOGENOUS NITRIC OXIDE, S-NITROSYLATES THE CSF1 RECEPTOR TO SENSITIZE THE CASTRATION-RESISTANT PROSTATE CANCER CELLS TO CSF1R BLOCKADE

You have accessJournal of UrologyCME1 Apr 2023MP20-18 EXOGENOUS NITRIC OXIDE, S-NITROSYLATES THE CSF1 RECEPTOR TO SENSITIZE THE CASTRATION-RESISTANT PROSTATE CANCER CELLS TO CSF1R BLOCKADE Fakiha Firdaus, Derek Van Booven, Rehana Qureshi, Ranjith Ramasamy, and Himanshu Arora Fakiha FirdausFakiha Firdaus More articles by this author , Derek Van BoovenDerek Van Booven More articles by this author , Rehana QureshiRehana Qureshi More articles by this author , Ranjith RamasamyRanjith Ramasamy More articles by this author , and Himanshu AroraHimanshu Arora More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003245.18AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Sustained oxidative stress in castration-resistant prostate cancer (CRPC) cells potentiates the overall tumor microenvironment (TME). Targeting the TME using colony-stimulating factor 1 receptor (CSF1R) inhibition is a promising therapy for CRPC. However, the therapeutic response to sustained CSF1R inhibition (CSF1Ri) is limited as a monotherapy. We hypothesized that one of the underlying causes for the reduced efficacy of CSF1Ri and increased oxidation in CRPC is the upregulation and uncoupling of endothelial nitric oxide synthase (NOS3). METHODS: Patient biopsies belonging to different Gleason grades were used to determine the levels of NOS3, CSF1, and GSNOR activity. A CSF1-receptor inhibitor, GW2580, was tested in-vitro and in-vivo, singularly and in combination with S-nitrosoglutathione (GSNO), an active NO donor. In-vivo dosage of 40mg/kg/day was used for GW2580, and 10mg/kg/day for GSNO was considered. Markers were checked for their expression in tumor grafts and human specimens using immunohistochemistry. Moreover, we evaluated the percentage of different immune cells using immune phenotyping in tumor cells exposed to different treatment conditions. RESULTS: We show that in high-grade PCa human specimens, NOS3 abundance positively correlates with CSF1-CSF1R signaling and remains uncoupled. The uncoupling diminishes NOS3 generation of sufficient nitric oxide (NO) required for S-nitrosylation of CSF1R at specific cysteine sites (Cys 224, Cys 278, and Cys 830). Exogenous S-nitrosothiol administration (with S-nitrosoglutathione (GSNO)) induces S-nitrosylation of CSF1R and rescues the excess oxidation in tumor regions, in turn suppressing the tumor-promoting cytokines, which are ineffectively suppressed by CSF1R blockade. Together these results suggest that the NO administration could act as an effective combinatorial partner with the CSF1R blockade against CRPC. In this context, we further show that exogenous NO treatment with GSNOR successfully augments the anti-tumor ability of CSF1Ri to reduce the overall tumor burden effectively, decreases the intratumoral percentage of anti-inflammatory macrophages, myeloid-derived progenitor cells and increases the percentage of pro-inflammatory macrophages, cytotoxic T lymphocytes, and effector T cells, respectively. CONCLUSIONS: Together, these findings support the concept that the NO-CSF1Ri combination can act as a therapeutic agent that restores control over TME, which in turn could improve the outcomes of PCa patients. Source of Funding: AUA Research Scholar Award to HAAmerican Cancer Society Grant to R.R. © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e282 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Fakiha Firdaus More articles by this author Derek Van Booven More articles by this author Rehana Qureshi More articles by this author Ranjith Ramasamy More articles by this author Himanshu Arora More articles by this author Expand All Advertisement PDF downloadLoading ...

Nitric oxide, calmodulin and calcium protein kinase interactions in the response of Brassica napus to salinity stress.

Involvement of nitric oxide (NO) in plant metabolism and its connection with phytohormones has not been fully described, thus information about the role of this molecule in signalling pathways remains fragmented. In this study, the effects of NO on calmodulin (CAM), calcium protein kinase (CPK), content of phytohormones and secondary metabolites in canola plants under salinity stress were investigated. We applied 100 μM sodium nitroprusside as an NO source to canola plants grown under saline (100 mM NaCl) and non-saline conditions at the vegetative stage. Plant growth was negatively affected by salinity, but exogenous NO treatment improved growth. NO caused a significant increase in activity of CAT, SOD and POX through their enhanced gene expression in stressed canola. Salinity-responsive genes, namely CAM and CPK, were induced by NO in plants grown under salinity. NO application enhanced phenolic compounds, such as gallic acid and coumaric acid and flavonoid compound,s catechin, diadzein and kaempferol, in plants subjected to salinity. NO treatment enhanced abscisic acid and brassinosteroids but decreased auxin and gibberellin in stressed canola plants. The impacts of NO in improving stress tolerance in canola required CAM and CPK. Also, NO signalling re-established the phytohormone balance and resulted in enhanced tolerance to salt stress. Furthermore, NO improved salinity tolerance in canola by increasing enzymatic and non-enzymatic antioxidant content.

S-nitrosylation of CSF1 receptor increases the efficacy of CSF1R blockage against prostate cancer

Sustained oxidative stress in castration-resistant prostate cancer (CRPC) cells potentiates the overall tumor microenvironment (TME). Targeting the TME using colony-stimulating factor 1 receptor (CSF1R) inhibition is a promising therapy for CRPC. However, the therapeutic response to sustained CSF1R inhibition (CSF1Ri) is limited as a monotherapy. We hypothesized that one of the underlying causes for the reduced efficacy of CSF1Ri and increased oxidation in CRPC is the upregulation and uncoupling of endothelial nitric oxide synthase (NOS3). Here we show that in high-grade PCa human specimens, NOS3 abundance positively correlates with CSF1-CSF1R signaling and remains uncoupled. The uncoupling diminishes NOS3 generation of sufficient nitric oxide (NO) required for S-nitrosylation of CSF1R at specific cysteine sites (Cys 224, Cys 278, and Cys 830). Exogenous S-nitrosothiol administration (with S-nitrosoglutathione (GSNO)) induces S-nitrosylation of CSF1R and rescues the excess oxidation in tumor regions, in turn suppressing the tumor-promoting cytokines which are ineffectively suppressed by CSF1R blockade. Together these results suggest that NO administration could act as an effective combinatorial partner with CSF1R blockade against CRPC. In this context, we further show that exogenous NO treatment with GSNOR successfully augments the anti-tumor ability of CSF1Ri to effectively reduce the overall tumor burden, decreases the intratumoral percentage of anti-inflammatory macrophages, myeloid-derived progenitor cells and increases the percentage of pro-inflammatory macrophages, cytotoxic T lymphocytes, and effector T cells, respectively. Together, these findings support the concept that the NO-CSF1Ri combination has the potential to act as a therapeutic agent that restores control over TME, which in turn could improve the outcomes of PCa patients.

Nitric oxide promotes energy metabolism and protects mitochondrial DNA in peaches during cold storage.

The mitochondria are important organelles related to energy metabolism and are susceptible to oxidative damage. In this experiment, peaches (Prunus persica) were treated with distilled water (as the control), 15 μmol L−1 of nitric oxide (NO), and 20 μmol L−1 of carboxy-PTIO (NO scavenger). The changes in mitochondrial physiological indicators, energy metabolism process, and mitochondrial DNA (mtDNA) damage and repair were quantified. Compared with the control, NO treatment reduced mitochondrial oxygen consumption and the reactive oxygen species content, increased mitochondrial respiration control rate, and promoted energy metabolism by influencing the activities of citrate synthase, aconitase, isocitrate dehydrogenase, and α‐ketoglutarate dehydrogenase in the tricarboxylic acid cycle and ATPase activity in peach mitochondria. NO treatment also maintained the relative copy number of mtDNA and the relative amplification of long PCR in peaches, decreased the level of 8-hydroxy-2 deoxyguanosine, and upregulated the expression of PpOGG1, PpAPE1, and PpLIG1. These results indicated that exogenous NO treatment (15 μmol L−1) could reduce mtDNA oxidative damage, maintain mtDNA molecular integrity, and inhibit mtDNA copy number reduction by reducing the reactive oxygen species content, thereby promoting mitochondrial energy metabolism and prolonging the storage life of peaches at low temperatures.

Alleviation of iron deficiency in pear by ammonium nitrate and nitric oxide

BackgroundIron is essential for the growth and development of trace elements in plants, and iron deficiency can lead to leaf chlorosis. Ammonium and nitrate are the major forms of nitrogen present in soils. Ammonium nitrate alleviates the chlorosis of leaves caused by iron deficiency, but the mechanism is not clear in pear.ResultsAmmonium nitrate induced the increase of nitric oxide (NO) under iron deficiency. We further analyzed the effect of NO by exogenous NO treatment. The results showed that ammonium nitrate and NO increased the activity of ferric chelate reductase. NO induced the expression of multiple IRT genes and promoted the transmembrane transport of irons. Ammonium nitrate and NO promoted the activity of nitrogen assimilation-related enzymes and the nitrogen absorption capacity, and they also increased glutamine synthetase activity. Finally, ammonium nitrate and NO increased chlorophyll synthesis, with subsequent increase in the photosynthetic capacity of plants and accumulation of biomass.ConclusionAmmonium nitrate indirectly alleviates the symptoms of plant yellowing by promoting the increase of NO, which increases the response of iron transporters. Both substances increase the nitrogen accumulation in plants. This study demonstrates a new option for minimizing Fe deficiency by regulating the balance between nutrients.

Role of Nitric Oxide in Postharvest Senescence of Fruits.

Nitric oxide (NO) acts as a gaseous signalling molecule and is considered to be a key regulator in the postharvest storage of fruits. Postharvest senescence is one of the most serious threats affecting the usage and economic value of fruits. Most recent studies have found that exogenous NO application can effectively improve the quality and prolong the shelf life of fruit postharvest by inhibiting postharvest diseases and alleviating chilling injury. Understanding the roles of NO is essential to elucidating how NO activates the appropriate set of responses to postharvest senescence. Here, we concluded that exogenous NO treatment alleviated senescence in postharvest fruit and attributed this to the following factors: (1) ethylene biosynthesis, (2) the antioxidant system, (3) polyamine metabolism and γ-aminobutyric acid (GABA) shunting, (4) cell wall metabolism, (5) sugar metabolism, (6) energy metabolism, (7) the CRT/DRE-binding factor (CBF) pathway and (8) S-nitrosylation. Moreover, crosstalk between NO and hydrogen sulfide (H2S), hydrogen peroxide (H2O2), oxalic acid (OA), arginine (Arg), GATA or plant hormone abscisic acid (ABA), melatonin (MT), and methyl jasmonate (MeJA), along with the regulation of key genes, were found to be very important in responses to postharvest senescence. In this study, we focus on the recent knowledge concerning the alleviative effect of NO on postharvest senescence, covering ethylene biosynthesis, the antioxidant system and related gene and protein expression.

Nitric Oxide Crosstalk With Phytohormone Is Involved in Enhancing Photosynthesis of Tetrastigma hemsleyanum for Photovoltaic Adaptation.

Photovoltaic agriculture is a newly emerging ecological planting pattern. In view of the adverse effect on production, a better understanding of photovoltaic adaptation responses is essential for the development of the innovative agriculture mode in sustainable crop production. Here, we investigated the impact of photovoltaic condition on endogenous hormone composition and transcriptome profile of Tetrastigma hemsleyanum. A total of 16 differentially accumulated phytohormones and 12,615 differentially expressed genes (DEGs) were identified. Photovoltaic adaptation significantly decreased the contents of phytohormones especially salicylic acid (SA) and jasmonic acid (JA). DEGs were the most relevant to photosynthesis and mitogen-activated protein kinase (MAPK) signaling pathway especially the key genes encoding proteins involved in photosystem I (PS I) and photosystem II (PS II) reaction center. Nitric oxide (NO), JA, and SA treatment alone significantly enhanced the photosynthetic efficiency which was decreased by exposure to photovoltaic condition, but the combined treatment of “NO + SA” could weaken the enhancement effect by regulating the expression level of psaL, CHIL, petF1, psbQ, and psaE genes. Exogenous phytohormones and NO treatment mitigated the accumulation of reactive oxygen species (ROS) and potentiated antioxidant capacity, which would be weakened by the combined treatment of “NO + SA.” SA and JA significantly decreased endogenous NO burst triggered by photovoltaic adaptation. SA might be a potent scavenger of NO and counter the restoration effect of NO on growth and photosynthetic potential in T. hemsleyanum. The results could provide reference for the application of phytohormones/other signaling molecules in photovoltaic agriculture.

Ameliorative effects of nitric oxide on growth, physiology and biochemistry of chickpeaplants under salinity stress

Salinity is one of the major environmental constraints affecting agriculture in major regions of the world. This study was conducted to evaluate the effect of exogenous nitric oxide (NO) treatments on two chickpea cultivars (Cagatay and Inci) under salt stress conditions. Different NO doses (0. 75 and 100 μM sodium nitroprusside (SNP)) as an NO source were applied to chickpea plants grown under saline (presence of 50 and 100 mM of NaCl) and nonsaline conditions. In this study, plant shoot fresh and dry weight, root fresh and dry weight, chlorophyll a, b, total chlorophyll, chlorophyll reading value (CRV), relative water content (RWC), electrical conductivity (EC), malondialdehyde (MDA), hydrogen peroxide (H2O2), antioxidant enzyme activity [superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX)], K/Na and Ca/Na ratio were examined. Plant growth, RWC, and chlorophyll content were negatively affected by salinity conditions but exogenous NO treatment improved the parameters. EC, H2O2, and MDA content were increased with salinity conditions while exogenous NO treatment decreased the searched parameters. K/Na and Ca/Na ratios were decreased with 50 and 100 mM of NaCl treatments. Although the cultivars response to salt stress is similar in general, Inci cultivars were found to be more sensitive to salt stress than Cağatay cultivar. The present study revealed that the exogenous NO treatment supported chickpea seedlings against salinity stress by regulating uptaking mineral elements, the antioxidant enzyme activity, and RWC.

Effects of exogenous nitric oxide on wild barley (Hordeum brevisubulatum) under salt stress

Soil salinization has become more and more serious. Exogenous nitric oxide (NO) could act in alleviating toxicity in plants. In this study, we aimed to explore the growth, photosynthetic pigments, water-solubles content, proteins, antioxidant enzyme parameters, and element contents of two types of wild barley (Hordeum brevisubulatum (Trin.) Link.), wild-type barley and Saertu wild barley cultivars, in response to salt stress. Both cultivars were first treated with 300 µmol·L −1 NaCl (increased in 25 µmol·L −1 increments to 300 µmol·L −1 for 7 days). Next, plants were sprayed with different NO concentrations on days 1, 5, 10, 15 and 20 after the NaCl concentration reached 300 µmol·L −1. The results showed that salt stress alone decreased all growth parameters [plant height (HT), fresh weight (FW), total dry weight (DW)], the photosynthetic pigment and protein contents, and the activity of the antioxidant enzymes [ascorbic acid peroxidase (APX), peroxidase (POD), catalase (CAT), superoxide dismutase (SOD)], and significantly increased the K+ and Na+ elements contents, water solubles and malondialdehyde (MDA) compared with the controls. However, the inhibitory effects of salt stress in both wild barley cultivars were alleviated by exogenous NO treatment, and 200 µmol·L −1 NO was the most effective concentration to improve plant growth, ion element levels and the physiology of wild barley under high salt stress. Altogether, this study demonstrated the beneficial role of exogenous NO donor, sodium nitroprusside, on wild barley under salinity stress and the underlying physiological and biochemical mechanisms.

Exogenous nitric oxide reduces postharvest anthracnose disease and maintains quality of custard apple (Annona squamosa L.) fruit during ripening

Custard apple is the most delicious fruit of tropical and subtropical areas. The storage life of custard apple is very limited due to fast ripening and attack of several diseases after harvesting. Anthracnose caused by the fungus Colletotrichum gloeosporioides is the most damaging postharvest disease of custard apple. The effects of postharvest nitric oxide (NO) treatment on anthracnose disease and quality of custard apple were investigated in this study. The fruit were dipped in 50, 100 and 200 µM sodium nitroprusside (SNP), the NO-donor compound, and stored for 8 days at 25 °C. The results showed that custard apple treated with 100 µM SNP treatment significantly reduced anthracnose disease incidence (97.25%) and disease severity (92.88%) after 8 days of storage. However, SNP did not exhibit substantial effect on mycelial growth and spore germination of C. gloeosporioides. Custard apple treated with SNP effectively reduced weight loss and total soluble solids. SNP treatment retained a higher level of firmness, titratable acidity, ascorbic acid and total phenolics compared to the control fruit. Additionally, the same treatment enhanced DPPH and FRAP antioxidant activities of custard apple. These results indicated that exogenous NO treatment could be a promising approach to increase resistance against fungal pathogens and maintain postharvest quality of custard apple.

Nitric oxide is essential for cadmium-induced peroxule formation and peroxisome proliferation.

Nitric oxide (NO) and nitrosylated derivatives are produced in peroxisomes, but the impact of NO metabolism on organelle functions remains largely uncharacterised. Double and triple NO-related mutants expressing cyan florescent protein (CFP)-SKL (nox1 × px-ck and nia1 nia2 × px-ck) were generated to determine whether NO regulates peroxisomal dynamics in response to cadmium (Cd) stress using confocal microscopy. Peroxule production was compromised in the nia1 nia2 mutants, which had lower NO levels than the wild-type plants. These findings show that NO is produced early in the response to Cd stress and was involved in peroxule production. Cd-induced peroxisomal proliferation was analysed using electron microscopy and by the accumulation of the peroxisomal marker PEX14. Peroxisomal proliferation was inhibited in the nia1 nia2 mutants. However, the phenotype was recovered by exogenous NO treatment. The number of peroxisomes and oxidative metabolism were changed in the NO-related mutant cells. Furthermore, the pattern of oxidative modification and S-nitrosylation of the catalase (CAT) protein was changed in the NO-related mutants in both the absence and presence of Cd stress. Peroxisome-dependent signalling was also affected in the NO-related mutants. Taken together, these results show that NO metabolism plays an important role in peroxisome functions and signalling.

Nitric Oxide Enhances Salt Tolerance through Regulating Antioxidant Enzyme Activity and Nutrient Uptake in Pea

Background: Salinity is one of the environmental stress factors that restrict the crop production by endangering agricultural areas. Nitric oxide (NO) protects plants from damage caused by oxidative stress conditions in various biological ways. Methods: In this greenhouse investigation during 2018, pea plants were irrigated with three levels of NaCl (0, 50 and 100 mM) solutions. NO solutions were prepared with three different doses (0, 75 and 100 µM SNP). These solutions were applied to the seeds before sowing and then to the leaves of the pea cultivars. The study was conducted to analyze the impact of NO on growth, malondialdehyde (MDA), hydrogen peroxide (H2O2), antioxidant enzyme activity and nutrient uptake in two pea cultivars under salinity conditions. Result: Salinity reduced fresh-dry weight, relative water content (RWC), and chlorophyll a and b content of pea. However, NO enhanced these parameters under salt stress. Salinity increased tissue electrical conductance (TEC), H2O2 and MDA content, which were decreased by combined application of NaCl and NO. Salinity caused an increase in antioxidant enzyme activity in pea and NO made a significant improvement in their activities under salinity conditions. Salinity treatments decreased the ratio of K+/Na+ and Ca2+/Na+ in both cultivars, and application of NO elevated them as compared to the control under salt stress. In conclude, exogenous NO treatment could help pea to tolerate salinity stress by increasing the chlorophyll content and regulating antioxidant enzyme activity and nutrient uptake.

Nitric oxide alleviates the effects of copper-induced DNA methylation, genomic instability, LTR retrotransposon polymorphism and enzyme activity in lettuce

Copper is an essential element for plant growth, but higher concentration can damage proteins, DNA and lipids. Nitric oxide (NO) is a highly reactive and lipophilic molecule and is functional during plant defense responses. Hence, this study aims to evaluate the role of the exogenous NO treatment (0 µM, 200 µM and 300 µM of sodium nitroprusside) on the DNA damage levels, DNA methylation, retrotransposon polymorphism and enzyme activity in lettuce seedlings grown under the non-stress and copper stressed conditions (200 and 400 µM of CuSO4·7H2O). The inter-retrotransposon amplified polymorphism (IRAP) and couple restriction enzyme digestion-random amplification (CRED-RA) were applied to define the genomic template stability (GTS) levels, DNA methylation, and retrotransposon polymorphism. Copper stress (400 µM) decreased the POD activity as compared to control, whereas combined application of NO (300 µM) and copper increased it as compared to the plants treated with 400 µM copper and without NO. The results of this study highlighted that copper stress increased genomic template instability, DNA methylation and long terminal repeat retrotransposon polymorphism. However, simultaneous treatment of NO and copper caused a decrease in retrotransposon polymorphism and DNA methylation, and an increase in GTS and enzyme activity accompanied it. The results implied that in the presence of excess copper the exogenous NO treatment mitigate the adverse effects of copper stress on the GTS, DNA methylation and retrotransposon polymorphism in lettuce seedlings by increasing antioxidant enzyme activity.

Nitric oxide alleviates toxicity of hexavalent chromium on tall fescue and improves performance of photosystem II

Tall fescue (Festuca arundinacea Schreb) was widely studied for phytoremediation of organic or heavy metal contaminated soils. However, there is still little information concerning toxicity of chromium (Cr) to tall fescue and roles of nitric oxide (NO) in plants against Cr(VI) stress. In this study, different Cr(VI) treatments (0, 1, 5 and 10 mg/L Cr(VI)) and NO treatments were applied with different combinations in hydroponics culture and their interactions to tall fescue were studied. Specifically, 100 µM sodium nitroprusside (SNP) and 100 µM NG-nitro-L-arginine-methyl ester (L-NAME) treatments were used to apply exogenous NO or inhibit synthesis of NO respectively. Our results showed that tall fescue exhibits comparable Cr(VI) tolerance as wheat (Triticum aestivum L.). Additionally, Cr(VI) accumulation in tall fescue leaves were carefully studied and discussed. Moreover, we observed the significantly increased reactive oxygen species (ROS) contents of tall fescue when subjected to Cr(VI) stress, as well as decreased photosynthetic activities induced by Cr(VI) stress by methods of chlorophyll a fluorescence transient, slow chlorophyll fluorescence kinetics and rapid light response curves. Decreased behaviors of photosynthetic activities may due to destruction of antennae pigments by Cr(VI), ROS burst induced by Cr(VI), and down regulation of photosystem II (PSII) by non-photochemical quenching to avoid over reduction of quinone A, which could be considered as an important strategy to cope with Cr(VI) stress. Meanwhile, exogenous NO treatment improves overall physiological and photosynthetic behaviors of tall fescue against Cr(VI) stress. Moreover, increased translocation factors and improved Cr(VI) tolerance of plants under exogenous NO treatment suggest that SNP treatment could be a useful application for Cr phytoremediation.

Nitric oxide signaling in yeast.

As a cellular signaling molecule, nitric oxide (NO) is widely conserved from microorganisms, such as bacteria, yeasts, and fungi, to higher eukaryotes including plants and mammals. NO is mainly produced by NO synthase (NOS) or nitrite reductase (NIR) activity. There are several NO detoxification systems, including NO dioxygenase (NOD) and S-nitrosoglutathione reductase (GSNOR). NO homeostasis based on the balance between NO synthesis and degradation is important for the regulation of its physiological functions because an excess level of NO causes nitrosative stress due to the high reactivity of NO and NO-derived compounds. In yeast, NO may be involved in stress responses, but NO and its signaling have been poorly understood due to the lack of mammalian NOS orthologs in the genome. Even though the activities of NOS and NIR have been observed in yeast cells, the gene encoding NOS and the NO production mechanism catalyzed by NIR remain unclear. On the other hand, yeast cells employ NOD and GSNOR to maintain an intracellular redox balance following endogenous NO production, exogenous NO treatment, or environmental stresses. This article reviews NO metabolism (synthesis, degradation) and its regulation in yeast. The physiological roles of NO in yeast, including the oxidative stress response, are also discussed here. Such investigations into NO signaling are essential for understanding the NO-dependent genetic and physiological modulations. In addition to being responsible for the pathology and pharmacology of various degenerative diseases, NO signaling may be a potential target for the construction and engineering of industrial yeast strains.