Exogenous Application Of Nitric Oxide Research Articles

Positive Effects of Exogenous Application of Nitric Oxide on Lipid Composition in Sesbania grandiflora (L.) Pers. under Elevated Conditions of Chromium and EDTA

Positive Effects of Exogenous Application of Nitric Oxide on Lipid Composition in <i>Sesbania grandiflora</i> (L.) Pers. under Elevated Conditions of Chromium and EDTA

Auxin acts upstream of nitric oxide to regulate cell wall xyloglucan and its aluminium-binding capacity in Arabidopsis thaliana.

Auxin acts upstream of NO through NOA and XXT5 pathways to regulate the binding capacity of the root cell wall to Al. In our previous study, we identified an unknown mechanism by which 1-naphthaleneacetic acid (NAA) decreased the fixation of aluminum (Al) in the cell wall. Here, we observed that external application of the nitric oxide (NO) donor S-nitrosoglutathion (GSNO) increased the inhibition of Al on root elongation. Further analysis indicated that GSNO could induce Al accumulation in the roots and root cell walls, which is consistent with lower xyloglucan content. In comparison to the Columbia-0 (Col-0) wild type (WT), endogenous NO-reduced mutants noa1 (NOA pathway) and nia1nia2 (NR pathway) were more resistant to Al, with lower root Al content, higher xyloglucan content, and more Al accumulation in the root cell walls. By contrast, the xxt5 mutant with reduced xyloglucan content exhibited an Al-sensitive phenotype. Interestingly, Al treatment increased the endogenous auxin and NO levels, and the auxin levels induced under Al stress further stimulated NO production. Auxin application reduced Al retention in hemicellulose and decreased the xyloglucan content, similar to the effects observed with GSNO. In yucca and aux1-7 mutants, exogenous application of NO resulted in responses similar to those of the WT, whereas exogenous auxin had little effect on the noa1 mutant under Al stress. In addition, as auxin had similar effects on the nia1nia2 mutant and the WT, exogenous auxin and NO had little effect on the xxt5 mutant under Al stress, further confirming that auxin acts upstream of NO through NOA and XXT5 pathways to regulate the binding capacity of the root cell wall to Al.

Metabolomics and Physiological Changes Underlying Increased Tolerance to Salt Stress Induced by Applied Nitric Oxide in Fatsia japonica Seedlings

Fatsia japonica (Thunb.) Decne. et Planch. is an important woody landscape plant, and its distribution is commonly limited by salt stress. Although the application of exogenous nitric oxide (NO) has been known to be effective in alleviating abiotic stress in plants, the underlying mechanism by which NO induces salt resistance in F. japonica remains unknown. In this study, the physiological and metabolic characteristics of F. japonica seedlings with the application of NO under salt stress conditions were investigated. We demonstrated that exogenous NO (0.1 mM sodium nitroprusside, SNP) mitigated the growth inhibition caused by 0.4% NaCl. This alleviation could be attributed to NO-induced enhancement in photosynthesis, osmotic adjustment, antioxidant enzyme activities, and a reduction in oxidative damage when exposed to salt stress. Furthermore, the metabolomic analysis revealed that salt stress significantly disrupts the growth of F. japonica by downregulating sugars, sugar alcohols, amino acids, and organic acids. However, the application of exogenous NO improves sugar metabolism, enhancing the levels of fructose, glucose, mannose, galactose, xylose, ribose, inositol, and sorbitol, as well as the metabolism of amino acids and organic acids. These findings provide new insights into the physiological and metabolic homeostasis adjustments induced by NO that promote salt stress tolerance in F. japonica, enhancing our understanding of plant resilience mechanisms.

Modulation of AsA-GSH cycle by exogenous nitric oxide and hydrogen peroxide to minimize the Cd-induced damages in photosynthetic cyanobacteria

Cyanobacteria, the prominent nitrogen fixers, are facing many stressful situations throughout their life span, hence in recent years the yield and productivity of paddy crops are highly compromised. To address this problem, this study is structured to investigate how signaling molecules can positively influence the ability of tested cyanobacteria to counteract the adverse effects of metal stress. Thus, the main objective of this study is to elucidate the importance and crosstalk of intracellular signaling molecules, nitric oxide (NO), and hydrogen peroxide (H2O2) during Cd stress tolerance in cyanobacteria. The effect of exogenous gasotransmitter, NO and redox molecule, H2O2, in mitigation of cadmium (Cd, 6 µM) toxicity on different physiological and biochemical activities were well recorded in economically important cyanobacteria Nostoc muscorum ATCC 27893 and Anabaena sp. PCC 7120. Under Cd stress increased Cd accumulation and oxidative stress in test cyanobacteria, impaired the functioning of the ascorbate-glutathione (AsA-GSH) cycle. Exogenous application of NO (10 µM) and H2O2 (1 µM) ameliorated the negative effects of Cd through boosting-up the activities of enzymatic (ascorbate peroxidase, glutathione reductase and dehydroascorbate reductase) and the contents of non-enzymatic (cysteine, proline, ascorbate, glutathione and non-protein-thiols) antioxidants. The application of NO scavenger (PTIO) or NO synthase enzyme inhibitor (LNAME) to the Cd-stressed cells abolished the recovery of the above parameters, even in the presence of exogenous H2O2. Notwithstanding to this, under similar stress exogenous addition of scavenger of H2O2 (NAC) or inhibitor of NADPH oxidase enzyme (DPI) to the growth medium could not restrict the recovery of the above parameters in the presence of NO, hence pointing towards the major role of NO in tolerance of the test organisms to Cd stress. In conclusion, the finding revealed that NO plays a vital role in H2O2 signaling to attain Cd stress tolerance in cyanobacteria. Moreover, the study has created a scope to search for deeper insight into signaling interactions between other gasotransmitters and redox molecules in cyanobacteria. Further, the current finding recommends using a lower dose of SNP (NO donor, a cost-effective chemical) in paddy fields may ensure better growth of cyanobacteria (biofertilizer) even under prevailing stress conditions for sustainable agriculture to maintain productivity of rice crops.

Physiological response and molecular regulatory mechanism reveal a positive role of nitric oxide and hydrogen sulfide applications in salt tolerance of Cyclocarya paliurus.

As a multifunctional tree species, Cyclocarya paliurus leaves are rich in bioactive substances with precious healthy values. To meet the huge requirement of C. paliurus leaf production, sites with some environmental stresses would be potential land for developing its plantations due to the limitation of land resources in China. Nitric oxide (NO) and hydrogen sulfide (H2S) are common gas messengers used to alleviate abiotic stress damage, whereas the mechanism of these messengers in regulating salt resistance of C. paliurus still remains unclear. We performed a comprehensive study to reveal the physiological response and molecular regulatory mechanism of C. paliurus seedlings to the application of exogenous NO and H2S under salt stress. The results showed that the application of sodium hydrosulfide (NaHS) and sodium nitroprusside (SNP) not only maintained the photosynthetic capacity and reduced the loss of leaf biomass, but also promoted endogenous NO synthesis and reduced oxidative damage by activating antioxidant enzyme activity and increasing the content of soluble protein and flavonoids. Moreover, transcriptome and metabolome analysis indicated the expression of genes encoding phenylalanine ammonia lyase (PAL), cytochromeP450 (CYP), chalcone synthase (CHS), dihydroflavonol 4-reductase (DFR) and flavonol synthase (FLS) in flavonoid biosynthesis pathway was all up-regulated by the application of NO and H2S. Meanwhile, 15 transcriptional factors (TFs) such as WRKY, ERF, bHLH and HY5 induced by NO were found to regulated the activities of several key enzymes in flavonoid biosynthesis pathway under salt stress, via the constructed co-expression network. Our findings revealed the underlying mechanism of NO and H2S to alleviate salt stress and regulate flavonoid biosynthesis, which provides a theoretical basis for establishing C. paliurus plantations in the salt stress areas.

SNP application improves drought tolerance in soybean

As an important bioactive molecule, nitric oxide (NO) can effectively alleviate the effects of drought stress on crops. However, it is still unclear whether it can increase the stress resistance of soybean. Therefore, in this study, our objective was to explore the effect of exogenous NO application on the physiological characteristics of soybean seedlings under drought stress. As test material, two soybean varieties, HN65 and HN44, were used, while sodium nitroprusside (SNP) of 100 μmol L−1, 200 μmol L−1, 500 μmol L−1, 1000 μmol L−1 served as an exogenous NO donor, and PEG-6000 as an osmotic regulator to simulate drought stress. The effects of irrigation with different SNP concentrations for different days on the physiological characteristics of the soybean seedlings under drought conditions were then investigated. The results obtained showed that the activities of antioxidant enzymes, osmotic regulator contents, as well as the abscisic acid and salicylic acid contents of the plant leaves increased with increasing SNP concentration and treatment time. However, we observed that excessively high SNP concentrations decreased the activities of key nitrogen metabolism enzymes significantly. This study provides a theoretical basis for determining a suitable exogenous NO concentration and application duration. It also highlights strategies for exploring the mechanism by which exogenous NO regulates crop drought resistance.

Alleviating the Injuries of NaCl Exposure on Respiratory Activities, Leaf Stomatal and Antioxidant Defense of Silybum marianum L. Seedlings by Exogenous Nitric Oxide

Nitric oxide (NO) is recognized as an endogenous signaling molecule that plays an important role in the defence responses of medicinal plants to NaCl stress. In this study, we investigated the effects of sodium nitroprusside (SNP) as an NO donor at three concentrations (0, 100, and 200 µmol l−1) to alleviate the deleterious effects of salt stress (100 mM NaCl) on leaf gas exchange and biochemical characteristics of Silybum marianum L. seedlings. This study showed that salt stress significantly decreased relative water content (RWC), chlorophyll b content, endogenous NO concentration, maximum quantum yield (Fv/Fm), leaf gas exchange, stomatal size, K+/Na+ ratio, and plant dry weight, and increased malondialdehyde (MDA) content, hydrogen peroxide (H2O2) content, proline content, stomatal density, and enzyme activities. SNP treatment increased Fv/Fm, photosynthetic pigments, K+/Na+ ratio, and dry weights of the shoots and roots of NaCl-exposed plants. The exogenous application of NO increased the proline content under salinity stress more than under stress conditions without SNP application, so that the proline content increased from 32 to 47 µmol g−1. Application of 100 µM SNP also increased endogenous NO concentration (up to 43%) and consequently protected plants against salt stress-induced damage by improving enzyme activity and reducing the H2O2 generation rate (up to 14%) and MDA content (up to 50%) compared to plants treated with NaCl alone. Foliar application of NO to salt-stressed plants increased root and shoot respiration rates from 20 and 12%, respectively, under salinity stress to 57% under the application of SNP and stress conditions, and decreased stomatal conductance by up to 70%, resulting in improved RWC. Increased internal NO generation in plants induced by 100 µM SNP application has the potential to mitigate salinity injury in Silybum marianum L. plants.

Different responses of Chlorella vulgaris to silver nanoparticles and silver ions under modulation of nitric oxide.

Silver nanoparticles (Ag-NPs) are widely used in daily life because of their antibacterial properties. A fraction of Ag-NPs are released into the ecosystem during their production and utilization. The toxicity of Ag-NPs has been reported. However, it is still disputed whether the toxicity is mainly due to the released silver ions (Ag+). In addition, few studies have reported the response of algae to metal nanoparticles under modulation of nitric oxide (NO). In this study, Chlorella vulgaris (C. vulgaris) was used as a model organism to study the toxic effects of Ag-NPs and Ag+ released from Ag-NPs on algae under the modulation of NO. The results showed that the biomass inhibition rate of Ag-NPs (44.84%) to C. vulgaris was higher than that of Ag+ (7.84%). Compared with Ag+, Ag-NPs induced more severe damage to photosynthetic pigments, photosynthetic system II (PSII) performance, and lipid peroxidation. More serious damage to cell permeability led to higher internalization of Ag under Ag-NPs stress. Application of exogenous NO reduced the inhibition ratio of photosynthetic pigments and chlorophyll autofluorescence. Further, NO reduced the MDA levels by scavenging reactive oxygen species induced by Ag-NPs. NO modulated the secretion of extracellular polymers and hampered the internalization of Ag. All these results showed that NO alleviates the toxicity of Ag-NPs to C. vulgaris. However, NO did not improve the toxic effects of Ag+. Our results provide new insights into the toxicity mechanism of Ag-NPs to algae modulated by the signal molecule NO.

Effects of Exogenous Sodium Nitroprusside Spraying on Physiological Characteristics of Soybean Leaves at the Flowering Stage under Drought Stress.

Nitric oxide (NO) plays a significant role in plant drought resistance. However, the effects of the exogenous application of NO to crops under drought stress vary within and among species. In this study, we explored the influence of exogenous sodium nitroprusside (SNP) on the drought resistance of soybean leaves in the full flowering stage using two varieties: drought-tolerant HN44 and non-drought-tolerant HN65. Spraying SNP on soybean leaves at the full flowering period under drought stress improved the NO content in soybean leaves. The activities of nitrite reductase (NiR) and nitrate reductase (NR) in leaves were affected by NO inhibition. The activity of antioxidant enzymes in leaves increased with the extension of SNP application time. Contents of osmomodulatory substances, including proline (Pro), soluble sugar (SS), and soluble protein (SP) increased gradually with the extension of SNP application time. The malondialdehyde (MDA) content decreased as the NO content increased, thus reducing membrane system damage. Overall, spraying SNP reduced damage and improved the ability of soybean to cope with drought. This study explored the physiological changes of SNP soybean under drought stress and provided theoretical basis for improving drought-resistant cultivation of soybean.

Sodium Nitroprusside Improves the Growth and Behavior of the Stomata of Silybum marianum L. Subjected to Different Degrees of Drought.

The use of growth-stimulating signals to increase the tolerance of plants to water deficits can be an important strategy in the production of plants in dry areas. Therefore, a split-plot experiment with three replications was conducted to evaluate the effects of sodium nitroprusside (SNP) application rate as an NO donor (0, 100, and 200 µM) on the growth and yield parameters of Silybum marianum L. (S. marianum) under different irrigation cut-off times (control, irrigation cut-off from stem elongation, and anthesis). The results of this study showed that with increasing drought severity, leaf RWC, proline content and capitula per plant, 1000 grain weight, plant height, branch per plant, capitula diameter, and the biological and grain yield of S. marianum decreased significantly, whereas the number of grains per capitula increased compared with the control. Also, by irrigation cut-off from the stem elongation stage, the density of leaf stomata at the bottom and top epidermis increased by 64% and 39%, respectively, and the length of the stomata at the bottom epidermis of the leaf decreased up to 28%. In contrast, the results of this experiment showed that the exogenous application of nitric oxide reduced the negative effects of irrigation cut-off, such that the application of 100 µM SNP enhanced RWC content (up to 9%), proline concentration (up to 40%), and grain (up to 34%) and biological (up to 44%) yields in plants under drought stress compared with non-application of SNP. The decrease in the number of capitula per plant and capitula diameter was also compensated by foliar application of 100 µM SNP under stress conditions. In addition, exogenous NO changed the behavior of the stomata during the period of dehydration, such that plants treated with SNP showed a decrease in the stomatal density of the leaf and an increase in the length of the stomata at the leaf bottom epidermis. These results indicate that SNP treatment, especially at 100 µM, was helpful in alleviating the deleterious effects of water deficiency and enhancing the tolerance of S. marianum to withholding irrigation times.

Enhancement of Salinity Stress Tolerance in Lettuce (Lactuca sativa L.) via Foliar Application of Nitric Oxide.

Salt stress negatively affects the growth, development, and yield of horticultural crops. Nitric oxide (NO) is considered a signaling molecule that plays a key role in the plant defense system under salt stress. This study investigated the impact of exogenous application of 0.2 mM of sodium nitroprusside (SNP, an NO donor) on the salt tolerance and physiological and morphological characteristics of lettuce (Lactuca sativa L.) under salt stress (25, 50, 75, and 100 mM). Salt stress caused a marked decrease in growth, yield, carotenoids and photosynthetic pigments in stressed plants as compared to control ones. Results showed that salt stress significantly affected the oxidative compounds (superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX)) and non-oxidative compounds (ascorbic acid, total phenols, malondialdehyde (MDA), proline, and H2O2) in lettuce. Moreover, salt stress decreased nitrogen (N), phosphorous (P), and potassium ions (K+) while increasing Na ions (Na+) in the leaves of lettuce under salt stress. The exogenous application of NO increased ascorbic acid, total phenols, antioxidant enzymes (SOD, POD, CAT, and APX) and MDA content in the leaves of lettuce under salt stress. In addition, the exogenous application of NO decreased H2O2 content in plants under salt stress. Moreover, the exogenous application of NO increased leaf N in control, and leaf P and leaf and root K+ content in all treatments while decreasing leaf Na+ in salt-stressed lettuce plants. These results provide evidence that the exogenous application of NO on lettuce helps mitigate salt stress effects.

Effects of exogenous NO on the growth and photosynthetic fluorescence characteristics of ryegrass seedlings under B[a]P stress

Benzoapyrene (B[a]P) pollution poses a threat to the environment and the food chain and consequently to human health. However, the alleviation of the harmful effects of B[a]P pollution in perennial ryegrass (Lolium perenne L.) by the application of exogenous nitric oxide (NO) has been ignored. Thus, in this paper the effects of exogenous sodium nitroprusside (SNP, a NO donor) on the growth, photosynthetic fluorescence characteristics, and antioxidant enzyme activity of ryegrass exposed to B[a]P stress are investigated. B[a]P stress induced the reduction of the aboveground and belowground dry weights, chlorophyll (a, b), the total chlorophyll contents, the carotenoid content, the net photosynthetic rate (Pn), the intercellular carbon dioxide concentration (Ci), the water use efficiency (WUE), the photosystem II (PSII) potential activity (Fv/F0), the maximum quantum yield of PSII photochemistry (Fv/Fm), the steady-state fluorescence yield (Fs), and the non-photochemical quenching (qN), while enhancement was recorded in response to the foliar spray of SNP at 200 and 300 μmol·L-1 under B[a]P stress. Gray correlation and principal component analyses show that 200 μmol·L 1 of SNP more drastically alleviated the damage caused by B[a]P stress than 300 μmol·L 1 of SNP. The exogenous NO-mediated alleviation of B[a]P toxicity in ryegrass was associated with preserved photosynthetic characteristics and activation of antioxidant enzymes.

Effects of NO, H2S and CO on Thiol/Disulfide Balance and Advanced Oxidation Protein Products in Hippocampus and Serum

Introduction: Nitric oxide (NO), hydrogen sulfide (H2S), and carbon monoxide (CO) are known as gaseous autocoids. It is not clear how the application of exogenous NO, H2S and CO alters the thiol/disulfide balance and advanced oxidation protein products (AOPPs) in the hippocampus and serum. Materials and Methods: In the study, rats were exogenously injected with L-arginine (100 mg/kg) as a NO donor, NaHS (10 mg/ kg) as a H2S donor, and CORM-2 (10 mg/kg) as a CO donor (II) (a tricarbonyldichlororuthenium dimer). Thiol/disulfide balance and advanced protein oxidation products were analyzed in hippocampus and serum samples. Results: The native thiol level in the hippocampus of the L-arginine group was statistically decreased compared to the native thiol level of the control group (p≤0.0001). The disulfide level in the hippocampus of the L-arginine group was statistically increased compared to the control group (p=0.009). Hippocampal total thiol level of NaHS group and CORM-2 group increased statistically (p=0.008,p=0.0157, respectively), while serum disulfide level of CORM-2 group decreased (p=0.0005). Serum and hippocampus AOPPs levels of the NaHS group were statistically increased compared to the control group (***p=0.0006, **p=0.0047, respectively). Similarly, the hippocampal AOPP level in the CORM-2 group was found to be statistically increased compared to the AOPP level in the control group (p=0.0437). Conclusion: As NaHS can improve thiol/disulfide balance, new studies are needed for CORM-2 and L-Arginine. This study is the first to report the effects of NO, H2S and CO on thiol/disulfide balance and AOPPs in the hippocampus and serum. Keywords: NO, H2S, CO, AOPPs, Thiol/disulfide

A Novel RHS1 Locus in Rice Attributes Seed-Pod Shattering by the Regulation of Endogenous S-Nitrosothiols.

Seed or pod shattering in rice (Oryza sativa) is considered to be one of the major factors involved in the domestication of rice as a crop. High seed shattering results in significant yield losses. In this study, we characterize the RICEHIGHSHATTERING 1 (RHS1) that corresponds to the locus LOC_Os04g41250 from a greenhouse screen, involving 145 Ac/Ds transposon mutant rice lines. The knockout mutant line rhs1 exhibited a significantly high shattering of grains in comparison to the wild-type plants. The exogenous application of nitric oxide (NO) resulted in a significant reduction in the expression of RHS1 in wild-type rice plants. The absence of RHS1, which encodes a putative armadillo/beta-catenin repeat family protein, resulted in high sensitivity of the rhs1 plants to nitrosative stress. Interestingly, the basal expression levels of QSH1 and SHAT1 genes (transcription factors that regulate seed-pod shattering in rice) were significantly lower in these plants than in wild-type plants; however, nitrosative stress negatively regulated the expression of QSH1 and SHAT1 in both WT and rhs1 plants, but positively regulated QSH4 expression in rhs1 plants alone. The expression levels of genes responsible for NO production (OsNIA1, OsNIA2, and OsNOA1) were lower in rhs1 plants than in WT plants under normal conditions. However, under nitrosative stress, the expression of OsNIA2 significantly increased in rhs1 plants. The expression of CPL1 (a negative regulator of seed shattering in rice) was significantly lower in rhs1 plants, and we found that CPL1 expression was correlated with S-nitrosothiol (SNO) alteration in rhs1. Interestingly noe1, a rice mutant with high SNO levels, exhibited low seed shattering, whereas rhs1 resulted in low SNO levels with high seed shattering. Therefore, RHS1 is a novel gene that negatively regulates the shattering trait in rice via regulation of endogenous SNO levels. However, the molecular mechanisms involved in the control of RHS1-mediated regulation of seed shattering and its interaction with nitric oxide and involvement in plant defense need to be investigated further.

Arbuscular mycorrhizal fungi enhanced rice proline metabolism under low temperature with nitric oxide involvement.

Arbuscular mycorrhizal fungi (AMF) are known to improve plant stress tolerance by regulating proline accumulation, and nitric oxide (NO) plays an important signaling role in proline metabolism. Environmental nitrogen (N) affects AMF colonization and its contribution to host plants resistance to stress conditions. However, the relationship between proline metabolism and NO in mycorrhizal rice and the effect of N application on symbiont proline metabolism under low temperature have not been established. Pot culture experiments with different temperature, N and exogenous NO donor treatments were conducted with non-mycorrhizal and mycorrhizal rice. The results showed that AMF enhanced rice proline accumulation under low-temperature stress and decreased glutamate (Glu) and ornithine (Orn) concentrations significantly. In comparison with non-mycorrhizal rice, AMF colonization significantly decreased the Glu concentration, but had little effect on the Orn concentration under low-temperature stress, accompanied by increasing expression of OsP5CS2, OsOAT and OsProDH1. Exogenous application of NO increased proline concentration both under normal and low temperature, which exhibited a higher increase in mycorrhizal rice. NO also triggered the expression of key genes in the Glu and Orn pathways of proline synthesis as well as proline degradation. Higher N application decreased the AMF colonization, and AMF showed greater promotion of proline metabolism at low N levels under low temperature stress by regulating the Glu synthetic pathway. Meanwhile, AMF increased rice nitrate reductase (NR) and nitric oxide synthase (NOS) activities and then enhanced NO accumulation under low N levels. Consequently, it could be hypothesized that one of the mechanisms by which AMF improves plant resistance to low-temperature stress is the accumulation of proline via enhancement of the Glu and Orn synthetic pathways, with the involvement of the signaling molecule NO. However, the contribution of AMF to rice proline accumulation under low-temperature stress was attenuated by high N application.

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.

Transcriptomic and metabolmic approaches to counter the effect of Botrytis cinerea in grape berry with the application of nitric oxide

The application of exogenous nitric oxide (NO) is convenient and safe approach to preserve fruits, though, the hidden genetic mechanism in treated grape berries is to be explored. In this study, the results depicted that the application of exogenous NO improved the shelf life of grape berries compared with the control group. The SNP treatment(400 μM) significantly increased the antioxidant enzymes activities including: POD, SOD and CAT. NO inhibited the mycelial growth of Botrytis cinerea (B. cinerea) in the grape berry. RNA-Seq data showed that NO upregulated 2,226 and downregulated 1,249 DEGs, and 300 metabolomes were identified including: NOT.vs.NOC_pos annotated 202 metabolites, NOT.vs.NOC_neg annotated 98 metabolites. The RNA-Seq data is coherent with the metabolome that STSs and CHSs expression levels were significantly increased against disease resistance and antioxidant-associated stilbene synthase pathway, and the associated metabolites content were also significantly increased. These changes led to an increase in the content of secondary metabolites such as resveratrol, which ultimately improved the shelf-life of the grapes.

Nitric Oxide Alleviates Photochemical Damage Induced by Cadmium Stress in Pea Seedlings

Cadmium (Cd), a life threatening hazardous heavy metal is abundant in nature. Cd amounts are greater in leaves than other plant parts, and it shows considerable effects on photosynthesis. Nitric oxide (NO), a free radical present in living organisms, is now known as an important signaling molecule playing various physiological processes in plants. In this study, the possible ameliorative effect of NO on photosynthesis was examined on pea seedlings grown under Cd stress. Results showed that chlorophyll, net photosynthetic rate, transpiration rate, stomatal conductance, photochemical efficiency of Photosystem II and Photosystem I decreased, and Fo and non-photochemical parameters for PSII and PSI significantly increased due to Cd stress. This suggests that Cd affects the photochemistry efficiency at both the PSII and PSI levels. Nitric oxide supplementation through SNP ameliorated Cd stress by enhancing all the above mentioned parameters but causing a reduction in the Fo, and non-photochemical parameters of PSII and PSI in pea plants. These data indicate that the exogenous application of NO was useful in mitigating Cd-induced damage to photosynthesis in pea seedling.

Transcriptome Profiling Reveals the Effects of Nitric Oxide on the Growth and Physiological Characteristics of Watermelon under Aluminum Stress.

Excessive aluminum ions (Al3+) in acidic soil can have a toxic effect on watermelons, restricting plant growth and reducing yield and quality. In this study, we found that exogenous application of nitric oxide (NO) could increase the photochemical efficiency of watermelon leaves under aluminum stress by promoting closure of leaf stomata, reducing malondialdehyde and superoxide anion in leaves, and increasing POD and CAT activity. These findings showed that the exogenous application of NO improved the ability of watermelon to withstand aluminum stress. To further reveal the mitigation mechanism of NO on watermelons under aluminum stress, the differences following different types of treatments—normal growth, Al, and Al + NO—were shown using de novo sequencing of transcriptomes. In total, 511 differentially expressed genes (DEGs) were identified between the Al + NO and Al treatment groups. Significantly enriched biological processes included nitrogen metabolism, phenylpropane metabolism, and photosynthesis. We selected 23 genes related to antioxidant enzymes and phenylpropane metabolism for qRT-PCR validation. The results showed that after exogenous application of NO, the expression of genes encoding POD and CAT increased, consistent with the results of the physiological indicators. The expression patterns of genes involved in phenylpropanoid metabolism were consistent with the transcriptome expression abundance. These results indicate that aluminum stress was involved in the inhibition of the photosynthetic pathway, and NO could activate the antioxidant enzyme defense system and phenylpropane metabolism to protect cells and scavenge reactive oxygen species. This study improves our current understanding by comprehensively analyzing the molecular mechanisms underlying NO-induced aluminum stress alleviation in watermelons.

Nitric oxide modified growth, nutrient uptake and the antioxidant defense system in tomato seedlings stressed with arsenic

Nitric oxide is a gaseous molecule that improves the defense system of plants under stress. This study investigated whether the application of exogenous nitric oxide (NO) improves the growth, nutrient uptake, defense system and modifies the translocation of arsenic (As) in tomato seedlings. NO was applied via foliar using sodium nitroferricyanide at 0, 50, 100 and 150 μM, while As contamination in irrigation water was simulated using a single dose of As(V) (3.2 mg L−1). NO at 100 and 150 μM, in the presence of As(V), decreased the height of the seedling and increased the number of leaves. NO at 100 μM, in the presence and absence of As(V), decreased chlorophylls, while As(V) increased them. NO improved seedling nutrient uptake and concentration in the presence of As. NO did not improve arsenic translocation. NO at 50 μM reduced the H2O2 concentration in roots. NO at 150 µM, in the presence of As(V), reduced the enzymatic activities of SOD, GPX and APX in roots, increased the GSH concentration in roots, and decreased the GSH concentration in leaves.