SNP Treatment Research Articles

SNP alleviates mitochondrial homeostasis dysregulation-mediated developmental toxicity in diabetic zebrafish larvae

The incidence of diabetes is increasing annually, and the disease is uncurable due to its complex pathogenesis. Therefore, understanding diabetes pathogenesis and developing new treatments are crucial. This study showed that the NO donor SNP (8 µM) significantly alleviated high glucose-induced developmental toxicity in zebrafish larvae. High glucose levels caused hyperglycemia, leading to oxidative stress and mitochondrial damage from excessive ROS accumulation. This promoted mitochondrial-dependent apoptosis and lipid peroxidation (LPO)-induced ferroptosis, along with immune inflammatory reactions that decreased mitochondrial function and altered intracellular grid morphology, causing imbalanced kinetics and autophagy. After SNP treatment, zebrafish larvae showed improved developmental toxicity and glucose utilization, reduced ROS accumulation, and increased antioxidant activity. The NO-sGC-cGMP signaling pathway, inhibited by high glucose, was significantly activated by SNP, improving mitochondrial homeostasis, increasing mitochondrial count, and enhancing mitochondrial function. It's worth noting that apoptosis, ferroptosis and immune inflammation were effectively alleviated. In summary, SNP improved high glucose-induced developmental toxicity by activating the NO-sGC-cGMP signaling pathway to reduce toxic effects such as apoptosis, ferroptosis and inflammation resulting from mitochondrial homeostasis imbalance.

Glutathione is required for nitric oxide-induced chilling tolerance by synergistically regulating antioxidant system, polyamine synthesis, and mitochondrial function in cucumber (Cucumis sativus L.)

In this paper, we discussed the physiological mechanism of enhanced chilling tolerance with combined treatment of nitric oxide (NO) and reduced glutathione (GSH) in cucumber seedlings. With prolonged low temperature (10 °C/6 °C), oxidative stress improved, which was manifested as an increase the hydrogen peroxide (H2O2) and malondialdehyde (MDA), causing cell membrane damage, particularly after 48 h of chilling stress. Exogenous sodium nitroprusside (SNP, NO donor) enhanced the activity of nitric oxide synthase NOS-like, the contents of GSH and polyamines (PAs), and the cellular redox state, thus regulating the activities of mitochondrial oxidative phosphorylation components (CI, CII, CIV, CV). However, buthionine sulfoximine (BSO, a GSH synthase inhibitor) treatment drastically reversed or attenuated the effects of NO. Importantly, the combination of SNP and GSH treatment had the best effect in alleviating chilling-induced oxidative stress by upregulating the activities of antioxidant enzyme, including superoxidase dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and peroxidase (POD) and improved the PAs content, thereby increased activities of CI, CII, CIII, CIV, and CV. This potentially contributes to the maintenance of oxidative phosphorylation originating from mitochondria. In addition, the high activity of S-nitrosoglutathione reductase (GSNOR) in the combined treatment of SNP and GSH possibly mediates the conversion of NO and GSH to S-nitrosoglutathione. Our study revealed that the combined treatment with NO and GSH to synergistically improve the cold tolerance of cucumber seedlings under prolonged low-temperature stress.

Exploring Nitric Oxide as a Regulator in Salt Tolerance: Insights into Photosynthetic Efficiency in Maize.

The growing issue of salinity is a significant threat to global agriculture, affecting diverse regions worldwide. Nitric oxide (NO) serves as an essential signal molecule in regulating photosynthetic performance under physiological and stress conditions. The present study reveals the protective effects of different concentrations (0-300 µM) of sodium nitroprusside (SNP, a donor of NO) on the functions of the main complexes within the photosynthetic apparatus of maize (Zea mays L. Kerala) under salt stress (150 mM NaCl). The data showed that SNP alleviates salt-induced oxidative stress and prevents changes in the fluidity of thylakoid membranes (Laurdan GP) and energy redistribution between the two photosystems (77K chlorophyll fluorescence ratio F735/F685). Chlorophyll fluorescence measurements demonstrated that the foliar spray with SNP under salt stress prevents the decline of photosystem II (PSII) open reaction centers (qP) and improves their efficiency (Φexc), thereby influencing QA- reoxidation. The data also revealed that SNP protects the rate constants for two pathways of QA- reoxidation (k1 and k2) from the changes caused by NaCl treatment alone. Additionally, there is a predominance of QA- interaction with plastoquinone in comparison to the recombination of electrons in QA QB- with the oxygen-evolving complex (OEC). The analysis of flash oxygen evolution showed that SNP treatment prevents a salt-induced 10% increase in PSII centers in the S0 state, i.e., protects the initial S0-S1 state distribution, and the modification of the Mn cluster in the OEC. Moreover, this study demonstrates that SNP-induced defense occurs on both the donor and acceptor sides of the PSII, leading to the protection of overall photosystems performance (PIABS) and efficient electron transfer from the PSII donor side to the reduction of PSI end electron acceptors (PItotal). This study clearly shows that the optimal protection under salt stress occurs at approximately 50-63 nmoles NO/g FW in leaves, corresponding to foliar spray with 50-150 µM SNP.

Straw return with fertilizer improves soil CO2 emissions by mitigating microbial nitrogen limitation during the winter wheat season

Straw return is the key measure of green agricultural production. Nitrogen (N) and phosphorus (P) play pivotal roles in crop growth and carbon (C) cycling in agroecosystems. However, the mechanism of soil CO2 emissions and enzyme stoichiometry regulation by straw return with N and P application remain unknown. Therefore, this study is aimed to use enzyme stoichiometry to investigate the effects of straw return with N and P fertilizer application on soil CO2 emissions, enzyme activity, and microbial nutrient limitation through a two-year field experiment. A split-plot experimental design was used (straw as the main plot and fertilizer as the sub plot). The results indicated that the addition of N, P (SNP) increased CO2 emissions by 25.54 %, and N application (SN) reduced CO2 emissions by 27.01 %, compared with straw return (SW). Enzyme stoichiometry indicated that straw return with N and P application exhibited significant C and N limitations. In soil nutrients and nutrient stoichiometry, compared with the S0W treatment, straw return with fertilizer (SNP, SN) significantly increased microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), dissolved organic carbon (DOC) and dissolved organic nitrogen (DON); SNP treatment increased β-1,4- n −acetylaminoglucosidase (NAG) enzyme activity by 53.72 %, increased l −leucine aminopeptidase (LAP) enzyme activity by 58.11 %, and increased one P-acquiring enzyme alkaline monoalkaline phosphatase (AKP) enzyme activity by 39.49 % (P < 0.05). Structural equation modeling suggested that straw return and fertilization can influence microbial biomass phosphorus (MBP) and vector length (VL) by affecting MBN, which, in turn, affects CO2 emissions. Soil microbes regulate CO2 emissions using stoichiometric flexibility to maintain a stoichiometric balance of nutrients and microbes. Therefore, straw return with N and P fertilizers to winter wheat soils can meet the requirements of microbial stoichiometry, modulate microbial and extracellular enzyme activities, and effectively regulate CO2 emissions and resource limitations.

Abstract 3187: Enhancing STING activation by cyclic dinucleotide-manganese particles for systemic cancer immunotherapy

Abstract Background: Activating the innate immune pathway of stimulator of interferon genes (STING) can elicit potent anti-tumor immunity via the production of type-I interferons (IFN-I). However, cyclic-dinucleotide (CDN) STING agonists have undesirable pharmacological properties. Most CDNs in clinical development are administered intratumorally, thus precluding their utility against advanced cancer. Here, we report the development of a new nanoparticle system for the systemic delivery of CDN STING agonists with potent efficacy, favorable pharmaceutical properties, and acceptable safety profiles. Methods: Various metal ions were screened for synergy with CDNs for IFN-I response from bone marrow-derived dendritic cells. Lipid nanoparticles carrying CDN and manganese ions (termed SNP) were synthesized. Mice bearing syngenetic tumors (including CT26 and B16F10) as well as genetically engineered mouse models were treated by intravenous administration of SNP, followed by tumor monitoring and immune profiling of the tumor microenvironment. White New Zealand rabbits bearing VX2 tumors as well as healthy mongrel dogs were treated with SNP and evaluated. Lastly, human tumor biopsies derived from head and neck squamous cell carcinoma (HNSCC) patients were incubated with SNP or soluble STING agonists and analyzed for immune activation. Results: We identified that Mn2+ achieved strong synergy with CDN STING agonists for inducing IFN-I production. SNP carrying CDN and Mn2+ was dosed intravenously in mice, leading to robust IFN-I response, remodeling of the immunosuppressive tumor microenvironment, and expansion of anti-tumor CD8+ T cells. Intravenous SNP therapy resulted in robust anti-tumor efficacy in multiple murine tumor models, including CT26, B16F10, and a genetically engineered mouse model of MMTV-PyMT triple-negative breast cancer. We have also observed robust anti-tumor efficacy of SNP against VX2 squamous carcinomas in rabbits and have demonstrated the safety of intravenous SNP therapy in healthy dogs. Mechanistically, the efficacy of SNP therapy was dependent on the host STING expression but independent of the tumor STING expression. In addition, the anti-tumor efficacy of SNP was decreased in mice lacking Ifnar1 or Ifngr1 expression in the B16F10 melanoma model, showing the crucial effects of IFN-I and IFN-II responses. Moreover, SNP treatment led to robust IFN-I responses from fresh human tumor biopsies derived from HNSCC patients. Conclusions: SNP empowers highly effective systemic cancer immunotherapy via nanotechnology. It also underscores the potential of utilizing metal ions for immune-mediated disease treatment. Citation Format: Xingwu Zhou, Xiaoqi Sun, Wang Gong, Ziye Wan, Teresa Krieger-Burke, Vilma Yuzbasiyan-Gurkan, Yu Leo Lei, James Moon. Enhancing STING activation by cyclic dinucleotide-manganese particles for systemic cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3187.

Nitric Oxide Promoted the Seed Germination of Cynanchum auriculatum under Cadmium Stress

Cynanchum auriculatum, an early food-medicine homologous plant native to Asia, possesses significant nutritional and health benefits. However, the presence of cadmium (Cd) in the soil poses a hazard to the germination and growth of C. auriculatum. As nitric oxide (NO) plays a vital role in plant resistance to heavy metal stress, we used three different concentrations of SNP treatment during the germination phase, aiming to alleviate the inhibitory effects of Cd stress on the seed germination of C. auriculatum. The results indicated that when compared to seeds treated with SNP concentrations of 0.2 mM and 0.8 mM, C. auriculatum seeds treated with 0.4 mM SNP exhibited an improved germination rate and germination index, as well as longer hypocotyl. Furthermore, in comparison to NOS-like, the SNP application stimulated the production of endogenous NO through NR catalysis. Additional investigations showed that the ABA level decreased while the GA level increased under normal conditions, while the SNP application enhanced the accumulation of both ABA and GA in C. auriculatum seeds under Cd stress. Histochemical staining and biochemical indicators demonstrated that SNP treatment enhanced the enzymatic activity of SOD, POD, and CAT, while inhibiting the production of hydrogen peroxide and superoxide anion. Moreover, SNP treatment resulted in increased α-amylase activity, which facilitated starch hydrolysis and the generation of soluble sugar. Ultimately, the seed vitality of C. auriculatum under Cd stress was promoted. Our findings present a theoretical framework for the application of SNP in the seed germination mechanism of C. auriculatum and establish the groundwork for comprehending the physiological role of NO under Cd stress.

Nitric Oxide (NO) Improves Wheat Growth under Dehydration Conditions by Regulating Phytohormone Levels and Induction of the Expression of the TADHN Dehydrin Gene

Nitric oxide (NO) is a universal signaling molecule with important regulatory functions in the plant’s life cycle and adaptation to a wide spectrum of environmental stresses including drought. The effect of pre-sowing seed treatment with the donor of NO sodium nitroprusside (SNP, 200 μM) on wheat Triticum aestivum L. plants subjected to dehydration (PEG-8000, 12%) was investigated. SNP pretreatment stimulated germination and seedling growth in normal conditions and protected them under dehydration. These effects were confirmed by percentage of seed germination, changes in fresh and dry weight of 5–6-day-old seedlings, as well as by seedlings’ linear dimensions, visual appearance, and mitotic index of the root apical meristem. Assessment of the transpiration intensity (TI) and relative water content (RWC) showed that SNP pretreatment helped to maintain the water status of seedlings subjected to dehydration stress. The data obtained by enzyme-linked immunosorbent assay (ELISA) suggested that the positive effects of SNP may be due to its influence on the phytohormonal system. SNP pretreatment induced an increase in the level of indolylacetic acid (IAA) and especially cytokinins (CK), while essential changes in ABA content were not detected. Water deficiency caused a substantial increase in ABA content and a decrease in the levels of CK and IAA. Pre-sowing SNP treatment decreased stress-induced fluctuations in the content of all studied phytohormones. Using reverse-transcription PCR (RT-PCR), we obtained data on the increase in expression of the TADHN dehydrin gene in SNP-pretreated seedlings under normal and, especially, under dehydration conditions. These findings may indicate the participation of dehydrins in NO-induced defense reactions in wheat plants under water stress. Furthermore, exogenous NO had a stabilizing effect on membrane cellular structures, as evidenced by the reduction of electrolyte leakage (EL) levels and malondialdehyde (MDA) content in dehydrated wheat seedlings under the influence of pre-sowing SNP treatment.

Involvement of GA3-oxidase in inhibitory effect of nitric oxide on primary root growth in Arabidopsis.

Both NO and GAs are essential for regulating various physiological processes and stress responses in plants. However, the interaction between these two molecules remains unclear. We investigated the distinct response patterns of Arabidopsis thaliana Col-0 and GA synthesis functional deficiency mutants to NO by measuring root length. To investigate underlying mechanisms, we detected bioactive GA content using UHPLC-ESI-MS/MS, assessed the accumulation of ROS by chemical staining Arabidopsis roots. We also conducted RNA-seq analysis and compared results between Col-0 and ga3ox1, with and without SNP (as NO donor) treatment. Phenotypic results revealed that the inhibitory effect of NO on primary roots of Arabidopsis was primarily mediated by GA3-oxidase, rather than GA20-oxidase or GA2-oxidase. The content of GA3 decreased in Col-0 treated with SNP, whereas this decrease was not observed in ga3ox1. The deficiency of GA3-oxidase alleviated the buildup of H2 O2 in roots when treated with SNP. We identified 222 DEGs. GO annotation of these DEGs revealed that all top 20 GO terms were related to stress responses. Moreover, three DEGs were annotated to GA-related processes (DDF1, DDF2, EXPA1), and seven DEGs were associated with root development (RAV1, RGF2, ERF71, ZAT6, MYB77, XT1, and DTX50). In summary, NO inhibits primary root growth partially by repressing GA3-oxidase catalysed GA3 synthesis in Arabidopsis. ROS, Ca2+ , DDF1, DDF2, EXPA1 and seven root development-related genes may be involved in crosstalk between NO and GAs.

Effects of sinapic acid on lead acetate-induced oxidative stress, apoptosis and inflammation in testicular tissue.

In this study, the effect of lead acetate (PbAc) and sinapic acid (SNP) administration on oxidative stress, apoptosis, inflammation, sperm quality and histopathology in testicular tissue of rats was tried to be determined. PbAc was administered at a dose of 30 mg/kg/bw for 7 days to induce testicular toxicity in rats. Oral doses of 5 and 10 mg/kg/bw SNP were administered to rats for 7 days after PbAc administration. According to our findings, while PbAc administration increased MDA content in rats, it decreased GPx, SOD, CAT activity and GSH content. NF-kB, IL-1β, TNF-α, and COX-2, which are among the inflammation parameters that increased due to PbAc, decreased with the administration of SNP. Nrf2, HO-1, and NQO1 mRNA transcript levels decreased with PbAc, but SNP treatments increased these mRNA levels in a dose-dependent manner. RAGE and NLRP3 gene expression were upregulated in PbAc treated rats. MAPK14, MAPK15, and JNK relative mRNA levels decreased with SNP treatment in PbAc treated rats. While the levels of apoptosis markers Bax, Caspase-3, and Apaf-1 increased in rats treated with PbAc, the level of Bcl-2 decreased, but SNP inhibited this apoptosis markers. PbAc caused histopathological deterioration in testis tissue and negatively affected spermatogenesis. When the sperm quality was examined, the decrease in sperm motility and spermatozoon density caused by PbAc, and the increase in the ratio of dead and abnormal spermatozoa were inhibited by SNP. As a result, while PbAc increased apoptosis and inflammation by inducing oxidative stress in testicles, SNP treatment inhibited these changes and increased sperm quality.

Preharvest Application of Sodium Nitroprusside Alleviates Yellowing of Chinese Flowering Cabbage via Modulating Chlorophyll Metabolism and Suppressing ROS Accumulation.

Chinese flowering cabbage is prone to senescence and yellowing after harvest, leading to a huge postharvest loss. Nitric oxide (NO) is a multifunctional plant growth regulator, but the effect of preharvest application of NO on the storage quality of Chinese flowering cabbage remains unclear. Preharvest application of 50 mg L-1 sodium nitroprusside (SNP, a NO donor) to the roots obviously reduced leaf yellowing in Chinese flowering cabbage during storage. Proteomic analysis reveals 198 differentially expressed proteins (DEPs) in SNP-treated plants compared to the control. The main DEPs were significantly enriched in chlorophyll metabolisms, phenylpropanoid synthesis, and antioxidant pathways. SNP treatment enhanced chlorophyll biosynthesis and suppressed chlorophyll-degradation-related proteins and genes. It also modulated flavonoid-biosynthesis-related genes, and 21 significantly regulated flavonoids were identified in SNP-treated plants. The enhanced antioxidant capacity in SNP-treated plants was able to decrease chlorophyll catabolism by inhibiting peroxidase-mediated chlorophyll bleaching. Collectively, preharvest SNP treatment modulated chlorophyll metabolism and preserved chlorophyll content in leaves during storage. Moreover, SNP treatment enhanced flavonoid synthesis, suppressed reactive oxygen species accumulation, and delayed the senescence process, thereby maintaining leaf greening in Chinese flowering cabbage. These findings highlight the role of exogenous NO in alleviating yellowing of leafy vegetables.

Peroxynitrite is essential for aerenchyma formation in rice roots under waterlogging conditions

In this study, we report that peroxynitrite is necessary for ethylene-mediated aerenchyma formation in rice roots under waterlogging conditions. Plants under waterlogging stress face anoxygenic conditions which reduce their metabolism and induce several adaptations. The formation of aerenchyma is of paramount importance for the survival of plants under waterlogging conditions. Though some studies have shown the involvement of ethylene in aerenchyma formation under waterlogging conditions, the implication of peroxynitrite (ONOO-) in such a developmental process remains elusive. Here, we report an increase in aerenchyma formation in rice roots exposed to waterlogging conditions under which the number of aerenchyma cells and their size was further enhanced in response to exogenous ethephon (a donor of ethylene) or SNP (a donor of nitric oxide) treatment. Application of epicatechin (a peroxynitrite scavenger) to waterlogged plants inhibited the aerenchyma formation, signifying that ONOO- might have a role in aerenchyma formation. Interestingly, epicatechin and ethephon co-treated waterlogged plants were unable to form aerenchyma, indicating the necessity of ONOO- in ethylene-mediated aerenchyma formation under waterlogging conditions. Taken together, our results highlight the role of ONOO- in ethylene-mediated aerenchyma formation in rice and could be used in the future to develop waterlogging stress-tolerant varieties of rice.

Effects of Exogenous Nitric Oxide Treatment on Grape Berries Against Botrytis cinerea and Alternaria alternata Related Enzymes and Metabolites.

Postharvest losses of grape berries caused by the pathogenic fungi Botrytis cinerea and Alternaria alternata have been widely reported, and nitric oxide (NO) as a plant signaling molecule to control postharvest diseases has recently become an active research topic. This study aimed to investigate the regulatory effect of NO on the interaction between grape berries and fungi. During interactions between grape berries and pathogenic fungi, treatment with 10 mM sodium nitroprusside (SNP, an NO donor) delayed the decline of the physiological quality of the grape berries and had positive effects on the weight loss rate, firmness, and respiration intensity. SNP treatment increased the activities of superoxide dismutase (SOD) and polyphenol oxidase (PPO) and inhibited the activities of peroxidase (POD) and catalase (CAT) of grape berries during the resistance to fungal pathogen infection. In addition, the increase in browning degree and the accumulation of hydrogen peroxide were inhibited by SNP treatment. In the phenylpropane metabolic pathway, the activities of phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H), and 4-coumaric acid coenzyme A ligase (4CL) were increased during the activation of grape berries during the resistance to pathogen infection by SNP, and the intermediate metabolites lignin, flavonoids, and total phenols were accumulated. In addition, SNP treatment had a regulatory effect on the gene expression levels of SOD, POD, PPO, PAL, and 4CL. These results suggested that SNP treatment was effective for the preservation and disease reduction of grape berries.

Nitric oxide promotes adventitious root formation in cucumber under cadmium stress through improving antioxidant system, regulating glycolysis pathway and polyamine homeostasis.

Cadmium (Cd) as a potentially toxic heavy metal that not only pollutes the environment but also interferes with plant growth. Nitric oxide (NO) regulates plant growth and development as well as abiotic stress response. However, the mechanism underpinning NO-induced adventitious root development under Cd stress remains unclear. In this study, cucumber (Cucumis sativus 'Xinchun No. 4') was used as the experimental material to investigate the effect of NO on the development of adventitious roots in cucumber under Cd stress. Our results revealed that, as compared to Cd stress, 10 μM SNP (a NO donor) could considerably increase the number and length of adventitious roots by 127.9% and 289.3%, respectively. Simultaneously, exogenous SNP significantly increased the level of endogenous NO in cucumber explants under Cd stress. Our results revealed that supplementation of Cd with SNP significantly increased endogenous NO content by 65.6% compared with Cd treatment at 48 h. Furthermore, our study indicated that SNP treatment could improve the antioxidant capacity of cucumber explants under Cd stress by up-regulating the gene expression level of antioxidant enzymes, as well as reducing the levels of malondialdehyde (MDA), hydrogen peroxide (H2O2) and superoxide anion ( ) to alleviate oxidative damage and membrane lipid peroxidation. Application of NO resulted in a decrease of the , MDA, and H2O2 level by 39.6%, 31.4% and 60.8% as compared to Cd-alone treatment, respectively. Besides that, SNP treatment significantly increased the expression level of related genes involved in glycolysis processes and polyamine homeostasis. However, application of NO scavenger 2-(4-carboxy -2-phenyl)-4, 4, 5, 5-tetramethy limidazoline -1-oxyl -3-oxide (cPTIO) and the inhibitor tungstate significantly reversed the positive role of NO in promoting the adventitious root formation under Cd stress. These results suggest that exogenous NO can increase the level of endogenous NO, improve antioxidation ability, promote glycolysis pathway and polyamine homeostasis to enhance the occurrence of adventitious roots in cucumber under Cd stress. In summary, NO can effectively alleviate the damage of Cd stress and significantly promote the development of adventitious root of cucumber under Cd stress.

Mitigation of gravitropic bending of snapdragon cut flowers through SNP treatment via ROS asymmetry elimination and auxin sensitivity reduction

Snapdragons (Antirrhinum majus L.) are an important fresh-cut flower in the international flower market. During storage and transportation, snapdragons often undergo a gravitropic response that has a substantial adverse effect on their ornamental and market value. The gravitropic response is a complex physiological and biochemical process that is affected by signals such as auxins and reactive oxygen species (ROS). In this study, we found that the pretreatment of exogenous nitric oxide (NO) donor sodium nitroprusside (SNP, 0.2 mM) effectively inhibited the gravitropic bending of snapdragon cut flowers after horizontal placement. The gravitropic stimulus induced higher ROS (O2−∙ and H2O2) accumulation in the lower side compared to the upper side of the bending zone of the control flower stems. Compared to the control, a substantially higher accumulation of ROS was induced through the SNP treatment, correlating with the increased activity of catalase (CAT) and ascorbate peroxidase (APX), as well as the enhanced expression of AmAPX1 and AmCAT1. However, unlike the control, no ROS asymmetric distribution was found for the SNP-treated flowers. Four free auxins, IAA, IBA, ME-IAA and ICA, were detected in the flower stems, among which, only IBA showed asymmetric distribution after the gravitropic stimulus. An IBA content that was approximately 26% higher was detected in the lower side compared to the upper side of the control flower at 2 h, but no difference was found for the SNP-treated flowers. A higher expression of the AmPIN3 gene at the lower sides compared to the upper sides of the control may be correlated with the transient IBA asymmetric distribution. Interestingly, an expression of AmIAA2 and AmSUR50 that was around 2-fold was detected in the lower side compared to the upper side of the control, indicating that higher auxin sensitivity may be induced in the lower side. However, the expression of AmIAA2 and AmSUR50 was reduced by the SNP treatment, implying that high ROS levels may reduce auxin sensitivity. Furthermore, a higher AmExp1 and AmH+–ATPase1 expression in the lower side compared to the upper side was found for the control but not for the SNP-treated flowers, indicating the two genes may be involved in the bending of the flower stems. The above results reveal that SNP treatment eliminates the asymmetric distribution of ROS and reduced auxin sensitivity of snapdragon flower stems, thereby eliminating their asymmetric growth and further inhibiting their gravitropic response.

Allantoin overaccumulation enhances production of metabolites under excess of metals but is not tightly regulated by nitric oxide

The aln-3 mutant overaccumulating allantoin and respective wild type (WT) strain of Arabidopsis thaliana were exposed to cadmium (Cd) or mercury (Hg) with or without nitric oxide (NO) donor (sodium nitroprusside, SNP) to study cross-talk, metabolic and oxidative changes between these nitrogen sources (organic vs. inorganic). The aln-3 accumulated over 10-fold more allantoin than WT with the effect of Cd and Hg differing in leaf and root tissue: aln-3 contained more ascorbic acid and phytochelatins when treated with Cd or Hg and more Cd in both organs. SNP depleted leaf Cd and root Hg accumulation in aln3 but had a positive impact on the amount of metabolites typically in WT plants, indicating potentially negative relation between allantoin and NO. In agreement, aln-3 roots showed lower NO signals in control or metal treatments, but higher ROS signal, and SNP had more pronounced impact in WT roots. Flavonol glycosides were more abundant in aln-3 and were affected more by metals than by SNP. Malate was the most affected Krebs acid with strong reaction to SNP and Hg treatment. Data indicate that allantoin overaccumulation influences the accumulation of specific metabolites but nitric oxide has a greater impact on the metabolite profile in WT.

Nitric Oxide Improves Salt Tolerance of Cyclocarya paliurus by Regulating Endogenous Glutathione Level and Antioxidant Capacity.

Cyclocarya paliurus is commonly used to treat diabetes in China. However, the natural habitats of C. paliurus are typically affected by salt stress. Previous studies showed that nitric oxide (NO) level was related to salt tolerance of C. paliurus, and its synthesis was induced by exogenous hydrogen sulfide. However, the effects of different NO donors in alleviating the negative effect of salt stress are still unclear. In the present study, C. paliurus seedlings pretreated with three NO donors (S-nitroso-N-acetylpenicillamine, SNAP and S-nitrosoglutathione, GSNO and sodium nitroprusside, SNP) were exposed to salt stress, and then, the total biomass, chlorophyll fluorescence parameters, NO and glutathione levels, oxidative damage, and antioxidant enzyme activities were investigated. The results showed that pretreatment of NO donors maintained chlorophyll fluorescence and attenuated the loss of plant biomass under salt stress, and the best performance was observed in C. paliurus under SNP treatment. We also found that pretreatment of NO donors further increased the endogenous NO content and nitrate reductase (NR) activity compared with salt treatment. Moreover, pretreatment with NO donors, especially SNP, alleviated salt-induced oxidative damage, as indicated by lowered lipid peroxidation, through an enhanced antioxidant system including glutathione accumulation and increased antioxidant enzyme activities. The supply of NO donors is an interesting strategy for alleviating the negative effect of salt on C. paliurus. Our data provide new evidence contributing to the current understanding of NO-induced salt stress tolerance.

The Interaction of NO and H2S in Boar Spermatozoa under Oxidative Stress.

Simple SummaryThe most recent experiments performed on somatic cells describe the interaction of nitric oxide (NO) and hydrogen sulfide (H2S) on various levels. In male gametes, these two gasotransmitters have been studied individually up until today. Both NO and H2S participate in crucial sperm structural and functional changes before and after ejaculation. Moreover, the two gasotransmitters can augment or mitigate the negative impact of oxidative stress, depending on the concentration. Oxidative stress is a concomitant condition to various male reproduction disorders. In this experiment, we investigated in vitro the simultaneous application of NO and H2S donors, which was compared to single-donor application (NO or H2S) at 100 nM concentrations in boar spermatozoa under oxidative stress. The evaluation of sperm qualitative traits revealed a positive effect of the combination of the two donors in DD treatment on progressive motility and plasma membrane integrity compared to the control sample under oxidative stress (CtrOX). The results of this experiment indicate that the combination of NO and H2S donors exceeds the effect of single-donor application under given conditions. In conclusion, our research indicates the importance of gasotransmitter interaction in male gametes.Various recent studies dedicated to the role of nitric oxide (NO) and hydrogen sulfide (H2S) in somatic cells provide evidence for an interaction of the two gasotransmitters. In the case of male gametes, only the action of a single donor of each gasotransmitter has been investigated up until today. It has been demonstrated that, at low concentrations, both gasotransmitters alone exert a positive effect on sperm quality parameters. Moreover, the activity of gaseous cellular messengers may be affected by the presence of oxidative stress, an underlying condition of several male reproductive disorders. In this study, we explored the effect of the combination of two donors SNP and NaHS (NO and H2S donors, respectively) on boar spermatozoa under oxidative stress. We applied NaHS, SNP, and their combination (DD) at 100 nM concentration in boar spermatozoa samples treated with Fe2+/ascorbate system. After 90 min of incubation at 38 °C, we have observed that progressive motility (PMot) and plasma membrane integrity (PMI) were improved (p < 0.05) in DD treatment compared to the Ctr sample under oxidative stress (CtrOX). Moreover, the PMot of DD treatment was higher (p < 0.05) than that of NaHS. Similar to NaHS, SNP treatment did not overcome the PMot and PMI of CtrOX. In conclusion, for the first time, we provide evidence that the combination of SNP and NaHS surmounts the effect of single-donor application in terms of PMot and PMI in porcine spermatozoa under oxidative stress.

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 cadmium-impeded growth by limiting ROS accumulation in pea seedlings

Cadmium (Cd) causes oxidative stress, which leads to the oxidation of various biomolecules by the production of reactive oxygen species (ROS) to facilitate programmed cell death (PCD). The antioxidant defense system fails to detoxify ROS when it is produced in excess. Nitric oxide (NO), a gaseous free radical and a phytohormone, regulates various physiological processes of plants. Therefore, this work was undertaken to study the effects of the application of exogenous sodium nitroprusside (SNP, a NO donor) on growth parameters, oxidative stress, accumulation of secondary metabolites, and activities of antioxidant enzymes under Cd stress. Mild (50 µM) and severe (200 µM) Cd stress were applied to hydroponically grown pea (Pisum sativum L.) plants with or without 50 µM SNP. Severe Cd stress had a substantial impact on the plants. The effectiveness of NO in reducing Cd-induced negative effects on plant height, fresh weight, dry weight, protein content, nitrite content, nitrate reductase (NR) activity, catalase activity, and peroxidase activity were investigated. Seedling development, protein content, nitrite content, nitrate reductase (NR) activity, antioxidant defense systems disruption, overproduction of reactive oxygen species, and oxidative damage were observed. The antioxidant defense system (catalase and peroxidase activities) was activated by NO, which resulted in lower lipid peroxidation and lower hydrogen peroxide (H2O2) levels in Cd-exposed plants. SNP treatment boosted endogenous NO levels and NR activity in Cd-stressed plants while also enhanced proline levels to preserve osmotic equilibrium. The presence of total phenols and flavonoids increased after SNP treatment, indicating that SNP enhanced stress recovery and boosted plant development in Cd-stressed plants.

Comparative transcriptome analysis provides insight into nitric oxide suppressing lignin accumulation of postharvest okra (Abelmoschus esculentus L.) during cold storage

In plants, NO has been proved the function of improving abiotic stress resistance. However, the role of NO in the lignin metabolism of okra under cold stress has not been clarified. Here, histochemical staining and lignin content analysis showed that cold stress promoted the lignin accumulation of cold stored okra pods, and NO inhibited the lignin accumulation and delayed lignification process. To better understand the roles of NO in okra cold stress resistance mechanism, the full-length transcriptome data of ‘Hokkaido’ was analyzed. The SNP-treated okra transcriptome and cPTIO-treated okra transcriptome were obtained. A total of 41957 unigenes were screened out from three groups at 10 d, among which, 33, 78 and 18 DEGs were found in ddH2O-treat, SNP-treat and cPTIO-treat group, respectively. Transcriptomic data suggested that the genes involved in lignin biosynthesis showed downregulation under SNP treatment. Transcriptomic data and enzyme activity showed that exogenous NO significantly promoted the biosynthesis of endogenous NO by enhancing NOS activity. Transcriptomic data and plant hormone data showed that NO played an important role in the process of inhibiting the ethylene and ABA synthesis mechanism of okra and thereby reducing the endogenous ethylene and ABA content under chilling stress. Relevant physiological data showed that NO helped to the protection of ROS scavenging system and removed the MDA and H2O2 induced by cold stress. These results provided a reference for studying the molecular mechanism of nitric oxide delaying the lignification of okra, and also provided a theoretical basis for postharvest storage of vegetables.