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Rapid production of nitric oxide (NO) and reactive oxygen species (ROS) has been implicated in the regulation of innate immunity in plants. A potato calcium-dependent protein kinase (StCDPK5) activates an NADPH oxidase StRBOHA to D by direct phosphorylation of N-terminal regions, and heterologous expression of StCDPK5 and StRBOHs in Nicotiana benthamiana results in oxidative burst. The transgenic potato plants that carry a constitutively active StCDPK5 driven by a pathogen-inducible promoter of the potato showed high resistance to late blight pathogen Phytophthora infestans accompanied by HR-like cell death and H₂O₂ accumulation in the attacked cells. In contrast, these plants showed high susceptibility to early blight necrotrophic pathogen Alternaria solani, suggesting that oxidative burst confers high resistance to biotrophic pathogen, but high susceptibility to necrotrophic pathogen. NO and ROS synergistically function in defense responses. Two MAPK cascades, MEK2-SIPK and cytokinesis-related MEK1-NTF6, are involved in the induction of NbRBOHB gene in N. benthamiana. On the other hand, NO burst is regulated by the MEK2-SIPK cascade. Conditional activation of SIPK in potato plants induces oxidative and NO bursts, and confers resistance to both biotrophic and necrotrophic pathogens, indicating the plants may have obtained during evolution the signaling pathway which regulates both NO and ROS production to adapt to wide-spectrum pathogens.

Introduction. Persea americana (avocado) fruit is known to be a rich source of proteins and minerals, as well as vitamins. Although many biological activities have been reported for avocado fruit, far less attention has been paid to the biological properties of its lipid-soluble bioactive substances. The aim of this study was to evaluate the antioxidant and antihemolytic activity of lipid-soluble bioactive compounds of avocado fruit. Materials and methods. Antioxidant and antihemolytic activity of lipid-soluble bioactive compounds of avocado fruit was assessed by employing different methods. Also, the ability of avocado fruit to protect fluorescein against oxidant-induced bleaching was evaluated. Results and discussion. The tested sample showed good antioxidant and antihemolytic activities. There was no significant difference between the reducing power of lipid-soluble bioactive substances in avocado fruits and ascorbic acid (p < 0.05). The tested sample showed weak ferrous ion-chelating activity. The sample exhibited moderate hydrogen peroxide scavenging activity, but exhibited good antioxidant activity. Avocado fruit showed very good activity against 2,2′-azobis(2-amidinopropane) dihydrochloride- and hydrogen peroxide-induced hemolysis in erythrocytes. Furthermore, it showed good protective effects against peroxyl radical-induced bleaching in fluorescein. Conclusion. Lipid-soluble bioactive substances of avocado fruit showed good activity in all of the studied models. Introduction. Les fruits de Persea americana, ou avocats, sont connus pour être riches en protéines et minéraux, ainsi qu’en vitamines. Bien que de nombreuses activités biologiques aient été signalées pour ce fruit, beaucoup moins d'attentions n’ont été accordées aux propriétés biologiques de ses substances bioactives liposolubles. L’objectif de notre étude a été d'évaluer l'activité antioxydante et antihémolytique de composés bioactifs liposolubles du fruit de l'avocat. Matériel et méthodes. L'activité antioxydante et antihémolytique des composés bioactifs liposolubles de l'avocat a été évaluée par différents moyens. En outre, la capacité des avocats à protéger la fluorescéine contre le blanchiment induit par un oxydant a été évaluée. Résultats et discussion. L'échantillon étudié a montré de bonnes activités antioxydante et antihémolytique. Il n'y a pas eu de différences significatives entre le pouvoir réducteur des substances bioactives liposolubles des fruits et celui de l’acide ascorbique (p < 0,05). L'échantillon testé a montré une faible activité de chélation des ions ferreux et une activité modérée de piégeage du péroxyde d'hydrogène, mais il a présenté une bonne activité antioxydante. Il a révélé une très bonne activité contre le 2,2′-azobis(2-amidinopropane) dihydrochloride et le peroxyde d’hydrogène induisant l’hémolyse dans les érythrocytes. Par ailleurs, il a montré de bons effets protecteurs contre les radicaux péroxyles induisant le blanchiment dans la fluorescéine. Conclusion. Les substances bioactives liposolubles du fruit de l'avocat ont montré une bonne activité dans tous les modèles étudiés. Introducción. Las frutas de Persea americana, o aguacates, son conocidas por ser ricas tanto en proteínas y minerales como en vitaminas. Aunque ya se habían señalado numerosas actividades biológicas de esta fruta, se había prestado mucho menos atención a las propiedades biológicas de sus sustancias bioactivas liposolubles. El objetivo de nuestro estudio fue evaluar la actividad antioxidante y antihemolítica de los compuestos bioactivos liposolubles de la fruta del aguacate.  Material y métodos. La actividad antioxidante y antihemolítica de los compuestos bioactivos liposolubles del aguacate se evaluó a través de distintos medios. Se evaluó asimismo la capacidad de los aguacates para proteger la fluoresceína contra el blanqueamiento inducido por un oxidante. Resultados y métodos. La muestra estudiada demostró unas actividades antioxidante y antohemolítica positivas. No se registraron diferencias significativas entre el poder reductor de las sustancias bioactivas liposolubles de las frutas frente al del ácido ascórbico (p < 0,05). La muestra del ensayo presentó una actividad débil de quelación de los iones ferrosos y una actividad moderada de captura del peróxido de hidrógeno, pero, en cambio, presentó una buena actividad antioxidante. Presentó una actividad muy buena contra el dihidrocloruro de 2,2'-azobis (2-amidinopropano) y el peróxido de hidrógeno, que inducen la hemólisis de los eritrocitos. Además, demostró contar con buenos efectos protectores contra los radicales peroxilos, que inducen el blanqueamiento de la fluoresceína. Conclusion. Las sustancias bioactivas liposolubles de la fruta del aguacate presentaron una buena actividad en todos los modelos estudiados.

Nitric oxide (NO) is known for its role in the activation of plant defense responses. To examine the involvement and mode of action of NO in plant defense responses, we introduced calmodulin-dependent mammalian neuronal nitric oxide synthase (nNOS), which controls the CaMV35S promoter, into wild-type and NahG tobacco plants. Constitutive expression of nNOS led to NO production and triggered spontaneous induction of leaf lesions. Transgenic plants accumulated high amounts of H₂O₂, with catalase activity lower than that in the wild type. nNOS transgenic plants contained high levels of salicylic acid (SA), and they induced an array of SA-, jasmonic acid (JA)-, and/or ethylene (ET)-related genes. Consequently, NahG co-expression blocked the induction of systemic acquired resistance (SAR)-associated genes in transgenic plants, implying SA is involved in NO-mediated induction of SAR genes. The transgenic plants exhibited enhanced resistance to a spectrum of pathogens, including bacteria, fungi, and viruses. Our results suggest a highly ranked regulatory role for NO in SA-, JA-, and/or ET-dependent pathways that lead to disease resistance.

Reactive oxygen species are believed to perform multiple roles during plant defense and possibly as cellular signaling molecules. In animals, nitric oxide (NO) is an important redox-active signaling molecule. Here we show that infection of resistant, but not susceptible, tobacco with tobacco mosaic virus resulted in enhanced NO synthase (NOS) activity. Furthermore, administration of NO donors or recombinant mammalian NOS to tobacco plants or tobacco suspension cells triggered expression of the defense-related genes encoding pathogenesis-related 1 protein and phenylalanine ammonia lyase (PAL). These genes were also induced by cyclic GMP (cGMP) and cyclic ADP-ribose, two molecules that can serve as second messengers for NO signaling in mammals. Consistent with cGMP levels. Furthermore, NO-induced activation of PAL was blocked by 6-anilino-5,8-quinolinedione and 1H-(1,2,4)-oxadizole[4,3-alpha]quinoxalin-1-one, two inhibitors of guanylate cyclase. Although 6-anilino-5,8-quinolinedione fully blocked PAL activation, inhibition by 1H-(1,2,4)-oxadiozole[4,3-alpha]quinoxalin-1-one was not entirely complete, suggesting the existence of cGMP-independent, as well as cGMP-dependent, NO signaling. We conclude that several critical players of animal NO signaling are also operative in plants

Mechanical stimulation (MS), existing widely but ignored usually in nature, is one of the environmental stress factors. MS not only affects growth, development, morphogenesis, and even survival of plants, but also induces the formation of cross-adaptation. In cross-adaptation, plants make use of common pathways and components to adapt to a range of different stresses after exposure to one specific stress. Here, we summarize current knowledge of MS-induced cross-adaptation to chilling, heat, salt, drought, and pathogen stress, as well as its possible mechanisms.

The present study was carried out to elucidate the protective role of sodium nitroprusside (SNP) against salt (NaCl) stress given as seed soaking in tomato (Solanum lycopersicum Mill. cv. K-21). For this experiment prior to sowing, the surface sterilized tomato seeds were soaked in different concentrations of NaCl solution (50, 100, and 150 mM) for 8 hours. Some NaCl soaked seeds were then transferred to the 10−5 M of SNP solution for 8 hours. The plants were sampled at 60 DAS to assess the nitrate reductase activity, proline content and the activities of antioxidant enzymes. The antioxidant enzyme activity and proline content increased in the plants where SNP was applied as a follow up treatment of the NaCl as seed soaking over the control plants thereby providing stress tolerance to the plants. In case of the nitrate reductase activity the toxic effects generated by the lowest concentration of NaCl (50 mM) was completely neutralized by SNP and partly at higher concentrations (100/150 mM). These results suggest that nitric oxide can be used as a stress alleviator in plants which are grown in the soil contaminated with salinity stress.

H₂S is a signaling molecule associated with protection against vascular diseases, including atherosclerosis. This protection involves the stimulation of vasorelaxation, but other possible contributing mechanisms have not been extensively explored. In this study, we found that the vascular H₂S-producing enzyme, cystathionine-γ-lyase (CSE), was down-regulated by oscillatory shear stress (OSS) among various vaso-regulators. Consistently, NaHS, an H₂S donor, appeared to inhibit OSS-induced THP-1 cell adhesion. We also found that NaHS activated the nitric oxide (NO)-producing Akt/endothelial nitric oxide synthase (eNOS) signaling pathway in response to OSS, whereas NaHS had no effect on IκB, a well-known molecule regulating pro-inflammatory signaling pathways. Moreover, NaHS increased OSS-dependent eNOS expression and decreased expression of intercellular adhesion molecule-1 (ICAM-1). NG-nitro-L-arginine methyl ester (L-NAME), an eNOS inhibitor, abrogated the inhibitory effects of NaHS on OSS-induced endothelial ICAM-1 expression and monocyte adhesion to endothelial cells. These data suggest that down-regulation of CSE resulting in decreased levels of H₂S is a key factor for OSS-associated atherogenesis and further suggest that regulation of H₂S production can be a potential target for preventing cardiovascular diseases.

Nitric oxide and reactive oxygen species are important signal molecules that play key roles in plant defense responses. We investigated the involvement of nitric oxide elicitation in the synthesis of secondary metabolites within the adventitious roots of Echinacea purpurea. When roots were treated with 100 μM sodium nitroprusside (SNP), an exogenous nitric oxide producer, the accumulation of phenolics, flavonoids, and caffeic acid derivatives was enhanced. This level of SNP also induced an antioxidant defense, as indicated by increases in superoxide dismutase, ascorbate peroxidase, and ascorbic acid, along with decreases in hydrogen peroxide, lipid peroxidation, and dehydroascorbate/ascorbic acid.

The aim of this study was to investigate the preventive effect of Agrocybe chaxingu polysaccharide on streptozocin (STZ)-induced pancreatic β-cells destruction. Agrocybe chaxingu polysaccharide markedly reduced nitric oxide (NO) production and iNOS expression levels in RINm5F cells in a dose-dependent manner. In addition, Agrocybe chaxingu polysaccharide significantly inhibited iNOS expression and blood glucose levels in STZ-induced diabetic mice. Moreover, immunohistochemical analysis revealed that it enhanced pancreatic β-cells resistance to destruction by STZ. These results suggest that Agrocybe chaxingu polysaccharide may have value as a therapeutic agent against diabetes mellitus.

Arginase II catalyzes the conversion of arginine to urea and ornithine in many extrahepatic tissues. We investigated the protective role of arginase II on lipopolysaccharide- mediated apoptosis in the macrophage cells. Adenoviral gene transfer of full length of arginase II was performed in the murine macrophage cell line RAW264.7. The role of arginase II was investigated with cell viability, cytoplasmic histone-associated DNA fragmentation assay, arginase activity, nitric oxide production, and Western blot analysis. Arginase II is localized in mitochondria of macrophage cells, and the expression of arginase II was increased by lipopolysaccharide (LPS). LPS significantly increased cell death which was inhibited by AMT, a specific inducible nitric oxide synthase (iNOS) inhibitor. In contrast, LPS-induced cell death and nitric oxide production were increased by 2-boronoethyl-L-cysteine, a specific inhibitor of arginase. Adenoviral overexpression of arginase II significantly inhibited LPS-induced cell death and cytoplasmic histone-associated DNA fragmentation. LPS-induced iNOS expression and poly ADP-ribose polymerase cleavage were significantly suppressed by arginase II overexpression. Furthermore, arginase II overexpression resulted in a decrease in the Bax protein level and the reverse induction of Bcl-2 protein. Our data demonstrated that inhibition of NO production by arginase II may be due to arginine depletion as well as iNOS suppression though its reaction products. Moreover, arginase II plays a protective role of LPS-induced apoptosis in RAW264.7 cells.