Functional role of nitric oxide in plants

ISSN 1021�4437, Russian Journal of Plant Physiology, 2010, Vol. 57, No. 4, pp. 451–461. © Pleiades Publishing, Ltd., 2010.Original Russian Text © Yu.A. Krasylenko, A.I. Yemets, Ya.B. Blume, 2010, published in Fiziologiya Rastenii, 2010, Vol. 57, No.4, pp. 483–494.

451

INTRODUCTION

Since the first description of nitric oxide by JosephPriestley in 1772, NO(II) was considered a highlytoxic compound; indeed, it is a component of exhaustgas and industrial wastes. However, the discovery inthe late 1980s of NO signaling role in regulation of car�diovascular system by R.F. Furchgott, L.J. Ignarro,and F. Murad (Nobel Prize winners in Physiology andMedicine, 1998) has changed the paradigm concern�ing the cytotoxicity of free�radical substances. Therecognition of NO signaling role became a revolution�ary event in medicine, as it led to invention of newpharmaceutical agents with a targeted therapeuticimpact, acting upon different stages in signaling path�ways of nitric oxide. It was also a revolutionaryadvance for the whole biology. In the last decade, itbecame evident that NO is a ubiquitous signaling mol�ecule in representatives of phylogenetically distantspecies; however, the occurrence of NO in living cellswas first described for plants [1]. Particular emphasison investigation of NO in plant biology was given afterrecognizing that gaseous nitric oxide is involved insenescence and the plant defense against infectionswith invasive pathogens [2, 3]. Physiological functionsof NO were first investigated with an example of ani�mal cells. The role of NO in plants is also considerable:NO is involved in the cell cycle regulation, differenti�ation and morphogenesis, including flowering androot formation. Furthermore, NO promotes the adap�tive plasticity upon pathogen infections, accounts forthe hypersensitive response and the acquired systemicresponse, and increases resistance to abiotic stressesthrough its antioxidant action [4, 5].

NO is electroneutral lipophilic gas with moderatesolubility in water. The half�life of NO in biologicaltissues depends on local concentrations of its potentialtargets (proteins, hemoproteins, bound iron and cop�per ions, cysteine, ascorbic acid, oxygen, and hydro�gen peroxide); the half�time usually ranges between3 and 5 s, although some authors reported the half�lifeas long as 15 s [6]. In cells NO can exist in the form ofthree interconverting compounds: a free�radical nitricoxide (NO•), a nitrosonium cation (NO+), and anitroxyl anion (NO–) [4]. A small size and the lack ofelectric charge determine the ability of NO to transmitintercellular signals. The long�distance NO transportin plant cells is carried out by S�nitrosoglutathione(GSNO) with the help of S�to�N� and S�to�S�trans�nitrosylation of protein thiol groups [7]. Nitric oxide ischaracterized by the following reactions: nitration(addition of nitryl); nitrosylation (addition of nitrosylresidue from NO+ to amide, thiol, or aromatichydroxyl group); nitrosation (addition of NO• free rad�ical) with the formation of C–N, N–N, S–N, and O–N bonds; and oxidation (self�oxidation and produc�tion of peroxynitrite ONOO–) [6].

SOURCES OF NITRIC OXIDE IN PLANTS

Nitric oxide originates in plant cells from the reac�tions of several enzymes, particularly, nitrate reductasethat catalyzes nitrite reduction to NO in vivo andin vitro. A minor role belongs to nitrite reductase andthe enzymes similar to animal NO synthases [8].There is immunological evidence for tissue�specificproperties of NO�synthases and for their localization

REVIEWS

Functional Role of Nitric Oxide in Plants Yu. A. Krasylenko, A. I. Yemets, and Ya. B. Blume

Institute of Food Biotechnology and Genomics, National Academy of Sciences of Ukraine,ul. Osipovskogo 2a, Kiev�123, 04123 Ukraine;

fax: 38 (044) 434�3777; e�mail: [email protected] August 31, 2009

Abstract—The review considers involvement of nitric oxide (NO) in regulation of basic physiological pro�cesses underlying growth, development, and senescence in plants. The NO sources in plants, as well as directand indirect NO signaling mechanisms are also reviewed. Particular attention is paid to the role of this sec�ondary messenger in plant responses to various abiotic stresses, such as mechanical injury, salinity, drought,UV irradiation, high and low temperatures, ozonation, hypoxia, the impacts of heavy metals and herbicides.The role of NO in the hypersensitive response and in a systemic response upon plant infection with invasivepathogens is described.

Key words: plants, nitric oxide, sources for synthesis, signaling mechanisms, growth, development, senes�cence, abiotic stress factors, biotic stress factors

DOI: 10.1134/S1021443710040011

452

RUSSIAN JOURNAL OF PLANT PHYSIOLOGY Vol. 57 No. 4 2010

KRASYLENKO et al.

in particular compartments or organelles, e.g., nuclei,peroxisomes, or mitochondria in various plant species[9]. A notable advance in studies on enzymatic NOsynthesis in plants was achieved after identification ofArabidopsis nitric oxide synthase (AtNOS1), a proteinwith mol wt of 60 kD, which is homologous to NO syn�thases of a grapevine snail. This enzyme utilizes L�argin�ine as a substrate and needs Ca2+, calmodulin, andNADPH as cofactors, but it is independent of flavin ortetrahydrobiopterin [6, 10]. As for the physiologicalrole of putative NO synthase in plants, it was foundthat the product of atnos1 gene, which is expressed ina presumably constitutive manner, is required for NOproduction in vivo and for NO involvement into sig�naling pathways activated by ABA and lipopolysac�charides [10]. However, later investigations showedthat the pathogen�induced NO�synthesizing enzymeis a variant form of the P�protein of the glycine decar�boxylase complex or a variant of the chloroplastGTPase required for correct assembling of ribosomes;the latter enzyme does not exhibit the NO synthaseactivity [4, 6, 8]. It is possible that plant enzymesexhibiting NO synthase�like activity are not structur�ally homologous to NO synthases of animals. Reportson the existence of NO synthase in plants should betaken with caution, considering the imperfectness ofL�arginine tests and insufficient specificity of animalNO synthase inhibitors in their action on plant pro�teins with NO�synthesizing activity [7]. Eventually,the L�arginine�dependent mechanism of NO synthe�sis in the plant cell remains unproven, which may beexplained by insufficiency of data.

Apart from aforementioned NO sources, plants arethought to possess an analog of a complex molybde�num� and flavon�containing enzyme, xanthine oxi�doreductase (xanthine oxidase or xanthine dehydro�genase) capable of producing NO [11]. Under anaero�bic conditions, the enzyme catalyzes reduction ofnitrate and nitrite to NO in the presence of NADH orxanthine as reducing substrates [11]. Nonenzymaticproduction of NO in plants mediated by dismutationof nitrite to NO and nitrate is predominant at pH < 7[6]. In the acidic media, nitrite is reduced by ascorbicacid with the production of NO, semihydroascorbateradicals, and dehydroascorbate; this reaction occurs inchloroplasts and the apoplast in the presence of suffi�cient quantities of ascorbate [6]. The light�dependentconversion of NO2 to NO mediated by carotenoidswas also observed [11]. In addition, the apoplastic syn�thesis of NO was shown to occur during nonenzymaticreduction of nitrite added to the medium for in vitroculturing of barley aleurone layer and during decom�position of nitrous acid [12].

TRANSDUCTION OF NITRIC OXIDE SIGNAL IN PLANTS

The signaling function of NO mediated by directand indirect interactions can be accomplished in indi�

vidual cells and even in microcompartments, which isconsistent with a recently suggested notion on the roleof calcium ions, hydrogen peroxide, and cyclic nucle�otides.

Direct interactions. NO is capable of producingcomplexes with metal�containing proteins, namely,with hemoglobins, cytosolic and mitochondrial aconi�tase, catalase, ascorbate peroxidase, and cytochrome сoxidase [7]. Furthermore, a great deal of attention ispaid to covalent posttranslational protein modificationscaused by synergistic action of NO and other reactiveforms of nitrogen and oxygen. Nitrosylation of proteinson specific cysteine residues (S�nitrosylation) or glu�tathione (S�glutathionylation) [11] were the first dis�covered mechanisms of direct NO impact on the cell.The reversible reaction of S�nitrosylation involved infunctional regulation of more than 100 proteins in vitroand/or in vivo is a key point of the new paradigm on sig�nal transduction. It is also a prospective mechanism forthe redox NO signaling in phylogenetically distant spe�cies [8, 11]. The extracts of Arabidopsis leaves werefound to contain a series of S�nitrosylated proteinsinvolved in a diversity of processes, including photosyn�thesis, control of redox balance, growth and develop�ment, stress responses, regulation of phytohormoneproportions, programmed cell death, etc. [8].

Although S�nitrosylation is a commonly recog�nized posttranslational protein modification involvedin NO signal transduction, nitrotyrosylation is also acandidate for the role of regulatory protein modifier inanimals and plants; however, the reversibility of thisreaction remains unproven [13, 14]. One of the way forintracellular production of 3�nitrotyrosine is interac�tion of protein with a strong oxidant, peroxynitrite(ONOO–) [9]. During NO stress in plants exposed tohigh salinity, nitrotyrosylation occurred in many pro�teins extracted from Olea europaea leaves and fromsuspension culture of Nicotiana tabacum BY�2 cell linetreated with elicitor of Phytophthora infestans [15].Recent studies revealed the posttranslational inactiva�tion of Medicaga truncatula glutamine synthase 1 dur�ing peroxynitrite�dependent tyrosine nitration [7, 13].Since NO mediates in plants a number of physiologi�cal and pathological processes dependent on cytoskel�etal components, microtubules in particular, it is pos�sible that nitration of tyrosine residues of tubulin andother cytoskeletal proteins is a direct way for imple�mentation of NO signaling cascades [16, 17]. Thenitrotyrosylation of α�tubulin in plants might be a reg�ulatory posttranslational modification acting in paral�lel with tyrosine phosphorylation [9, 13, 16, 17].

Indirect interactions. The modulating effect of NOon signal transduction in plant cells might be mediatedby its influence on cGMP, cADP�ribose, and Ca2+

levels [1, 18], as well as on MAPK kinases [9] and ongene expression profiles [8]. It is known, for example,that development of adventitious roots under theaction of IAA involves NO and cGMP [18]. The NOactivity is functionally interconnected with that of


FUNCTIONAL ROLE OF NITRIC OXIDE IN PLANTS 453

Ca2+, a well�known intracellular secondary messengerin signaling cascades [19]. For example, simultaneousincreases of NO concentration and cytosolic level offree Ca2+ were found to occur during signal transduc�tion initiated by biotic and abiotic stress factors [6].The function of proteins exhibiting NO synthase�likeactivity was found to depend in several plant speciesupon the presence of Ca2+ and calmodulin as cofac�tors. This finding suggests that Ca2+ or calmodu�lin/Ca2+ complex may interact with NO synthase�likeenzymes in plants [19].

The first notes that Ca2+ receives signal from NO ina signaling cascade appeared with regard to inhibitoryaction of nicotinamide (antagonist of cADP�ribose)on NO�induced accumulation of the defense proteinPR�1 [19]. Later studies revealed that the NO donorinduced the release of Ca2+ from intracellular stores instomata of Vicia faba leaves and in suspensions ofN. tabacum cells [20].

The NO�dependent activation of protein kinaseswas observed in roots and suspension cultures ofA. thaliana, Cucumis sativa explants, as well as inleaves and suspension cultures of N. tabacum [19].Furthermore, sodium nitroprusside enhanced thephosphorylation activity of p34�cdc2�cyclin�depen�dent kinase targeted on histone H1 in auxin�treatedM. trumcatula protoplasts [21]. Many authors supposethat activation of the aforementioned kinases can beintegrated into the pathway enabling plant responsesto stress and/or apoptosis; it may also participate incell division and auxin�induced formation of adventi�tious roots [18, 21]. It should be mentioned that invitro S�nitrosylation was demonstrated for phospho�glycerate kinase, nucleotide diphosphate kinase, andadenosine kinase [8]. Recent studies revealed that NOmodulates the activity of plant SNF1�protein kinase 2,subfamily SnRK2 [20]. Representative enzymes of thisgroup, e.g., a 42�kD kinase NtOSAK of N. tabacumactivated by osmotic stress, are engaged in signalingpathways operating upon abiotic stresses [19].

It was shown also that exogenous NO and endoge�nously synthesized NO affect the expression profiles ofgenes that ensure signal transduction, plant defenseagainst pathogen invasion, apoptosis, photosynthesis,cell transport processes, and production and detoxifi�cation of reactive oxygen species (ROS) [8]. The treat�ment of N. tabacum leaves with NO was shown to inducethe expression of defense genes [3]. The hypo� andhyperexpression of genes can be explained by S�nitrosy�lation of transcription factors [22]. The plants werefound to contain a series of transcription factors that areprincipally capable of regulation by virtue of S�nitrosyla�tion [8]. In addition to transcription factors modifiedby direct S�nitrosylation, the signaling cascade pro�teins, e.g., the nuclear factor jB kinase and proteintyrosine phosphatase 1B can also undergo this modifi�cation [22]. Comparative transcriptome analysis ofmain NO�controlled gene groups in Arabidopsis waspresented by Besson�Bard et al. [8].

It should be taken into account that the major partof data concerning physiological role of nitric oxidewas obtained upon application of exogenous NOdonors of diverse origin. This diversity may account forcontradictory results obtained in some studies,because biological effects of these substances aredetermined by their chemical structure, stability, fac�tors promoting the release of active components,including temperature and irradiance, tissue type,local pH in microcompartments, the adequacy ofnutrient medium to experimental conditions, dura�tion of treatment, and many other factors acting invitro and in planta [23]. Moreover, the lack of definiteknowledge on endogenous NO sources in plants com�plicates the task of finding clear relations between theaction of stress factor and activation or inhibition ofspecific enzymatic or nonenzymatic pathways of NOsynthesis. Nevertheless, here we attempted to summa�rize the functions of nitric oxide in plants.

PLANT GROWTH

It was noted that NO stimulates growth of wholeplants [5] as well as of individual plant parts: primaryroot [24], hypocotyl [25], mesocotyl [26], adventitiousand lateral roots [1, 18], leaves [27], and the shoot [26,27]. In the presence of low concentrations of the NOdonor nitroprusside, an acceleration of growth wasnoted for A. thaliana primary root, whereas inhibitionof growth was observed at higher concentrations [17].The antisense modulation of nitrite reductase inN. tabacum plants induced accumulation of nitrite,the release of NO in significant amounts, and retarda�tion of plant growth [13, 15]. In addition, it was shownthat exogenous NO donors inhibit the elongation ofhypocotyls and internodes in dark�grown seedlings ofArabidopsis and Lactuca sativa [25]. An importantpoint is that NO donors, namely sodium nitroprussideand S�nitroso�N�acetyl�D�penicillamine suppressedalso growth and differentiation in unicellular greenalga Micrasterias denticulata; the suppression wascaused by defects in formation of secondary cell wallsand by malfunctioning of dictiosomes [28].

DIFFERENTIATION OF PLANT TISSUES

The involvement of NO in regulation of cell divi�sion and subsequent differentiation of M. trumcatulamesophyll protoplasts in the presence of auxins wasdemonstrated; nevertheless, the presence of NO wasonly needed for the induction of cell cycle but not forits subsequent progress [21]. It is established that NOparticipates in differentiation of Zinnia elegans xylemby regulating cell lignification and the programmedcell death [6]. In addition, the inhibitors known toimpair the cGMP�mediated transduction of NO sig�nal in mammalian cells had a conspicuous influenceon aerenchyma formation in Zea mays roots [9]. It wasfound that NO, Ca2+, and cGMP are mediators in

454


KRASYLENKO et al.

maintaining cell polarity in the fern Ceratopteris richa�rdii [29].

The development of cytoarchitecture in roots wasshown to depend on auxins and NO [18]. For exam�ple, the development of adventitious roots under theaction of IAA proceeds with the involvement of NOand cGMP [18]. Later studies demonstrated theability of exogenous NO donors—nitroprusside andS�nitroso�N�acetylpenicillamine—to mimick theaction of IAA by inducing de novo organogenesis ofadventitious roots in explants of C. sativus with uni�form anatomical structure [1, 18]. Experiments withSolanum lycopersicum plants showed that NO partici�pates in lateral root formation initiated by contact withrhizobacteria Azospirillum and that NO, together withROS and glutathione, is involved in the genesis ofsymbiotic interactions between legumes and respec�tive microorganisms [30]. Enhanced synthesis of NOwas noticed upon interaction of M. truncatula andnodulating bacterium Sinorhizobium meliloti [31]. Thesignificance of NO for gravitropic responses of Glycinemax roots was also described [24]. Sodium nitroprus�side is known to provoke rearrangements of corticalmicrotubules in various root cells of A. thaliana seed�lings, thus inducing formation of root hairs togetherwith lateral and adventitious roots. For this reason onemay assume that NO acts as a triggering signal for differ�entiation of root tissues, while the microtubules operateas downstream effectors that facilitate signal transductionby means of α�tubulin nitrotyrosylation [17].

FLOWERING AND POLLINATION OF PLANTS

It is known that plants with elevated production ofNO enter the flowering stage somewhat later thanplants with physiologically normal NO level [32]. Thisphenomenon can be explained by assumption that NOacts as a signal that controls the timing of flowering atthe genetic level [32]. Indeed, it was found that NOdonors inhibit expression of the genes constans andgigantea while enhancing expression of the floweringlocus C gene [6]. Germinating and even nongerminat�ing pollen grains produce NO and nitrate required forthe reproduction process. The NO generation is possi�bly an important component of the signaling systemactivated by pollen–stigma interaction [33]. Earlierstudies revealed that NO regulates the direction of pol�len tube growth, which is important for fertilization[34]. It was found that interaction of NO produced bythe pollen with ROS generated by the pistil stigma caninitiate pollination through the onset of signaling cas�cades between pollen grains and stigmas [33].

SEED MATURATION

Exposure of Arabidopsis, L. sativa, and Panicumvirgatum plants to nitric oxide under illumination andin darkness stimulated ripening and germination of

seeds [25]. Exogenous NO donors are thought to beeffective agents for plant release from dormancy,because the treatment of Arabidopsis (C24 and Col�1ecotypes) and Hordeum vulgare seeds with micromolarconcentrations of sodium nitroprusside broke seeddormancy [12]. Current explanations of this effectimplicate either the impact of NO on synthesis andmetabolism of ABA known to suppress ripening andgermination of seeds or stimulation of ethylene biosyn�thesis [35]. It is known also that NO and spermine areable to restore germination of Lotus japonicus seeds afterits inhibition with high concentration of glucose [35].

PLANT SENESCENCE AND PROGRAMMED CELL DEATH

The deficiency of NO synthesis is related to plantsenescence and associated ethylene production [6].For example, Pisum sativum leaves were found torelease nitric oxide in parallel with the release of NOantagonist, ethylene [36]. The accelerated ethyleneformation during ripening of Fragaria anannasa andPersea americana fruits coincided in time with loweredNO emission [36]. Nitric oxide can accelerate senes�cence of Oryza sativa leaves acting synergistically withROS or, conversely, can provoke a delay in leaf senes�cence induced by hydrogen peroxide (H2O2); in thelatter case, NO acted as ROS scavenger [36].

The controversy of data regarding NO role in plantsenescence can be explained by multiple factors, suchas operation in plant cells of enzymatic and nonenzy�matic NO sources, plant sensitivity to abiotic andbiotic environmental factors, the balance betweenintracellular content of NO and its derivatives, and therate of NO catabolism in reactions involving, in par�ticular, S�nitrosoglutathione reductase and hemoglo�bins. It is known, for example, that endogenous NOproduced by mitochondrial NO synthase of Arabidop�sis, NOS1 exhibits antioxidant properties and preventssenescence�related changes by means of diminishingthe ROS level [6]. Conversely, the expression in Arabi�dopsis of NO�degrading enzyme led to the appearanceof phenotypical traits of senescence, which was pre�ceded by lowered expression of photosynthetic genesand by enhanced expression of senescence genes [8].The addition of sodium nitroprusside promoted theretention of photosynthetic pigments and deceleratedlipid peroxidation in G. max cotyledons [37].

The involvement of NO and ROS in apoptosis wasfirst noticed during investigation of acute and systemicresponses of plants to infection with invasive patho�gens [2]. At the same time, the sufficiency of NO alonefor apoptosis induction in plant cells is still a disputedissue [4].

Plant mitochondria were also reported to be thetarget of NO action, because S�nitrosoglutathione,peroxynitrite, and S�nitroso�N�acetylpenicillamineinhibited mitochondrial respiration at the level ofcytochrome oxidase [38]. Furthermore, nitric oxide



directly activated opening of mitochondrial pores,thus inhibiting electron transport in mitochondria,which could lead to apoptosis [38]. In addition, NOwas reported to decelerate cell respiration and inhibitoxidative phosphorylation because of the suppressionof electron transport at the cytochrome level [39].

Nitric oxide is able not only to initiate programmedcell death [2, 20] but also to delay its occurrence [40].While considering apoptosis, which is closely related tooxidative stress, the antioxidant properties of NOshould be mentioned. For example, mutant Arabidopsisplants with defective NO synthase were found to restorefertility, chlorophyll content, and normal growth ratesafter pretreatment with the NO donor [10].

The pretreatment of Phaseolus vulgaris leaves withsodium nitroprusside was found to mitigate injuries tophotosynthetic apparatus, which were induced by UV�B irradiation [41]. At the cell level, the antioxidantproperties of NO were manifested in its ability to sup�press proteasome activity and lipid peroxidation [42].Recent findings suggest that S�nitrosylation of inac�tive form of metacaspase 9 (AtMC9) is effective in reg�ulation of its proteolytic activity in vivo [42].

NITRIC OXIDE AND ABIOTIC STRESS

Apart from promoting plant responses to abioticstress cues, accompanied by the development of oxi�dative stress [25], NO is involved in plant responses toother environmental factors, such as light and gravity[24]. Long exposure of plants to stress conditions mayresult in the enhanced production of NO and its deriv�atives, which would produce a series of intracellularalterations, known under collective term of nitrosativestress (NO�stress) [15]. Recent studies revealed thatthe osmotic stress in Olea europaea plants resulted inthe enhanced production of reactive nitrogen speciesand, consequently, led to the increase in the content ofnitrosylated proteins that are reliable markers of NO�stress [15].

Mechanical wounding was among the first abioticstress factors that came into focus of researcher inter�est. It turned out that plant wounding resulted in theenhanced production of H2O2 and NO [2]. Nitricoxide was found to act as a negative modulator of plantresponse to mechanical wounding in S. lycopersicum,because it blocked the H2O2 production and protein�ase I inhibitor synthesis that was induced by systemin,oligouronides, and jasmonic acid [8]. According toother authors, NO is engaged in regeneration ofinjured Solanum tuberosum leaves, because NO donorscaused accumulation of transcripts for extensin andphenylalanine ammonia�lyase, together with deposi�tion of callose [43]. The centrifugation of cell culturesor whole leaves of several plant species resulted in theenhanced NO production that induced apoptosis [8,44]. The level of free 3�nitrotyrosine in suspensioncultures of T. cuspidata increased within few hoursafter cutting the stem and leaves, which could lead to

nitrotyrosylation of glutathione�S�transferase and therespective decrease of its activity [44]. The increase inNO concentration in epidermal cells of T. cuspidataleaves was also noted after mimicking mechanicalstress conditions in a special chamber [44].

Mesophytic plants, a wider ecological plant groupcompared to xerophytes and halophytes, are charac�terized by low capacity of adaptation to changes inwater availability, e.g., upon drought and salinity. It isknown that these abiotic factors affect plant metabo�lism by inducing elevated synthesis of signaling mole�cules, such as Ca2+, NO, jasmonic and salicylic acids.Nitric oxide was shown to improve salinity resistancein calluses of two Phragmites communis ecotypes withdifferent salt tolerance. This was achieved through thedecrease in the Ca2+ level and the shift of the K+/Na+

ratio in favor of Na+ content [45]. There is evidencethat NO promoted growth of Triticum aestivum rootsafter its retardation by low concentrations of sodiumchloride (in the range of 150 mM) and activatedsuperoxide dismutase and ascorbate peroxidase, thusprotecting root apical cells against salinity�inducedoxidative damage [5]. The treatment of Z. mays seed�lings with sodium nitroprusside stimulated K+ uptakeand transport to shoots with a concurrent decelerationof Na+ accumulation and transport, which preventedthe electrolyte leakage [46]. The treatment withsodium nitroprusside of P. communis suspension cul�tures exposed to stressful action of polyethylene glycolPEG�6000 was accompanied by deceleration of ionleakage, lowering of H2O2 and superoxide anion

content, and by activation of antioxidantdefense enzymes [45]. It was shown that the inhibitoryeffect of sodium chloride on germination of Lupinusluteus seeds could be released by the pretreatment ofseeds with sodium nitroprusside [47]. The osmoticstress in mannitol�treated T. aestivum seedlings, man�ifested in lowered water losses by leaves in parallel withABA accumulation, was partly relieved after inhibitionof NO synthase and application of a specific NO scav�enger [5]. The significance of NO for plant resistanceto salinity can be related to its regulatory influence onexpression of specific genes, particularly Osnoa1 cod�ing for NO synthase in O. sativa; the expression of thisgene was observed in Arabidopsis mutants with defectsof NO synthase (Atnoa1) [48]. Moreover, the activityof NO synthase AtNOS1 in vivo is needed for provid�ing salt resistance to Arabidopsis [49].

The NO�synthesizing activity in wheat plants wasfound to increase under drought conditions [45]. Thenewly synthesized NO together with Н2О2 partici�pated in the regulation of ABA�induced closing of sto�mata in various plant species [5]. This role of NO ispossibly mediated by changes in activity of К+� andСl–�channels in guard cells owing to S�nitrosylation ofthe respective proteins [45]. The closure of stomatainduced by NO and ABA involves independent path�ways, though NO and ABA can act synergistically [5].

O2–

( ),

456


KRASYLENKO et al.

The stomata closing induced in maize mesophyll byhyperproduction of ABA during salinity stress andwater deficit was regulated by signaling cascadesinvolving H2O2 and NO [5]. It was also shown thatABA synthesis in wheat roots under water deficit con�ditions was enhanced in the presence of ROS and NOdonors, which indicates the synergism of NO and ROSaction [45]. The ABA impact on guard and non�guardepidermal cells of Vicia faba, P. sativum, and Arabidop�sis leaves elevated the endogenous NO level [5]. Subse�quent stages of this signaling cascade are presentlyunknown; however, the addition of exogenous NO suf�ficed to induce stomatal closure through the Ca2+�dependent pathway [5]. Furthermore, nicotinamide,the antagonist of cADP�ribose inhibited both ABA�and NO�induced effects, indicating the involvement ofcADP�ribose in NO synthesis pathway and signaltransduction [5].

Being autotrophic sessile organisms, plants arerather sensitive to UV�A and UV�B components ofsolar radiation, which is manifested in the impairedproduction of secondary metabolites, alterations ofphotosynthetic activity, formation of defensive mor�phological structures, vulnerability of hereditarymaterial, and other responses. Nitric oxide plays adual role in plant responses to UV�A and UV�B irradi�ation. After pretreatment of S. tuberosum tubers andZ. mays seedlings with NO donors, the deleteriouseffect of UV�A and UV�B irradiation was mitigated inparallel with activation of NO synthase in microsomesand cytosol; these changes were also accompanied bythe decrease in endo� and exo�β�glucanase activitiesand by the biomass reduction [27]. The treatment ofV. faba leaves with sodium nitroprusside alleviated theinjurious effect of UV�B, leading to the increasedchlorophyll content and to the increase in potentialand effective quantum yields of electron flow in pho�tosystem II; the oxidative damage to thylakoid mem�branes was reduced to minimum owing to activation ofsuperoxide dismutase, ascorbate peroxidase, and cata�lase [41]. The alleviating effects of NO were alsoobserved in experiments with an algal culture of Spir�ulina platensis, which was evident from protectiveaction on total biomass and physiological parameters,such as the content of chlorophyll a, proline, andreduced glutathione [50]. Although sodium nitroprus�side mitigated the inhibitory effect of UV�B irradia�tion, the endogenous NO was found to be the mainfactor responsible for inhibition of mesocotyle growthupon UV�B irradiation [23]. In this case the possibleNO role relates to chemical modification of cell wallpolysaccharides and formation of covalent crosslinksin proteins, which appear upon synergistic action ofNO and ROS on activities of exo� and endo�β�gluco�nases and on the content of cell wall proteins [23].

Although NO usually operates as an antioxidant,there are also reports of its opposite action. For exam�ple, UV�B irradiation of Arabidopsis was followed dur�ing post�stress recovery by expression of chalcone syn�

thase, enhancement of NO synthase�like activity, andthe increase in NO content [41]. It was found that NOacts as a secondary messenger during inhibition ofmesocotyl elongation after UV�B irradiation [25, 26].The treatment of Z. mays leaves with apocynin (aceto�vanillone) stimulated NO synthesis significantly; fur�thermore, the pretreatment with apocynin minimizedinjuries of mesophyll cells and ROS production inleaves exposed to UV�B irradiation [51].

The plant tolerance to heavy metals is an adaptiveresponse possibly involving NO [52]. For example,endogenous NO production was enhanced in roots ofP. sativum and Brassica juncea in the presence of cad�mium, copper, and zinc [53]. The opposite resultswere obtained with leaves and roots of P. sativum plantsgrown in the presence of Cd2+. In this case, a substan�tial decrease in endogenous NO content was noted,which occurred concurrently with inhibition ofgrowth due to oxidative stress [54]. In addition, theapplication of solubilized aluminum form suppressedroot elongation and inhibited the NO synthase activity[55]. The pretreatment of Helianthus annuum leaveswith sodium nitroprusside averted the toxic effect ofCd2+ by preventing the oxidative stress development[53]. Similar effects were also noted for the L. luteusroots grown on the medium supplemented with Cd2+

and Pb2+ [47]. Nitric oxide donors were found to mit�igate Cd2+ toxicity in O. sativa leaves [57], prevent thedevelopment of Cd2+�induced oxidative stress in rootsof Cassia tora, and counteract the inhibition of Hibis�cus moscheutos root elongation caused by excessive Alcontent [57]. Under the action of Cd2+ and spermineon T. aestivum roots, the induction of NO synthesiswas observed, which was related to inhibition of rootelongation [53].

The action of NO on Chlamydomonas reinhardtiiwas shown to promote proline synthesis and synergis�tically counteract Cu2+�induced toxicity, which wasevident from the prevention of oxidative stress [49].The antioxidant effect of sodium nitroprusside mightaccount for the reduction of toxic effects of CuSO4 onO. sativa plants [58]. Exogenous NO was reported to alle�viate toxicity of arsenic, whose application suppressedelongation of rice roots and coleoptiles. In these experi�ments NO restored growth of roots and coleoptiles, decel�erated malonic dialdehyde (MDA) production, anddiminished the content of superoxide anion and hydrogenperoxide by acting as a ROS scavenger [59].

It is supposed that regulation of NO level in plantcells may involve aconitase, a Fe–S protein that pro�vides for intracellular homeostasis of iron ions [60].Conversely, NO is capable of maintaining ironhomeostasis and improve internal iron transport,thereby promoting chlorophyll biosynthesis and chlo�roplast development [61]. Experimental evidence forthe regulatory role of NO in iron metabolism camefrom the fact that exogenous NO donors—sodiumnitroprusside and S�nitroso�N�acetylpenicillamine—reversed the chlorotic phenotype of maize mutants



yellow stripe1 and yellow stripe3 characterized by inef�fective Fe utilization [61].

Since synergistic influence of ROS and nitric oxidederivatives attracts a great deal of attention, the level ofatmospheric ozone (O3) should be mentioned asanother relevant abiotic environmental factor. Exper�imental ozonation of Arabidopsis plants was shown toenhance the activity of NO synthases, which occurredprior to accumulation of salicylic acid and to theprogress of apoptosis [62]. The treatment of P. commu�nis leaves with O3 was followed by the increase in NOconcentration regulated by endogenous isoprene [62].Nitric oxide was shown to enhance the expression ofgenes responsible for ethylene and salicylic acid bio�syntheses after weakening of expression by O3 treat�ment [63].

The anthropogenic intrusion significantly modifiesthe composition of atmosphere, thus affecting plantmetabolism. The autotrophic organisms are especiallysensitive to the disbalance between oxygen and carbondioxide content in the atmosphere. Under hypoxicconditions M. truncatula leaves were found to releasesubstantial amounts of NO [64]. It is also known thatNO is engaged in plant adaptation to hypoxia, as wellas in the formation of aerenchyma during hypoxia andanoxia [65].

Another important property of NO is its cryopro�tective action. The treatment of plants with exogenousNO donors enhanced their tolerance of low tempera�tures [5]. High temperature treatments stimulated NOsynthesis, whereas the application of exogenous NOimproved cold resistance of S. lycopersicum, Z. mays,and T. aestivum [5, 66]. Nitric oxide might mediate theABA�induced thermotolerance of P. communis cal�luses [66]. The NO scavengers, i.e., isoprene and trun�cated hemoglobin (trHb) improved germination ofArabidopsis seeds at elevated temperatures owing toelimination of excess NO produced under high�tem�perature stress [67]. It was found that the applicationof exogenous NO during heat shock in Phaseolus radi�atus ensured the stability of chlorophyll a fluorescenceparameters, membrane integrity, H2O2 content, andactivity of antioxidant enzymes at the levels compara�ble to those in the absence of stress factor [66].

Apart from natural abiotic environmental factors,anthropogenic factors, such as application of fertiliz�ers and herbicides, should be kept in mind. Earlierstudies demonstrated that herbicide treatments ele�vated NO content in G. max plants [25]. Later worksestablished that the destructive action of diquat andparaquat (herbicides from methyl viologen group) canbe avoided by the pretreatment of S. tuberosum andO. sative leaves with NO donors [25]. When the cultureof Chlorella vulgaris was exposed to the herbicidesatrazine and glyphosate in combination with exoge�nous NO, such treatment substantially lowered theconcentrations of MDA, H2O2, and other ROS, whichwas paralleled by the increase in the content of chloro�phyll and antioxidant enzymes [68].

BIOTIC STRESS: INFECTION BY PATHOGENS

In addition to NO role in plant resistance to abioticenvironmental factors, NO serves as a signaling mole�cule during biotic stresses that arise upon intrusion ofpathogens of viral, bacterial, or eukaryotic origin [6,30]. One of the key mechanisms of plant defenseagainst pathogens is the hypersensitive response,which is implemented through the programmed celldeath at the infection site [69] and is regulated by theproportions of ROS and reactive nitrogen species [69].Nitric oxide interacts also with the key enzymes ofearly defense system, including catalase and ascorbateperoxidase [70]; this interaction gradually raises theintracellular H2O2 level and prolongs the local effectsof hydrogen peroxide [30].

It was shown that synergistic interaction of H2O2and NO molecules underlies the cell wall lignificationand induces the hypersensitive response [4]. In addi�tion, NO elevates the content of salicylic acid knownas a component of signaling pathways during bioticstresses [70]. Salicylic acid may in turn stimulate syn�thesis of NO in Arabidopsis, acting via enzyme withNO�synthesizing activity [71]. The dose�dependentaccumulation of NO in S. lycopersicum plants afterinoculation with the elicitor xylanase led to theenhanced synthesis of phosphatidic acid owing to acti�vation of phospholipase C and diacylglycerol kinase[72]. It is known that phosphatidic acid is an indispen�sible plant defense component during biotic stresseswhose protective action is implemented through thehypersensitive response [72].

In experiments with infection of Pennisetum glau�cum by pathogen of downy mildew disease, the treat�ment with NO donors promoted the development ofthe hypersensitive response, deposition of lignin, andexpression of phenylalanine ammonia�lyase [73].

The local hypersensitive response in plants is oftenassociated with the systemic acquired resistance in tis�sues located at a distance from the site of injury [74]. Itwas reported that NO enhanced the activity of NOsynthase in N. tabacum plants resistant to the tobaccomosaic virus. This defense response was due to theexpression of genes coding for pathogenesis�relatedprotein PR�1 [70], phenylalanine ammonia�lyase,and chalcone synthase [74]. It was shown that expres�sion of aforementioned defense genes was initiated ofcGMP and cADP�ribose [3]. However, it is not yetproven that NO production is a sufficient condition forthe hypersensitive response manifested in the form ofapoptosis, whose onset depends on the balancebetween ROS and NO content.

Upon the infection of G. max plants with a fungusDiaporthe phaseolorum f. sp. meridionalis, nitric oxideinduced not only expression of PR�1 protein but alsosynthesis of phytoalexins from the group of isoflavones(daidzein and genisteine) and pterocarpans from thegroup of glyceolins and flavones (epigenin and luteo�

458


KRASYLENKO et al.

lin) [30]. At the same time, experiments with the sus�pension tobacco culture BY�2 revealed neither theenhanced expression of phenylalanine ammonia�lyasenor the apoptosis induction under the action of NO;the only discernible phenomenon was an insignificantmodification of ascorbate and glutathione metabolism[4]. It was found that the gene targets affected by NOand H2O2 overlap partially; for example, the expres�sion of genes coding for defense proteins can be mod�ulated by both signaling molecules [4].

It was shown that H. annuum plants susceptible tothe pathogen Plasmopara halstedii were distinguishedby the elevated content of S�nitrosothiols and, espe�cially, 3�nitrotyrosylated proteins (NO2�Tyr), which isa biological marker of NO�stress induced in plants bybiotic factors [4, 75].

Phytopathogenic fungi from the genera Pythium, Bot�rytis and Fusarium can produce NO as a virulent factor[30]. For example, the expression of genes coding forNO�detoxifying proteins, e.g., NOD and NorR, areadditional virulent factors of bacterial phytopathogens[30]. A suitable example is arginase of Xylella fastidiosaand a homolog of NO synthase of Streptomyces turgidis�cabies; the latter enzyme accounts for the nitration of aphytotoxic dipeptide, which is necessary for the virulenceof the given pathogen [30].

The data presented above provide evidence thatnitric oxide is a key secondary messenger in plants,which is involved in the development of the hypersen�sitive response and systemic acquired resistance.

CONCLUSION

Thus, numerous experimental evidence suggestthat nitric oxide is involved in the regulation of mainand subsidiary processes in living plant cells, bothunder normal conditions and under the action ofbiotic and abiotic stress factors, which ensures plastic�ity and adaptation of plants to constantly changingenvironmental conditions. The defense mechanismsof plants are important for their survival, because thesessile way of life does not allow them to implementthe “fight�or�flight” strategy characteristic of animals.These features account for the diversity and cross�talksof metabolic pathways in plants, which involve sec�ondary messengers such as NO, Ca2+, and H2O2. Par�ticular attention should be given to mechanisms of NOsignaling in plant cells, which include both indirectpathways (mediated by cGMP, Ca2+, and proteinkinases) and direct regulation of key proteins by meansof their posttranslational modifications (S�nitrosyla�tion and nitrotyrosylation). Other perspective topics inthis area include interactions of NO with phytohor�mones (ABA, auxins, cytokinins, brassinosteroids,ethylene) and ROS, changes in gene expression pro�files under the action of NO, and the existence ofenzymatic and nonenzymatic NO sources within theplant cell. Since investigations of nitric oxide regula�tory roles in plants have started comparatively recently,

the comprehension of functional significance of thismolecule would depend on elucidation of the path�ways for NO synthesis and detoxification, on under�standing the cell and molecular mechanisms of NOsignaling, and, especially, on clarifying the role ofposttranslational modifications of key proteins andNO interactions with other signaling molecules.

REFERENCES

1. Correa�Aragunde, N., Graziano, M., Chevalier, C.,and Lamattina, L., Nitric Oxide Mediates the Expres�sion of Cell�Cycle Regulatory Genes during LateralRoot Formation in Tomato, J. Exp. Bot., 2006, vol. 57,pp. 581–588.

2. Delledonne, M., Xia, Y., and Dixon, R.A., NitricOxide Functions as a Signal in Plant Disease Resis�tance, Nature, 1998, vol. 394, pp. 585–588.

3. Durner, J., Wendehenne, D., and Klessig, D.F.,Defense Gene Induction in Tobacco by Nitric Oxide,Cyclic GMP, and Cyclic ADP Ribose, Proc. Natl. Acad.Sci. USA, 1998, vol. 95, pp. 10328–10333.

4. Hong, J.K., Yun, B.�W., Kang, J.�G., Raja, M.U.,Kwon, E., Sorhagen, K., Chu, C., Wang, Y., andLoake, G.J., Nitric Oxide Function and Signalling inPlant Disease, J. Exp. Bot., 2008, vol. 59, pp. 147–154.

5. Neill, S., Barroso, R., Bright, J., Desikan, R., Han�cock, J., Harrison, J., Morris, P., Ribeiro, D., and Wil�son, J., Nitric Oxide, Stomatal Closure, and AbioticStress, J. Exp. Bot., 2008, vol. 59, pp. 165–176.

6. Arasimowicz, M. and Floryszak�Wieczorek, J., NitricOxide as a Bioactive Signalling Molecule in Plant StressResponses, Plant Sci., 2007, vol. 172, pp. 876–887.

7. Besson�Bard, A., Pugin, A., and Wendehenne, D.,New Insights into Nitric Oxide Signaling in Plants,Annu. Rev. Plant Biol., 2008, vol. 59, pp. 21–39.

8. Besson�Bard, A., Astier, J., Rasul, S., Wawera, I.,Dubreuil�Maurizi, C., Jeandroz, M., andWendehenne, D., Current View of Nitric Oxide�Responsive Genes in Plants, Plant Sci., 2009, vol. 177,pp. 302–309.

9. Leitner, M., Vandelle, E., Gaupels, F., Bellin, D., andDelledonne, M., NO Signals in the Haze. Nitric OxideSignalling in Plant Defence, Curr. Opin. Plant Biol.,2009, vol. 12, pp. 451–458.

10. Guo, F.Q., Okamoto, M., and Crawford, N.M., Iden�tification of a Plant Nitric Oxide Synthase GeneInvolved in Hormonal Signaling, Science, 2003,vol. 302, pp. 100–103.

11. Wilson, I.D., Neil, S.J., and Hancock, D.T., NitricOxide Synthesis and Signalling in Plants, Plant CellEnviron., 2008, vol. 31, pp. 622–631.

12. Bethke, P.C., Badger, M.R., and Jones, R.L., Apoplas�tic Synthesis of Nitric Oxide by Plant Tissues, PlantCell, 2004, vol. 16, pp. 332–341.

13. Blume, Ya.B., Krasylenko, Yu.A., and Yemets, A.I.Tyrosine Nitration as Regulatory Protein Posttransla�tional Modification, Ukr. Biochem. J., 2009, vol. 81,no. 5, pp. 5–15.

14. Montenero, H., Arai, R., and Travassos, L.R., ProteinTyrosine Phosphorylation and Protein Tyrosine Nitra�



tion in Redox Signaling, Antioxid. Redox Signal., 2008,vol. 10, pp. 843–889.

15. Valderrama, R., Corpas, F.J., Carreras, A., Fernández�Oca a, A., Chaki, M., Luquea, F., Gómez�Rodríguez,M.R., Colmenero�Varea, P., del Río, L.A., and Bar�roso, J.B., Nitrosative Stress in Plants, FEBS Lett.,2007, vol. 581, pp. 453–461.

16. Blume, Ya.B., Nyporko, A.Yu., and Yemets, A.I.,Nitrotyrosination of α�Tubulin: Structural Analysis ofFunctional Significance in Plants and Animals, CellBiology and Instrumentation: UV Irradiation, NitricOxide and Cell Death in Plants, Blume, Ya.B., Durzan, D.J.,and Smertenko, P., Eds., Amsterdam: IOS Press, 2006,pp. 325–333.

17. Yemets, A.I., Krasylenko, Yu.A., Sheremet, Ya.A., andBlume, Ya.B., Microtubule Reorganization as aResponse to Realization of Nitric Oxide (II) Signals inPlant Cell, Tsitol. Genet., 2009, vol. 43, no. 2, pp. 3–10.

18. Pagnussat, G.C., Lanteri, M.L., Lombardo, M.C., andLamattina, L., Nitric Oxide Mediates the IndolaceticAcid Induction of a Mitogen�Activated Protein KinaseCascade Involved in Adventitious Roots Development,Plant Physiol., 2004, vol. 135, pp. 279–286.

19. Courtois, C., Besson, A., Dahan, J., Bourque, S.,Dobrowolska, G., Pugin, A., and Wendehenne, D.,Nitric Oxide Signalling in Plants: Interplays with Ca2+

and Protein Kinases, J. Exp. Bot., 2008, vol. 3, pp. 1–9.

20. Lamotte, O., Courtois, C., Dobrowolska, G., Besson, A.,Pugin, A., and Wendehenne, D., Mechanisms ofNitric�Oxide�Induced Increase of Free Cytosolic Ca2+

Concentration in Nicotiana plumbaginifolia Cells, FreeRadic. Biol. Med., 2006, vol. 40, pp. 1369–1376.

21. Ötvös, K., Pasternak, T., Miskolczi, P., Domoki, M.,Dorjgotov, D., Szücs, A., Bottka, S., Dudits, S., andFehér, A., Nitric Oxide Is Involved in the Activation ofCell Division and Somatic Embryo Formation inAlfalfa, Plant J., 2005, vol. 43, pp. 849–860.

22. Grün, S., Lindermayr, C., Sell, S., and Durner, J.,Nitric Oxide and Gene Regulation in Plants, J. Exp.Bot., 2006, vol. 57, pp. 507–516.

23. Ederli, L., Reale, L., Madeo, L., Ferranti, F.,Gehring, C., Fornaciari, M., Romano, B., and Pas�qualini, S., NO Release by Nitric Oxide DonorsIn Vitro and In Planta, Plant Physiol. Biochem., 2009,vol. 47, pp. 42–48.

24. Hu, X., Neill, S., Tang, Z., and Cai, W., Nitric OxideMediates Gravitropic Bending in Soybean Roots, PlantPhysiol., 2005, vol. 137, pp. 663–670.

25. Beligni, M.V. and Lamattina, L., Nitric Oxide Inter�feres with Plant Photo�Oxidative Stress by DetoxifyingReactive�Oxygen Species, Plant Cell Environ., 2002,vol. 25, pp. 737–748.

26. Zhang, M., An, L., Feng, P., Chen T., Chen K., Liu Y.,Tang, H., Chang, J., and Wang, X., The CascadeMechanisms of Nitric Oxide as a Second Messenger ofUltraviolet�B in Inhibiting Mesocotyl Elongations,Photochem. Photobiol., 2003, vol. 77, pp. 219–225.

27. An, L., Liu, Z., Yang, M., Chen, T., and Wang, X.,Effects of Nitric Oxide on Growth of Maize SeedlingLeaves in the Presence or Absence of Ultraviolet Radi�ation, J. Plant Physiol., 2005, vol. 162, pp. 317–326.

n

ˆ

28. Lehner, C., Kerschbaum, H.H., and Lütz�Meindl, U.,Nitric Oxide Suppresses Growth and Development inthe Unicellular Green Alga Micrasterias denticulata,J. Plant Physiol., 2009, vol. 166, pp. 117–127.

29. Salmi, M.L., Morris, K.E., Roux, S.J., andPorterfield, D.M., Nitric Oxide and cGMP Signaling inCalcium�Dependent Development of Cell Polarity inCeratopteris richardii, Plant Physiol., 2007, vol. 144,pp. 94–104.

30. Mur, L.A.J., Carver, T.L.V., and Prats, E., NO Way toLive: The Various Roles of Nitric Oxide in Plant–Pathogen Interactions, J. Exp. Bot., 2006, vol. 57,pp. 489–505.

31. Baudouin, E., Pieuchot, L., Engler, G., Pauly, N., andPuppo, A., Nitric Oxide Is Formed in Medicago trunca�tula–Sinorhizobium meliloti Functional Nodules, Mol.Plant–Microbe Interact., 2006, vol. 19, pp. 970–975.

32. He, Y., Tang, R.H., Hao, Y., Stevens, R.D.,Cook, C.W., Ahn, S.M., Jing, L., Yang, Z., Chen, L.,Guo, F., Fiorani, F., Jackson, R.B., Crawford, N.M.,and Pei, Z.�M., Nitric Oxide Represses the ArabidopsisFloral Transition, Science, 2004, vol. 305, pp. 1968–1971.

33. Bright, J., Hiscock, S.J., James, P.E., and Hancock, J.T.,Pollen Generates Nitric Oxide and Nitrite: A PossibleLink to Pollen�Induced Allergic Responses, PlantPhysiol. Biochem., 2009, vol. 47, pp. 49–55.

34. Prado, A.M., Porterfield, D.M., and Feijo, J.A., NitricOxide Is Involved in Growth Regulation and Re�Ori�entation of Pollen Tubes, Development, 2004, vol. 131,pp. 2707–2714.

35. Zhao, M.�G., Liu, R.�J., Chen, L., Tian, Q.�Y., andZhang, W.�H., Glucose�Induced Inhibition of SeedGermination in Lotus japonicus Is Alleviated by NitricOxide and Spermine, J. Plant Physiol., 2009, vol. 166,pp. 213–218.

36. Hung, K.T. and Kao, C.H., Nitric Oxide Counteractsthe Senescence of Rice Leaves Induced by HydrogenPeroxide, 21 Bot. Bull. Acad. Sinica, 2005, vol. 46,pp. 21–28.

37. Jasid, S., Galatro, A., Villordo, J.J., Puntarulo, S., andSimontacchi, M., Role of Nitric Oxide in SoybeanCotyledon Senescence, Plant Sci., 2009, vol. 176,pp. 662–668.

38. Borutaite, V., Budriunaite, A., and Brown, G.C.,Reversal of Nitric Oxide, Peroxynitrite� and S�Nitro�sothiol�Induced Inhibition of Mitochondrial Respira�tion or Complex I Activity by Light and Thiols, Bio�chim. Biophys. Acta, 2000, vol. 1459, pp. 405–412.

39. Takahashi, S. and Yamasaki, H., Reversible Inhibitionof Photophosphorylation in Chloroplasts by NitricOxide, FEBS Lett., 2002, vol. 512, pp. 145–148.

40. De Pinto, M.C., Tommasi, F., and de Gara, L.,Changes in the Antioxidant Systems as Part of the Sig�naling Pathway Responsible for the Programmed CellDeath Activated by Nitric Oxide and Reactive OxygenSpecies in Tobacco Bright�Yellow 2 Cells, Plant Phys�iol., 2002, vol. 130, pp. 698–708.

41. Shi, S., Wang, G., Wang, Y., Zhang, L., and Zhang, L.,Protective Effect of Nitric Oxide against OxidativeStress under Ultraviolet�B Radiation, Nitric Oxide,2005, vol. 13, pp. 1–9.

460


KRASYLENKO et al.

42. Belenghi, B., Romero�Puertas, M.C., Vercammen, D.,Brackenier, A., Inze, D., Delledonne, M., andvan Breusegem, F., Metacaspase Activity of Arabidopsisthaliana Is Regulated by S�Nitrosylation of a CriticalCysteine Residue, J. Biol. Chem., 2007, vol. 282,pp. 1352–1358.

43. Paris, R., Lamattina, L., and Casalongue, C.A., NitricOxide Promotes Wound�Healing Response of PotatoLeaflets, Plant Physiol. Biochem., 2007, vol. 45, pp. 80–86.

44. Cheng, J.�S. and Yuan, Y.�J., Release of Proteins:Insights into Oxidative Response of Taxus cuspidateCells Induced by Shear Stress, J. Mol. Catalysis, B:Enzymatic, 2009, vol. 58, pp. 84–92.

45. Zhao, L., He, J., Wang, X., and Zhang, L., Nitric OxideProtects against Polyethylene Glycol�Induced Oxida�tive Damage in Two Ecotypes of Reed Suspension Cul�tures, J. Plant Physiol., 2008, vol. 165, pp. 182–191.

46. Zhang, Y.Y., Liu, J., and Liu, Y.L., Nitric Oxide Allevi�ates Growth Inhibition of Maize Seedlings under NaClStress, Nitric Oxide, 2004, vol. 30, pp. 455–459.

47. Kopyra, M. and Gwozdz, E., Nitric Oxide StimulatesSeed Germination and Counteracts the InhibitoryEffect of Heavy Metals and Salinity of Root Growth ofLupinus luteus, Plant Physiol. Biochem., 2003, vol. 41,pp. 1011–1017.

48. Qiao, W., Xiao, S., Yu, L., and Fan, L.�M., Expressionof a Rice Gene OsNOA1 Re�Establishes Nitric OxideSynthesis and Stress�Related Gene Expression for SaltTolerance in Arabidopsis nitric oxide�associated 1Mutant Atnoa1, Environ. Exp. Bot., 2009, vol. 65,pp. 90–98.

49. Zhang, A., Jiang, M., Zhang, J., Ding, H., Xu, S.,Hu, X., and Tan, M., Nitric Oxide Induced by Hydro�gen Peroxide Mediates Abscisic Acid�Induced Activa�tion of the Mitogen�Activated Protein Kinase CascadeInvolved in Antioxidant Defense in Maize Leaves, NewPhytol., 2007, vol. 175, pp. 36–50.

50. Xue, L.J., Li, S.W., and Xu, S.J., Alleviative Effects ofNitric Oxide on the Biological Damage of Spirulinaplatensis Induced by Enhanced Ultraviolet�B, NitricOxide, 2006, vol. 46, pp. 561–564.

51. Tossi, V., Cassia, R., and Lamattina, L., Apocynin�Induced Nitric Oxide Production Confers AntioxidantProtection in Maize Leaves, J. Plant Physiol., 2009,vol. 166, pp. 1336–1341.

52. Corpas, F.J., Barroso, J.B., Carreras, A., Valderrama, R.,Palma, J.M., and del Rio, L.A., Nitrosative Stress inPlants: A New Approach to Understand the Role of NOin Abiotic Stress, Nitric Oxide in Plant Growth, Develop�ment and Stress Physiology, vol. 6, Lamattina, L. andPolacco, J.C., Eds., Berlin: Springer�Verlag, 2007.

53. Groppa, M.D., Rosales, E.P., Iannone, M.F., andBenavides, M.P., Nitric Oxide, Polyamines and Cd�Induced Phytotoxicity in Wheat Roots, Phytochemistry,2008, vol. 69, pp. 2609–2615.

54. Barroso, J.B., Corpas, F.J., Carreras, A., Rodríguez�Serrano, M., Esteban, F.J., Fernández�Ocaña, A.,Chaki, M., Romero�Puertas, M.C., Valderrama, R.,Sandalio, L.M., and del Río, L.A., Localization ofS�Nitrosoglutathione and Expression of S�Nitrosoglu�

tathione Reductase in Pea Plants under CadmiumStress, J. Exp. Bot., 2006, vol. 57, pp. 1785–1793.

55. Tian, Q.Y., Sun, D.H., Zhao, M.G., and Zhang, W.H.,Inhibition of Nitric Oxide Synthase (NOS) UnderliesAluminium�Induced Inhibition of Root Elongation inHibiscus moscheutos, New Phytol., 2007, vol. 175,pp. 36–50.

56. Hsu, Y.T. and Kao, C.H., Cadmium Toxicity IsReduced by Nitric Oxide in Rice Leaves, Plant GrowthRegul., 2005, vol. 42, pp. 227–238.

57. Wang, Y.�S. and Yang, Z.�M., Nitric Oxide ReducesAluminum Toxicity by Preventing Oxidative Stress inthe Roots of Cassia tora L., Plant Cell Physiol., 2005,vol. 46, pp. 1915—1923.

58. Yu, C.C., Hung, K.T., and Kao, C.H., Nitric Oxide

Reduces Cu Toxicity and Cu�Induced NH4+ Accumu�

lation in Rice Leaves, J. Plant Physiol., 2005, vol. 162,pp. 1319–1330.

59. Singh, H.P., Kaur, S., Batish, D.R., Sharma, V.P.,Sharma, N., and Kohli, R.K., Nitric Oxide AlleviatesArsenic Toxicity by Reducing Oxidative Damage in theRoots of Rice, Nitric Oxide, 2009, vol. 20, pp. 289–297.

60. Navarre, D.A., Wendehenne, D., and Durner, D.,Nitric Oxide Modulates the Activity of Tobacco Aconi�tase, Plant Physiol., 2000, vol. 122, pp. 573–582.

61. Graziano, M. and Lamattina, L., Nitric Oxide and Ironin Plants: An Emerging and Converging Story, TrendsPlant Sci., 2005, vol. 10, pp. 4–8.

62. Kolbert, Zs., Sahin, N., and Erdei, L., Early NitricOxide (NO) Responses to Osmotic Stress in Pea, Ara�bidopsis and Wheat, Acta Biol. Szeged, 2008, vol. 52,pp. 63–65.

63. Ahlfors, R., Brosché, M., Kollist, H., andKangasjärvi, J., Nitric Oxide Modulates Ozone�Induced Cell Death, Hormone Biosynthesis and GeneExpression in Arabidopsis thaliana, Plant J., 2008,vol. 58, pp. 1–12.

64. Dordas, C., Rivoal, J., and Hill, R.D., Plant Hemoglo�bins, Nitric Oxide and Hypoxic Stress, Ann. Bot., 2003,vol. 91, pp. 173–178.

65. Hebelstrup, K.H., Igamberdiev, A.U., and Hill, R.D.,Metabolic Effects of Hemoglobin Gene Expression inPlants, Gene, 2007, vol. 398, pp. 86–93.

66. Song, L., Ding, W., Shen, J., Zhang, Z., Bi, Y., andZhang, L., Nitric Oxide Mediates Abscisic AcidInduced Thermotolerance in the Calluses from TwoEcotypes of Reed under Heat Stress, Plant Sci., 2008,vol. 175, pp. 826–832.

67. Hossain, K.K., Tokuda, G., Itoh, R.D., andYamasaki, H., Scavenging of Nitric Oxide ImprovesPlant Tolerance against High Temperature Stress,Nitric Oxide, 2006, vol. 14, pp. 27–38.

68. Qian, H., Chen, W., Li, J., Wang, J., Zhou, Z., Liu, W.,and Fu, Z., The Effect of Exogenous Nitric Oxide onAlleviating Herbicide Damage in Chlorella vulgaris,Aquat. Toxicol., 2009, vol. 92, pp. 250–257.

69. Delledonne, M., Zeier, J., Marocco, A., and Lamb, C.,Signal Interactions between Nitric Oxide and ReactiveOxygen Intermediates in the Plant Hypersensitive Dis�ease Resistance Response, Proc. Natl. Acad. Sci. USA,2001, vol. 98, p. 13 454—13 459.



70. Klessig, D.F., Durner, J., Noad, R., Navarre, D.A.,Wendehenne, D., Kumar, D., Zhou, J.M., Shali, S.,Zhang, S., Kachroo, P., Trifa, Y., Pontier, D., Lam, E.,and Silva, H., Nitric Oxide and Salicylic Acid Signalingin Plant Defense, Proc. Natl. Acad. Sci. USA, 2000,vol. 97, pp. 8849–8855.

71. Zottini, M., Costa, A., de Michele, R., Ruzzene, M.,Carimi, C., and Lo Schiavo, F., Salicylic Acid ActivatesNitric Oxide Synthesis in Arabidopsis, J. Exp. Bot.,2007, vol. 58, pp. 1397–1405.

72. Laxalt, A.M., Raho, N., ten Have, A., andLamattina, L., Nitric Oxide Is Critical for InducingPhosphatidic Acid Accumulation in Xylanase�ElicitedTomato Cells, J. Biol. Chem., 2007, vol. 282,pp. 21160–21168.

73. Manjunatha, G., Raj, S.N., Shetty, N.P., andShetty, S.H., Nitric Oxide Donor Seed PrimingEnhances Defense Responses and Induces Resistanceagainst Pearl Millet Downy Mildew Disease, Pestic.Biochem. Physiol., 2008, vol. 91, pp. 1–11.

74. Romero�Puertas, M.C. and Delledonne, M., NitricOxide Signaling in Plant–Pathogen Interactions, Life,2003, vol. 55, pp. 579–583.

75. Chaki, M., Valderrama, R., Carreras, A., Esteban, F.J.,Luque, F., Rodriguez, M.V., Begara�Morales, J.C.,Corpas, F.J., and Barroso, J.B., Involvement of Reac�tive Nitrogen and Oxygen Species (RNS and ROS) inSunflower–Mildew Interaction, Plant Cell Physiol.,2009, vol. 50, pp. 265–279.

Documents

Functional role of nitric oxide in plants