Monoxyde d'azote et immunité chez les plantes : identification et caractérisation de protéines cibles

Nitric oxide synthase in plants: Where do we stand?

Thaxtomin A-induced defense responses in Arabidopsis thaliana cells require an early Ca2+ influx

International audience

Free Radicals Mediate Systemic Acquired Resistance

Summary: Systemic acquired resistance (SAR) is a form of resistance that protects plants against a broad spectrum of secondary infections. However, exploiting SAR for the protection of agriculturally important plants warrants a thorough investigation of the mutual interrelationships among the various signals that mediate SAR. Here, we show that nitric oxide (NO) and reactive oxygen species (ROS) serve as inducers of SAR in a concentration-dependent manner. Thus, genetic mutations that either inhibit NO/ROS production or increase NO accumulation (e.g., a mutation in S-nitrosoglutathione reductase [GSNOR]) abrogate SAR. Different ROS function additively to generate the fatty-acid-derived azel…

Nitric oxide: a new player in plant signalling and defence responses.

There is increasing evidence that nitric oxide (NO), which was first identified as a unique diffusible molecular messenger in animals, plays important roles in diverse (patho)physiological processes in plants. NO functions include the modulation of hormonal, wounding and defence responses, as well as the regulation of cell death. Enzymes that catalyse NO synthesis and signalling cascades that mediate NO effects have recently been discovered, providing a better understanding of the mechanisms by which NO influences plant responses to various stimuli. Additionally, growing evidence suggests that NO signalling interacts with the salicylic acid and jasmonic acid signalling pathways.

NO-Based Signaling in Plants

In animals, nitric oxide (NO) is an endogenously produced radical involved in cell communication and signal transduction. Its functions in plants are currently being discovered at an unprecedented pace, and insight into NO-derived mechanisms has mainly been gained from research on signal transduction. Numerous studies have firmly placed NO as one component of the signal perception–transduction network that connects plant responses to primary signals, including hormones, elicitors of defence responses or abiotic stresses. Protein kinases and the second messengers Ca 2+, cGMP, and cADPR convey part of the NO signal within cells. Furthermore, NO-based protein modifications are emerging as broa…

β-Aminobutyric Acid Primes an NADPH Oxidase–Dependent Reactive Oxygen Species Production During Grapevine-Triggered Immunity

International audience; The molecular mechanisms underlying the process of priming are poorly understood. In the present study, we investigated the early signaling events triggered by β-aminobutyric acid (BABA), a well-known priming-mediated plant resistance inducer. Our results indicate that, in contrast to oligogalacturonides (OG), BABA does not elicit typical defense-related early signaling events nor defense-gene expression in grapevine. However, in OG-elicited cells pretreated with BABA, production of reactive oxygen species (ROS) and expression of the respiratory-burst oxidase homolog RbohD gene were primed. In response to the causal agent of downy mildew Plasmopara viticola, a strong…

Some Plant Defense Stimulators can induce IL-1β production in human immune cells in vitro

8 pages; International audience; Among Plant Protection Products (PPP), a new emerging category of pesticides act by stimulating plant defense in order to improve plant resistance against microbial pathogens. Given that these compounds, the so-called Plant Defense Stimulators (PDS) act on innate immunity, we tested, using an in vitro approach on human mononuclear leucocytes (PBMC), the potential toxicity (XTT assay) and inflammatory effects (production of IL-1β) of 4 PPP belonging to different chemical families. We found that two products (LBG-01F34® and Regalis®) did not induce any cytotoxicity or IL-1 β production. The product BION-50 WG®, that contains Acibenzolar-S-methyl (ASM) and sili…

Analysis of the role of nitric oxide (NO) in the cross‐regulation between immunity, growth and iron homeostasis in plants

Studies performed in our Agroecology Department show that the immune response of plants is linked to their iron nutrition and is modulated by pyoverdine, a siderophore produced by the plant beneficial rhizobacteria Pseudomonas fluorescens C7R12. Accordingly, Arabidopsis thaliana plantlets exposed to iron deficiency and treated with pyoverdine in its iron non‐chelated structure (apo‐pyo) show an enhanced growth but a decreased immune response capacity. We hypothesize that nitric oxide (NO), a universal signaling molecule, is a key component of the regulation of the immune response in plants exposed to apo‐pyo and to the C7R12 strain. We checked by fluorescence microscopy that NO is actually …

Does regulation of redox status of plant leaves under salinity conditions involve ABA-non responsive SnRK2 kinases

Regulation of Nicotiana tabacum osmotic stress-activated protein kinase and its cellular partner GAPDH by nitric oxide in response to salinity

Several studies focusing on elucidating the mechanism of NO (nitric oxide) signalling in plant cells have highlighted that its biological effects are partly mediated by protein kinases. The identity of these kinases and details of how NO modulates their activities, however, remain poorly investigated. In the present study, we have attempted to clarify the mechanisms underlying NO action in the regulation of NtOSAK (Nicotiana tabacum osmotic stress-activated protein kinase), a member of the SNF1 (sucrose non-fermenting 1)-related protein kinase 2 family. We found that in tobacco BY-2 (bright-yellow 2) cells exposed to salt stress, NtOSAK is rapidly activated, partly through a NO-dependent pr…

Type-II histone deacetylases: elusive plant nuclear signal transducers

Since the beginning of the 21st century, numerous studies have concluded that the plant cell nucleus is one of the cellular compartments that define the specificity of the cellular response to an external stimulus or to a specific developmental stage. To that purpose, the nucleus contains all the enzymatic machinery required to carry out a wide variety of nuclear protein post-translational modifications (PTMs), which play an important role in signal transduction pathways leading to the modulation of specific sets of genes. PTMs include protein (de)acetylation which is controlled by the antagonistic activities of histone acetyltransferases (HATs) and histone deacetylases (HDACs). Regarding p…

New insights about the role of the chaperon-like protein Cdc48, a target for nitric oxide in plant immunity

Evaluation des projets intégrés de recherche innovation (PARI). Fiche projet intégré AGRALE 8 - Interactions Plantes- Microorganismes : Mécanismes et Applications

The glutaredoxin ATGRXS13 is required to facilitate Botrytis cinerea infection of Arabidopsis thaliana plants

Summary Botrytis cinerea is a major pre- and post-harvest necrotrophic pathogen with a broad host range that causes substantial crop losses. The plant hormone jasmonic acid (JA) is involved in the basal resistance against this fungus. Despite basal resistance, virulent strains of B. cinerea can cause disease on Arabidopsis thaliana and virulent pathogens can interfere with the metabolism of the host in a way to facilitate infection of the plant. However, plant genes that are required by the pathogen for infection remain poorly described. To find such genes, we have compared the changes in gene expression induced in A. thaliana by JA with those induced after B. cinerea using genome-wide micr…

Glutathione deficiency of the Arabidopsis mutant pad2-1 affects oxidative stress-related events, defense gene expression and hypersensitive response

L'article original est publié par The American Society of Plant Biologists; International audience; The Arabidopsis (Arabidopsis thaliana) phytoalexin-deficient mutant pad2-1 displays enhanced susceptibility to a broad range of pathogens and herbivorous insects that correlates with deficiencies in the production of camalexin, indole glucosinolates, and salicylic acid (SA). The pad2-1 mutation is localized in the GLUTAMATE-CYSTEINE LIGASE (GCL) gene encoding the first enzyme of glutathione biosynthesis. While pad2-1 glutathione deficiency is not caused by a decrease in GCL transcripts, analysis of GCL protein level revealed that pad2-1 plants contained only 48% of the wild-type protein amoun…

Current view of nitric oxide-responsive genes in plants

International audience; Significant efforts have been directed towards the identification of genes differentially regulated through nitric oxide (NO)-dependent processes. These efforts comprise the use of medium- and large-scale transcriptomic analyses including microarray and cDNA-amplification fragment length polymorphism (AFLP) approaches. Numerous putative NO-responsive genes have been identified in plant tissues and cell suspensions with transcript levels altered by artificially released NO, or endogenously produced. Comparative analysis of the data from such transcriptomic analyses in Arabidopsis reveals that a significant part of these genes encode proteins related to plant adaptive …

Functional characterization of the chaperon-like protein Cdc48 in cryptogein-induced immune response in tobacco. Communication orale et poster

International audience; Cdc48, a molecular chaperone conserved in diff erent kingdoms, is a member of the AAA+ family contributing to numerous processes in mammalian including proteins quality control and degradation, vesicular traffi cking, autophagy and immunity. The functions of Cdc48 plant orthologues are less understood. We previously reported that Cdc48 is regulated by S-nitrosylation in tobacco cells undergoing an immune response triggered by cryptogein, an elicitin produced by the oomycete Phytophthora cryptogea. Here, we investigated the function of NtCdc48 in cryptogein signaling and induced hypersensitive-like cell death. NtCdc48 was found to accumulate in elicited cells both at …

Nitric oxide inhibits the ATPase activity of the chaperone-like AAA+ ATPase CDC48, a target for S-nitrosylation in cryptogein signalling in tobacco cells

NO has important physiological functions in plants, including the adaptative response to pathogen attack. We previously demonstrated that cryptogein, an elicitor of defence reaction produced by the oomycete Phytophthora cryptogea , triggers NO synthesis in tobacco. To decipher the role of NO in tobacco cells elicited by cryptogein, in the present study we performed a proteomic approach in order to identify proteins undergoing S-nitrosylation. We provided evidence that cryptogein induced the S-nitrosylation of several proteins and identified 11 candidates, including CDC48 (cell division cycle 48), a member of the AAA+ ATPase (ATPase associated with various cellular activities) family. In vit…

Electrochemical detection of nitric oxide in plant cell suspensions

SPE IPM UB; Nitric oxide is a hydrophobic radical acting as a physiological mediator in plants. Because of its unique properties, the detection of NO in plant tissues and cell suspensions remains a challenge. For this purpose, several techniques are used, each having certain advantages and limitations such as interferences with other species, questionable sensitivity, and/or selectivity or ex situ measurement. Here we describe a very attractive approach for tracking NO in plant cell suspensions using a NO-sensitive homemade platinum/iridium-based electrochemical microsensor. This method constitutes the absolute real-time proof of the production of free NO in physiological conditions.

Mechanisms of nitric-oxide-induced increase of free cytosolic Ca2+ concentration in Nicotiana plumbaginifolia cells.

In this study, we investigated a role for nitric oxide (NO) in mediating the elevation of the free cytosolic Ca(2+) concentration ([Ca(2+)](cyt)) in plants using Nicotiana plumbaginifolia cells expressing the Ca(2+) reporter apoaequorin. Hyperosmotic stress induced a fast increase of [Ca(2+)](cyt) which was strongly reduced by pretreating cell suspensions with the NO scavenger carboxy PTIO, indicating that NO mediates [Ca(2+)](cyt) changes in plant cells challenged by abiotic stress. Accordingly, treatment of transgenic N. plumbaginifolia cells with the NO donor diethylamine NONOate was followed by a transient increase of [Ca(2+)](cyt) sensitive to plasma membrane Ca(2+) channel inhibitors …

The Pseudomonas fluorescens Siderophore Pyoverdine Weakens Arabidopsis thaliana Defense in Favor of Growth in Iron-Deficient Conditions

SPE EA BIOME IPM UB INRA; International audience; Pyoverdines are siderophores synthesized by fluorescent Pseudomonas spp. Under iron-limiting conditions, these high-affinity ferric iron chelators are excreted by bacteria in the soil to acquire iron. Pyoverdines produced by beneficial Pseudomonas spp. ameliorate plant growth. Here, we investigate the physiological incidence and mode of action of pyoverdine from Pseudomonas fluorescens C7R12 on Arabidopsis (Arabidopsis thaliana) plants grown under iron-sufficient or iron-deficient conditions. Pyoverdine was provided to the medium in its iron-free structure (apo-pyoverdine), thus mimicking a situation in which it is produced by bacteria. Rema…

Nitric oxide: comparative synthesis and signaling in animal and plant cells.

Since its identification as an endothelium-derived relaxing factor in the 1980s, nitric oxide has become the source of intensive and exciting research in animals. Nitric oxide is now considered to be a widespread signaling molecule involved in the regulation of an impressive spectrum of mammalian cellular functions. Its diverse effects have been attributed to an ability to chemically react with dioxygen and its redox forms and with specific iron- and thiol-containing proteins. Moreover, the effects of nitric oxide are dependent on the dynamic regulation of its biosynthetic enzyme nitric oxide synthase. Recently, the role of nitric oxide in plants has received much attention. Plants not only…

NO signaling in cryptogein-induced immune responses in tobacco

SPEIPM; International audience

Protein S-nitrosylation: specificity and identification strategies in plants

SPE Pôle IPM UB; International audience; The role of nitric oxide (NO) as a major regulator of plant physiological functions has become increasingly evident. To further improve our understanding of its role, within the last few years plant biologists have begun to embrace the exciting opportunity of investigating protein S-nitrosylation, a major reversible NO-dependent post-translational modification (PTM) targeting specific Cys residues and widely studied in animals. Thanks to the development of dedicated proteomic approaches, in particular the use of the biotin switch technique (BST) combined with mass spectrometry, hundreds of plant protein candidates for S-nitrosylation have been identi…

Involvement of Free Calcium in Action of Cryptogein, a Proteinaceous Elicitor of Hypersensitive Reaction in Tobacco Cells

Treatment of suspension-cultured tobacco (Nicotiana tabacum var Xanthi) cells with cryptogein, a proteinaceous elicitor from Phytophthora cryptogea, induced a great stimulation of Ca2+ influx within the first minutes. Ca2+ influx is essential for the initiation of cryptogein-induced responses, since ethyleneglycol-bis([beta]-amino-ethyl ether)-N,N[prime]-tetraacetic acid or La3+, which block Ca2+ entrance, suppress cryptogein-induced responses such as extracellular alkalinization, active oxygen species, and phytoalexin production. Moreover, once initiated, these responses require sustained Ca2+ influx within the 1st h. A Ca2+ ionophore (A23187) was able to trigger an extracellular alkaliniz…

GAPDH, ntosak and cdc48, a conserved chaperone-like aaa-atpase, as nitric oxide targets in response to (a)biotic stresses

S-nitrosylation: An emerging post-translational protein modification in plants

International audience; Increasing evidences support the assumption that nitric oxide (NO) acts as a physiological mediator in plants. Understanding its pleiotropic effects requires a deep analysis of the molecular mechanisms underlying its mode of action. In the recent years, efforts have been made in the identification of plant proteins modified by NO at the post-translational level, notably by S-nitrosylation. This reversible process involves the formation of a covalent bond between NO and reactive cysteine residues. This research has now born fruits and numerous proteins regulated by S-nitrosylation have been identified and characterized. This review describes the basic principle of S-n…

Cryptogein signaling in tobacco: in search for nitric oxide targets

Nitric oxide (NO) triggers various physiological responses in plants. Notably, NO is recognized to account for the response to biotic stresses. We previously reported that NO is produced in tobacco cells exposed to cryptogein, a 10 kDa elicitor secreted by the oomycete Phytophthora cryptogea. To decipher the role of NO, we identified and characterized S-nitrosylated proteins in tobacco cell suspensions elicited by cryptogein. Several candidates were identified including the chaperone-like AAA+ATPase CDC48 and a calmodulin isoform (CaM). Interestingly, the Cys residue undergoing S-nitrosylation in CaM is located in the first Ca2+ binding EF hand and is not or poorly conserved in other organi…

Nitric oxide production in tobacco leaf cells: a generalized stress response?

The function of nitric oxide (NO), a gaseous free radical emitted by many plants, is incompletely understood. In the present study the hypothesis that NO generation, like that of the reactive oxygen species, occurs as a general response to different environmental cues was tested. Leaf peels and mesophyll cell suspensions of Nicotiana tabacum cv. Xanthi were loaded with the NO-specific fluorophore, diaminofluorescein, and subjected to an abiotic stressor. Light stress and mechanical injury had no apparent effect on NO production. In contrast, high temperatures, hyperosmotic stress, salinity and epi-illumination in a microscope all led to rapid surges in NO-induced fluorescence. The fluoresce…

Identification et analyse du rôle de protéines S‐nitrosylées lors de la modulation de la réponse immunitaire d’Arabidopsis thaliana par l’apo-pyoverdine produite par la souche bactérienne bénéfique Pseudomonas fluorescens C7R12

Des travaux de l’UMR Agroécologie montrent que la réponse immunitaire des plantes est corrélée à leur nutrition en fer et est modulable par la pyoverdine, un sidérophore produit par la souche bactérienne bénéfique Pseudomonas fluorescens C7R12. Le traitement d’Arabidopsis thaliana exposée à une carence en fer par la pyoverdine dépourvue de fer (apo-pyo) restaure en effet la croissance de la plante aux dépens de son immunité. Nous avons émis l’hypothèse que le monoxyde d’azote (NO), une molécule signalétique ubiquitaire, est un acteur de la modulation de la réponse immunitaire des plantes exposées à l’apo-pyo et à sa souche productrice. Afin d’étayer cette hypothèse, trois axes seront dévelo…

Plant iNOS: conquest of the Holy Grail

In animals, nitric oxide (NO) is produced by a family of enzymes named nitric oxide synthases (NOSs). Although no NOS-like gene has been found in the Arabidopsis thaliana genome, biochemical studies have suggested that a NOS-like protein is likely to be activated in plants resisting pathogens. This protein has been recently identified as a variant P protein of glycine decarboxylase. This discovery means that studies of nitric oxide signalling functions in plants are now entering a new phase.

Nuclear involvement of the Cell Division Cycle 48 protein during the plant immune response

The control of protein homeostasis, a balance between their synthesis and degradation, also called proteostasis, is essential for cell survival. Any imbalance of the proteome, for instance triggered by a stress, leads to an accumulation of misfolded proteins leading to proteotoxic stress that can induce cell death. The ubiquitin proteasome system (UPS) is a major actor in the selective degradation of misfolded proteins to preserve proteome balance.The chaperone-like Cdc48 is a member of the AAA+ ATPase enzyme family which isconserved in mammals (VCP), yeasts and plants (Cdc48: Cell Division Cycle 48/p97).Cdc48/VCP is a cytosolic and nuclear protein which segregates misfolded proteins fromsu…

ABA-independent SnRK2 kinases are involved in plant response to salinity

Un poster a été présenté lors de cet événement SPE IPM CT non renseigné car non soutenu par INRA; International audience; Sucrose non-fermenting 1-Related Protein Kinases type 2 family (known as SnRK2) are important group of kina- ses present in all tested plant species. It is known that all SnRK2 (excluding SnRK2.9) are activated in response to salinity and hyperosmolarity in Arabidopsis thaliana protoplasts after short time of treatment. In plants, they are in- volved in the early responses to drought and salinity. Recently published data indicate that SnRK2.4 plays important role in the maintenance of root system architecture during salt stress and in response to cadmium treatment. It wa…

Interaction between Medicago truncatula and the pathogenic oomycete Aphanomyces euteiches: effects of nitrogen nutrition and plant genotype

Plants are under the constant threat of microbial pathogens. To defend themselves, plants have developed immune responses (including for example synthesis of antimicrobial secondary metabolites, production of PR proteins or reinforcement of cell wall) that can lead to resistance. However, these plant defense responses are costly and lead plants to continuously face a dilemma regarding the partitioning of their available resources. In order to better understand relationships between plant nutrition and defense, we analyzed the impact of nitrogen (N) nutrition on the capacity of different M. truncatula genotypes to resist against A. euteiches, the causal agent of legume root rot disease. N st…

Proteinaceous and oligosaccharidic elicitors induce different calcium signatures in the nucleus of tobacco cells.

We previously reported elevated cytosolic calcium levels in tobacco cells in response to elicitors [D. Lecourieux, C. Mazars, N. Pauly, R. Ranjeva, A. Pugin, Analysis and effects of cytosolic free calcium elevations in response to elicitors in Nicotiana plumbaginifolia cells, Plant Cell 14 (2002) 2627-2641]. These data suggested that in response to elicitors, Ca2+, as a second messenger, was involved in both systemic acquired resistance (RSA) and/or hypersensitive response (HR) depending on calcium signature. Here, we used transformed tobacco cells with apoaequorin expressed in the nucleus to monitor changes in free nuclear calcium concentrations ([Ca2+](nuc)) in response to elicitors. Two …

Type-2 histone deacetylases as new regulators of elicitor-induced cell death in plants

 voir Addenda, notes additionnelles complétant l'article : "Dahan, J., Hammoudi, V., Wendehenne, D., Bourque, S. (2011). Type 2 histone deacetylases play a major role in the control of elicitor-induced cell death in tobacco. Plant signaling & behavior, 6 (11), 1865-1867. DOI : 10.4161/psb.6.11.17848".; International audience; Plant resistance to pathogen attack is often associated with a localized programmed cell death called hypersensitive response (HR). How this cell death is controlled remains largely unknown. Upon treatment with cryptogein, an elicitor of tobacco defence and cell death, we identified NtHD2a and NtHD2b, two redundant isoforms of type-2 nuclear histone deacetylases (HDACs…

The Sulfated Laminarin Triggers a Stress Transcriptome before Priming the SA- and ROS-Dependent Defenses during Grapevine’s Induced Resistance against Plasmopara viticola

Grapevine (Vitis vinifera) is susceptible to many pathogens which cause significant losses to viticulture worldwide. Chemical control is available, but agro-ecological concerns have raised interest in alternative methods, especially in triggering plant immunity by elicitor treatments. The b-glucan laminarin (Lam) and its sulfated derivative (PS3) have been previously demonstrated to induce resistance in grapevine against downy mildew (Plasmopara viticola). However, if Lam elicits classical grapevine defenses such as oxidative burst, pathogenesis-related (PR)-proteins and phytoalexin production, PS3 triggered grapevine resistance via a poorly understood priming phenomenon. The aim of this st…

Nitric oxide in plants: occurence, function and useEdited by Y.Y. Leshem with the participation of J.-S. Huang, D.D-S. Tzeng and C-C Chou, Kluwer Academic Publishers, Dordrecht, The Netherlands, 2000, 154 pp., ISBN: 0792360885 (Price: EUR 99.50, NLG 220.00, USD 117, GBP 72.5)

Effet de la nutrition azotée et du génotype de la plante sur la résistance de Medicago truncatula à Aphanomyces euteiches

Evolutionary diversification of type-2 HDAC structure, function and regulation in Nicotiana tabacum

Ministère de l'Education Nationale et de la Recherche ; Conseil Régional de Bourgogne (PARI AGRALE8) ; Association pour la Recherche sur les Nicotianacées ; Conseil Régional de Bourgogne; International audience; Type-2 HDACs (HD2s) are plant-specific histone deacetylases that play diverse roles during development and in responses to biotic and abiotic stresses. In this study we characterized the six tobacco genes encoding HD2s that mainly differ by the presence or the absence of a typical zinc finger in their C-terminal part. Of particular interest, these HD2 genes exhibit a highly conserved intron/exon structure. We then further investigated the phylogenetic relationships among the HD2 gen…

The impact of the plant-associated siderophore ornicorrugatin on Arabidopsis thaliana

International audience; Most microorganisms produce siderophores when they are faced with iron-limiting conditions. Fluorescent pseudomonads produce a yellow-green, fluorescent siderophore, called pyoverdine. Besides pyoverdine, sev-eral other secondary siderophores, which have a relatively lower affinity for iron, have been identified in Pseu-domonas spp. Examples are pyochelin, pseudomonine and thioquinolobactin (Cornelis and Matthijs 2002). An atypical set of secondary siderophores, due to their lipopeptidic nature, are the siderophores corrugatin (Risse et al., 1998), ornicorrugatin (Matthijs et al., 2008) and histicorrugatin (Matthijs et al., 2016). These siderophores consist out of an…

Cryptogein-Induced Anion Effluxes

Anion effluxes are amongst the earliest reactions of plant cells to elicitors of defence responses. However, their properties and their role in disease resistance remain almost unknown. We previously demonstrated that cryptogein, an elicitor of tobacco defence responses, induces a nitrate (NO(3) (-)) efflux. This efflux is an early prerequisite to the cryptogein-triggered hypersensitive response (HR). Here, we analyzed the electrophysiological properties of the elicitor-mediated NO(3) (-) efflux and clarified the mechanisms through which it contributes to cell death. Application of the discontinuous single electrode voltage-clamp technique in tobacco cells elicited with cryptogein enabled u…

Nitric oxide contributes to cadmium toxicity in Arabidopsis by promoting cadmium accumulation in roots and by up-regulating genes related to iron uptake.

Abstract Nitric oxide (NO) functions as a cell-signaling molecule in plants. In particular, a role for NO in the regulation of iron homeostasis and in the plant response to toxic metals has been proposed. Here, we investigated the synthesis and the role of NO in plants exposed to cadmium (Cd2+), a nonessential and toxic metal. We demonstrate that Cd2+ induces NO synthesis in roots and leaves of Arabidopsis (Arabidopsis thaliana) seedlings. This production, which is sensitive to NO synthase inhibitors, does not involve nitrate reductase and AtNOA1 but requires IRT1, encoding a major plasma membrane transporter for iron but also Cd2+. By analyzing the incidence of NO scavenging or inhibition …

Le monoxyde d’azote

Le monoxyde d’azote (NO) est un mediateur physiologique associe a divers processus chez les animaux, dont l’immunite. Des travaux conduits recemment montrent que les plantes, confrontees a l’attaque d’agents pathogenes, produisent egalement du NO. Le NO est donc un acteur des voies de signalisation cellulaire activees en reponse a la reconnaissance par les plantes d’agresseurs exterieurs. L’etude des molecules cibles du NO et, plus particulierement, la caracterisation de proteines S-nitrosylees, a permis d’avoir un premier apercu des mecanismes fins inherents a ses fonctions. Le NO serait ainsi implique dans l’activation ainsi que dans la desensibilisation des voies de signalisation mobilis…

Type 2 histone deacetylases play a major role in the control of elicitor-induced cell death in tobacco

article addendum : Bourque S, Dutartre A, Hammoudi V, Blanc S, Dahan J, Jeandroz S, Pichereaux C, Rossignol M, Wendehenne D., 2011. Type-2 histone deacetylases as new regulators of elicitorinduced cell death in plants. New Phytologist, 192 (1), 127–139. DOI: 10.1111/j.1469-8137.2011.03788.x; International audience; The cell death which characterizes the onset of the Hypersensitive Response (HR) is a very important weapon evolved by plants to block pathogen development. By the use of numerous plant/avirulent pathogen or plant/elicitor models, we have now obtained detailed signalling pathways allowing, after pathogen or elicitor perception, the control of the expression of specific sets of ge…

Plant responses to biotic/abiotic stresses: lessons from cell signalin

prod 2017-284a SPE IPM UB AGROSUP CNRS CT; International audience; About this Research Topic : Facing up to stressful conditions imposed by their environment that could affect their growth and their development throughout their life cycle, plants must be able to perceive, to process and to translate different stimuli into adaptive responses. From a human point of view, knowledge about plant stress response is also vital for the development of breeding and biotechnological strategies to improve stress tolerance in crops. Understanding the organism-coordinated responses involves fine description of the mechanisms occurring at the cellular and molecular level. These mechanisms involve numerous…

Emerging functions of nitric oxide in plant immunity

SPEIPMUBAgrosupCNRS; The importance of nitric oxide (NO) in innate and adaptive immunity in mammals is well recognised. NO exerts antimicrobial properties against invaders but also displays immunoregulatory functions in which S-nitrosylation represents a signalling process of major importance. Over the last two decades, a growing body of evidence suggests that NO is also a major component of plant immunity. Our understanding of its role in plant defence has been enriched by the identification and functional analysis of S-nitrosylated proteins. The recent identification of new S-nitrosylated proteins including the chaperone-like enzyme cell division cycle 48 (CDC48), histone deacetylases (HD…

POLYSACCHARIDE COMPOUNDS AND USE OF SAME FOR STIMULATING DEFENCE RESPONSES OF PLANTS AGAINST PATHOGENIC MICROORGANISMS

The present invention relates to novel oligogalacturonans having a degree of methylation of 0 and a degree of polymerisation of 1 to 10, and to use there of for stimulating defence responses of plants against pathogenic microorganisms.

La pyoverdine, un sidérophore produit par la souche bénéfique du sol Pseudomonas fluorescens C7R12, impacte l’homéostasie du fer et promeut la croissance aux dépens des réactions de défense d’Arabidopsis thaliana cultivée en condition de carence en fer

Study of the chaperone protein CDC48 and its involvement in plant immunity

CDC48 is a conserved chaperone protein belonging to the AAA+ ATPase family (ATPase associated with various activities). This protein uses binding and hydrolysis of ATP to generate forces to affect the transformation of polypeptide substrate in numerous cellular processes. Studies on mammalian CDC48 orthologue revealed that it recognizes ubiquitylated polypeptides, directly or via partners, leading to substrate degradation or recycling. In plants, functions of CDC48 is less understood. The aim of my thesis, is to decipher the role of CDC48 in plant defense response context. First, I have to characterize NtCDC48 in tobacco (Nicotiana tabacum) suspension cells elicited by cryptogein, an elicit…

Identification and functional characterization of S-nitrosated proteins from Klebsormidium nitens

The small gaseous molecule nitric oxide (NO) is well established as a major ubiquitous component of cell signalling. A key signalling mechanism mediating NO effects is S-nitrosation, a post-translational modification by which NO can impact the target protein activities, subcellular localizations and capacities to form protein complexes. The identification of proteins targeted by NO is of major interest in order to elucidate NO functions. Interestingly, land plants lack NO synthase (NOS), which is the main enzyme for NO synthesis in metazoans, while a few algal species possess it, thus raising many interrogations. Therefore, we focused on the identification of S-nitrosated proteins during sa…

Identification and functional characterization of S-nitrosated proteins from Klebsormidium nitens, a model alga to study plant adaptation to land

The small gaseous molecule nitric oxide (NO) is well established as a major ubiquitous component of cell signalling. A key signalling mechanism mediating NO effects is S-nitrosation, a post-translational modification by which NO can impact the target protein activities, subcellular localizations, and capacities to form protein complexes. The identification of proteins targeted by NO is of major interest in order to elucidate NO functions. Interestingly, land plants lack NO synthase (NOS), which is the main enzyme for NO synthesis in metazoans, while a few algal species possess it, thus raising many interrogations. Therefore, we focused on the identification of S-nitrosated proteins during s…

Changes in carbohydrate metabolism in Plasmopara viticola-infected grapevine leaves.

International audience; The oomycete Plasmopara viticola is responsible for downy mildew, a severe grapevine disease. In infected grapevine leaves, we have observed an abnormal starch accumulation at the end of the dark period, suggesting modifications in starch metabolism. Therefore, several complementary approaches, including transcriptomic analyses, measurements of enzyme activities, and sugar quantification, were performed in order to investigate and to understand the effects of P. viticola infection on leaf starch and-to a larger extent-carbohydrate metabolism. Our results indicate that starch accumulation is associated with an increase in ADP-glucose pyrophosphorylase (AGPase) activit…

NO contributes to cadmium toxicity in Arabidopsis thaliana by mediating an iron deprivation response

Nitric oxide (NO) functions as a cell-signaling molecule in plants. In particular, a role for NO in the regulation of iron homeostasis and in the plant response to toxic metals has been proposed. Here, we investigated the synthesis and the role of NO in plants exposed to cadmium (Cd(2+)), a nonessential and toxic metal. We demonstrate that Cd(2+) induces NO synthesis in roots and leaves of Arabidopsis (Arabidopsis thaliana) seedlings. This production, which is sensitive to NO synthase inhibitors, does not involve nitrate reductase and AtNOA1 but requires IRT1, encoding a major plasma membrane transporter for iron but also Cd(2+). By analyzing the incidence of NO scavenging or inhibition of …

Effect of commercially available Plant Defence Stimulators on human innate immunity

PDS (Plant defence stimulators) constitute a recent alternative to pesticides used for crop protection. These compounds are of diverse nature, they all act by stimulating plant innate immune system and plants can better fight pathogens. There are many similarities in pathogen perception systems and cellular signalling in plants and animals. Many elicitors stimulate both human and plant innate immunity (Zipfel and Felix, 2005). Therefore, it is likely that human innate immunity could be modulated by PDS. The aim of this study is to evaluate pro/anti-inflammatory activity of five different commercially available PDS on human cell models. We studied the pro/anti-inflammatory effect of PDS on h…

Study of oligogalacturonides-triggered Nitric Oxide (NO) production provokes new questioning about the origin of NO biosynthesis in plants

Addendum to: Rasul S, Dubreuil-Maurizi C, Lamotte O, Koen E, Poinssot B, Alcaraz G, et al. Nitric oxide production mediates oligogalacturonide-triggered immunity and resistance to Botrytis cinerea in Arabidopsis thaliana. Plant Cell Environ 2012; PMID:22394204; http://dx.doi. org/10.1111/j.1365-3040.2012.02505.x.; International audience; We investigated the production and function of nitric oxide (NO) in Arabidopsis thaliana leaf discs as well as whole plants elicited by oligogalacturonides (OGs). Using genetic, biochemical and pharmacological approaches, we provided evidence that OGs induced a Nitrate Reductase (NR)-dependent NO production together with an increased NR activity and NR tran…

Interplays between nitric oxide and reactive oxygen species in cryptogein signalling

The cellular messenger nitric oxide (NO) has many functions in plants. In this study, we investigated its interplays with Reactive Oxygen Species (ROS) in the defense responses triggered by the elicitin cryptogein produced by the oomycete Phytophthora cryptogea. The production of NO induced by cryptogein in tobacco cell suspensions was partly regulated through a ROS-dependent pathway involving the NADPH oxidase NtRBOHD. In turn, NO down-regulated the level of H2O2 derived from NtRBOHD activity. Both NO and ROS synthesis appeared to be under the control of two redundant isoforms of histone deacetylases of type 2 acting as negative regulators of cell death. Occurrence of an interplay between …

Impact de la S-nitrosylation sur la structure des calmoduline chez les plantes

Nuclear protein acetylation in the control of plant defense responses: role of type-2 histone deacetylases

Silencing of plant defensin type 1 reduces sensitivity to pathogens and zinc toxicity in arabidopsis thaliana

Ectopic expression of defensins in plants correlates with their increased capacity to withstand abiotic and biotic stresses(Carvalho & Gomes, 2011). However, few studies have explored the effects of decreased plant endogenous defensin transcripts on these stress responses.When over-expressed in Arabidopsis thaliana, some of the seven members of thePlant Defensin type 1 family (PDF1) are recognised to improve plant responses tonecrotrophic pathogens(De Conincket al.,2010)and increase seedling tolerance to excess zinc (Zn;Mirouzeet al., 2006). We carried out an extensive physiological and biochemical comparative characterisation of i) novel transgenic amiRNA lines silenced for the five most s…

Nitric Oxide, a key player in plant immunity

Priming: getting ready for battle

International audience; Infection of plants by necrotizing pathogens or colonization of plant roots with certain beneficial microbes causes the induction of a unique physiological state called “priming.” The primed state can also be induced by treatment of plants with various natural and synthetic compounds. Primed plants display either faster, stronger, or both activation of the various cellular defense responses that are induced following attack by either pathogens or insects or in response to abiotic stress. Although the phenomenon has been known for decades, most progress in our understanding of priming has been made over the past few years. Here, we summarize the current knowledge of p…

Nitric oxide and signalling in plants, Préface.

SPE IPM UB

Real-time electrochemical detection of extracellular nitric oxide in tobacco cells exposed to cryptogein, an elicitor of defence responses

International audience; It was previously reported that cryptogein, an elicitor of defence responses, induces an intracellular production of nitric oxide (NO) in tobacco. Here, the possibility was explored that cryptogein might also trigger an increase of NO extracellular content through two distinct approaches, an indirect method using the NO probe 4,5-diaminofluorescein (DAF-2) and an electrochemical method involving a chemically modified microelectrode probing free NO in biological media. While the chemical nature of DAF-2-reactive compound(s) is still uncertain, the electrochemical modified microelectrodes provide real-time evidence that cryptogein induces an increase of extracellular N…

Effects of plant nutrition and genotype on Medicago truncatula defense responses against Aphanomyces euteiches

SPEIPM; International audience

S-Nitrosation of Arabidopsis thaliana Protein Tyrosine Phosphatase 1 Prevents Its Irreversible Oxidation by Hydrogen Peroxide

Tyrosine-specific protein tyrosine phosphatases (Tyr-specific PTPases) are key signaling enzymes catalyzing the removal of the phosphate group from phosphorylated tyrosine residues on target proteins. This post-translational modification notably allows the regulation of mitogen-activated protein kinase (MAPK) cascades during defense reactions. Arabidopsis thaliana protein tyrosine phosphatase 1 (AtPTP1), the only Tyr-specific PTPase present in this plant, acts as a repressor of H2O2 production and regulates the activity of MPK3/MPK6 MAPKs by direct dephosphorylation. Here, we report that recombinant histidine (His)-AtPTP1 protein activity is directly inhibited by H2O2 and nitric oxide (NO) …

An early Ca2+ influx is a prerequisite to thaxtomin A-induced cell death in Arabidopsis thaliana cells

International audience; The pathogenicity of various Streptomyces scabies isolates involved in potato scab disease was correlated with the production of thaxtomin A. Since calcium is known as an essential second messenger associated with pathogen-induced plant responses and cell death, it was investigated whether thaxtomin A could induce a Ca 2+ influx related to cell death and to other putative plant responses using Arabidopsis thaliana suspension cells, which is a convenient model to study plant–microbe interactions. A. thaliana cells were treated with micromolar concentrations of thaxto-min A. Cell death was quantified and ion flux variations were analysed from electrophysiological measu…

Analysis of the cross‐regulation between immunity, growth and iron homeostasis in plants

The existence of a tightly regulated balance between growth and immunity in plants has recently emerged. In this study, we challenged this concept thanks to the biological model pyoverdine-Arabidopsis thaliana. Pyoverdine is a siderophore produced by the plant growth promoting rhizobacteria Pseudomonas fluorescens C7R12. Under iron deficiency, P. fluorescens excretes the iron free form of pyoverdine (apo‐pyo) in the soil. Once chelated with iron (ferri‐pyo), the complex is internalized by the bacteria. We demonstrated that Arabidopsis thaliana plants treated by apo‐pyo in a medium containing or not iron internalize pyoverdine. Interestingly, apo‐pyo-treated plants did not show a typical gro…

Role of nitric oxide synthase (NOS) of Klebsormidium nitens: Identification and characterization of partners

National audience; Nitric oxide (NO) is an important cellular signaling molecule across kingdoms. During bioticor abiotic stresses, NO burst is detected in both plants and mammals although no sequenceencoding the well described mammalian NO synthase (NOS) is highlighted in plants. Comparedto terrestrial plants, some algae present transcripts encoding the NOS-like enzyme. Amongthem, Klebsormidium nitens the model alga to study the early transition step from aquatic algaeto land plants is found. As mechanisms governing NO synthesis and signaling in green lineageremain unclear, the study of NOS from K. nitens (KnNOS) through (i) the identification ofregulator proteins, (ii) the identification …

Nuclear protein kinases: still enigmatic components in plant cell signalling

International audience; Plants constantly face changing conditions in their environment. Unravelling the transduction mechanisms from signal perception at the plasma membrane level down to gene expression in the nucleus is a fascinating challenge. Protein phosphorylation, catalysed by protein kinases, is one of the major posttranslational modifications involved in the specificity, kinetic(s) and intensity of a signal transduction pathway. Although commonly assumed, the involvement of nuclear protein kinases in signal transduction is often poorly characterized. In particular, both their regulation and mode of action remain to be elucidated and may lead to the unveiling of new original mechan…

Role of nitric oxide synthases from Klebsormidium nitens: structural characterization and identification of protein partners

Nitric oxide (NO) is an important cellular signalling molecule regulating various physiological processes, in both animals andplants. In animals, NO synthesis is mainly catalysed by NO synthase (NOS) enzymes. During biotic or abiotic stresses, NOSlike activities that are sensitive to mammalian NOS inhibitors have been detected in plants, although no sequences encodingthe well described mammalian NOS are highlighted in land plants. Interestingly, we identified NOS-like sequences in 20 algaespecies. Among them, NOSs are found in Klebsormidium nitens the model alga to study the early transition step from aquaticalgae to land plants.As mechanisms governing NO synthesis and signalling in green l…

The plant resistance inducer β-aminobutyric acid (BABA) induces an iron deficiency response in A. thaliana

β-aminobutyric acid (BABA) is a well-known plant resistance inducer. However, the molecular mechanisms underlying its effects are poorly understood. In the present study, we investigated whether BABA could act through the modification of iron homeostasis in Arabidopsis thaliana. Supporting this assumption, we obtained first evidences that BABA chelates iron with high affinity. We showed that pre-treatment of plants with BABA induced a drastic but transient iron deficiency response. Quantification of iron indicated that this response is related to the perturbation of iron distribution/availability rather than a reduction of iron assimilation. Finally, we provided evidence that the iron defic…

NO Signalling in Plant Immunity

The importance of nitric oxide (NO) in innate and adaptive immunity in mammals is well recognised. NO exerts antimicrobial properties against invaders but also displays immunoregulatory functions in which S-nitrosylation represents a signalling process of major importance. Over the last two decades, a growing body of evidence suggests that NO is also a major component of plant immunity. Our understanding of its role in plant defence has been enriched by the identification and functional analysis of S-nitrosylated proteins. The recent identification of new S-nitrosylated proteins including the chaperone-like enzyme cell division cycle 48 (CDC48), histone deacetylases (HDACs) and calmodulin (…

NO signaling in tobacco elicited by the MAMP cryptogein

SPEPôle IPM; International audience; During the past years, nitric oxide (NO) has been shown to be a major cell signaling messenger in plants. Its importance has been highlighted during plant responses to pathogen attack or MAMPs (microbe associated molecular patterns) and during induced resistance or priming phenomenon. The major focus of our research is to understand how nitric oxide can modulate the activity of protein involved in plant defense. We identified several proteins undergoing S-nitrosylation, a redox-based post-translational modification of proteins, in tobacco cells elicited by cryptogein, a 10 kDa protein produced by the oomycete Phytophthora cryptogea and inducing immune re…

The evolution of nitric oxide signalling diverges between the animal and the green lineages

AbstractNitric oxide (NO) is a ubiquitous signalling molecule with widespread distribution in prokaryotes and eukaryotes where it is involved in countless physiological processes. While the mechanisms governing nitric oxide (NO) synthesis and signalling are well established in animals, the situation is less clear in the green lineage. Recent investigations have shown that NO synthase, the major enzymatic source for NO in animals, is absent in land plants but present in a limited number of algae. The first detailed analysis highlighted that these new NO synthases are functional but display specific structural features and probably original catalytic activities. Completing this picture, analy…

Nitric oxide signalling in plants: interplays with Ca2+ and protein kinase

International audience; Much attention has been paid to nitric oxide (NO)research since its discovery as a physiological mediator of plant defence responses. In recent years, newer roles have been attributed to NO, ranging from root development to stomatal closure. The molecular mechanisms underlying NO action in plants are just begun to emerge. The currently available data illustrate that NO can directly influence the activity of target proteins through nitrosylation and has the capacity to act as a Ca2+-mobilizing intracellular messenger. The interplay between NO and Ca2+ has important functional implications, expanding and enriching the possibilities for modulating transduction processes…

Functional characterization of the chaperon-like protein Cdc48 in cryptogein-induced immune response in tobacco

SPEIPMUBINRASUPDATDOCT; Cdc48, a molecular chaperone conserved in different kingdoms, is a member of the AAA+ family contributing to numerous processes in mammals including proteins quality control and degradation, vesicular trafficking, autophagy and immunity. The functions of Cdc48 plant orthologues are less understood. We previously reported that Cdc48 is regulated by S-nitrosylation in tobacco cells undergoing an immune response triggered by cryptogein, an elicitin produced by the oomycete Phytophthora cryptogea. Here, we inv estigated the function of NtCdc48 in cryptogein signalling and induced hypersensitive-like cell death. NtCdc48 was found to accumulate in elicited cells at both th…

Advances in Botanical Research

SPE Pôle IPM

Involvement of the glutamate receptor AtGLR3.3 in plant defense signaling and resistance toHyaloperonospora arabidopsidis

Like their animal counterparts, plant glutamate receptor-like (GLR) homologs are intimately associated with Ca(2+) influx through plasma membrane and participate in various physiological processes. In pathogen-associated molecular patterns (PAMP)-/elicitor-mediated resistance, Ca(2+) fluxes are necessary for activating downstream signaling events related to plant defense. In this study, oligogalacturonides (OGs), which are endogenous elicitors derived from cell wall degradation, were used to investigate the role of Arabidopsis GLRs in defense signaling. Pharmacological investigations indicated that GLRs are partly involved in free cytosolic [Ca(2+)] ([Ca(2+)]cyt) variations, nitric oxide (N…

The Sulfated Laminarin Triggers a Stress Transcriptome before Priming the SA- and ROS-Dependent Defenses during Grapevine's Induced Resistance against Plasmopara viticola

Grapevine (Vitis vinifera) is susceptible to many pathogens which cause significant losses to viticulture worldwide. Chemical control is available, but agro-ecological concerns have raised interest in alternative methods, especially in triggering plant immunity by elicitor treatments. The β-glucan laminarin (Lam) and its sulfated derivative (PS3) have been previously demonstrated to induce resistance in grapevine against downy mildew (Plasmopara viticola). However, if Lam elicits classical grapevine defenses such as oxidative burst, pathogenesis-related (PR)-proteins and phytoalexin production, PS3 triggered grapevine resistance via a poorly understood priming phenomenon. The aim of this st…

Free radical-mediated systemic immunity in plants.

SPE IPM; Systemic acquired resistance (SAR) is a form of defense that protects plants against a broad-spectrum of secondary infections by related or unrelated pathogens. SAR related research has witnessed considerable progress in recent years and a number of chemical signals and proteins contributing to SAR have been identified. All of these diverse constituents share their requirement for the phytohormone salicylic acid, an essential downstream component of the SAR pathway. However, recent work demonstrating the essential parallel functioning of nitric oxide (NO)-derived and reactive oxygen species (ROS)-derived signaling together with SA provides important new insights in the overlapping …

Plant Science

David Wendehenne est Editeur en Chef de la revue Plant ScienceSPEIPMUB; Plant Science

Are grapevine stomata involved in the elicitor-induced protection against downy mildew?

Stomata, natural pores bordered by guard cells, regulate transpiration and gas exchanges between plant leaves and the atmosphere. These natural openings also constitute a way of penetration for microorganisms. In plants, the perception of potentially pathogenic microorganisms or elicitors of defense reactions induces a cascade of events, including H2O2 production, that allows the activation of defense genes, leading to defense reactions. Similar signaling events occur in guard cells in response to the perception of abscisic acid (ABA), leading to stomatal closure. Moreover, few elicitors were reported to induce stomatal closure in Arabidopsis and Vicia faba leaves. Because responses to ABA…

Role of nitric oxide synthases from klebsormidium nitens: first structural characterization and partners identification

Objectives: Nitric oxide (NO) is an important cellular signaling molecule regulating various physiologicalprocesses, in both animals and plants. In animals, NO synthesis is mainly catalyzed by NO synthase(NOS) enzymes. In plants, NOS-like activities sensitive to mammalian NOS inhibitors have beenmeasured, although no sequences encoding mammalian NOSs have been found in land plants.Interestingly, we identified NOS-like sequences in 20 algae species. These latter include thefilamentous charophyte green algae Klebsormidium nitens, a biological model to study the earlytransition step from aquatic algae to land plants. In order to understand the mechanisms governingNO synthesis and signaling in …

Arabidopsis thaliana nicotianamine synthase 4 is required for proper response to iron deficiency and to cadmium exposure.

International audience; The nicotianamine synthase (NAS) enzymes catalyze the formation of nicotianamine (NA), a non-proteinogenic amino acid involved in iron homeostasis. We undertook the functional characterization of AtNAS4, the fourth member of the Arabidopsis thaliana NAS gene family. A mutant carrying a T-DNA insertion in AtNAS4 (atnas4), as well as lines overexpressing AtNAS4 both in the atnas4 and the wild-type genetic backgrounds, were used to decipher the role of AtNAS4 in NA synthesis, iron homeostasis and the plant response to iron deficiency or cadmium supply. We showed that AtNAS4 is an important source for NA. Whereas atnas4 had normal growth in iron-sufficient medium, it dis…

Effects of nitrogen nutrition and plant genotype on Medicago truncatula resistance against Aphanomyces euteiches

Nitric oxide production mediates oligogalacturonide-triggered immunity and resistance to Botrytis cinerea in Arabidopsis thaliana

Nitric oxide (NO) regulates a wide range of plant processes from development to environmental adaptation. In this study, we investigated the production and/or function of NO in Arabidopsis thaliana leaf discs and plants elicited by oligogalacturonides (OGs) and challenged with Botrytis cinerea. We provided evidence that OGs triggered a fast and long lasting NO production which was Ca(2+) dependent and involved nitrate reductase (NR). Accordingly, OGs triggered an increase of both NR activity and transcript accumulation. NO production was also sensitive to the mammalian NO synthase inhibitor L-NAME. Intriguingly, we showed that L-NAME affected NO production by interfering with NR activity, t…

Nitric Oxide Signalling in Plants: Cross-Talk With Ca2+, Protein Kinases and Reactive Oxygen Species

International audience; Nitric oxide (NO) is a gaseous free radical recognized as a ubiquitous signal transducer that contributes to various biological processes in animals. It exerts most of its effects by regulating the activities of various proteins including Ca2+ channels, protein kinases and transcription factors. In plants, studies conducted over the past ten years revealed that NO also functions as an endogenous mediator in diverse physiological processes ranging from root development to stomatal closure. Its biological role as an intracellular plant messenger molecule, however, remains poorly understood. Here, we review the molecular basis of NO signaling in animals and discuss curr…

Identification of Partner Proteins of the Algae Klebsormidium nitens NO Synthases: Toward a Better Understanding of NO Signaling in Eukaryotic Photosynthetic Organisms

In animals, NO is synthesized from L-arginine by three isoforms of nitric oxide synthase (NOS) enzyme. NO production and effects have also been reported in plants but the identification of its sources, especially the enzymatic ones, remains one of the critical issues in the field. NOS-like activities have been reported, although there are no homologs of mammalian NOS in the land plant genomes sequenced so far. However, several NOS homologs have been found in algal genomes and transcriptomes. A first study has characterized a functional NOS in the chlorophyte Ostreococcus tauri and the presence of NOS homologs was later confirmed in a dozen algae. These results raise the questions of the sig…

Identification and functional characterization of S-nitrosated proteins from Klebsormidium nitens in response to salt stress

The small gaseous molecule nitric oxide (NO) is well established as a major ubiquitouscomponent of cell signalling. A key signalling mechanism mediating NO effects is Snitrosation, a post-translational modification by which NO can impact the target proteinactivities, subcellular localizations, and capacities to form protein complexes. The identificationof proteins targeted by NO is of major interest in order to elucidate NO functions. Interestingly,land plants lack NO synthase (NOS), which is the main enzyme for NO synthesis in metazoans,while a few algal species possess it, thus raising many interrogations. Therefore, we focused onthe identification of S-nitrosated proteins during salt str…

The role of NtRBOHD in regulation of response to cryptogein in tobacco cells

International audience

Nitric oxide synthase in plants: Where do we stand?

International audience

Arginase induction represses gall development during clubroot infection in Arabidopsis.

Arginase induction can play a defensive role through the reduction of arginine availability for phytophageous insects. Arginase activity is also induced during gall growth caused by Plasmodiophora brassicae infection in roots of Arabidopsis thaliana; however, its possible role in this context has been unclear. We report here that the mutation of the arginase-encoding gene ARGAH2 abrogates clubroot-induced arginase activity and results in enhanced gall size in infected roots, suggesting that arginase plays a defensive role. Induction of arginase activity in infected roots was impaired in the jar1 mutant, highlighting a link between the arginase response to clubroot and jasmonate signaling. C…

Effect of commercially available Plant Defence Stimulators (PDS) on human innate immunity

PDS (Plant defence stimulators) constitute a recent alternative to pesticides used for crop protection. These compounds called elicitors are of diverse nature, but they all act by stimulating innate immune system of plants. So, plants can better fight pathogens. Furthermore, there are many similarities in pathogen perception systems and cellular signalling in plants and animals. It is well established that many elicitors stimulate both human and plant innate immunity (Zipfel and Felix, 2005). Therefore, it is likely that human innate immunity could be modulated by PDS. The aim of this study is to evaluate pro/anti-inflammatory activity of five different commercially available PDS on human c…

Integrated signaling network involving calcium, nitric oxide, active oxygen species but not mitogen-activated protein kinases in BcPG1-elicited grapevine defenses.

We have already reported the identification of the endopolygalacturonase 1 (BcPG1) from Botrytis cinerea as a potent elicitor of defense responses in grapevine, independently of its enzymatic activity. The aim of the present study is the analysis of the signaling pathways triggered by BcPG1 in grapevine cells. Our data indicate that BcPG1 induces a Ca2+ entry from the apoplasm, which triggers a phosphorylation-dependent nitric oxide (NO) production via an enzyme probably related to a NO synthase. Then NO is involved in i) cytosolic calcium homeostasis, by activating Ca2+ release from internal stores and regulating Ca2+ fluxes across the plasma membrane, ii) plasma membrane potential variat…

Protein S-nitrosylation: What's going on in plants?

International audience; Nitric oxide (NO) is now recognized as a key regulator of plant physiological processes. Understanding the mechanisms by which NO exerts its biological functions has been the subject of extensive research. Several components of the signaling pathways relaying NO effects in plants, including second messengers, protein kinases, phytohormones, and target genes, have been characterized. In addition, there is now compelling experimental evidence that NO partly operates through posttranslational modification of proteins, notably via S-nitrosylation and tyrosine nitration. Recently, proteome-wide scale analyses led to the identification of numerous protein candidates for S-…

Nitric oxide production and signalling in algae

International audience

Nitric oxide signaling in plants: cross-talk with Ca2+, protein kinases and reactive oxygen species

The chaperone-like protein Cdc48 regulates ubiquitin-proteasome system in plants

There's More to the Picture Than Meets the Eye: Nitric Oxide Cross Talk with Ca2+ Signaling

Abstract Calcium and nitric oxide (NO) are two important biological messengers. Increasing evidence indicates that Ca2+ and NO work together in mediating responses to pathogenic microorganisms and microbe-associated molecular patterns. Ca2+ fluxes were recognized to account for NO production, whereas evidence gathered from a number of studies highlights that NO is one of the key messengers mediating Ca2+ signaling. Here, we present a concise description of the current understanding of the molecular mechanisms underlying the cross talk between Ca2+ and NO in plant cells exposed to biotic stress. Particular attention will be given to the involvement of cyclic nucleotide-gated ion channels and…

Evidence for specific, high-affinity binding sites for a proteinaceous elicitor in tobacco plasma membrane

Abstract Binding of cryptogein, a proteinaceous elicitor, was studied on tobacco plasma membrane. The binding of the [125I]cryptogein was saturable, reversible and specific with an apparent Kd of 2 nM. A single class of cryptogein binding sites was found with a sharp optimum pH for binding at about pH 7.0. The high-affinity correlates with cryptogein concentrations required for biological activity in vivo.

Importance de la diversité des Pseudomonas rhizosphériques et de celle de leurs sidérophores dans la nutrition en fer de la plante hôte

Early signaling events induced by elicitors of plant defenses

International audience; Plant pathogen attacks are perceived through pathogenissued compounds or plant-derived molecules that elicit defense reactions. Despite the large variety of elicitors, general schemes for cellular elicitor signaling leading to plant resistance can be drawn. In this article, we review early signaling events that happen after elicitor perception, including reversible protein phosphorylations, changes in the activities of plasma membrane proteins, variations in free calcium concentrations in cytosol and nucleus, and production of nitric oxide and active oxygen species. These events occur within the first minutes to a few hours after elicitor perception. One specific eli…

Involvement of putative glutamate receptors in plant defence signaling and NO production

International audience; Ionotropic glutamate receptors (iGluRs) are non-selective cation channels permeable to calcium, present in animals and plants. In mammals, glutamate is a well-known neurotransmitter and recently has been recognized as an immunomodulator. As animals and plants share common mechanisms that govern innate immunity with calcium playing a key role in plant defence activation, we have checked the involvement of putative iGluRs in plant defence signaling. Using tobacco cells, we first provide evidence supporting the activity of iGluRs as calcium channels and their involvement in NO production as reported in animals. Thereafter, iGluRs were shown to be activated in response t…

Stimulation of Defense Reactions in Medicago truncatula by Antagonistic Lipopeptides from Paenibacillus sp. Strain B2

ABSTRACT With the aim of obtaining new strategies to control plant diseases, we investigated the ability of antagonistic lipopolypeptides (paenimyxin) from Paenibacillus sp. strain B2 to elicit hydrogen peroxide (H 2 O 2 ) production and several defense-related genes in the model legume Medicago truncatula . For this purpose, M. truncatula cell suspensions were used and a pathosystem between M. truncatula and Fusarium acuminatum was established. In M. truncatula cell cultures, the induction of H 2 O 2 reached a maximum 20 min after elicitation with paenimyxin, whereas concentrations higher than 20 μM inhibited H 2 O 2 induction and this was correlated with a lethal effect. In plant roots in…

Etude du rôle du monoxyde d’azote (NO) dans la réponse du transcriptome d’Arabidopsis thaliana aux oligogalacturonides, un éliciteur des réactions de défense

SPEIPM; International audience; Le monoxyde d’azote (NO) est capable de réguler chez les plantes de nombreux processus physiologiques dont les réponses des plantes aux pathogènes. Peu d’informations sont disponibles aujourd’hui sur les mécanismes expliquant le rôle du NO endogène dans ce contexte physiologique. Grâce à une étude transcriptomique, nous avons caractérisé chez Arabidopsis thaliana, des gènes cibles du NO produit en réponse à un éliciteur des réactions de défense, les oligogalacturonides (OG). L’analyse a permis d’identifier parmi ces gènes cibles, un nombre important de gènes impliqués dans les réponses aux stress biotiques tels que des facteurs de transcription ou des protéin…

Nitric oxide and glutathione impact the expression of iron uptake- and iron transport-related genes as well as the content of metals in A. thaliana plants grown under iron deficiency

International audience; Mounting evidence indicate that nitric oxide (NO) acts as a signaling molecule mediating iron deficiency responses through the upregulation of the expression of iron uptake-related genes. Accordingly, NO donors such as nitrosoglutathione (GSNO) were reported to improve the fitness of plants grown under iron deficiency. Here, we showed that glutathione, a by-product of GSNO, triggered the upregulation of the expression of iron uptake- and transport-related gene and an increase of iron concentration in Arabidopsis thaliana seedlings facing iron deficiency. Furthermore, we provided evidence that under iron deficiency, NO released by GSNO did not improve the root iron co…

Effets de la nutrition et du génotype de la plante sur la résistance de Medicago truncatula à Aphanomyces euteiches

SPEIPMUBAGROSUPINRA; Dans la nature, les plantes ont la capacité de mettre en oeuvre des réponses immunitaires pour faire face aux microorganismes pathogènes. Cependant, ces réponses de défense sont coûteuses en énergie et conduisent la plante à détourner une partie de ces ressources destinées à d’autres traits de vie comme la croissance. Ce compromis défense/croissance est largement conditionné par la disponibilité extérieure en nutriments. Afin de mieux décrire et comprendre les liens entre la nutrition et la défense, nous avons analysé l’impact de la nutrition azotée et l’effet de la variabilité génétique végétale sur la capacité de la légumineuse Medicago truncatula à résister à un agen…

NO signaling in plant immunity: A tale of messengers

International audience; Nitric oxide (NO) is a free radical gas involved in a myriad of plant physiological processes including immune responses. How NO mediates its biological effects in plant facing microbial pathogen attack is an unresolved question. Insights into the molecular mechanisms by which it propagates signals reveal the contribution of this simple gas in complex signaling pathways shared with reactive oxygen species (ROS) and the second messenger Ca2+. Understanding of the subtle cross-talks operating between these signals was greatly improved by the recent identification and the functional analysis of proteins regulated through S-nitrosylation, a major NO-dependent post-transl…

In vivo imaging of an elicitor-induced nitric oxide burst in tobacco

A growing body of evidence suggests that nitric oxide (NO), an important signalling and defence molecule in mammals, plays a key role in activating disease resistance in plants, acting as signalling molecule and possibly as direct anti-microbial agent. Recently, a novel fluorophore (diaminofluorescein diacetate, DAF-2 DA) has been developed which allows bio-imaging of NO in vivo. Here we use the cell-permeable DAF-2 DA, in conjunction with confocal laser scanning microscopy, for real-time imaging of NO in living plant cells. Epidermal tobacco cells treated with cryptogein, a fungal elicitor from Phytophthora cryptogea, respond to the elicitor with a strong increase of intracellular NO. NO-i…

The chaperone-like protein Cdc48 regulates ubiquitin-proteasome system in plants.

The degradation of misfolded proteins is mainly mediated by the ubiquitin-proteasome system (UPS). UPS can be assisted by the protein Cdc48 but the relationship between UPS and Cdc48 in plants has been poorly investigated. Here, we analyzed the regulation of UPS by Cdc48 in tobacco thanks to two independent cell lines overexpressing Cdc48 constitutively and plant leaves overexpressing Cdc48 transiently. In the cell lines, the accumulation of ubiquitinated proteins was affected both quantitatively and qualitatively and the amount of proteasomal subunits was modified, while proteolytic activities were unchanged. Similarly, the over-expression of Cdc48 in planta impacted the accumulation of ub…

Activation of a nuclear-localized SIPK in tobacco cells challenged by cryptogein, an elicitor of plant defence reactions.

When a plant cell is challenged by a well-defined stimulus, complex signal transduction pathways are activated to promote the modulation of specific sets of genes and eventually to develop adaptive responses. In this context, protein phosphorylation plays a fundamental role through the activation of multiple protein kinase families. Although the involvement of protein kinases at the plasma membrane and cytosolic levels are now well-documented, their nuclear counterparts are still poorly investigated. In the field of plant defence reactions, no known study has yet reported the activation of a nuclear protein kinase and/or its nuclear activity in plant cells, although some protein kinases, e.…

New frontiers in nitric oxide biology in plant.

Preface; International audience

Involvement of plasma membrane proteins in plant defense responses. Analysis of the cryptogein signal transduction in tobacco

International audience; Cryptogein, a 98 amino acid protein secreted by the fungus Phytophthora cryptogea, induces a hypersensitive response and systemic acquired resistance in tobacco plants (Nicotiana tabacum var Xanthi). The mode of action of cryptogein has been studied using tobacco cell suspensions. The recognition of this elicitor by a plasma membrane receptor leads to a cascade of events including protein phosphorylation, calcium influx, potassium and chloride effluxes, plasma membrane depolarization, activation of a NADPH oxidase responsible for active oxygen species (AOS) production and cytosol acidification, activation of the pentose phosphate pathway, and activation of two mitoge…

β-Aminobutyric Acid (BABA)-Induced Resistance in Arabidopsis thaliana: Link with Iron Homeostasis

International audience; Bêta-Aminobutyric acid (BABA) is a nonprotein amino acid inducing resistance in many different plant species against a wide range of abiotic and biotic stresses. Nevertheless, how BABA primes plant natural defense reactions remains poorly understood. Based on its structure, we hypothesized and confirmed that BABA is able to chelate iron (Fe) in vitro. In vivo, we showed that it led to a transient Fe deficiency response in Arabidopsis thaliana plants exemplified by a reduction of ferritin accumulation and disturbances in the expression of genes related to Fe homeostasis. This response was not correlated to changes in Fe concentrations, suggesting that BABA affects the…

Nitric Oxide in Plants: Production and Cross-talk with Ca2+ Signaling

International audience; Nitric oxide (NO) is a diatomic gas that performs crucial functions in a wide array of physiological processes in animals. The past several years have revealed much about its roles in plants. It is well established that NO is synthesized from nitrite by nitrate reductase (NR) and via chemical pathways. There is increasing evidence for the occurrence of an alternative pathway in which NO production is catalysed from L-arginine by a so far non-identified enzyme. Contradictory results have been reported regarding the respective involvement of these enzymes in specific physiological conditions. Although much remains to be proved, we assume that these inconsistencies can …

Production et signalisation dépendante du monoxyde d'azote dans la lignée verte la surprise des microalgues

National audience

Monoxyde d'azote et immunité chez les plantes

Nitric oxide: Chemistry and bioactivity in animal and plant cells

Abstract In mammals, nitric oxide (NO) is a reactive free radical involved in diverse physiological functions. NO and its redox-related forms NO + and NO − react with di(oxygen) and its derivatives, with metalloproteins and thiol-containing proteins. NO-mediated nitrosation of proteins represents an important cellular regulatory mechanism. Biosynthesis of NOis catalysed by nitric oxide synthase (NOS). Three isoenzymes representing distinct gene products have been identified: the inducible NOS isoform, the constitutive neuronal and endothelial isoforms. Inducible and constitutive NOSs have the same structural features, but their activities differ in their dependence to calcium and the rate o…