BABA-induced resistance in Arabidopsis thaliana: Links with iron homeostasis

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Science Dijon : une ambassadrice du savoir

Département SPE Pôle IPMNational audienceChercheuse à l’Université de Bourgogne, Angélique Besson-Bard sera l’une des ambassadrices du programme “Pour les filles et la science”, destiné à promouvoir la science auprès des lycéennes

Effets de l’apo-pyoverdine de <em>Pseudomonas fluorescens</em> C7R12 sur l’homéostasie du fer et les réactions de défense d’<em>Arabidopsis thaliana</em>

National audienceLe GDR est un réseau de ressources et de compétences en microbiologie clinique et environnementale sur le thème principal des bactéries Pseudomonas aeruginosa (pathogène de l’homme) et fluorescents du sol (P. putida et P. fluorescens)</em

New insights into nitric oxide signaling in plants

International audienceA decade-long investigation of nitric oxide (NO) functions in plants has led to its characterization as a biological mediator involved in key physiological processes. Despite the wealth of information gathered from the analysis of its functions, until recently little was known about the mechanisms by whichNOexerts its effects. In the past few years, part of the gap has been bridged. NO modulates the activity of proteins through nitrosylation and probably tyrosine nitration. Furthermore, NO can act as a Ca2+-mobilizing messenger, and researchers are beginning to unravel the mechanisms underlying the cross talk between NO and Ca2+. Nonetheless, progress in this area of research is hindered by our ignorance of the pathways forNOproduction in plants. This review summarizes the basic concepts of NO signaling in animals and discusses new insights into NO enzymatic sources and molecular signaling in plants

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

National audienceDes 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 développés : - Identification de protéines S‐nitrosylées en réponse à l’apo-pyo et à P. fluorescens C7R12. La S-nitrosylation est un mécanisme majeur de modification posttraductionnelle de protéines impliquant le NO et ciblant les résidus cystéines (Cys). - Analyse du rôle du NO sur la fonction/structure des protéines cibles. Il s’agira d’analyser in vitro l’incidence du NO sur l’activité et la structure des protéines d’intérêt puis d’identifier les résidus Cys régulés par le NO. - Etude de l’incidence de la S-nitrosylation des protéines d’intérêt in planta. Des plantes d’A. thaliana invalidées dans l’expression des protéines d’intérêt ou exprimant celles-ci sous une forme non nitrosylable seront générées puis leur interaction avec des micro-organismes pathogènes ou bénéfiques sera étudiée

Electrochemical detection of nitric oxide in plant cell suspensions

SPE IPM UBInternational audienceNitric 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

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

National audienceβ-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 deficiency response triggered by BABA could be one of the determinants of its protective effects against Botrytis cinerea

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

Communication orale invitée, résumé SPE IPM CT1In 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 Ca2+-dependent and involved nitrate reductase (NR). Accordingly, OGs triggered an increase of both NR activity and transcripts accumulation. NO production was also sensitive to the mammalian nitric oxide synthase inhibitor L-NAME. Intriguingly, we showed that L-NAME affected NO production by interfering with NR activity, thus questioning the mechanisms of how this compound impairs NO synthesis in plants. Using candidate genes and transcriptomic approaches, we further demonstrated that NO participates to the regulation of genes induced by OGs such as genes encoding disease related proteins and transcription factors. The over-representation of certain regulatory elements in promoter sequences of target genes also suggests the involvement of specific transcription factors in the NO response. Mutant plants impaired in several selected NO responsive genes, as well as Col-0 plants treated with the NO scavenger cPTIO, were more susceptible to Botrytis cinerea. Taken together, our investigation deciphers part of the mechanisms linking NO production, NO-induced effects and basal resistance to B. cinerea

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

International audienceMounting 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 concentration but impacted the content of copper. Collectively, our data highlight the complexity of interpreting data based on the use of NO donors when investigating the role of NO in iron homeostas

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

National audienceThe 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 salt stress in Klebsormidium nitens, a freshwater algal species possessing a NOS and established as a model to study plants adaptation to land. We applied the Biotin Switch method followed by mass spectrometry analysis. This method allows the purification of S-nitrosated proteins. We found 43 proteins with significantly higher S-nitrosation levels in salt response condition. Orthology analysis were performed against the model plant Arabidopsis thaliana, therefore we established a classification of these proteins according to their localization, molecular function and biological process they are involved in. This is done with the PANTHER classification system, based on Gene Ontology terms (GO terms). Then, from this list, we selected an interesting protein called INOSITOL POLYPHOSPHATE MULTIKINASE 2a/b (IPK2a/b), potentially involved in cell signaling and stress response. We produced it in Escherichia coli and are currently measuring its activity. This protein will then be Snitrosated in vitro and we will determine if its activity is impaired. Through the identification and functional analysis of Snitrosated proteins in K. nitens, this project will provide a better understanding of the functions of NO in unicellular green algae with NO