Effect of a fungal chitosan preparation on Brettanomyces bruxellensis,a wine contaminant

To investigate the action mechanisms of a specific fungal origin chitosan preparation on Brettanomyces bruxellensis. METHODS AND RESULTS: Different approaches in a wine-model synthetic medium were carried out: optical and electronic microscopy, flow cytometry, ATP flow measurements and zeta potential characterization. The inactivation effect was confirmed. Moreover, fungal origin chitosan induced both physical and biological effects on B. bruxellensis cells. Physical effect led to aggregation of cells with chitosan likely due to charge interactions. At the same time, a biological effect induced a leakage of ATP and thus a viability loss of B. bruxellensis cells. CONCLUSIONS: The antimicrobial action mode of chitosan against B. bruxellensis is not a simple mechanism but the result of several mechanisms acting together. SIGNIFICANCE AND IMPACT OF THE STUDY: Brettanomyces bruxellensis, a yeast responsible for the production of undesirable aromatic compounds (volatile phenols), is a permanent threat to wine quality. Today, different means are implemented to fight against B. bruxellensis, but are not always sufficient. The chitosan of fungal origin is introduced as a new tool to control B. bruxellensis in winemaking and has poorly been studied before for this application

Etude de techniques de linéarisation d'amplificateurs pour stations de base radiocellulaires de troisième génération

Ce travail, fruit de la collaboration entre le laboratoire de l'IRCOM et MOTOROLA Semiconducteurs SAS, traite de l'étude de techniques de linéarisation appliquées aux amplificateurs pour stations de base radio-cellulaires de troisième génération. Ces techniques permettent de rendre la partie amplificatrice plus linéaire pour un rendement en puissance ajoutée donné. Le premier chapitre présente le contexte des communications radio-mobiles dans lequel cette étude fut réalisée. Le deuxième chapitre montre une étude bibliographique des différentes techniques de line arisation existantes et susceptibles d'être utilisées dans les systèmes de communications actuels. Dans le troisième chapitre, deux techniques de linéarisation furent conçues, appliquées et testées sur des amplificateurs RadioFréquence (RF) de puissance : -la technique du feed-back RF : un amplificateur 900 MHz / 10 W EDGE ainsi linéarisé montre une puissance au dB de compression supérieure de 1 dB à celle d'un amplificateur conventionnel de taille équivalente et un comportement beaucoup plus linéaire, -la technique de la prédistortion analogique fut appliquée à un amplificateur conçu pour le standard UMTS de troisième génération montrant, dans la bande de fréquence concernée, un apport en linéarité de 7 dB en ACPr à pleine puissance et un gain de 1,5 dB en puissance au dB de compression. De plus, une simulation des performances d'un amplificateur à haut rendement de type Doherty fut réalisé. Le gain en rendement associé est de 20 points (sur 3 dB de dynamique en puissance) et d'au moins 10 points sir la majeure partie de la dynamique en puissanceLIMOGES-BU Sciences (870852109) / SudocSudocFranceF

Unravelling physiological signatures of tomato bacterial wilt and xylem metabolites exploited by Ralstonia solanacearum

The plant pathogen Ralstonia solanacearum uses plant resources to intensely proliferate in xylem vessels and provoke plant wilting. We combined automatic phenotyping and tissue/xylem quantitative metabolomics of infected tomato plants to decipher the dynamics of bacterial wilt. Daily acquisition of physiological parameters such as transpiration and growth were performed. Measurements allowed us to identify a tipping point in bacterial wilt dynamics. At this tipping point, the reached bacterial density brutally disrupts plant physiology and rapidly induces its death. We compared the metabolic and physiological signatures of the infection to drought stress, and found that similar changes occur. Quantitative dynamics of xylem content enabled us to identify glutamine (and asparagine) as primary resources R. solanacearum consumed during its colonization phase. An abundant production of putrescine was also observed during the infection process and was strongly correlated with in planta bacterial growth. Dynamic profiling of xylem metabolites confirmed that glutamine is the favored substrate of R. solanacearum. On the other hand, a triple mutant strain unable to metabolize glucose, sucrose and fructose appears to be only weakly reduced for in planta growth and pathogenicity.Towards a Unified theory of biotic Interactions: the roLe of environmentalUniversité Fédérale de ToulouseDéveloppement d'une infrastructure française distribuée pour la métabolomique dédiée à l'innovatio

Metabolomics to Exploit the Primed Immune System of Tomato Fruit.

Targeted and untargeted metabolomics were used to investigate the metabolic regulations that underpin the priming of tomato fruit against pathogenic microbes that present different infection strategies. Metabolomic analyses revealed major changes after BABA treatment and after inoculation. Remarkably, primed responses seemed specific to the type of infection, rather than showing a common fingerprint of BABA-induced priming. Furthermore, top-down modelling from the detected metabolic markers allowed for the accurate prediction of the measured resistance to fruit pathogens and demonstrated that soluble sugars are essential to predict resistance to fruit pathogens. Altogether, our results demonstrate that metabolomics is particularly insightful for a better understanding of defence priming in fruit. Further experiments are underway in order to identify key metabolites that mediate broad-spectrum BABA-induced priming in tomato fruit

Metabolomics to Exploit the Primed Immune System of Tomato Fruit.

Targeted and untargeted metabolomics were used to investigate the metabolic regulations that underpin the priming of tomato fruit against pathogenic microbes that present different infection strategies. Metabolomic analyses revealed major changes after BABA treatment and after inoculation. Remarkably, primed responses seemed specific to the type of infection, rather than showing a common fingerprint of BABA-induced priming. Furthermore, top-down modelling from the detected metabolic markers allowed for the accurate prediction of the measured resistance to fruit pathogens and demonstrated that soluble sugars are essential to predict resistance to fruit pathogens. Altogether, our results demonstrate that metabolomics is particularly insightful for a better understanding of defence priming in fruit. Further experiments are underway in order to identify key metabolites that mediate broad-spectrum BABA-induced priming in tomato fruit

15N nitrogen labelling on tomato fruit pericarp using plants cultivated in semi-controlled green house conditions

Estimer la stabilité des protéines dans un tissu végétal est une question essentielle mais complexe. Aujourd’hui, il n’existe que très peu de travaux montrant la faisabilité de mesurer le turnover d’un large panel de protéines végétales. Aussi, nous avons tenté d’incorporer l’azote 15N dans le péricarpe de fruit de tomate en ajoutant 5 % de Ca (15NO 3)2 à la solution nutritive classiquement utilisée. Au bout d’un mois de culture avec notation d’anthèses, quatre cinétiques d’incorporation ont été réalisées sur des fruits à différents stades de développement. Démarrées simultanément, elles ont duré 11 jours. Le dosage des rapports isotopiques réalisés par EA-IRMS (Elementary Analysis - Isotopic Ratio by Mass Spectrometry) sur résidus insolubles après extraction hydro-alcoolique rend compte d’une bonne incorporation du marquage. Associés au dosage des protéines totales (Bradford), les résultats obtenus révèlent la très bonne linéarité de l’incorporation de l’azote 15N dans le péricarpe de tomate en phase d’expansion cellulaireEstimating the stability of proteins in plant tissue is an essential but complex question. Today there is very little work showing the feasibility of measuring the turnover of a large panel of plant proteins. Also, we attempted to incorporate labelled nitrogen (15N) into the tomato fruit by adding 5% Ca ( 15NO3)2, to the conventionally used nutrient solution. One month of culture later (with anthesis notation), four 15N incorporation kinetics were performed on fruits at different stages of development during 11 days. Assays of isotopic ratios carried out by EA-IRMS (Elementary Analysis - Isotopic Ratio by Mass Spectrometry) on insoluble residues after hydro-alcoholic extraction show a good in-corporation of the labelling. Combined with total protein assays (Bradford), the results reveal the perfect linearity of 15N enrichment in tomato pericarp during cell expansion phase

Differences between tree stem CO 2 efflux and O 2 influx rates cannot be explained by internal CO 2 transport or storage in large beech trees

Tree stem respiration (R S) is a substantial component of the forest carbon balance. The mass balance approach uses stem CO 2 efflux and internal xylem fluxes to sum up R S , while the oxygen-based method assumes O 2 influx as a proxy of R S. So far, both approaches have yielded inconsistent results regarding the fate of respired CO 2 in tree stems, a major challenge for quantifying forest carbon dynamics. We collected a data set of CO 2 efflux, O 2 influx, xylem CO 2 concentration, sap flow, sap pH, stem temperature, nonstructural carbohydrates concentration and potential phosphoenolpyruvate carboxylase (PEPC) capacity on mature beech trees to identify the sources of differences between approaches. The ratio of CO 2 efflux to O 2 influx was consistently below unity (0.7) along a 3-m vertical gradient, but internal fluxes did not bridge the gap between influx and efflux, nor did we find evidence for changes in respiratory substrate use. PEPC capacity was comparable with that previously reported in green current-year twigs. Although we could not reconcile differences between approaches, results shed light on the uncertain fate of CO 2 respired by parenchyma cells across the sapwood. Unexpected high values of PEPC682512-OXYFLU

From fruit growth to ripening in plantain: a careful balance between carbohydrate synthesis and breakdown

We investigated the fruit development in two plantain banana cultivars from two weeks after bunch emergence till twelve weeks through high-throughput proteomics, major metabolite quantification and metabolic flux analyses. We aimed to investigate for the first time different fruit development stages and gain unique insights into the order of appearance and dominance of specific enzymes/fluxes. Starch synthesis and breakdown are processes that take place simultaneously. During the first ten weeks fruits accumulated up to 48% of starch. Glucose 6-phosphate and fructose were important starch precursors. We found a unique amyloplast transporter and hypothesize that it facilitates the import of fructose. We identified an invertase originating from the M. balbisiana genome that would enable to flow carbon back to growth and starch synthesis and keep a high starch content even during ripening. Enzymes associated to the initiation of ripening were involved in ethylene and auxin metabolism, starch breakdown, pulp softening and ascorbate biosynthesis. The initiation of ripening was cultivar specific. A faster initiation was particularly linked to 1-aminocyclopropane-1-carboxylate oxidase and 4-alpha glucanotransferase disproportioning enzyme. This knowledge is fundamental to determine the ideal harvest moment, reduce postharvest losses and improve product quality through breeding

Enzyme-based kinetic modelling of ASC–GSH cycle during tomato fruit development reveals the importance of reducing power and ROS availability

The ascorbate–glutathione (ASC–GSH) cycle is at the heart of redox metabolism, linking the major redox buffers with central metabolism through the processing of reactive oxygen species (ROS) and pyridine nucleotide metabolism. Tomato fruit development is underpinned by changes in redox buffer contents and their associated enzyme capacities, but interactions between them remain unclear. Based on quantitative data obtained for the core redox metabolism, we built an enzyme-based kinetic model to calculate redox metabolite concentrations with their corresponding fluxes and control coefficients. Dynamic and associated regulations of the ASC–GSH cycle throughout the whole fruit development were analysed and pointed to a sequential metabolic control of redox fluxes by ASC synthesis, NAD(P)H and ROS availability depending on the developmental phase. Furthermore, we highlighted that monodehydroascorbate reductase and the availability of reducing power were found to be the main regulators of the redox state of ASC and GSH during fruit growth under optimal conditions. Our kinetic modelling approach indicated that tomato fruit development displayed growth phase-dependent redox metabolism linked with central metabolism via pyridine nucleotides and H2O2 availability, while providing a new tool to the scientific community to investigate redox metabolism in fruits.The GLOMICAVE project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 95290

From fruit growth to ripening in plantain: a careful balance between carbohydrate synthesis and breakdown

We investigated the fruit development in two plantain banana cultivars from two weeks after bunch emergence till twelve weeks through high-throughput proteomics, major metabolite quantification and metabolic flux analyses. We give for the first time an insight at early stages of starch synthesis and breakdown. Starch and sugar synthesis and breakdown are processes that take place simultaneously. During the first eight to ten weeks the balance between synthesis and breakdown is clearly in favour of sugar breakdown and a net starch synthesis occurs. During this period, plantain fruit accumulates up to 48% of starch. The initiation of the ripening process is accompanied with a shift in balance towards net starch breakdown. The key enzymes related to this are phosphoglucan water dikinase (PWD), phosphoglucan phosphatase, α-1,6-glucosidase starch debranching enzyme (DBE), alpha glucan phosphorylase (PHS) and 4-alpha glucanotransferase disproportioning enzyme (DPE). The highest correlations with sucrose have been observed for PHS and DPE. There is also a significant correlation between the enzymes involved in ethylene biosynthesis, starch breakdown, pulp softening and ascorbate biosynthesis. The faster ending of maturation and starting of ripening in the Agbagba cultivar are linked to the key enzymes 1-aminocyclopropane-1-carboxylate oxidase and DPE. This knowledge of the mechanisms that regulate starch and sugar metabolisms during maturation and ripening is fundamental to determine the harvest moment, reduce postharvest losses and improve final product quality of breeding programs.Centre français de phénomique végétal