68 results on '"Villaume S"'
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2. Review of preparative and analytical procedures for the study of proteins in grape juice and wine
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Le Bourse, D., Jégou, S., Conreux, A., Villaume, S., and Jeandet, P.
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- 2010
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3. Quantification of chitinase and thaumatin-like proteins in grape juices and wines
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Le Bourse, D., Conreux, A., Villaume, S., Lameiras, P., Nuzillard, J.-M., and Jeandet, P.
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- 2011
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4. Erratum to: Quantification of chitinase and thaumatin-like proteins in grape juices and wines
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Le Bourse, D., Conreux, A., Villaume, S., Lameiras, P., Nuzillard, J.-M., and Jeandet, P.
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- 2011
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5. Transforming growth factor-beta 1 or ascorbic acid are able to differentiate Wharton’s jelly mesenchymal stem cells towards a smooth muscle phenotype
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Mesure, B., primary, Huber-Villaume, S., additional, Menu, P., additional, and Velot, É., additional
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- 2017
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6. Esca, BDA and Eutypiosis: foliar symptoms, trunk lesions and fungi observed in diseased vinestocks in two vineyards in Alsace
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Kuntzmann, P., Villaume, S., Larignon, P., and Bertsch, C.
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The French vineyard is affected by three principal wood diseases: Eutypa dieback, esca and black dead arm (BDA). Phaeomoniella chlamydospora, Phaeocremonium aleophilum, Eutypa lata, Fomitiporia mediterranea, Diplodia seriata, Diplodia mutila and Neofusicoccum parvum are the main fungi isolated in France and associated with grapevine trunk diseases. The aim of this study was to highlight the type of wood lesions and the fungus present in the Alsace vineyards (France) and to compare it with those identified in the other french vine-growing regions or with the German vineyards. Therefore, we have studied two vineyards with two different grapevine varieties ('Auxerrois', 'Gewürztraminer'). The foliar symptoms showed that the plots planted with 'Auxerrois' and 'Gewürztraminer' varieties had respectively 12 and 21 % grapevines with symptoms in 2005. Different cross sections were made on trunks and arms of 55 vines showing foliar symptoms, totalizing 162 microbiological isolations. Visual characterisations of the different lesions were described. The isolations made from the different necrosis showed the presence of species of fungi involved in grapevine trunk diseases and other fungi. Microbiological observations showed that for the Auxerrois vineyard the majority of the vines were infected with D. seriata, P. chlamydospora, E. lata and F. mediterranea. In the Gewürztraminer vineyard, the fungus most frequently isolated was P. chlamydospora, followed by D. seriata. The presence of D. seriata in different parts of the grapevine wood and in young wood is related to the severe damages observed on the vegetation., VITIS - Journal of Grapevine Research, Vol. 49 No. 2 (2010): Vitis
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- 2015
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7. Transfert des colis de déchets de la surface au fond (présentation de l'entreprise POMA)
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Villaume, S., primary
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- 2016
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8. Noradrenaline and a thiol analogue on gold surfaces : An infrared reflection-absorption spectroscopy, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy study
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Vahlberg, C., Linares, M., Villaume, S., Norman, Patrick, Uvdal, K., Vahlberg, C., Linares, M., Villaume, S., Norman, Patrick, and Uvdal, K.
- Abstract
Self-assembled monolayers and multilayers of a noradrenaline analogue (Nor-Pt) on gold substrates as well as multilayers of noradrenaline have been investigated by means of the molecular orientation, the molecule-surface interaction, the molecular composition and the functional group availability for further biointeraction processes, using X-ray photoelectron spectroscopy (XPS), infrared reflection-absorption spectroscopy (IRAS), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. A chemical shift (1.7 eV) of the S 2p peak to lower binding energies is observed, in the XPS spectrum, indicating that the Nor-Pt molecules are chemisorbed onto the gold substrate. The IR results show that Nor-Pt adsorbate has the C=O stretching vibration modes parallel oriented relative to the gold substrate. The average tilt angle of the aromatic ring relative to the gold surface normal is determined to be approximately 51°, based on the NEXAFS measurements on Nor-Pt monolayers. The experimental results and assignments are supported with theoretical studies where we use the building block principle in the spectral analysis and compare with the measurements of noradrenaline and Nor-Pt. The theoretical calculations are shown to be useful; for angle dependence NEXAFS studies as resonances with fully φ* or σ* character are preferred for correct analysis., QC 20161222
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- 2011
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9. Linear complex polarization propagator in a four-component Kohn-Sham framework
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Villaume, S., Saue, T., Norman, Patrick, Villaume, S., Saue, T., and Norman, Patrick
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An algorithm for the solution of the linear response equation in the random phase approximation is presented. All entities including frequency arguments, matrices, and vectors, are assumed to be complex, and it represents the core equation solver needed in complex polarization propagator approaches where nonstimulated relaxation channels are taken into account. Stability and robustness of the algorithm are demonstrated in applications regarding visible, ultraviolet, and x-ray spectroscopies. An implementation of the algorithm at the level of four-component relativistic, noncollinear, density functional theory for imaginary (but not complex) frequency arguments has been achieved and is used to determine the electric dipole dispersion interaction coefficients for the rubidium and cesium dimers. Our best estimates for the C6 coefficients of Rb2 and Cs2 are equal to 14.0× 103 and 21.9× 103 a.u., respectively., QC 20161222
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- 2010
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10. Near sulfur L-edge X-ray absorption spectra of methanethiol in isolation and adsorbed on a Au(111) surface : A theoretical study using the four-component static exchange approximation
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Villaume, S., Ekström, U., Ottosson, H., Norman, Patrick, Villaume, S., Ekström, U., Ottosson, H., and Norman, Patrick
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The relativistic four-component static exchange approach for calculation of near-edge X-ray absorption spectra has been reviewed. Application of the method is made to the Au(111) interface and the adsorption of methanethiol by a study of the near sulfur L-edge spectrum. The binding energies of the sulfur 2p 1/2 and 2p3/2 sublevels in methanethiol are determined to be split by 1.2 eV due to spin-orbit coupling, and the binding energy of the 2p3/2 shell is lowered from 169.2 eV for the isolated system to 167.4 and 166.7-166.8 eV for methanethiol in mono- and di-coordinated adsorption sites, respectively (with reference to vacuum). In the near L-edge X-ray absorption fine structure spectrum only the σ*(S-C) peak at 166 eV remains intact by surface adsorption, whereas transitions of predominantly Rydberg character are largely quenched in the surface spectra. The σ*(S-H) peak of methanethiol is replaced by low-lying, isolated, σ*(S-Au) peak(s), where the number of peaks in the latter category and their splittings are characteristic of the local bonding situation of the sulfur., QC 20161222
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- 2010
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11. On circular dichroism and the separation between chromophore and chiral center : The near carbon K-Edge X-ray absorption and circular dichroism spectra of noradrenaline and L-DOPA
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Villaume, S., Norman, Patrick, Villaume, S., and Norman, Patrick
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The near carbon K-edge X-ray absorption and circular dichroism spectra of noradrenaline (neutral and protonated forms) and L-DOPA (protonated form) have been determined with use of the complex polarization propagator method in conjunction with Kohn-Sham density functional theory. A Coulomb attenuated exchange-correlation functional and London atomic orbitals have been employed to address the issues of hole-electron interactions and gauge-origin dependence of the magnetic-dipole operator, respectively. Results show that the characteristics of the chromophore part of the circular dichroism spectra are shared for all three considered systems, whereas protonation qualitatively alters the part of the spectrum assigned to the chiral side chain. The comparatively larger spatial separation of chromophore and chiral center in L-DOPA inflicts larger differences in spectral intensities between the chromophore and chiral center part of the circular dichroism spectra., QC 20161222
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- 2009
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12. Detection of Bacterial Endophytes in Vitis vinifera L. and Antibiotic Activity against Grapevine Fungal Pathogens
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S. Lo Piccolo, A. Alfonzo, S. Burruano, G. Moschetti, Compant, S., Mathieu, F., Zanzotto, A., Morroni, M., Yousaf, S. Anees, M., Campisano, A., Cardinale, M., Berg, G., Aziz, A., Verhagen, B., Villaume, S., Höfte, M., Baillieul, F., Clément, C., Trotel-Aziz, P., Ben-Maachia, S., Errakhi, R., Lebrihi, A., Bouteau, F., Barakate, M., Muzammil, S., Saria, R., Yu, Z. Graillon, C., Burruano, S., Mondello, V., Conigliaro, G., Angeli, D., Micheli, S., Maurhofer, M., Pertot, I., Gerbore, J. Bruez, E. Vallance, J. Grizard, D. Regnault-Roger, C. Rey, P., Islam, M. T., Costadone, L., Gubler, W. D., Mounier, E., Boulisset, F., Cortes, F., Cadiou, M., Dubournet, P., Pajot, E., Pierron, R. J. G., Pouzoulet, J., Meziane, A., Mailhac, N., Jacques, A., Dachoupakan, C., Strub, C., Martinez, V., Baccou, J. C., Schorr-Galindo, S., Brader, G., Gangl, H., Sessitsch, A., Bulgari, D., Casati, P., Quaglino, F., Bianco, P. A., Lo Piccolo, S, Alfonzo, A, Burruano, S, and Moschetti, G
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Settore AGR/12 - Patologia Vegetale ,bacterial endophytes, detection, vitis vinifera ,Settore AGR/16 - Microbiologia Agraria - Abstract
This chapter presents the results of studies conducted to (i) detect and localize endophytic bacteria in symptomless and symptomatic leaf tissues of grapevine (Vitis vinifera) using fluorescence in situ hybridization (FISH) in combination with confocal laser scanning microscopy (CLSM); and (ii) test the antagonistic activity of Bacillus amyloliquefaciens AG1, previously isolated from grape wood affected by the esca syndrome, against grapevine fungal pathogens: Alternaria alternata, obtained from grapevine leaves showing necrotic concentric spots; Aspergillus carbonarius, A. ochraceus and Penicillium verrucosum, isolated from grapes affected by secondary rot; Botrytis cinerea, isolated from grapes with grey mould; Cladosporium viticola, agent of grapevine leaf spots; Fomitiporia mediterranea, obtained from grapevines with white rot symptoms; Fusarium oxysporum, isolated from the grapevine rhizosphere; Lasiodiplodia theobromae, isolated from vine wood with cortical cankers; Phaeoacremonium aleophilum and Phaeomoniella chlamydospora, both isolated from grapevine showing esca symptoms; Phoma glomerata from grape leaves showing necrotic spots; and Verticillium dahliae, obtained from decaying vine. The FISH/CLSM approach was successfully applied to visualize endophytic bacteria in grapevine leaves, including also those that it is not possible to cultivate in sterilized medium. Also, B. amyloliquefaciens AG1 showed a potential role as a biological control agent against trunk fungal pathogens as well as other fungal phytopathogens.
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- 2016
13. Sleep and Daily Affect and Risk for Major Depression: Day-to-day and Prospective Associations in Late Adolescence and Early Adulthood.
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Collier Villaume S, Stephens JE, Craske MG, Zinbarg RE, and Adam EK
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- Adult, Humans, Adolescent, Depression psychology, Emotions, Affect, Sleep physiology, Depressive Disorder, Major psychology
- Abstract
Purpose: Poor sleep is associated with short-term dysregulation of mood and is a risk factor for major depressive disorder (MDD). This study examines whether objectively measured sleep in late adolescence prospectively predicts major depressive episode (MDE) onset in early adulthood as well as whether daily affect mediates this association., Methods: The present study draws on subjective and objective sleep data, ecological momentary assessment, and diagnostic data from the longitudinal Youth Emotion Project to examine whether: a) short sleep predicts dysregulated ecological momentary assessment-measured mood the next day; b) sleep predicts depressive episodes over the subsequent 5 years; and c) dysregulated daily moods mediate the associations between short sleep and later MDD. Fixed effects, logistic regression, and formal mediation analyses were employed., Results: Our results showed that nights with less sleep are followed by days with more negative affect; short sleep predicted MDEs over the subsequent 5 years (adjusting for prior MDD); and negative affect mediates the relationship between short sleep and later MDEs., Discussion: Overall, our findings show sleep to be an important risk factor and hence a promising point of intervention for improving mood and reducing the risk of future MDEs in adolescents and early adults., (Copyright © 2023 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.)
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- 2024
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14. Global seasonal prediction of fire danger.
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Di Giuseppe F, Vitolo C, Barnard C, Libertá G, Maciel P, San-Miguel-Ayanz J, Villaume S, and Wetterhall F
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The European Centre for Medium range weather forecast (ECMWF) on behalf of the Copernicus Emergency Management Service (CEMS) has recently widened the fire danger data offering in the Climate Data Store (CDS) to include a set of fire danger forecasts with lead times up to 7 months. The dataset incorporates fire danger indices for three different models developed in Canada, United States and Australia. The indices are calculated using ECMWF Seasonal Forecasting System 5 (SEAS5) and verified against the relevant reanalysis of fire danger based on the ECMWF Re-Analysis (ERA5). The data set is made openly available for the period 1981 to 2023 and will be updated regularly providing a resource to assess the predictability of fire weather at the seasonal time scale. The data set complements the availability of seasonal forecast provided by the Copernicus Emergency Management Service in real time.A preliminary analysis shows that globally anomalous conditions for fire weather can be predicted with confidence 1 month ahead. In some regions the prediction can extend to 2 months ahead. In most situations beyond this horizon, forecasts do not show more skill than climatology. However an extended predictability window, up to 6-7 months ahead is possible when anomalous fire weather is the results of large scale phenomena such as the El Niño Southern Oscillation and the Indian Ocean Dipole, often conducive of extensive fire burning in regions such as Indonesia and Australia., (© 2024. The Author(s).)
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- 2024
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15. Protecting-group free synthesis of glycoconjugates displaying dual fungicidal and plant defense-eliciting activities.
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Noël N, Duchateau S, Messire G, Massicot F, Vasse JL, Villaume S, Aziz A, Dorey S, Crouzet J, and Behr JB
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- Antifungal Agents pharmacology, Plants, Glycoconjugates pharmacology, Carbohydrates, Fungicides, Industrial
- Abstract
A straightforward synthesis of carbohydrate templated isoxazolidines is described, by reaction of unprotected glycosylhydroxylamines (operating as 1,3-dipoles) with methyl acrylate using microwave activation. Rhamno- and erythro-isoxazolidines are recognized by plant cells, resulting in a strong ROS-production as a plant immune response, and exert a high antifungal activity against Botrytis cinerea., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)
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- 2023
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16. Age Disparities in Prevalence of Anxiety and Depression Among US Adults During the COVID-19 Pandemic.
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Collier Villaume S, Chen S, and Adam EK
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- Female, Humans, Adult, Middle Aged, Aged, Male, Prevalence, Cross-Sectional Studies, Depression epidemiology, Anxiety epidemiology, Anxiety Disorders, Pandemics, COVID-19 epidemiology
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Importance: High levels of anxiety and depression were documented shortly after the arrival of the COVID-19 pandemic and were more prevalent in younger adults than in older adults. Knowing whether these age disparities persisted throughout multiple years of the COVID-19 pandemic and identifying associated factors will help guide health policy., Objective: To investigate age disparities in anxiety and depression during the COVID-19 pandemic., Design, Setting, and Participants: This cross-sectional study consisted of a nationally representative online survey administered between April 2020 and August 2022 and included US adults who were not incarcerated. Data were analyzed between March and September 2022., Exposures: The first 27 months of the COVID-19 pandemic included wide variation in infection rates, turbulence in US political and social life, and geopolitical instability. Primary exposures include individuals' age and economic precarity and pandemic-related events (eg, weekly state-level case counts and individual vaccination status)., Main Outcomes and Measures: Symptoms of anxiety and depression were assessed via responses to 2-item screeners (Generalized Anxiety Disorder 2-item for anxiety and Patient Health Questionnaire-2 for depression). An individual's symptoms were identified as clinically elevated if scores exceeded validated thresholds., Results: This study included 3 028 923 respondents (mean [SD] age, 48.9 [17.0] years; 1 567 603 [51.8%] female). In multiple regression analyses that include state fixed effects and survey-week fixed effects, likely anxiety and depressive disorders among 291 382 (40%) and 238 505 (33%) of adults aged 18 to 39 years, respectively, compared with 357 820 (31%) and 274 534 (24%) of adults aged 40 to 59 years and 225 295 (20%) and 183 695 (16%) adults aged 60 years and older. Levels declined throughout the pandemic period for those aged 40 years and older but remained elevated for younger adults. Analyses identified several associated factors of these age disparities. Younger adults' anxiety and depression increased more than older adults' after surges in COVID-19 case counts but decreased less following vaccination against the virus. Additionally, approximately one third of the age gap among individuals with depression and anxiety was attributed to economic precarity, to which younger adults are disproportionately exposed., Conclusions and Relevance: In this cross-sectional study of anxiety and depression during the COVID-19 pandemic, economic precarity was associated with high anxiety and depression among younger adults in the US compared with older adults in the US. These findings suggest a need for greater mental health care and economic policies targeted toward younger adults.
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- 2023
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17. L-Rhamnose and Phenolic Esters-Based Monocatenar and Bolaform Amphiphiles: Eco-Compatible Synthesis and Determination of Their Antioxidant, Eliciting and Cytotoxic Properties.
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Kordkatooli E, Bacha K, Villaume S, Dorey S, Monboisse JC, Brassart-Pasco S, Mbakidi JP, and Bouquillon S
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- Esters pharmacology, Phenols pharmacology, Glycosylation, Coumaric Acids, Antioxidants pharmacology, Antioxidants metabolism, Rhamnose
- Abstract
Symmetrical and dissymmetrical bolaforms were prepared with good to high yields from unsaturated L-rhamnosides and phenolic esters (ferulic, phloretic, coumaric, sinapic and caffeic) using two eco-compatible synthetic strategies involving glycosylation, enzymatic synthesis and cross-metathesis under microwave activation. The plant-eliciting activity of these new compounds was investigated in Arabidopsis model plants. We found that the monocatenar rhamnosides and bolaforms activate the plant immune system with a response depending on the carbon chain length and the nature of the hydrophilic heads. Their respective antioxidant activities were also evaluated, as well as their cytotoxic properties on dermal cells for cosmetic uses. We showed that phenolic ester-based compounds present good antioxidant activities and that their cytotoxicity is low. These properties are also dependent on the carbon chains used.
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- 2023
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18. Priming of camalexin accumulation in induced systemic resistance by beneficial bacteria against Botrytis cinerea and Pseudomonas syringae pv. tomato DC3000.
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Nguyen NH, Trotel-Aziz P, Villaume S, Rabenoelina F, Clément C, Baillieul F, and Aziz A
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- Botrytis physiology, Gene Expression Regulation, Plant, Immunity, Innate, Indoles, Plant Diseases microbiology, Pseudomonas syringae physiology, Salicylic Acid metabolism, Thiazoles, Arabidopsis metabolism, Solanum lycopersicum metabolism
- Abstract
Plants harbor various beneficial microbes that modulate their innate immunity, resulting in induced systemic resistance (ISR) against a broad range of pathogens. Camalexin is an integral part of Arabidopsis innate immunity, but the contribution of its biosynthesis in ISR is poorly investigated. We focused on camalexin accumulation primed by two beneficial bacteria, Pseudomonas fluorescens and Bacillus subtilis, and its role in ISR against Botrytis cinerea and Pseudomonas syringae Pst DC3000. Our data show that colonization of Arabidopsis thaliana roots by beneficial bacteria triggers ISR against both pathogens and primes plants for enhanced accumulation of camalexin and CYP71A12 transcript in leaf tissues. Pseudomonas fluorescens induced the most efficient ISR response against B. cinerea, while B. subtilis was more efficient against Pst DC3000. Analysis of cyp71a12 and pad3 mutants revealed that loss of camalexin synthesis affected ISR mediated by both bacteria against B. cinerea. CYP71A12 and PAD3 contributed significantly to the pathogen-triggered accumulation of camalexin, but PAD3 does not seem to contribute to ISR against Pst DC3000. This indicated a significant contribution of camalexin in ISR against B. cinerea, but not always against Pst DC3000. Experiments with Arabidopsis mutants compromised in different hormonal signaling pathways highlighted that B. subtilis stimulates similar signaling pathways upon infection with both pathogens, since salicylic acid (SA), but not jasmonic acid (JA) or ethylene, is required for ISR camalexin accumulation. However, P. fluorescens-induced ISR differs depending on the pathogen; both SA and JA are required for camalexin accumulation upon B. cinerea infection, while camalexin is not necessary for priming against Pst DC3000., (© The Author(s) 2022. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)
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- 2022
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19. Diversity of Neofusicoccum parvum for the Production of the Phytotoxic Metabolites (-)-Terremutin and ( R )-Mellein.
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Trotel-Aziz P, Robert-Siegwald G, Fernandez O, Leal C, Villaume S, Guise JF, Abou-Mansour E, Lebrun MH, and Fontaine F
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Two Neofusicoccum parvum )-mellein, and it was the most aggressive on grapevine, triggering apoplexy. Similar symptoms were not induced by purified (-)-terremutin. The isolate Bourgogne S-116 (Np-B) produced 3-fold less (-)-terremutin and high amounts of ( R )-mellein, and it was the most aggressive on grapevine, triggering apoplexy. Similar symptoms were not induced by purified (-)-terremutin. The isolate Bourgogne S-116 (Np-B) produced 3-fold less (-)-terremutin and high amounts of ( R )-mellein, but it was less aggressive on grapevine than Np-Bt67. The UV9 mutant obtained from Np-B (NpB-UV9) no longer produced (-)-terremutin but overproduced ( R )-mellein by 2.5-fold, and it was as pathogenic as its parent. NpB-UV9 differed from its parent by simple mutations in two genes (transcription factor UCR-NP2_6692 , regulatory protein UCR-NP2_9007 ), not located neither near ( R )-mellein, nor (-)-terremutin biosynthetic genes, but likely involved in the control of (-)-terremutin biosynthesis. Grapevine immunity was disturbed upon challenge with these pathogens or purified phytotoxins, leading to an upregulation of SA-dependent defenses, while (-)-terremutin interfered with host JA/ET-dependent defenses. Our results suggest that neither (-)-terremutin nor ( R )-mellein alone is essential for the pathogenicity of N. parvum on grapevine, since isolate/mutant non-producing these toxins in vitro is pathogenic. However, these phytotoxins could play a quantitative role in the infection process.
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- 2022
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20. D-Tagatose-Based Product Triggers Sweet Immunity and Resistance of Grapevine to Downy Mildew, but Not to Gray Mold Disease.
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Mijailovic N, Richet N, Villaume S, Nesler A, Perazzolli M, Aït Barka E, and Aziz A
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The use of natural bio-based compounds becomes an eco-friendly strategy to control plant diseases. Rare sugars would be promising compounds as inducers of plant "sweet immunity". The present study aimed to investigate the induced resistance of grapevine leaves against Plasmopara viticola and Botrytis cinerea by a rare sugar-based product (IFP48) and its active ingredient D-tagatose (TAG), in order to elucidate molecular mechanism involved in defense-related metabolic regulations before and after pathogen challenge. Data showed that spraying leaves with IFP48 and TAG lead to a significant reduction of downy mildew, but not of gray mold disease. The induced protection against P. viticola relies on IFP48's and to a lesser extent TAG's ability to potentiate the activation of salicylic acid- and jasmonic acid/ethylene-responsive genes and stilbene phytoalexin accumulation. Most of defense responses remained upregulated in IFP48-treated plants after infection with P. viticola , but inconsistent following challenge with B. cinerea . The beneficial effects of IFP48 were associated with an enhanced accumulation of tagatose inside leaf tissues compared to TAG treatment. Meanwhile, the amounts of sugars, glucose, fructose, maltose, galactose and trehalose remained unchanged or decreased in IFP48-treated leaves after P. viticola infection, although only a few genes involved in sugar transport and metabolism showed transcriptional regulation. This suggests a contribution of sugar homeostasis to the IFP48-induced sweet immune response and priming plants for enhanced resistance to P. viticola , but not to B. cinerea .
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- 2022
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21. High Parental Education Protects Against Changes in Adolescent Stress and Mood Early in the COVID-19 Pandemic.
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Collier Villaume S, Stephens JE, Nwafor EE, Umaña-Taylor AJ, and Adam EK
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- Adolescent, Affect, Humans, Parents, SARS-CoV-2, COVID-19, Pandemics prevention & control
- Abstract
Purpose: The COVID-19 pandemic has brought dramatic changes to the daily lives of U.S. adolescents, including isolation from friends and extended family, transition to remote learning, potential illness and death of loved ones, and economic distress. This study's purpose is to measure changes in adolescents' perceived stress and mood early in the pandemic., Methods: The present study drew from a racially and ethnically diverse sample of high school student participants in an ongoing intervention study in the Midwestern U.S., 128 of whom provided reports of their daily stress and mood both before (December 2017 to March 2020) and during (March-July 2020) the COVID-19 pandemic. We expected to see increases in perceived stress, declines in positive mood states, and increases in negative mood states, with larger impacts on individuals from households with lower parental education levels., Results: Multilevel models revealed increases in perceived stress primarily for adolescents from low/moderate education families during the pandemic. Impacts on mood states also diverged by education: adolescents from low/moderate education households reported feeling more ashamed, caring, and excited than before the pandemic, changes that were not shared by their peers from high education households. Although changes in mood that arose with the onset of the pandemic became less pronounced over time, increased levels of home- and health-related stress stayed high for low/moderate education adolescents., Conclusions: During the COVID-19 period, we observed disparate impacts on adolescents according to household education level, with more dramatic and negative changes in the emotional well-being of adolescents from low/moderate education households., (Copyright © 2021 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.)
- Published
- 2021
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22. Bacterial rhamnolipids and their 3-hydroxyalkanoate precursors activate Arabidopsis innate immunity through two independent mechanisms.
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Schellenberger R, Crouzet J, Nickzad A, Shu LJ, Kutschera A, Gerster T, Borie N, Dawid C, Cloutier M, Villaume S, Dhondt-Cordelier S, Hubert J, Cordelier S, Mazeyrat-Gourbeyre F, Schmid C, Ongena M, Renault JH, Haudrechy A, Hofmann T, Baillieul F, Clément C, Zipfel C, Gauthier C, Déziel E, Ranf S, and Dorey S
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- Arabidopsis Proteins genetics, Arabidopsis Proteins immunology, Arabidopsis Proteins metabolism, Calcium Signaling, Disease Resistance immunology, Glycolipids chemistry, Host-Pathogen Interactions physiology, Immunity, Innate, Phosphorylation, Plant Diseases immunology, Plant Diseases microbiology, Plants, Genetically Modified, Protein Serine-Threonine Kinases genetics, Protein Serine-Threonine Kinases immunology, Protein Serine-Threonine Kinases metabolism, Pseudomonas syringae metabolism, Reactive Oxygen Species metabolism, Nicotiana genetics, Nicotiana metabolism, Arabidopsis immunology, Arabidopsis microbiology, Glycolipids metabolism, Plant Immunity physiology, Pseudomonas syringae pathogenicity
- Abstract
Plant innate immunity is activated upon perception of invasion pattern molecules by plant cell-surface immune receptors. Several bacteria of the genera Pseudomonas and Burkholderia produce rhamnolipids (RLs) from l-rhamnose and ( R )-3-hydroxyalkanoate precursors (HAAs). RL and HAA secretion is required to modulate bacterial surface motility, biofilm development, and thus successful colonization of hosts. Here, we show that the lipidic secretome from the opportunistic pathogen Pseudomonas aeruginosa , mainly comprising RLs and HAAs, stimulates Arabidopsis immunity. We demonstrate that HAAs are sensed by the bulb-type lectin receptor kinase LIPOOLIGOSACCHARIDE-SPECIFIC REDUCED ELICITATION/S-DOMAIN-1-29 (LORE/SD1-29), which also mediates medium-chain 3-hydroxy fatty acid (mc-3-OH-FA) perception, in the plant Arabidopsis thaliana HAA sensing induces canonical immune signaling and local resistance to plant pathogenic Pseudomonas infection. By contrast, RLs trigger an atypical immune response and resistance to Pseudomonas infection independent of LORE. Thus, the glycosyl moieties of RLs, although abolishing sensing by LORE, do not impair their ability to trigger plant defense. Moreover, our results show that the immune response triggered by RLs is affected by the sphingolipid composition of the plasma membrane. In conclusion, RLs and their precursors released by bacteria can both be perceived by plants but through distinct mechanisms., Competing Interests: Competing interest statement: Technical University of Munich has filed a patent application to inventors A.K., C.D., T.H., and S.R.
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- 2021
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23. Total synthesis, isolation, surfactant properties, and biological evaluation of ananatosides and related macrodilactone-containing rhamnolipids.
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Cloutier M, Prévost MJ, Lavoie S, Feroldi T, Piochon M, Groleau MC, Legault J, Villaume S, Crouzet J, Dorey S, Dìaz De Rienzo MA, Déziel E, and Gauthier C
- Abstract
Rhamnolipids are a specific class of microbial surfactants, which hold great biotechnological and therapeutic potential. However, their exploitation at the industrial level is hampered because they are mainly produced by the opportunistic pathogen Pseudomonas aeruginosa . The non-human pathogenic bacterium Pantoea ananatis is an alternative producer of rhamnolipid-like metabolites containing glucose instead of rhamnose residues. Herein, we present the isolation, structural characterization, and total synthesis of ananatoside A, a 15-membered macrodilactone-containing glucolipid, and ananatoside B, its open-chain congener, from organic extracts of P. ananatis . Ananatoside A was synthesized through three alternative pathways involving either an intramolecular glycosylation, a chemical macrolactonization or a direct enzymatic transformation from ananatoside B. A series of diasteroisomerically pure (1→2), (1→3), and (1→4)-macrolactonized rhamnolipids were also synthesized through intramolecular glycosylation and their anomeric configurations as well as ring conformations were solved using molecular modeling in tandem with NMR studies. We show that ananatoside B is a more potent surfactant than its macrolide counterpart. We present evidence that macrolactonization of rhamnolipids enhances their cytotoxic and hemolytic potential, pointing towards a mechanism involving the formation of pores into the lipidic cell membrane. Lastly, we demonstrate that ananatoside A and ananatoside B as well as synthetic macrolactonized rhamnolipids can be perceived by the plant immune system, and that this sensing is more pronounced for a macrolide featuring a rhamnose moiety in its native
1 C4 conformation. Altogether our results suggest that macrolactonization of glycolipids can dramatically interfere with their surfactant properties and biological activity., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)- Published
- 2021
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24. Bacillus subtilis and Pseudomonas fluorescens Trigger Common and Distinct Systemic Immune Responses in Arabidopsis thaliana Depending on the Pathogen Lifestyle.
- Author
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Nguyen NH, Trotel-Aziz P, Villaume S, Rabenoelina F, Schwarzenberg A, Nguema-Ona E, Clément C, Baillieul F, and Aziz A
- Abstract
Plants harbor various beneficial bacteria that modulate their innate immunity, resulting in induced systemic resistance (ISR) against various pathogens. However, the immune mechanisms underlying ISR triggered by Bacillus spp. and Pseudomonas spp. against pathogens with different lifestyles are not yet clearly elucidated. Here, we show that root drenching of Arabidopsis plants with Pseudomonas fluorescens PTA-CT2 and Bacillus subtilis PTA-271 can induce ISR against the necrotrophic fungus B. cinerea and the hemibiotrophic bacterium Pseudomonas syringae Pst DC3000. In the absence of pathogen infection, both beneficial bacteria do not induce any consistent change in systemic immune responses. However, ISR relies on priming faster and robust expression of marker genes for the salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) signaling pathways upon pathogen challenge. These responses are also associated with increased levels of SA, JA, and abscisic acid (ABA) in the leaves of bacterized plants after infection. The functional study also points at priming of the JA/ET and NPR1-dependent defenses as prioritized immune pathways in ISR induced by both beneficial bacteria against B. cinerea . However, B. subtilis -triggered ISR against Pst DC3000 is dependent on SA, JA/ET, and NPR1 pathways, whereas P. fluorescens -induced ISR requires JA/ET and NPR1 signaling pathways. The use of ABA-insensitive mutants also pointed out the crucial role of ABA signaling, but not ABA concentration, along with JA/ET signaling in primed systemic immunity by beneficial bacteria against Pst DC3000, but not against B. cinerea . These results clearly indicate that ISR is linked to priming plants for enhanced common and distinct immune pathways depending on the beneficial strain and the pathogen lifestyle.
- Published
- 2020
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25. Synthesis and evaluation of heterocycle structures as potential inhibitors of Mycobacterium tuberculosis UGM.
- Author
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Maaliki C, Fu J, Villaume S, Viljoen A, Raynaud C, Hammoud S, Thibonnet J, Kremer L, Vincent SP, and Thiery E
- Subjects
- 4-Butyrolactone chemical synthesis, 4-Butyrolactone pharmacology, Antitubercular Agents pharmacology, Drug Evaluation, Preclinical, Enzyme Inhibitors pharmacology, Humans, Indoles pharmacology, Microbial Sensitivity Tests, Molecular Docking Simulation, Molecular Structure, Mycobacterium tuberculosis drug effects, Mycobacterium tuberculosis enzymology, Protein Binding, 4-Butyrolactone analogs & derivatives, Antitubercular Agents chemical synthesis, Enzyme Inhibitors chemical synthesis, Indoles chemical synthesis, Intramolecular Transferases antagonists & inhibitors, Tuberculosis drug therapy
- Abstract
In this study, we screen three heterocyclic structures as potential inhibitors of UDP-galactopyranose mutase (UGM), an enzyme involved in the biosynthesis of the cell wall of Mycobacterium tuberculosis. In order to understand the binding mode, docking simulations are performed on the best inhibitors. Their activity on Mycobacterium tuberculosis is also evaluated. This study made it possible to highlight an "oxazepino-indole" structure as a new inhibitor of UGM and of M. tuberculosis growth in vitro., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)
- Published
- 2020
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26. The endogenous galactofuranosidase GlfH1 hydrolyzes mycobacterial arabinogalactan.
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Shen L, Viljoen A, Villaume S, Joe M, Halloum I, Chêne L, Méry A, Fabre E, Takegawa K, Lowary TL, Vincent SP, Kremer L, Guérardel Y, and Mariller C
- Subjects
- Amino Acid Sequence, Amoeba microbiology, Galactosyltransferases antagonists & inhibitors, Galactosyltransferases genetics, Hydrolysis, Kinetics, Phylogeny, Sequence Homology, Amoeba growth & development, Galactans metabolism, Galactosyltransferases metabolism, Mycobacterium tuberculosis enzymology
- Abstract
Despite impressive progress made over the past 20 years in our understanding of mycolylarabinogalactan-peptidoglycan (mAGP) biogenesis, the mechanisms by which the tubercle bacillus Mycobacterium tuberculosis adapts its cell wall structure and composition to various environmental conditions, especially during infection, remain poorly understood. Being the central portion of the mAGP complex, arabinogalactan (AG) is believed to be the constituent of the mycobacterial cell envelope that undergoes the least structural changes, but no reports exist supporting this assumption. Herein, using recombinantly expressed mycobacterial protein, bioinformatics analyses, and kinetic and biochemical assays, we demonstrate that the AG can be remodeled by a mycobacterial endogenous enzyme. In particular, we found that the mycobacterial GlfH1 (Rv3096) protein exhibits exo-β-d-galactofuranose hydrolase activity and is capable of hydrolyzing the galactan chain of AG by recurrent cleavage of the terminal β-(1,5) and β-(1,6)-Galf linkages. The characterization of this galactosidase represents a first step toward understanding the remodeling of mycobacterial AG., (© 2020 Shen et al.)
- Published
- 2020
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27. Osmotic Stress and ABA Affect Immune Response and Susceptibility of Grapevine Berries to Gray Mold by Priming Polyamine Accumulation.
- Author
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Hatmi S, Villaume S, Trotel-Aziz P, Barka EA, Clément C, and Aziz A
- Abstract
Abiotic factors inducing osmotic stress can affect plant immunity and resistance against pathogen attack. Although a number of studies have characterized grapevine responses to various forms of biotic and abiotic stresses, the relationships between osmotic stress response and susceptibility of mature berries to Botrytis cinerea still remain unknown. In this study, we investigated the effects of osmotic stress and abscisic acid (ABA) on defense responses of mature grapevine berries before and after B. cinerea infection. We focused on the possible involvement of polyamines in the interaction between osmotic stress response and susceptibility to B. cinerea . We showed that osmotic stress induced by PEG or sucrose, and exogenous ABA induce transient but low defense responses, including weak expression of PR genes and phytoalexin synthesis in mature berries. This was accompanied by an upregulation of NCED2 involved in ABA biosynthesis and a large production of free polyamines. However, osmotic stress followed by B. cinerea infection primed berries for enhanced accumulation of polyamines, but slowed down the defense responses and increased susceptibility to the pathogen. A weak increase of diamine- and polyamine-oxidase activities was also recorded in stressed berries, but declined after pathogen infection. The pretreatment of stressed berries with appropriate inhibitors of diamine- and polyamine-oxidases further increased polyamine level and greatly lowered defense responses, leading to higher susceptibility to B. cinerea . These results suggest that increased polyamine titer through low activation of their oxidative degradation in grape berries may contribute at least in part to the weakening of defense responses and subsequent disease susceptibility.
- Published
- 2018
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28. Synthetic Rhamnolipid Bolaforms trigger an innate immune response in Arabidopsis thaliana.
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Luzuriaga-Loaiza WP, Schellenberger R, De Gaetano Y, Obounou Akong F, Villaume S, Crouzet J, Haudrechy A, Baillieul F, Clément C, Lins L, Allais F, Ongena M, Bouquillon S, Deleu M, and Dorey S
- Subjects
- Green Chemistry Technology, Structure-Activity Relationship, Arabidopsis immunology, Glycolipids chemical synthesis, Glycolipids chemistry, Glycolipids pharmacology, Membranes, Artificial, Plant Immunity drug effects
- Abstract
Stimulation of plant innate immunity by natural and synthetic elicitors is a promising alternative to conventional pesticides for a more sustainable agriculture. Sugar-based bolaamphiphiles are known for their biocompatibility, biodegradability and low toxicity. In this work, we show that Synthetic Rhamnolipid Bolaforms (SRBs) that have been synthesized by green chemistry trigger Arabidopsis innate immunity. Using structure-function analysis, we demonstrate that SRBs, depending on the acyl chain length, differentially activate early and late immunity-related plant defense responses and provide local increase in resistance to plant pathogenic bacteria. Our biophysical data suggest that SRBs can interact with plant biomimetic plasma membrane and open the possibility of a lipid driven process for plant-triggered immunity by SRBs.
- Published
- 2018
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29. Different Arabidopsis thaliana photosynthetic and defense responses to hemibiotrophic pathogen induced by local or distal inoculation of Burkholderia phytofirmans.
- Author
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Su F, Villaume S, Rabenoelina F, Crouzet J, Clément C, Vaillant-Gaveau N, and Dhondt-Cordelier S
- Subjects
- Arabidopsis microbiology, Disease Resistance, Photosynthesis, Photosystem II Protein Complex, Plant Roots metabolism, Ribulose-Bisphosphate Carboxylase, Symbiosis, Arabidopsis metabolism, Arabidopsis Proteins metabolism, Burkholderia physiology, Gene Expression Regulation, Plant immunology, Plant Diseases microbiology, Pseudomonas syringae
- Abstract
Pathogen infection of plant results in modification of photosynthesis and defense mechanisms. Beneficial microorganisms are known to improve plant tolerance to stresses. Burkholderia phytofirmans PsJN (Bp), a beneficial endophytic bacterium, promotes growth of a wide range of plants and induces plant resistance against abiotic and biotic stresses such as coldness and infection by a necrotrophic pathogen. However, mechanisms underlying its role in plant tolerance towards (hemi)biotrophic invaders is still lacking. We thus decipher photosynthetic and defense responses during the interaction between Arabidopsis, Bp and the hemibiotrophic bacterium Pseudomonas syringae pv. tomato DC3000 (Pst). Different Bp inoculations allowed analyzes at both systemic and local levels. Despite no direct antibacterial action, our results showed that only local presence of Bp alleviates Pst growth in planta during the early stage of infection. Molecular investigations showed that seed inoculation of Bp, leading to a restricted presence in the root system, transiently primed PR1 expression after challenge with Pst but continuously primed PDF1.2 expression. Bacterization with Bp reduced Y(ND) but had no impact on PSII activity or RuBisCO accumulation. Pst infection caused an increase of Y(NA) and a decrease in ΦPSI, ETRI and in PSII activity, showed by a decrease in Fv/Fm, Y(NPQ), ΦPSII, and ETRII values. Inoculation with both bacteria did not display any variation in photosynthetic activity compared to plants inoculated with only Pst. Our findings indicated that the role of Bp here is not multifaceted, and relies only on priming of defense mechanisms but not on improving photosynthetic activity.
- Published
- 2017
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30. How Streptomyces anulatus Primes Grapevine Defenses to Cope with Gray Mold: A Study of the Early Responses of Cell Suspensions.
- Author
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Vatsa-Portugal P, Aziz A, Rondeau M, Villaume S, Morjani H, Clément C, and Ait Barka E
- Abstract
Gray mold, caused by Botrytis cinerea , is one of the most destructive diseases of grapevine and is controlled with an intense application of fungicides. As alternatives to chemicals, beneficial microbes may promote plant health by stimulating the plant's immune system. An actinomycete, Streptomyces anulatus S37, has been screened from the rhizosphere microbiome of healthy Vitis vinifera on the basis of its ability to promote grapevine growth and to induce resistance against various phytopathogens, including B. cinerea . However, molecular mechanisms involved locally after direct perception of these bacteria by plant cells still remain unknown. This study focuses on local defense events induced in grapevine cells during interactions with S. anulatus S37 before and after pathogen challenge. We demonstrated that S. anulatus S37 induced early responses including oxidative burst, extracellular alkalinization, activation of protein kinases, induction of defense gene expression and phytoalexin accumulation, but not the programmed cell death. Interestingly, upon challenge with the B. cinerea , the S. anulatus S37 primed grapevine cells for enhanced defense reactions with a decline in cell death. In the presence of the EGTA, a calcium channel inhibitor, the induced oxidative burst, and the protein kinase activity were inhibited, but not the extracellular alkalinization, suggesting that Ca
2+ may also contribute upstream to the induced defenses. Moreover, desensitization assays using extracellular pH showed that once increased by S. anulatus S37, cells became refractory to further stimulation by B. cinerea , suggesting that grapevine cells perceive distinctly beneficial and pathogenic microbes.- Published
- 2017
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31. Defense Responses in Grapevine (cv. Mourvèdre) after Inoculation with the Botryosphaeria Dieback Pathogens Neofusicoccum parvum and Diplodia seriata and Their Relationship with Flowering.
- Author
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Spagnolo A, Mondello V, Larignon P, Villaume S, Rabenoelina F, Clément C, and Fontaine F
- Subjects
- Gene Expression Profiling, Gene Expression Regulation, Plant, Ascomycota, Disease Resistance, Host-Pathogen Interactions, Plant Diseases microbiology, Vitis microbiology, Vitis physiology
- Abstract
As a result of the increasing economic impact of grapevine trunk diseases on viticulture worldwide, efficient and viable control strategies are urgently needed. However, understanding both plant-pathogen interactions and plant physiological changes related to these diseases is fundamental to such an achievement. In this study, we analyzed the effect of inoculation with the Botryosphaeria dieback fungal agents, Neofusicoccum parvum and Diplodia seriata , with and without inflorescence removal at the onset of G stage (separated clusters), I stage (flowering) and M stage (veraison). A measure of lesion size and real-time reverse-transcription polymerase chain reaction-based analysis were carried out. The results clearly show the importance of inflorescences in the development of lesions associated with Botryosphaeria dieback pathogens inoculated on green stems of adult vines, especially at the onset of flowering. At flowering, the biggest necroses were observed with the inflorescences present, as well as an activation of the studied defense responses. Thus, an ineffective response to the pathogen could be consistent with a possible metabolic reprogramming linked to the host phenophase.
- Published
- 2017
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32. 2-(Thienothiazolylimino)-1,3-thiazolidin-4-ones inhibit cell division cycle 25 A phosphatase.
- Author
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Huber-Villaume S, Revelant G, Sibille E, Philippot S, Morabito A, Dunand S, Chaimbault P, Bagrel D, Kirsch G, Hesse S, and Schohn H
- Subjects
- Breast Neoplasms drug therapy, Cell Proliferation drug effects, Female, Humans, Inhibitory Concentration 50, MCF-7 Cells, Molecular Structure, Thiazolidines chemical synthesis, Thiazolidines chemistry, Thiazolidines pharmacology, cdc25 Phosphatases antagonists & inhibitors
- Abstract
Cell division cycle dual phosphatases (CDC25) are essential enzymes that regulate cell progression in cell cycle. Three isoforms exist as CDC25A, B and C. Over-expression of each CDC25 enzyme is found in cancers of diverse origins. Thiazolidinone derivatives have been reported to display anti-proliferative activities, bactericidal activities and to reduce inflammation process. New 2-(thienothiazolylimino)-1,3-thiazolidin-4-ones were synthesized and evaluated as inhibitors of CDC25 phosphatase. Among the molecules tested, compound 6 inhibited CDC25A with an IC50 estimated at 6.2±1.0μM. The binding of thiazolidinone derivative 6 onto CDC25A protein was reversible. In cellulo, compound 6 treatment led to MCF7 and MDA-MB-231 cell growth arrest. To our knowledge, it is the first time that such 4-thiazolidinone derivatives are characterized as CDC25 potential inhibitor., (Copyright © 2016 Elsevier Ltd. All rights reserved.)
- Published
- 2016
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33. Burkholderia phytofirmans PsJN reduces impact of freezing temperatures on photosynthesis in Arabidopsis thaliana.
- Author
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Su F, Jacquard C, Villaume S, Michel J, Rabenoelina F, Clément C, Barka EA, Dhondt-Cordelier S, and Vaillant-Gaveau N
- Abstract
Several plant growth-promoting rhizobacteria (PGPR) are known to improve plant tolerance to multiple stresses, including low temperatures. However, mechanisms underlying this protection are still poorly understood. The aim of this study was to evaluate the role of the endophytic PGPR, Burkholderia phytofirmans strain PsJN (Bp PsJN), on Arabidopsis thaliana cold tolerance using photosynthesis parameters as physiological markers. Under standard conditions, our results indicated that Bp PsJN inoculation led to growth promotion of Arabidopsis plants without significant modification on photosynthesis parameters and chloroplast organization. However, bacterial colonization induced a cell wall strengthening in the mesophyll. Impact of inoculation modes (either on seeds or by soil irrigation) and their effects overnight at 0, -1, or -3°C, were investigated by following photosystem II (PSII) activity and gas exchanges. Following low temperatures stress, a decrease of photosynthesis parameters was observed. In addition, during three consecutive nights or days at -1°C, PSII activity was monitored. Pigment contents, RuBisCO protein abundance, expression of several genes including RbcS, RbcL, CBF1, CBF2, CBF3, ICE1, COR15a, and COR78 were evaluated at the end of exposure. To assess the impact of the bacteria on cell ultrastructure under low temperatures, microscopic observations were achieved. Results indicated that freezing treatment induced significant changes in PSII activity as early as the first cold day, whereas the same impact on PSII activity was observed only during the third cold night. The significant effects conferred by PsJN were differential accumulation of pigments, and reduced expression of RbcL and COR78. Microscopical observations showed an alteration/disorganization in A. thaliana leaf mesophyll cells independently of the freezing treatments. The presence of bacteria during the three successive nights or days did not significantly improved A. thaliana responses but prevented the plasmalemma disruption under freezing stress.
- Published
- 2015
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34. Pseudomonas fluorescens PTA-CT2 Triggers Local and Systemic Immune Response Against Botrytis cinerea in Grapevine.
- Author
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Gruau C, Trotel-Aziz P, Villaume S, Rabenoelina F, Clément C, Baillieul F, and Aziz A
- Subjects
- Cell Death, Gene Expression Regulation, Plant, Phenotype, Plant Diseases immunology, Plant Leaves immunology, Plant Leaves microbiology, Plant Roots immunology, Plant Roots microbiology, Up-Regulation, Vitis immunology, Phytoalexins, Botrytis physiology, Plant Diseases microbiology, Plant Immunity, Pseudomonas fluorescens physiology, Sesquiterpenes metabolism, Vitis microbiology
- Abstract
Although induced systemic resistance (ISR) is well-documented in the context of plant-beneficial bacteria interactions, knowledge about the local and systemic molecular and biochemical defense responses before or upon pathogen infection in grapevine is very scarce. In this study, we first investigated the capacity of grapevine plants to express immune responses at both above- and below-ground levels upon interaction with a beneficial bacterium, Pseudomonas fluorescens PTA-CT2. We then explored whether the extent of priming state could contribute to the PTA-CT2-induced ISR in Botrytis cinerea-infected leaves. Our data provide evidence that this bacterium colonized grapevine roots but not the above-ground plant parts and altered the plant phenotype that displayed multiple defense responses both locally and systemically. The grapevine roots and leaves exhibited distinct patterns of defense-related gene expression during root colonization by PTA-CT2. Roots responded faster than leaves and some responses were more strongly upregulated in roots than in leaves and vice versa for other genes. These responses appear to be associated with some induction of cell death in roots and a transient expression of HSR, a hypersensitive response-related gene in both local (roots) and systemic (leaves) tissues. However, stilbenic phytoalexin patterns followed opposite trends in roots compared with leaves but no phytoalexin was exuded during plant-bacterium interaction, suggesting that roots could play an important role in the transfer of metabolites contributing to immune response at the systemic level. Unexpectedly, in B. cinerea-infected leaves PTA-CT2-mediated ISR was accompanied in large part by a downregulation of different defense-related genes, including HSR. Only phytoalexins and glutathion-S-transferase 1 transcripts were upregulated, while the expression of anthocyanin biosynthetic genes was maintained at a higher level than the control. This suggests that decreased expression of HSR, as a marker of cell death, and activation of secondary metabolism pathways could be responsible for a reduced B. cinerea colonization capacity in bacterized plants.
- Published
- 2015
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35. Synthesis and biological evaluation of novel 2-heteroarylimino-1,3-thiazolidin-4-ones as potential anti-tumor agents.
- Author
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Revelant G, Huber-Villaume S, Dunand S, Kirsch G, Schohn H, and Hesse S
- Subjects
- Antineoplastic Agents chemical synthesis, Autophagy drug effects, Cell Cycle drug effects, Cell Line, Tumor, Chemistry Techniques, Synthetic, Drug Screening Assays, Antitumor, Humans, Inhibitory Concentration 50, Membrane Potential, Mitochondrial drug effects, Oxidation-Reduction, Structure-Activity Relationship, Thiazolidines chemistry, Antineoplastic Agents chemistry, Antineoplastic Agents pharmacology
- Abstract
A series of 35 heteroarylimino-1,3-thiazolidinones with three sites of functionalization were synthesized and their antiproliferative properties were studied. The in vitro screening by MTT assay was performed against five cancer cell lines (human colon cancer cell lines HT29, HCT116 and SW620 and breast cancer cell lines MCF7 and MDA-MB-231). It was observed that N3-substituted thiazolidinones had moderate activities whereas 5-benzylidene thiazolidinones showed promising activities. To investigate the mechanism of action, detailed biological studies of six selected compounds (those presenting the lower mitotic index) were carried out on the human colon cancer HT29 cell line. Cell cycle assay revealed that those compounds induced cell accumulation in G2/M and in subG0/G1 phases of cell cycle. Moreover, dissipation of mitochondria membrane potential was observed as well as redox changes in treated cells., (Copyright © 2015 Elsevier Masson SAS. All rights reserved.)
- Published
- 2015
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36. Drought stress tolerance in grapevine involves activation of polyamine oxidation contributing to improved immune response and low susceptibility to Botrytis cinerea.
- Author
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Hatmi S, Gruau C, Trotel-Aziz P, Villaume S, Rabenoelina F, Baillieul F, Eullaffroy P, Clément C, Ferchichi A, and Aziz A
- Subjects
- Amine Oxidase (Copper-Containing) metabolism, Homeostasis, Oxidation-Reduction, Oxidoreductases Acting on CH-NH Group Donors metabolism, Photosystem II Protein Complex metabolism, Plant Leaves enzymology, Plant Leaves genetics, Plant Leaves immunology, Plant Leaves physiology, Stress, Physiological, Vitis genetics, Vitis immunology, Polyamine Oxidase, Botrytis physiology, Droughts, Plant Immunity, Polyamines metabolism, Vitis microbiology, Vitis physiology
- Abstract
Environmental factors including drought stress may modulate plant immune responses and resistance to pathogens. However, the relationship between mechanisms of drought tolerance and resistance to pathogens remained unknown. In this study, the effects of drought stress on polyamine (PA) homeostasis and immune responses were investigated in two grapevine genotypes differing in their drought tolerance; Chardonnay (CHR), as sensitive and Meski (MSK), as tolerant. Under drought conditions, MSK plants showed the lowest leaf water loss and reduction of photosynthetic efficiency, and expressed a lower level of NCED2, a gene involved in abscisic acid biosynthesis, compared with CHR plants. The improved drought tolerance in MSK was also coincident with the highest change in free PAs and up-regulation of the genes encoding arginine decarboxylase (ADC), copper amine-oxidase (CuAO), and PA-oxidases (PAO) and their corresponding enzyme activities. MSK plants also accumulated the highest level of amino acids, including Arg, Glu, Gln, Pro, and GABA, emphasizing the participation of PA-related amino acid homeostasis in drought tolerance. Importantly, drought-tolerant plants also exhibited enhanced phytoalexin accumulation and up-regulation of PR genes, especially PR-2 and Chit4c, compared with the sensitive plants. This is consistent with a lower susceptibility of MSK than CHR to Botrytis cinerea. Data suggest a possible connection between water stress tolerance and immune response in grapevine. Pharmacological experiments revealed that under drought conditions CuAO and PAO pathways were involved in the regulation of photosynthetic efficiency, and also of immune response and resistance of grapevine to a subsequent pathogen attack. These results open new views to improve our understanding of crosstalk between drought tolerance mechanisms and immune response., (© The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)
- Published
- 2015
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37. Osmotic stress-induced polyamine oxidation mediates defence responses and reduces stress-enhanced grapevine susceptibility to Botrytis cinerea.
- Author
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Hatmi S, Trotel-Aziz P, Villaume S, Couderchet M, Clément C, and Aziz A
- Subjects
- Amine Oxidase (Copper-Containing) metabolism, Botrytis pathogenicity, Disease Susceptibility, Homeostasis, Osmotic Pressure, Oxidation-Reduction, Oxidoreductases Acting on CH-NH Group Donors metabolism, Plant Diseases microbiology, Plant Leaves enzymology, Plant Leaves immunology, Plant Leaves microbiology, Plant Leaves physiology, Plant Proteins genetics, Plant Proteins metabolism, Polyamines analysis, Polyethylene Glycols pharmacology, Sesquiterpenes analysis, Sesquiterpenes metabolism, Sucrose pharmacology, Vitis enzymology, Vitis microbiology, Vitis physiology, Phytoalexins, Polyamine Oxidase, Botrytis physiology, Gene Expression Regulation, Plant, Plant Diseases immunology, Plant Immunity, Polyamines metabolism, Vitis immunology
- Abstract
Abiotic factors inducing osmotic stress can influence the plant immune response and resistance to pathogen infections. In this study, the effect of polyethylene glycol (PEG)- and sucrose-induced osmotic stress on polyamine (PA) homeostasis and the basal immune response in grapevine plantlets before and after Botrytis cinerea infection was determined. Pharmacological approaches were also addressed to assess the contribution of osmotic stress-induced PA oxidation to the regulation of defence responses and the susceptibility of grapevine to B. cinerea. Following osmotic stress or pathogen infection, PA homeostasis was linked to enhanced activity of diamine oxidases (CuAO) and PA oxidases (PAO) and the production of 1,3-diaminopropane. These responses paralleled the accumulation of the main stilbenic phytoalexins, resveratrol and ε-viniferin and upregulation of gene transcripts including STS (a stilbene synthase), PR-2 (a β-1,3-glucanase), PR3-4c (acidic chitinase IV), and PR-5 (a thaumatin-like protein), as well as NCED2 involved in abscisic acid biosynthesis. It was also demonstrated that leaves pre-exposed to osmotic stress and later inoculated with B. cinerea showed enhanced PA accumulation and attenuation of CuAO and PAO activities. This was consistent with the impaired production of phytoalexins and transcript levels of defence- and stress-related genes following infection, and the enhanced susceptibility to B. cinerea. Pharmacological experiments revealed that, under osmotic stress conditions, CuAO and PAO were involved in PA homeostasis and in the regulation of defence responses. Specific inhibition of CuAO and PAO in osmotically stressed leaves strongly attenuated the induction of defence responses triggered by B. cinerea infection and enhanced susceptibility to the pathogen. Taken together, this study reveals a contribution of PA catabolism to the resistance state through modulation of immune response in grapevine following osmotic stress and/or after B. cinerea infection.
- Published
- 2014
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38. Evidence for an extracellular acid proteolytic activity secreted by living cells of Saccharomyces cerevisiae PlR1: impact on grape proteins.
- Author
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Younes B, Cilindre C, Villaume S, Parmentier M, Jeandet P, and Vasserot Y
- Subjects
- Enzyme Stability, Extracellular Space chemistry, Fermentation, Hydrogen-Ion Concentration, Hydrolysis, Molecular Weight, Peptide Hydrolases chemistry, Saccharomyces cerevisiae chemistry, Saccharomyces cerevisiae growth & development, Saccharomyces cerevisiae metabolism, Saccharomyces cerevisiae Proteins chemistry, Vitis chemistry, Extracellular Space enzymology, Peptide Hydrolases metabolism, Plant Proteins chemistry, Saccharomyces cerevisiae enzymology, Saccharomyces cerevisiae Proteins metabolism, Vitis microbiology
- Abstract
In this work, Saccharomyces cerevisiae PlR1, a strain isolated from Pinot noir grapes in the Champagne area, was shown to secrete an acid proteolytic activity against bovine serum albumin. This proteolytic activity was detectable in cell-free culture supernatants at the beginning of the exponential growth phase and increased with yeast growth. Using a zymography method, only one protease band with a molecular mass of 72 kDa was observed. This extracellular proteolytic activity was detected in the pH range from 2 to 4 with a maximal value at pH 2.5 and 38 °C and was completely inhibited by pepstatin A. The secretion of this protease did not need any protein inducer and seemed to be insensitive to nitrogen catabolic repression. S. cerevisiae PlR1 was also able to secrete this proteolytic activity during alcoholic fermentation, and it was found to be active against grape proteins, with a molecular mass around 25 kDa, at optimal conditions of 38 °C, pH 3.5.
- Published
- 2011
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39. Losses of dissolved CO2 through the cork stopper during Champagne aging: toward a multiparameter modeling.
- Author
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Liger-Belair G and Villaume S
- Subjects
- Kinetics, Solubility, Temperature, Carbon Dioxide chemistry, Models, Theoretical, Quercus, Wine
- Abstract
Measurements of dissolved CO(2) concentrations from Champagne bottles initially holding the same CO(2) level after having been elaborated (close to 11.5 g L(-1)), but having experienced different periods of aging after having been corked with natural cork stoppers, were done. Losses of dissolved CO(2) close to 3.5 g L(-1) experienced by the oldest Champagne samples aged for about 75 months were reported. This very significant loss of dissolved CO(2) was logically interpreted as a consequence of the continuous diffusion of gaseous CO(2) through the pores of the cork stopper. By combining the diffusion principle through a porous medium with Henry's law (which links the solubility of a gas species in a liquid medium with its partial pressure in the vapor phase), a multiparameter model was built that provides the dissolved CO(2) content found in Champagne during its whole aging period. Both Champagne temperature and bottle volume were found to be key parameters with regard to the kinetics of CO(2) losses through the cork.
- Published
- 2011
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40. Linear complex polarization propagator in a four-component Kohn-Sham framework.
- Author
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Villaume S, Saue T, and Norman P
- Abstract
An algorithm for the solution of the linear response equation in the random phase approximation is presented. All entities including frequency arguments, matrices, and vectors, are assumed to be complex, and it represents the core equation solver needed in complex polarization propagator approaches where nonstimulated relaxation channels are taken into account. Stability and robustness of the algorithm are demonstrated in applications regarding visible, ultraviolet, and x-ray spectroscopies. An implementation of the algorithm at the level of four-component relativistic, noncollinear, density functional theory for imaginary (but not complex) frequency arguments has been achieved and is used to determine the electric dipole dispersion interaction coefficients for the rubidium and cesium dimers. Our best estimates for the C(6) coefficients of Rb(2) and Cs(2) are equal to 14.0x10(3) and 21.9x10(3) a.u., respectively.
- Published
- 2010
- Full Text
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41. On the losses of dissolved CO(2) during champagne serving.
- Author
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Liger-Belair G, Bourget M, Villaume S, Jeandet P, Pron H, and Polidori G
- Subjects
- Diffusion, Solubility, Temperature, Carbon Dioxide chemistry, Carbonated Beverages analysis
- Abstract
Pouring champagne into a glass is far from being consequenceless with regard to its dissolved CO(2) concentration. Measurements of losses of dissolved CO(2) during champagne serving were done from a bottled Champagne wine initially holding 11.4 +/- 0.1 g L(-1) of dissolved CO(2). Measurements were done at three champagne temperatures (i.e., 4, 12, and 18 degrees C) and for two different ways of serving (i.e., a champagne-like and a beer-like way of serving). The beer-like way of serving champagne was found to impact its concentration of dissolved CO(2) significantly less. Moreover, the higher the champagne temperature is, the higher its loss of dissolved CO(2) during the pouring process, which finally constitutes the first analytical proof that low temperatures prolong the drink's chill and helps it to retain its effervescence during the pouring process. The diffusion coefficient of CO(2) molecules in champagne and champagne viscosity (both strongly temperature-dependent) are suspected to be the two main parameters responsible for such differences. Besides, a recently developed dynamic-tracking technique using IR thermography was also used in order to visualize the cloud of gaseous CO(2) which flows down from champagne during the pouring process, thus visually confirming the strong influence of champagne temperature on its loss of dissolved CO(2).
- Published
- 2010
- Full Text
- View/download PDF
42. Near sulfur L-edge X-ray absorption spectra of methanethiol in isolation and adsorbed on a Au(111) surface: a theoretical study using the four-component static exchange approximation.
- Author
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Villaume S, Ekström U, Ottosson H, and Norman P
- Abstract
The relativistic four-component static exchange approach for calculation of near-edge X-ray absorption spectra has been reviewed. Application of the method is made to the Au(111) interface and the adsorption of methanethiol by a study of the near sulfur L-edge spectrum. The binding energies of the sulfur 2p(1/2) and 2p(3/2) sublevels in methanethiol are determined to be split by 1.2 eV due to spin-orbit coupling, and the binding energy of the 2p(3/2) shell is lowered from 169.2 eV for the isolated system to 167.4 and 166.7-166.8 eV for methanethiol in mono- and di-coordinated adsorption sites, respectively (with reference to vacuum). In the near L-edge X-ray absorption fine structure spectrum only the sigma*(S-C) peak at 166 eV remains intact by surface adsorption, whereas transitions of predominantly Rydberg character are largely quenched in the surface spectra. The sigma*(S-H) peak of methanethiol is replaced by low-lying, isolated, sigma*(S-Au) peak(s), where the number of peaks in the latter category and their splittings are characteristic of the local bonding situation of the sulfur.
- Published
- 2010
- Full Text
- View/download PDF
43. Foaming properties of various Champagne wines depending on several parameters: grape variety, aging, protein and CO2 content.
- Author
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Cilindre C, Liger-Belair G, Villaume S, Jeandet P, and Marchal R
- Subjects
- Carbon Dioxide metabolism, Carbonated Beverages classification, Time Factors, Carbon Dioxide analysis, Carbonated Beverages analysis, Plant Proteins analysis, Vitis chemistry, Wine analysis
- Abstract
A comparison of the foaming parameters of various Champagne wines was undergone with two well distinct methods: (i) a classical gas-sparging method providing standardized but artificial effervescence conditions (the so-called Mosalux), and (ii) a computer assisted viewing equipment (CAVE), much closer to the real champagne tasting conditions. The latter one is the only apparatus which enables a thorough descriptive analysis of foam behavior, during the pouring process of a sparkling wine, and from the end of its pouring. Various Champagne wines elaborated from two grape varieties (Chardonnay and Pinot Meunier) and having experienced different aging-periods (15 months and 5 years) were analyzed and compared to a model sparkling wine, elaborated from a model base wine (devoid of grape colloids). The CO(2) and protein content was also investigated to discuss the foaming behavior of these wines. A significant loss of the CO(2) content during aging was observed and might be the reason for the worse foaming properties of the old champagnes, as determined with CAVE. It is worth noting that contradictory foaming parameters were obtained through the Mosalux method, which is indeed more intrusive than the CAVE, and finally far from the real champagne tasting conditions, since it requires filtration and champagne degassing prior experiment., (Copyright 2009 Elsevier B.V. All rights reserved.)
- Published
- 2010
- Full Text
- View/download PDF
44. CO2 volume fluxes outgassing from champagne glasses: the impact of champagne ageing.
- Author
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Liger-Belair G, Villaume S, Cilindre C, and Jeandet P
- Abstract
It was demonstrated that CO(2) volume fluxes outgassing from a flute poured with a young champagne (elaborated in 2007) are much higher than those outgassing from the same flute poured with an older champagne (elaborated in the early 1990s). The difference in dissolved-CO(2) concentrations between the two types of champagne samples was found to be a crucial parameter responsible for differences in CO(2) volume fluxes outgassing from one champagne to another. Nevertheless, it was shown that, for a given identical dissolved-CO(2) concentration in both champagne types, the CO(2) volume flux outgassing from the flute poured with the old champagne is, in average, significantly lower than that outgassing from the flute poured with the young one. Therefore, CO(2) seems to "escape" more easily from the young champagne than from the older one. The diffusion coefficient of CO(2) in both champagne types was pointed as a key parameter to thoroughly determine in the future, in order to unravel our experimental observation., (Copyright 2009 Elsevier B.V. All rights reserved.)
- Published
- 2010
- Full Text
- View/download PDF
45. Aromaticity changes along the lowest-triplet-state path for C=C bond rotation of annulenyl-substituted olefins probed by the electron localization function.
- Author
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Villaume S and Ottosson H
- Subjects
- Photochemistry, Quantum Theory, Alkenes chemistry, Carbon chemistry, Electrons, Hydrocarbons, Aromatic chemistry, Rotation
- Abstract
The pi-contribution to the electron localization function (ELF(pi)) was used to analyze changes in the aromaticity of annulenyl-substituted olefins in their lowest triplet state (T1) when the structure around the olefin C=C bond is twisted from planar to a structure (3p*) at which the planes of the two RR'C units are perpendicular. The ring closure bifurcation value and the range in the bifurcation values of the ELF(pi) basins serve as (anti)aromaticity indicators directly linked to the electronic structure. Both Hückel's 4n + 2 pi-electron rule for aromaticity in the singlet ground state (S0) and Baird's 4n pi-electron rule for aromaticity in the lowest pipi* triplet state are applied. Three olefins with S0 aromatic (T1 antiaromatic) substituents and four olefins with T1 aromatic (S0 antiaromatic) substituents were studied using the ELF(pi) topology at the OLYP/6-311G(d,p) density functional theory level. The changes in the substituent ELF(pi) bifurcation values upon rotation about the olefin bond in the T1 state reveal that aromatic character is recovered for the first three olefins and that it is reduced for the latter ones. These changes in aromatic character are reflected in the shapes of the T1 potential energy surfaces as a twist away from planar structures in olefins with T1 antiaromatic substituents is energetically favorable, but that in olefins with T1 aromatic substituents is unfavorable. Hence, aromaticity change is a driver for a photochemical reaction as for many ground-state reactions.
- Published
- 2009
- Full Text
- View/download PDF
46. CO2 volume fluxes outgassing from champagne glasses in tasting conditions: flute versus coupe.
- Author
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Liger-Belair G, Villaume S, Cilindre C, Polidori G, and Jeandet P
- Subjects
- Temperature, Carbon Dioxide analysis, Food Technology, Glass analysis, Wine analysis
- Abstract
Measurements of CO(2) fluxes outgassing from glasses containing a standard Champagne wine initially holding about 11.5 g L(-1) of dissolved CO(2) were presented, in tasting conditions, during the first 10 min following the pouring process. Experiments were performed at room temperature, with a flute and a coupe, respectively. The progressive loss of dissolved CO(2) concentration with time was found to be significantly higher in the coupe than in the flute, which finally constitutes the first analytical proof that the flute prolongs the drink's chill and helps it to retain its effervescence in contrast with the coupe. Moreover, CO(2) volume fluxes outgassing from the coupe were found to be much higher in the coupe than in the flute in the early moments following pouring, whereas this tendency reverses from about 3 min after pouring. Correlations were proposed between CO(2) volume fluxes outgassing from the flute and the coupe and their continuously decreasing dissolved CO(2) concentration. The contribution of effervescence to the global kinetics of CO(2) release was discussed and modeled by use of results developed over recent years. Due to a much shallower liquid level in the coupe, bubbles collapsing at the free surface of the coupe were found to be significantly smaller than those collapsing at the free surface of the flute, and CO(2) volume fluxes released by collapsing bubbles only were found to be approximately 60% smaller in the coupe than in the flute. Finally, the contributions of gas discharge by invisible diffusion through the free surface areas of the flute and coupe were also approached and compared for each type of drinking vessel.
- Published
- 2009
- Full Text
- View/download PDF
47. One step purification of the grape vacuolar invertase.
- Author
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Jégou S, Conreux A, Villaume S, Hovasse A, Schaeffer C, Cilindre C, Van Dorsselaer A, and Jeandet P
- Subjects
- Amino Acid Sequence, Chromatography, Ion Exchange, Electrophoresis, Polyacrylamide Gel, Molecular Sequence Data, Plant Extracts chemistry, Tandem Mass Spectrometry, beta-Fructofuranosidase chemistry, Vitis enzymology, beta-Fructofuranosidase isolation & purification
- Abstract
Invertase is a major protein of grape juice and wine. Accordingly, in order to study the biochemical and structural characteristics of this protein and for a better understanding of its physico-chemical properties, large amounts of the pure protein are needed. A simple method for the purification of the grape vacuolar invertase in a preparative-scale is described in this work. The grape protein was isolated and purified from must by ultrafiltration and anion exchange chromatography. The identification and purity determination of the grape invertase fraction were assessed by SDS-PAGE, and were then confirmed using nanoLC-chip-MS/MS analysis. The laboratory fractionation procedure presented in this work generated large quantities of pure grape vacuolar invertase from must.
- Published
- 2009
- Full Text
- View/download PDF
48. Kinetics of CO(2) fluxes outgassing from champagne glasses in tasting conditions: the role of temperature.
- Author
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Liger-Belair G, Villaume S, Cilindre C, and Jeandet P
- Subjects
- Humans, Kinetics, Temperature, Carbon Dioxide chemistry, Taste, Wine analysis
- Abstract
Measurements of CO(2) fluxes outgassing from a flute poured with a standard Champagne wine initially holding about 11 g L(-1) of dissolved CO(2) were presented, in tasting conditions, all along the first 10 min following the pouring process. Experiments were performed at three sets of temperature, namely, 4 degrees C, 12 degrees C, and 20 degrees C, respectively. It was demonstrated that the lower the champagne temperature, the lower CO(2) volume fluxes outgassing from the flute. Therefore, the lower the champagne temperature, the lower its progressive loss of dissolved CO(2) concentration with time, which constitutes the first analytical proof that low champagne temperatures prolong the drink's chill and helps retains its effervescence. A correlation was also proposed between CO(2) volume fluxes outgassing from the flute poured with champagne and its continuously decreasing dissolved CO(2) concentration. Finally, the contribution of effervescence to the global kinetics of CO(2) release was discussed and modeled by the use of results developed over recent years. The temperature dependence of the champagne viscosity was found to play a major role in the kinetics of CO(2) outgassing from a flute. On the basis of this bubbling model, the theoretical influence of champagne temperature on CO(2) volume fluxes outgassing from a flute was discussed and found to be in quite good accordance with our experimental results.
- Published
- 2009
- Full Text
- View/download PDF
49. On circular dichroism and the separation between chromophore and chiral center: the near carbon K-edge X-ray absorption and circular dichroism spectra of noradrenaline and L-DOPA.
- Author
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Villaume S and Norman P
- Subjects
- Carbon chemistry, Models, Chemical, Physical Phenomena, X-Rays, Circular Dichroism, Dopamine Agents chemistry, Levodopa chemistry, Neurotransmitter Agents chemistry, Norepinephrine chemistry
- Abstract
The near carbon K-edge X-ray absorption and circular dichroism spectra of noradrenaline (neutral and protonated forms) and L-DOPA (protonated form) have been determined with use of the complex polarization propagator method in conjunction with Kohn-Sham density functional theory. A Coulomb attenuated exchange-correlation functional and London atomic orbitals have been employed to address the issues of hole-electron interactions and gauge-origin dependence of the magnetic-dipole operator, respectively. Results show that the characteristics of the chromophore part of the circular dichroism spectra are shared for all three considered systems, whereas protonation qualitatively alters the part of the spectrum assigned to the chiral side chain. The comparatively larger spatial separation of chromophore and chiral center in L-DOPA inflicts larger differences in spectral intensities between the chromophore and chiral center part of the circular dichroism spectra., ((c) 2009 Wiley-Liss, Inc.)
- Published
- 2009
- Full Text
- View/download PDF
50. Triplet-state aromaticity of 4npi-electron monocycles: analysis of bifurcation in the pi contribution to the electron localization function.
- Author
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Villaume S, Fogarty HA, and Ottosson H
- Subjects
- Computer Simulation, Quantum Theory, Electrons, Hydrocarbons, Aromatic chemistry, Models, Chemical
- Abstract
The pi contribution to the electron localization function (ELF) is used to compare 4npi- and (4n+2)pi-electron annulenes, with particular focus on the aromaticity of 4npi-electron annulenes in their lowest triplet state. The analysis is performed on the electron density obtained at the level of OLYP density functional theory, as well as at the CCSD and CASSCF ab initio levels. Two criteria for aromaticity of all-carbon annulenes are set up: the span in the bifurcation values DeltaBV(ELF(pi)) should be small, ideally zero, and the bifurcation value for ring closure of the pi basin RCBV(ELF(pi)) should be high (> or = 0.7). On the basis of these criteria, nearly all 4npi-electron annulenes are aromatic in their lowest triplet states, similar to (4n+2)pi-electron annulenes in their singlet ground states. For singlet biradical cyclobutadiene and cyclooctatetraene constrained to D4h and D8h symmetry, respectively, the RCBV(ELF(pi)) at the CASSCF level is lower (0.531 and 0.745) than for benzene (0.853), even though they have equal proportions of alpha- and beta-electrons.
- Published
- 2008
- Full Text
- View/download PDF
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