Metabolic and physiological adjustment of Suaeda maritima to combined salinity and hypoxia

BACKGROUND AND AIMS: Suaeda maritima is a halophyte commonly found on coastal wetlands in the intertidal zone. Due to its habitat S. maritima has evolved tolerance to high salt concentrations and hypoxic conditions in the soil caused by periodic flooding. In the present work, the adaptive mechanisms of S. maritima to salinity combined with hypoxia were investigated on a physiological and metabolic level. METHODS: To compare the adaptive mechanisms to deficient, optimal and stressful salt concentrations, S. maritima plants were grown in a hydroponic culture under low, medium and high salt concentrations. Additionally, hypoxic conditions were applied to investigate the impact of hypoxia combined with different salt concentrations. A non-targeted metabolic approach was used to clarify the biochemical pathways underlying the metabolic and physiological adaptation mechanisms of S. maritima . KEY RESULTS: Roots exposed to hypoxic conditions showed an increased level of tricarboxylic acid (TCA)-cycle intermediates such as succinate, malate and citrate. During hypoxia, the concentration of free amino acids increased in shoots and roots. Osmoprotectants such as proline and glycine betaine increased in concentrations as the external salinity was increased under hypoxic conditions. CONCLUSIONS: The combination of high salinity and hypoxia caused an ionic imbalance and an increase of metabolites associated with osmotic stress and photorespiration, indicating a severe physiological and metabolic response under these conditions. Disturbed proline degradation in the roots induced an enhanced proline accumulation under hypoxia. The enhanced alanine fermentation combined with a partial flux of the TCA cycle might contribute to the tolerance of S. maritima to hypoxic conditions

The Arabidopsis pop2-1 mutant reveals the involvement of GABA transaminase in salt stress tolerance

<p>Abstract</p> <p>Background</p> <p>GABA (γ-aminobutyric acid) is a non protein amino acid that has been reported to accumulate in a number of plant species when subjected to high salinity and many other environmental constraints. However, no experimental data are to date available on the molecular function of GABA and the involvement of its metabolism in salt stress tolerance in higher plants. Here, we investigated the regulation of GABA metabolism in <it>Arabidopsis thaliana </it>at the metabolite, enzymatic activity and gene transcription levels upon NaCl stress.</p> <p>Results</p> <p>We identified the GABA transaminase (GABA-T), the first step of GABA catabolism, as the most responsive to NaCl. We further performed a functional analysis of the corresponding gene <it>POP2 </it>and demonstrated that the previously isolated loss-of-function <it>pop2-1 </it>mutant was oversensitive to ionic stress but not to osmotic stress suggesting a specific role in salt tolerance. NaCl oversensitivity was not associated with overaccumulation of Na⁺and Cl^-but mutant showed a slight decrease in K⁺. To bring insights into <it>POP2 </it>function, a promoter-reporter gene strategy was used and showed that <it>POP2 </it>was mainly expressed in roots under control conditions and was induced in primary root apex and aerial parts of plants in response to NaCl. Additionally, GC-MS- and UPLC-based metabolite profiling revealed major changes in roots of <it>pop2-1 </it>mutant upon NaCl stress including accumulation of amino acids and decrease in carbohydrates content.</p> <p>Conclusions</p> <p>GABA metabolism was overall up-regulated in response to NaCl in <it>Arabidopsis</it>. Particularly, GABA-T was found to play a pivotal function and impairment of this step was responsible for a decrease in salt tolerance indicating that GABA catabolism was a determinant of <it>Arabidopsis </it>salt tolerance. GABA-T would act in salt responses in linking N and C metabolisms in roots.</p

a planned ancillary analysis of the coVAPid cohort

Funding: This study was supported in part by a grant from the French government through the «Programme Investissement d’Avenir» (I-SITE ULNE) managed by the Agence Nationale de la Recherche (coVAPid project). The funders of the study had no role in the study design, data collection, analysis, or interpreta tion, writing of the report, or decision to submit for publication.BACKGROUND: Patients with SARS-CoV-2 infection are at higher risk for ventilator-associated pneumonia (VAP). No study has evaluated the relationship between VAP and mortality in this population, or compared this relationship between SARS-CoV-2 patients and other populations. The main objective of our study was to determine the relationship between VAP and mortality in SARS-CoV-2 patients. METHODS: Planned ancillary analysis of a multicenter retrospective European cohort. VAP was diagnosed using clinical, radiological and quantitative microbiological criteria. Univariable and multivariable marginal Cox's regression models, with cause-specific hazard for duration of mechanical ventilation and ICU stay, were used to compare outcomes between study groups. Extubation, and ICU discharge alive were considered as events of interest, and mortality as competing event. FINDINGS: Of 1576 included patients, 568 were SARS-CoV-2 pneumonia, 482 influenza pneumonia, and 526 no evidence of viral infection at ICU admission. VAP was associated with significantly higher risk for 28-day mortality in SARS-CoV-2 (adjusted HR 1.70 (95% CI 1.16-2.47), p = 0.006), and influenza groups (1.75 (1.03-3.02), p = 0.045), but not in the no viral infection group (1.07 (0.64-1.78), p = 0.79). VAP was associated with significantly longer duration of mechanical ventilation in the SARS-CoV-2 group, but not in the influenza or no viral infection groups. VAP was associated with significantly longer duration of ICU stay in the 3 study groups. No significant difference was found in heterogeneity of outcomes related to VAP between the 3 groups, suggesting that the impact of VAP on mortality was not different between study groups. INTERPRETATION: VAP was associated with significantly increased 28-day mortality rate in SARS-CoV-2 patients. However, SARS-CoV-2 pneumonia, as compared to influenza pneumonia or no viral infection, did not significantly modify the relationship between VAP and 28-day mortality. CLINICAL TRIAL REGISTRATION: The study was registered at ClinicalTrials.gov, number NCT04359693.publishersversionpublishe

La sinapine: caracterisation analytique, genetique, et metabolique d'un facteur antinutritionnel des graines de colza (Brassica napus L

Available from INIST (FR), Document Supply Service, under shelf-number : T 84429 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Phénotypage métabolique des réponses aux stress abiotiques chez Arabidopsis thaliana (analyse fonctionnelle et intégrative du métabolome)

Les stress abiotiques (températures extrêmes, salinité, sécheresse) ont un impact négatif sur la croissance et le développement végétal et constituent un défi agronomique majeur. La compréhension des réponses mises en œuvre par différentes espèces de plantes est un volet incontournable de toute stratégie d'amélioration variétale, mais offre aussi un modèle de choix pour l'étude intégrative de mécanismes qui opèrent à différents niveaux d'organisation biologique, selon des modalités hautement régulées. L'abondance de collections de génotypes et le progrès des outils d'analyse moléculaires, couplés à des traitements bioinformatiques performants, ont ouvert la perspective de caractériser la plasticité phénotypique de plantes modèles à l'échelle génomique et dans un contexte environnemental dynamique. La métabolomique en particulier, définie comme l'analyse quantitative non ciblée des métabolites d'un échantillon biologique, accède au cœur de nombreux processus physiologiques tels que la nutrition, l'adaptation biochimique et ultrastructurale ou la signalétique cellulaire. Les travaux réalisés constituent une approche de la physiologie du stress chez l'espèce considérée sensible /Arabidopsis thaliana/, par l'analyse du métabolome primaire dans une perspective exploratoire, diagnostique et corrélative.Abiotic stresses (extreme temperatures, salinity, drought) impair plant growth and development and are important agronomic challenges. Understanding stress responses developed by various species contributes to crop improvement and also constitutes an interesting approach of integrated mechanisms operating at different organisation levels in highly regulated ways. Availability of genotypes collections, molecular analysis tools and efficient bioinformatics pave the way to phenotyping of model plants at the genomic scale, in relation with their environment. Metabolmics, defined as unbiaised, nontargeted and exhaustive analysis of metabolites in biological samples, provide new insights into physiological processes like nutrition, biochemical and structural adaptation or cell signalling. Present work is an exploratory, diagnostic and correlative approach of primary metablome in the stress sensitive species Arabidopsis thaliana.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Plant Metabolomics in full swing Preface

International audienc

Diversité génétique et sélection du cacaoyer (Theobroma cacao L.) au Cameroun (approches participative, phénotypique et moléculaire)

La diversité génétique du cacaoyer (Theobroma cacao L.) existant dans les plantations paysannes et dans les banques de gènes au Cameroun, a été étudiée à l aide de 12 marqueurs microsatellites et par des évaluations phénotypiques de caractères d intérêt agronomique. Les connaissances des producteurs sur le matériel végétal collectées dans le cadre d un programme de sélection participative, ont été comparées avec les données moléculaires phénotypiques. La caractérisation moléculaire de ce matériel montre que les accessions des producteurs et des banques de gènes sont génétiquement proches. Les accessions des banques de gènes appartiennent à trois grands groupes génétiques de l espèce, à savoir les Forastero haut-amazoniens (HA), les Forastero bas-amazoniens (BA) et les Trinitario (Tr). Six groupes de référence (Amelonado, criollo, Nana, Iquitos Mixed Calabacillo, Parinari et Scavina) supposés être à l origine des cacaoyers cultivés au Cameroun, expliqueraient la quasi-totalité de la diversité génétique des accessions des poducteurs. Les gènes du groupe Amelonado étaient les plus représentés dans le matériel des producteurs. Très peu d allèles spécifiques aux Scavina et Criollo ont été détectés dans ce matériel. La forte diversité moléculaire et phénotypique et la présence d allèles uniques parmi les accessions des producteurs montrent l existence d un potentiel de sélection dans ce matériel. Ce potentiel a été mis en évidence par l identificatin de plusieurs génotypes résistants à la pourriture des fruits, contrainte majeure de la cacaoculture au Cameroun. L évaluation de la résistance à cette maladie suggère également que les connaissances des producteurs sur le niveau de résistance au champ de leurs cacaoyers, peuvent être exploitées efficacement dans la sélection participative.Génétic diversity of cacao (Theobroma cacao L.) accessions in farmers field and genebanks in Cameroon was studied with 12 microsatellite markers and several phenotypic traits of agronomic interest. Knowledge of farmers on their planting material was collected within the framework of a participatory selection programme, and subsequently compared with molecular and phenotypic data. The molecular assessment of the arm accessions are closely related. GA beong to three main genetic groups of the cacao species : Upper Amazon Forastero (UA), Lower Amazon Forastero (LA) and Trinitario (Tr). The genetic diversity among FA could be largely explained by the contribution of six reference genomes (Amelonado, Criollo, Iquitos Mixed Calabacillo, Nanay, Parinari and Scavina) supposed to be at the origin of cultivated cacao populations in Cameroon. The genes from the Amelonado group predominated in the FA whereas those from Scavina and Criollo were less represented. The large molecular and phenotypic diversity and the presence of private alleles among FA show the potential for selection of this material. This potential was further demonstrated by the identification of several resistant genotypes among FA tested for resistance to Phytophtora pod rot (Ppr), the major cacao production constraint in the country. The results from Ppr evaluations suggest also that farmers knowledge on the field resistance of individual cacao trees might be exploited efficiently in the participatory breeding programme.RENNES-Agrocampus-CRD (352382323) / SudocSudocFranceF

U-13C-glucose incorporation into source leaves of Brassica napus highlights light-dependent regulations of metabolic fluxes within central carbon metabolism

International audiencePlant central carbon metabolism comprises several important metabolic pathways acting together to support plant growth and yield establishment. Despite the emergence of 13 C-based dynamic approaches, the regulation of metabolic fluxes between light and dark conditions has not yet received sufficient attention for agronomically relevant plants. Here, we investigated the impact of light/dark conditions on carbon allocation processes within central carbon metabolism of Brassica napus after U-13 C-glucose incorporation into leaf discs. Leaf gas-exchanges and metabolite contents were weakly impacted by the leaf disc method and the incorporation of glucose. 13 Canalysis by GC-MS showed that U-13 C-glucose was converted to fructose for de novo biosynthesis of sucrose at similar rates in both light and dark conditions. However, light conditions led to a reduced commitment of glycolytic carbons towards respiratory substrates (pyruvate, alanine, malate) and TCA cycle intermediates compared to dark conditions. Analysis of 13 C-enrichment at the isotopologue level and metabolic pathway isotopic tracing reconstructions identified the contribution of multiple pathways to serine biosynthesis in light and dark conditions. However, the direct contribution of the glucose-6-phosphate shunt to serine biosynthesis was not observed. Our results also provided isotopic evidences for an active metabolic connection between the TCA cycle, glycolysis and photorespiration in light conditions through a rapid reallocation of TCA cycle decarboxylations back to the TCA cycle through photorespiration and glycolysis. Altogether, these results suggest the active coordination of core metabolic pathways across multiple compartments to reorganize C-flux modes