Evaluation des émissions de nitrate par les champs pour la conception de projets de territoire et l’accompagnement de la transition en aires d’alimentation de captage

Since the 2000’s the policy for the protection of catchment areas is based on territorial action plan, thesuccess of which is assessed by practices analysis. This assessment is mobilized to estimate pollutants emissions from fields (according to the cropping system) and the ability to maintain a good water quality. The methods for assessment of nitrate emissions was studied in territorial diagnosis of agricultural pressures in the catchment area of Saint Memmie (Marne) and in the setting up of the action plan in Brienon (Yonne).Nitrogen measurements in soil and the reporting of biomass and nitrogen quantities for crops are organized in an “observatory” of practices and cultivated fields’ states. They remain the most appropriate tool to estimate nitrates emissions and nitrogen dynamics but also to mobilize local actors. Simulation tools like Syst’N have a complementary role in extrapolating emissions from measurements to the whole territory, estimating nitrate leaching and expected water quality, like in a dashboard. They are also used to evaluate new cropping systems and scenarios for the territory.Depuis les années 2000, la politique de protection des aires d'alimentation des captages (AAC) reposesur la réussite de plans d’actions territoriaux, évaluée par l’analyse des pratiques agricoles.Cette évaluation est mobilisée lors des diagnostics et de la conception du plan d’action, pour estimer lesémissions de polluants par les champs suivant leurs systèmes de culture, et la capacité du territoire àproduire de l’eau de qualité. Les méthodes d’évaluation des émissions de nitrate ont été étudiées dansle diagnostic territorial des pressions agricoles de l’AAC de Saint Memmie (Marne), puis dans laconstruction et la mise en oeuvre du plan d’action de l’AAC de Brienon (Yonne).Organisées via un « observatoire » des pratiques et des états des champs cultivés, les mesures d’azotedans le sol et les observations des biomasses et des quantités d’azote qu’elles contiennent, restent lesoutils les plus pertinents pour estimer les émissions de nitrates et la dynamique de l’azote comme pourmobiliser les agriculteurs et d’autres acteurs via des outils de médiation comme des « tours de plaine ».Les outils de simulation comme Syst’N ont un rôle complémentaire pour extrapoler les émissions denitrate au-delà des quelques champs faisant l’objet de mesures, pour estimer le montant du lessivage etla qualité de l’eau à attendre dans le territoire, par exemple dans un « tableau de bord » utile àl’apprentissage et à l’aide à la décision des acteurs du territoire. Enfin ces simulations restent aussiessentielles pour évaluer a priori les résultats à attendre de nouvelles façons de cultiver, ou d’unnouveau scénario de territoire

Resolving the Role of Plant Glutamate Dehydrogenase. I. in vivo Real Time Nuclear Magnetic Resonance Spectroscopy Experiments

In higher plants the glutamate dehydrogenase (GDH) enzyme catalyzes the reversible amination of 2-oxoglutarate to form glutamate, using ammonium as a substrate. For a better understanding of the physiological function of GDH either in ammonium assimilation or in the supply of 2-oxoglutarate, we used transgenic tobacco (Nicotiana tabacum L.) plants overexpressing the two genes encoding the enzyme. An in vivo real time 15N-nuclear magnetic resonance (NMR) spectroscopy approach allowed the demonstration that, when the two GDH genes were overexpressed individually or simultaneously, the transgenic plant leaves did not synthesize glutamate in the presence of ammonium when glutamine synthetase (GS) was inhibited. In contrast we confirmed that the primary function of GDH is to deaminate Glu. When the two GDH unlabeled substrates ammonium and Glu were provided simultaneously with either [15N]Glu or 15NH4+ respectively, we found that the ammonium released from the deamination of Glu was reassimilated by the enzyme GS, suggesting the occurrence of a futile cycle recycling both ammonium and Glu. Taken together, these results strongly suggest that the GDH enzyme, in conjunction with NADH-GOGAT, contributes to the control of leaf Glu homeostasis, an amino acid that plays a central signaling and metabolic role at the interface of the carbon and nitrogen assimilatory pathways. Thus, in vivo NMR spectroscopy appears to be an attractive technique to follow the flux of metabolites in both normal and genetically modified plants

Transcriptional Plasticity of Autophagy-Related Genes Correlates with the Genetic Response to Nitrate Starvation in Arabidopsis Thaliana

In eukaryotes, autophagy, a catabolic mechanism for macromolecule and protein recycling, allows the maintenance of amino acid pools and nutrient remobilization. For a better understanding of the relationship between autophagy and nitrogen metabolism, we studied the transcriptional plasticity of autophagy genes (ATG) in nine Arabidopsis accessions grown under normal and nitrate starvation conditions. The status of the N metabolism in accessions was monitored by measuring the relative expression of 11 genes related to N metabolism in rosette leaves. The transcriptional variation of the genes coding for enzymes involved in ammonium assimilation characterize the genetic diversity of the response to nitrate starvation. Starvation enhanced the expression of most of the autophagy genes tested, suggesting a control of autophagy at transcriptomic level by nitrogen. The diversity of the gene responses among natural accessions revealed the genetic variation existing for autophagy independently of the nutritive condition, and the degree of response to nitrate starvation. We showed here that the genetic diversity of the expression of N metabolism genes correlates with that of the ATG genes in the two nutritive conditions, suggesting that the basal autophagy activity is part of the integral response of the N metabolism to nitrate availability

Body fatness, muscle fat oxidative capacity and insulin sensitivity are affected by the volume of sport exercise rather than by overall daily activity

Body fatness, muscle fat oxidative capacity and insulin sensitivity are affected by the volume of sport exercise rather than by overall daily activity. 4. European Congress on Nutrtion and Health in the Elderly Peopl

Impact du volume de sport et de la dépense énergétique sur le contrôle de la masse grasse, de l’oxydation lipidique et de la capacité du muscle à oxyder les acides gras chez l’homme âgé

Impact du volume de sport et de la dépense énergétique sur le contrôle de la masse grasse, de l’oxydation lipidique et de la capacité du muscle à oxyder les acides gras chez l’homme âgé. 5. Journées Francophones de Nutrition (JFN

Muscle fat oxidative capacity is not impaired by age but by physical inactivity : association with insulin sensitivity

International audienceThe study aimed at determining whether aging and/or sedentariness impairs muscle fat oxidative capacity (OXFA) and whether this was associated with increased risk to develop insulin resistance. We first examined muscle mitochondrial functions, OXFA and insulin sensitivity (ISI; evaluated during an oral glucose tolerance test) in a cross-sectional study with 32 sedentary (S) and endurance-trained (T), young (Y) and elderly (E) men (24.2+/-2.6 vs. 66.6+/-3.2 yr). As for mitochondrial functions, OXFA was higher in T than in S but similar between age groups (SY 41.8+/-11.3, TY 68.0+/-17.7, SE 40.1+/-14.1, TE 73.1+/-20.1 palmitate x min(-1) x g wet tissue(-1); activity P<0.0001, age P=NS, activity x age P=NS). Similar results were obtained with ISI (SY 6.2+/-2.2, TY 11.4+/-4.4, SE 5.9+/-1.5, TE 11.0+/-3.5, activity P<0.001, age P=NS, activity x age P=NS). Stepwise regression showed that, among body composition, VO2max and muscle biochemical characteristics, OXFA was the main predictor of ISI (r=0.60, P<0.001). We subsequently showed in eight sedentary elderly subjects (63.5+/-3.3 yr) that OXFA and insulin sensitivity (measured using insulin clamp) improved in parallel after 8 weeks of endurance training (r=0.79, P<0.01). We concluded that mitochondrial functions, OXFA and ISI, are not impaired by age but by physical inactivity and are closely correlated

Impact of the genetic-environment interaction on the dynamic of nitrogen pools in arabidopsis

Mineral nutrient availability and in particular nitrogen abundance has a huge impact on plant fitness and yield, so that plants have developed sophisticated adaptive mechanisms to cope with environmental fluctuations. The vast natural variation existing among the individuals of a single species constitutes a great potential to decipher complex traits such as nutrient use efficiency. By using natural accessions of Arabidopsis thaliana that differ for their pattern of adaptation to nitrogen stress, we investigated the plant response to nitrate supplies ranging from 0.01 mM up to 50 mM nitrate. The biomass allocation and the different nitrogen pools in shoot and in roots were monitored to establish the nutrition status of each plant. Analysis of variation for these traits revealed genetic differences between accessions for their sensibility to nitrate availability and for their capacity to produce shoot biomass with the same nitrogen nutrition index. From the correlation matrix of all traits measured, a statistical model was formulated to predict the shoot projected area from the nitrate supply. The proposed model points out the importance of genetic variation with respect to the correlation between root thickness and amino acids content in roots. The model provides potential new targets in plant breeding for nitrogen use efficiency

Towards an in situ product recovery of bio-based 3-hydroxypropionic acid: influence of bioconversion broth components on membrane-assisted reactive extraction

International audienceBACKGROUND: Bioconversion broths are complex media with microorganisms that convert substrates into products in the presence of salts and nitrogen sources and that may release biomolecules. This paper deals with the impact of bioconversion broth components on the membrane‐based reactive extraction of 3‐hydroxypropionic acid (3‐HP) by tri‐n‐octylamine (TOA) in n‐decanol in preparation for an in situ product recovery. The focus here is on the influence of 3‐HP concentration (0.5–10 g L−1), initial pH of the solution (3–5) and presence of proteins and salts on the extraction yield and kinetics.RESULTS: It was found that reducing the initial acid concentration caused an acceleration of the extraction kinetics because of a higher extent of complexation with TOA. pH effects were dramatic, as enhancing the pH from 3 to 5 decreased the extraction yield from 74% to only 5% due to acid dissociation. Proteins were shown to have negligible impact on the extraction yield and kinetics, probably because of their negligible mass transfer resistance at the liquid–liquid interface compared with the membrane. Conversely, the presence of salts (potassium chloride and potassium biphosphate) was highly detrimental. The decrease in extraction yield was shown to be due to an anion exchange between the carboxylate anion of 3‐HP in the organic phase and the anion of the salt in the aqueous phase. Chloride ions had more impact than biphosphate ions.CONCLUSION: These results give valuable information for the implementation of a membrane‐based reactive extraction as an in situ product recovery process, suggesting recommendations for bioconversion tuning