Glycogenesis and glyconeogenesis from glutamine, lactate and glycerol support human macrophage functions.

Macrophages fight infection and ensure tissue repair, often operating at nutrient-poor wound sites. We investigated the ability of human macrophages to metabolize glycogen. We observed that the cytokines GM-CSF and M-CSF plus IL-4 induced glycogenesis and the accumulation of glycogen by monocyte-derived macrophages.

Combining Gas Exchange and Rapid Quenching of Leaf Tissue for Mass Spectrometry and NMR Analysis Using an External Chamber.

We describe here a method to study and manipulate photorespiration in intact illuminated leaves. When the CO/O mole fraction ratio changes, instant sampling is critical, to quench leaf metabolism and thus trace rapid metabolic modification due to gaseous conditions. To do so, we combine CO labeling and gas exchange, using a large custom leaf chamber to facilitate fast sampling by direct liquid nitrogen spraying.

Leaf day respiration involves multiple carbon sources and depends on previous dark metabolism.

Day respiration (R) is the metabolic, nonphotorespiratory process by which illuminated leaves liberate CO during photosynthesis. R is used routinely in photosynthetic models and is thus critical for calculations. However, metabolic details associated with R are poorly known, and this can be problematic to predict how R changes with environmental conditions and relates to night respiration.

The nitrate transporter-sensor MtNPF6.8 regulates the branched chain amino acid/pantothenate metabolic pathway in barrel medic (Medicago truncatula Gaertn.) root tip.

Nitrogen is the most limiting nutrient for plants, and it is preferentially absorbed in the form of nitrate by roots, which adapt to nitrate fluctuations by remodelling their architecture. Although core mechanisms of the response to nitrate availability are relatively well-known, signalling events controlling root growth and architecture have not all been identified, in particular in Legumes. However, the developmental effect of nitrate in Legumes is critical since external nitrate not only regulates root architecture but also N-fixing nodule development.

Phloem Sap Composition: What Have We Learnt from Metabolomics?

Phloem sap transport is essential for plant nutrition and development since it mediates redistribution of nutrients, metabolites and signaling molecules. However, its biochemical composition is not so well-known because phloem sap sampling is difficult and does not always allow extensive chemical analysis. In the past years, efforts have been devoted to metabolomics analyses of phloem sap using either liquid chromatography or gas chromatography coupled with mass spectrometry.

Experimental Evidence for Seed Metabolic Allometry in Barrel Medic ( Gaertn.).

Seed size is often considered to be an important trait for seed quality, i.e., vigour and germination performance.

Exact mass GC-MS analysis: Protocol, database, advantages and application to plant metabolic profiling.

Plant metabolomics has been used widely in plant physiology, in particular to analyse metabolic responses to environmental parameters. Derivatization (via trimethylsilylation and methoximation) followed by GC-MS metabolic profiling is a major technique to quantify low molecular weight, common metabolites of primary carbon, sulphur and nitrogen metabolism. There are now excellent opportunities for new generation analyses, using high resolution, exact mass GC-MS spectrometers that are progressively becoming relatively cheap.

Compound-Specific N/N Analysis of Amino Acid Trimethylsilylated Derivatives from Plant Seed Proteins.

Isotopic analyses of plant samples are now of considerable importance for food certification and plant physiology. In fact, the natural nitrogen isotope composition (δN) is extremely useful to examine metabolic pathways of N nutrition involving isotope fractionations. However, δN analysis of amino acids is not straightforward and involves specific derivatization procedures to yield volatile derivatives that can be analysed by gas chromatography coupled to isotope ratio mass spectrometry (GC-C-IRMS).

Grain carbon isotope composition is a marker for allocation and harvest index in wheat.

The natural C abundance (δ C) in plant leaves has been used for decades with great success in agronomy to monitor water-use efficiency and select modern cultivars adapted to dry conditions. However, in wheat, it is also important to find genotypes with high carbon allocation to spikes and grains, and thus with a high harvest index (HI) and/or low carbon losses via respiration. Finding isotope-based markers of carbon partitioning to grains would be extremely useful since isotope analyses are inexpensive and can be performed routinely at high throughput.

C Isotope Labelling to Follow the Flux of Photorespiratory Intermediates.

Measuring the carbon flux through metabolic pathways in intact illuminated leaves remains challenging because of, e.g., isotopic dilution by endogenous metabolites, the impossibility to reach isotopic steady state, and the occurrence of multiple pools.

Non-targeted C metabolite analysis demonstrates broad re-orchestration of leaf metabolism when gas exchange conditions vary.

It is common practice to manipulate CO and O mole fraction during gas-exchange experiments to suppress or exacerbate photorespiration, or simply carry out CO response curves. In doing so, it is implicitly assumed that metabolic pathways other than carboxylation and oxygenation are altered minimally. In the past few years, targeted metabolic analyses have shown that this assumption is incorrect, with changes in the tricarboxylic acid cycle, anaplerosis (phosphoenolpyruvate carboxylation), and nitrogen or sulphur assimilation.

Protein synthesis increases with photosynthesis via the stimulation of translation initiation.

Leaf protein synthesis is an essential process at the heart of plant nitrogen (N) homeostasis and turnover that preferentially takes place in the light, that is, when N and CO fixation occur. The carbon allocation to protein synthesis in illuminated leaves generally accounts for ca. 1 % of net photosynthesis.

Plant sulphur metabolism is stimulated by photorespiration.

Intense efforts have been devoted to describe the biochemical pathway of plant sulphur (S) assimilation from sulphate. However, essential information on metabolic regulation of S assimilation is still lacking, such as possible interactions between S assimilation, photosynthesis and photorespiration. In particular, does S assimilation scale with photosynthesis thus ensuring sufficient S provision for amino acids synthesis? This lack of knowledge is problematic because optimization of photosynthesis is a common target of crop breeding and furthermore, photosynthesis is stimulated by the inexorable increase in atmospheric CO.

Seed quality and carbon primary metabolism.

Improving seed quality is amongst the most important challenges of contemporary agriculture. In fact, using plant varieties with better germination rates that are more tolerant to stress during seedling establishment may improve crop yield considerably. Therefore, intense efforts are currently being devoted to improve seed quality in many species, mostly using genomics tools.

In vivo phosphoenolpyruvate carboxylase activity is controlled by CO and O mole fractions and represents a major flux at high photorespiration rates.

Phosphenolpyruvate carboxylase (PEPC)-catalysed fixation of bicarbonate to C acids is commonly believed to represent a rather small flux in illuminated leaves. In addition, its potential variation with O and CO is not documented and thus is usually neglected in gas-exchange studies. Here, we used quantitative NMR analysis of sunflower leaves labelled with CO (99% C) under controlled conditions and measured the amount of C found in the four C-atom positions in malate, the major product of PEPC activity.

Responses to K deficiency and waterlogging interact via respiratory and nitrogen metabolism.

K deficiency and waterlogging are common stresses that can occur simultaneously and impact on crop development and yield. They are both known to affect catabolism, with rather opposite effects: inhibition of glycolysis and higher glycolytic fermentative flux, respectively. But surprisingly, the effect of their combination on plant metabolism has never been examined precisely.

Carbon allocation to major metabolites in illuminated leaves is not just proportional to photosynthesis when gaseous conditions (CO and O ) vary.

In gas-exchange experiments, manipulating CO and O is commonly used to change the balance between carboxylation and oxygenation. Downstream metabolism (utilization of photosynthetic and photorespiratory products) may also be affected by gaseous conditions but this is not well documented. Here, we took advantage of sunflower as a model species, which accumulates chlorogenate in addition to sugars and amino acids (glutamate, alanine, glycine and serine).

Metabolomics analysis of postphotosynthetic effects of gaseous O on primary metabolism in illuminated leaves.

The response of underground plant tissues to O2 limitation is currently an important topic in crop plants since adverse environmental conditions (e.g. waterlogging) may cause root hypoxia and thus compromise plant growth.

Direct assessment of the metabolic origin of carbon atoms in glutamate from illuminated leaves using C-NMR.

Glutamate (Glu) is the cornerstone of nitrogen assimilation and photorespiration in illuminated leaves. Despite this crucial role, our knowledge of the flux to Glu de novo synthesis is rather limited. Here, we used isotopic labelling with CO and C-NMR analyses to examine the labelling pattern and the appearance of multi-labelled species of Glu molecules to trace the origin of C-atoms found in Glu.

Iron isotopes reveal distinct dissolved iron sources and pathways in the intermediate versus deep Southern Ocean.

As an essential micronutrient, iron plays a key role in oceanic biogeochemistry. It is therefore linked to the global carbon cycle and climate. Here, we report a dissolved iron (DFe) isotope section in the South Atlantic and Southern Ocean.

Concerted Changes in the Phosphoproteome and Metabolome Under Different CO2/O2 Gaseous Conditions in Arabidopsis Rosettes.

Considerable efforts are currently devoted to understanding the regulation of primary carbon metabolism in plant leaves, which is known to change dramatically with environmental conditions, e.g. during light/dark transitions.

In vivo stoichiometry of photorespiratory metabolism.

Photorespiration is a major light-dependent metabolic pathway that consumes oxygen and produces carbon dioxide. In the metabolic step responsible for carbon dioxide production, two molecules of glycine (equivalent to two molecules of O2) are converted into one molecule of serine and one molecule of CO2. Here, we use quantitative isotopic techniques to determine the stoichiometry of this reaction in sunflower leaves, and thereby the O2/CO2 stoichiometry of photorespiration.

Isotopic evidence for nitrogen exchange between autotrophic and heterotrophic tissues in variegated leaves.

Many plant species or cultivars form variegated leaves in which blades are made of green and white sectors. On the one hand, there is little photosynthetic CO2 assimilation in white tissue simply because of the lack of functional chloroplasts and thus, leaf white tissue is heterotrophic and fed by photosynthates exported by leaf green tissue. On the other hand, it has been previously shown that the white tissue is enriched in nitrogenous compounds such as amino acids and polyamines, which can, in turn, be remobilised upon nitrogen deficiency.

Differential CO2 effect on primary carbon metabolism of flag leaves in durum wheat (Triticum durum Desf.).

C sink/source balance and N assimilation have been identified as target processes conditioning crop responsiveness to elevated CO2 . However, little is known about phenology-driven modifications of C and N primary metabolism at elevated CO2 in cereals such as wheat. Here, we examined the differential effect of elevated CO2 at two development stages (onset of flowering, onset of grain filling) in durum wheat (Triticum durum, var.