Nitrogen nutrition effects on δC of plant respired CO are mostly caused by concurrent changes in organic acid utilisation and remobilisation.

Nitrogen (N) nutrition impacts on primary carbon metabolism and can lead to changes in δC of respired CO. However, uncertainty remains as to whether (1) the effect of N nutrition is observed in all species, (2) N source also impacts on respired CO in roots and (3) a metabolic model can be constructed to predict δC of respired CO under different N sources. Here, we carried out isotopic measurements of respired CO and various metabolites using two species (spinach, French bean) grown under different NH :NO ratios.

The marriage between stable isotope ecology and plant metabolomics - new perspectives for metabolic flux analysis and the interpretation of ecological archives.

Even though they share many thematical overlaps, plant metabolomics and stable isotope ecology have been rather separate fields mainly due to different mass spectrometry demands. New high-resolution bioanalytical mass spectrometers are now not only offering high-throughput metabolite identification but are also suitable for compound- and intramolecular position-specific isotope analysis in the natural isotope abundance range. In plant metabolomics, label-free metabolic pathway and metabolic flux analysis might become possible when applying this new technology.

Biochemical and biophysical drivers of the hydrogen isotopic composition of carbohydrates and acetogenic lipids.

The hydrogen isotopic composition (δH) of plant compounds is increasingly used as a hydroclimatic proxy; however, the interpretation of δH values is hampered by potential coeffecting biochemical and biophysical processes. Here, we studied δH values of water and carbohydrates in leaves and roots, and of leaf -alkanes, in two distinct tobacco () experiments. Large differences in plant performance and biochemistry resulted from (a) soil fertilization with varying nitrogen (N) species ratios and (b) knockout-induced starch deficiency.

Drought resistance and resilience of rhizosphere communities in forest soils from the cellular to ecosystem scale - insights from C pulse labeling.

The link between above- and belowground communities is a key uncertainty in drought and rewetting effects on forest carbon (C) cycle. In young beech model ecosystems and mature naturally dry pine forest exposed to 15-yr-long irrigation, we performed C pulse labeling experiments, one during drought and one 2 wk after rewetting, tracing tree assimilates into rhizosphere communities. The C pulses applied in tree crowns reached soil microbial communities of the young and mature forests one and 4 d later, respectively.

Water limitation intensity shifts carbon allocation dynamics in Scots pine mesocosms.

Background And Aims: Tree species worldwide suffer from extended periods of water limitation. These conditions not only affect the growth and vitality of trees but also feed back on the cycling of carbon (C) at the plant-soil interface. However, the impact of progressing water loss from soils on the transfer of assimilated C belowground remains unresolved.

Tracing NO formation in full-scale wastewater treatment with natural abundance isotopes indicates control by organic substrate and process settings.

Nitrous oxide (NO) dominates greenhouse gas emissions in wastewater treatment plants (WWTPs). Formation of NO occurs during biological nitrogen removal, involves multiple microbial pathways, and is typically very dynamic. Consequently, NO mitigation strategies require an improved understanding of nitrogen transformation pathways and their modulating controls.

Intramolecular carbon isotope signals reflect metabolite allocation in plants.

Stable isotopes at natural abundance are key tools to study physiological processes occurring outside the temporal scope of manipulation and monitoring experiments. Whole-molecule carbon isotope ratios (13C/12C) enable assessments of plant carbon uptake yet conceal information about carbon allocation. Here, we identify an intramolecular 13C/12C signal at tree-ring glucose C-5 and C-6 and develop experimentally testable theories on its origin.

A high-temperature water vapor equilibration method to determine non-exchangeable hydrogen isotope ratios of sugar, starch and cellulose.

The analysis of the non-exchangeable hydrogen isotope ratio (δ H ) in carbohydrates is mostly limited to the structural component cellulose, while simple high-throughput methods for δ H values of non-structural carbohydrates (NSC) such as sugar and starch do not yet exist. Here, we tested if the hot vapor equilibration method originally developed for cellulose is applicable for NSC, verified by comparison with the traditional nitration method. We set up a detailed analytical protocol and applied the method to plant extracts of leaves from species with different photosynthetic pathways (i.

Carbon flux around leaf-cytosolic glyceraldehyde-3-phosphate dehydrogenase introduces a 13C signal in plant glucose.

Within the plant and Earth sciences, stable isotope analysis is a versatile tool conveying information (inter alia) about plant physiological and paleoclimate variability across scales. Here, we identify a 13C signal (i.e.

Drought alters the carbon footprint of trees in soils-tracking the spatio-temporal fate of C-labelled assimilates in the soil of an old-growth pine forest.

Above and belowground compartments in ecosystems are closely coupled on daily to annual timescales. In mature forests, this interlinkage and how it is impacted by drought is still poorly understood. Here, we pulse-labelled 100-year-old trees with CO within a 15-year-long irrigation experiment in a naturally dry pine forest to quantify how drought regime affects the transfer and use of assimilates from trees to the rhizosphere and associated microbial communities.

Rethinking temperature effects on leaf growth, gene expression and metabolism: Diel variation matters.

Plants have evolved to grow under prominently fluctuating environmental conditions. In experiments under controlled conditions, temperature is often set to artificial, binary regimes with constant values at day and at night. This study investigated how such a diel (24 hr) temperature regime affects leaf growth, carbohydrate metabolism and gene expression, compared to a temperature regime with a field-like gradual increase and decline throughout 24 hr.

Rhizosphere activity in an old-growth forest reacts rapidly to changes in soil moisture and shapes whole-tree carbon allocation.

Drought alters carbon (C) allocation within trees, thereby impairing tree growth. Recovery of root and leaf functioning and prioritized C supply to sink tissues after drought may compensate for drought-induced reduction of assimilation and growth. It remains unclear if C allocation to sink tissues during and following drought is controlled by altered sink metabolic activities or by the availability of new assimilates.

Nitrate and ammonium differ in their impact on δC of plant metabolites and respired CO from tobacco leaves.

The carbon isotopic composition (δC) of foliage is often used as proxy for plant performance. However, the effect of vs. supply on δC of leaf metabolites and respired CO is largely unknown.

Improving the extraction and purification of leaf and phloem sugars for oxygen isotope analyses.

Rationale: The oxygen isotopic composition (here shown as the δ O value) of soluble sugars in leaves and phloem tissue holds valuable information about plant functions in response to climatic changes. However, δ O analysis of sugars is prone to error, and thoroughly tested methods are lacking.

Methods: We performed three experiments to test if sample preparation modifies the δ O values of sugars.

Invasive knotweed has greater nitrogen-use efficiency than native plants: evidence from a N pulse-chasing experiment.

Habitats with fluctuating resource conditions pose specific challenges to plants, and they often favor a small subset of species that includes exotic invaders. These species must possess a superior ability to capitalize on resource pulses through faster resource uptake or greater resource-use efficiency. We addressed this question in an experiment with invasive knotweed, a noxious invader of temperate ecosystems that is known to benefit from nutrient fluctuations.

Measurement precision and accuracy of high artificial enrichment N and C tracer samples.

Rationale: Oversaturation of the Faraday cup amplifiers of isotope ratio mass spectrometers when using tracers that are highly enriched in heavier isotopes (up to 99.9%) remains a major bottleneck to obtaining high-precision measurements. The memory effect plays a key role in reducing tracer sample measurement precision and accuracy.

Influence of starch deficiency on photosynthetic and post-photosynthetic carbon isotope fractionations.

Carbon isotope (13C) fractionations occurring during and after photosynthetic CO2 fixation shape the carbon isotope composition (δ13C) of plant material and respired CO2. However, responses of 13C fractionations to diel variation in starch metabolism in the leaf are not fully understood. Here we measured δ13C of organic matter (δ13COM), concentrations and δ13C of potential respiratory substrates, δ13C of dark-respired CO2 (δ13CR), and gas exchange in leaves of starch-deficient plastidial phosphoglucomutase (pgm) mutants and wild-type plants of four species (Arabidopsis thaliana, Mesembryanthemum crystallinum, Nicotiana sylvestris, and Pisum sativum).

Fcγ Receptor Type I (CD64)-Mediated Impairment of the Capacity of Dendritic Cells to Activate Specific CD8 T Cells by IgG-opsonized Friend Virus.

Dendritic cells (DCs) express Fcγ receptors (FcγRs) for the binding immune complexes (ICs) consisting of IgG and antigens (Ags). IC⁻FcγR interactions have been demonstrated to enhance activation and antigen-presenting functions of DCs. Utilizing Friend virus (FV), an oncogenic mouse retrovirus, we investigated the effect of IgG-opsonization of retroviral particles on the infection of DCs and the subsequent presentation of viral antigens by DCs to virus-specific CD8 T cells.

H-fractionations during the biosynthesis of carbohydrates and lipids imprint a metabolic signal on the δ H values of plant organic compounds.

Hydrogen (H) isotope ratio (δ H) analyses of plant organic compounds have been applied to assess ecohydrological processes in the environment despite a large part of the δ H variability observed in plant compounds not being fully elucidated. We present a conceptual biochemical model based on empirical H isotope data that we generated in two complementary experiments that clarifies a large part of the unexplained variability in the δ H values of plant organic compounds. The experiments demonstrate that information recorded in the δ H values of plant organic compounds goes beyond hydrological signals and can also contain important information on the carbon and energy metabolism of plants.

Periodontal Ehlers-Danlos Syndrome Is Caused by Mutations in C1R and C1S, which Encode Subcomponents C1r and C1s of Complement.

Periodontal Ehlers-Danlos syndrome (pEDS) is an autosomal-dominant disorder characterized by early-onset periodontitis leading to premature loss of teeth, joint hypermobility, and mild skin findings. A locus was mapped to an approximately 5.8 Mb region at 12p13.

Reassessment of the NH NO thermal decomposition technique for calibration of the N O isotopic composition.

Rationale: In the last few years, the study of N O site-specific nitrogen isotope composition has been established as a powerful technique to disentangle N O emission pathways. This trend has been accelerated by significant analytical progress in the field of isotope ratio mass spectrometry (IRMS) and more recently quantum cascade laser absorption spectroscopy (QCLAS).

Methods: The ammonium nitrate (NH NO ) decomposition technique provides a strategy to scale the N site-specific (SP ≡ δ N - δ N ) and bulk (δ N  = (δ N  + δ N )/2) isotopic composition of N O against the international standard for the N/ N isotope ratio (AIR-N ).

Metabolic Fate of the Carboxyl Groups of Malate and Pyruvate and their Influence on δ(13)C of Leaf-Respired CO2 during Light Enhanced Dark Respiration.

The enhanced CO2 release of illuminated leaves transferred into darkness, termed "light enhanced dark respiration (LEDR)", is often associated with an increase in the carbon isotope ratio of the respired CO2 (δ(13)CLEDR). The latter has been hypothesized to result from different respiratory substrates and decarboxylation reactions in various metabolic pathways, which are poorly understood so far. To provide a better insight into the underlying metabolic processes of δ(13)CLEDR, we fed position-specific (13)C-labeled malate and pyruvate via the xylem stream to leaves of species with high and low δ(13)CLEDR values (Halimium halimifolium and Oxalis triangularis, respectively).

Organic Reference Materials for Hydrogen, Carbon, and Nitrogen Stable Isotope-Ratio Measurements: Caffeines, n-Alkanes, Fatty Acid Methyl Esters, Glycines, L-Valines, Polyethylenes, and Oils.

An international project developed, quality-tested, and determined isotope-δ values of 19 new organic reference materials (RMs) for hydrogen, carbon, and nitrogen stable isotope-ratio measurements, in addition to analyzing pre-existing RMs NBS 22 (oil), IAEA-CH-7 (polyethylene foil), and IAEA-600 (caffeine). These new RMs enable users to normalize measurements of samples to isotope-δ scales. The RMs span a range of δ(2)H(VSMOW-SLAP) values from -210.

Measurement of oxygen isotope ratios ((18)O/(16)O) of aqueous O2 in small samples by gas chromatography/isotope ratio mass spectrometry.

Rationale: Oxygen isotope fractionation of molecular O2 is an important process for the study of aerobic metabolism, photosynthesis, and formation of reactive oxygen species. The latter is of particular interest for investigating the mechanism of enzyme-catalyzed reactions, such as the oxygenation of organic pollutants, which is an important detoxification mechanism.

Methods: We developed a simple method to measure the δ(18) O values of dissolved O2 in small samples using automated split injection for gas chromatography coupled to isotope ratio mass spectrometry (GC/IRMS).

Mutations in AP3D1 associated with immunodeficiency and seizures define a new type of Hermansky-Pudlak syndrome.

Genetic disorders affecting biogenesis and transport of lysosome-related organelles are heterogeneous diseases frequently associated with albinism. We studied a patient with albinism, neutropenia, immunodeficiency, neurodevelopmental delay, generalized seizures, and impaired hearing but with no mutation in genes so far associated with albinism and immunodeficiency. Whole exome sequencing identified a homozygous mutation in AP3D1 that leads to destabilization of the adaptor protein 3 (AP3) complex.