Arabidopsis thaliana plants challenged with uranium reveal new insights into iron and phosphate homeostasis.

Uranium (U) is a naturally occurring radionuclide that is toxic to plants. It is known to interfere with phosphate nutrition and to modify the expression of iron (Fe)-responsive genes. The transporters involved in the uptake of U from the environment are unknown.

Performance and Limitations of Phosphate Quantification: Guidelines for Plant Biologists.

Phosphate (Pi) is a macronutrient that is essential for plant life. Several regulatory components involved in Pi homeostasis have been identified, revealing a very high complexity at the cellular and subcellular levels. Determining the Pi content in plants is crucial to understanding this regulation, and short real-time(33)Pi uptake imaging experiments have shown Pi movement to be highly dynamic.

ESCRT-III-Associated Protein ALIX Mediates High-Affinity Phosphate Transporter Trafficking to Maintain Phosphate Homeostasis in Arabidopsis.

Prior to the release of their cargoes into the vacuolar lumen, sorting endosomes mature into multivesicular bodies (MVBs) through the action of ENDOSOMAL COMPLEX REQUIRED FOR TRANSPORT (ESCRT) protein complexes. MVB-mediated sorting of high-affinity phosphate transporters (PHT1) to the vacuole limits their plasma membrane levels under phosphate-sufficient conditions, a process that allows plants to maintain phosphate homeostasis. Here, we describe ALIX, a cytosolic protein that associates with MVB by interacting with ESCRT-III subunit SNF7 and mediates PHT1;1 trafficking to the vacuole in Arabidopsis thaliana.

In vivo spectroscopy and NMR metabolite fingerprinting approaches to connect the dynamics of photosynthetic and metabolic phenotypes in resurrection plant Haberlea rhodopensis during desiccation and recovery.

The resurrection plant Haberlea rhodopensis was used to study dynamics of drought response of photosynthetic machinery parallel with changes in primary metabolism. A relation between leaf water content and photosynthetic performance was established, enabling us to perform a non-destructive evaluation of the plant water status during stress. Spectroscopic analysis of photosynthesis indicated that, at variance with linear electron flow (LEF) involving photosystem (PS) I and II, cyclic electron flow around PSI remains active till almost full dry state at the expense of the LEF, due to the changed protein organization of photosynthetic apparatus.

Energetic coupling between plastids and mitochondria drives CO2 assimilation in diatoms.

Diatoms are one of the most ecologically successful classes of photosynthetic marine eukaryotes in the contemporary oceans. Over the past 30 million years, they have helped to moderate Earth's climate by absorbing carbon dioxide from the atmosphere, sequestering it via the biological carbon pump and ultimately burying organic carbon in the lithosphere. The proportion of planetary primary production by diatoms in the modern oceans is roughly equivalent to that of terrestrial rainforests.

Interplay of Mg2+, ADP, and ATP in the cytosol and mitochondria: unravelling the role of Mg2+ in cell respiration.

In animal and plant cells, the ATP/ADP ratio and/or energy charge are generally considered key parameters regulating metabolism and respiration. The major alternative issue of whether the cytosolic and mitochondrial concentrations of ADP and ATP directly mediate cell respiration remains unclear, however. In addition, because only free nucleotides are exchanged by the mitochondrial ADP/ATP carrier, whereas MgADP is the substrate of ATP synthase (EC 3.

Corrigendum to: Metabolomic characterisation of the functional division of nitrogen metabolism in variegated leaves.

Many horticultural and natural plant species have variegated leaves, that is, patchy leaves with green and non-green or white areas. Specific studies on the metabolism of variegated leaves are scarce and although white (non-green) areas have been assumed to play the role of a 'nitrogen store', there is no specific studies showing the analysis of nitrogenous metabolites and the dynamics of nitrogen assimilation. Here, we examined the metabolism of variegated leaves of Pelargonium × hortorum.

An overview of the metabolic differences between Bradyrhizobium japonicum 110 bacteria and differentiated bacteroids from soybean (Glycine max) root nodules: an in vitro 13C- and 31P-nuclear magnetic resonance spectroscopy study.

Bradyrhizobium japonicum is a symbiotic nitrogen-fixing soil bacteria that induce root nodules formation in legume soybean (Glycine max.). Using (13)C- and (31)P-nuclear magnetic resonance (NMR) spectroscopy, we have analysed the metabolite profiles of cultivated B.

D2O solvent isotope effects suggest uniform energy barriers in ribulose-1,5-bisphosphate carboxylase/oxygenase catalysis.

d-Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the most abundant enzyme on Earth and is responsible for the fixation of atmospheric CO(2) into biomass. The reaction consists of incorporation of CO(2) and solvent H(2)O into d-ribulose 1,5-bisphosphate (RuBP) to yield 3-phospho-d-glycerate. The reaction involves several proton-dependent events: abstraction and protonation during enolization of RuBP and hydrolysis and reprotonation of the six-carbon reaction intermediate (carboxyketone).

Metabolomic characterisation of the functional division of nitrogen metabolism in variegated leaves.

Many horticultural and natural plant species have variegated leaves, that is, patchy leaves with green and non-green or white areas. Specific studies on the metabolism of variegated leaves are scarce and although white (non-green) areas have been assumed to play the role of a 'nitrogen store', there is no specific studies showing the analysis of nitrogenous metabolites and the dynamics of nitrogen assimilation. Here, we examined the metabolism of variegated leaves of Pelargonium×hortorum.

Short-term effects of CO(2) and O(2) on citrate metabolism in illuminated leaves.

Although there is now a considerable literature on the inhibition of leaf respiration (CO(2) evolution) by light, little is known about the effect of other environmental conditions on day respiratory metabolism. In particular, CO(2) and O(2) mole fractions are assumed to cause changes in the tricarboxylic acid pathway (TCAP) but the amplitude and even the direction of such changes are still a matter of debate. Here, we took advantage of isotopic techniques, new simple equations and instant freeze sampling to follow respiratory metabolism in illuminated cocklebur leaves (Xanthium strumarium L.

A simple and efficient method for the long-term preservation of plant cell suspension cultures.

Background: The repeated weekly subculture of plant cell suspension is labour intensive and increases the risk of variation from parental cells lines. Most of the procedures to preserve cultures are based on controlled freezing/thawing and storage in liquid nitrogen. However, cells viability after unfreezing is uncertain.

Massive production of butanediol during plant infection by phytopathogenic bacteria of the genera Dickeya and Pectobacterium.

Plant pathogenic bacteria of the genera Dickeya and Pectobacterium are broad-host-range necrotrophs which cause soft-rot diseases in important crops. A metabolomic analysis, based on (13)C-NMR spectroscopy, was used to characterize the plant-bacteria interaction. Metabolic profiles revealed a decline in plant sugars and amino acids during infection and the concomitant appearance of a compound identified as 2,3-butanediol.

The significance of glutathione for photoprotection at contrasting temperatures in the alpine plant species Soldanella alpina and Ranunculus glacialis.

The significance of total glutathione content was investigated in two alpine plant species with highly differing antioxidative scavenging capacity. Leaves of Soldanella alpina and Ranunculus glacialis incubated for 48 h in the presence of buthionine-sulfoximine had 50% lower glutathione contents when compared with leaves incubated in water. The low leaf glutathione content was not compensated for by activation of other components involved in antioxidative protection or electron consumption.

Experimental evidence of phosphoenolpyruvate resynthesis from pyruvate in illuminated leaves.

Day respiration is the cornerstone of nitrogen assimilation since it provides carbon skeletons to primary metabolism for glutamate (Glu) and glutamine synthesis. However, recent studies have suggested that the tricarboxylic acid pathway is rate limiting and mitochondrial pyruvate dehydrogenation is partly inhibited in the light. Pyruvate may serve as a carbon source for amino acid (e.

Changes in carbohydrate metabolism in Plasmopara viticola-infected grapevine leaves.

The oomycete Plasmopara viticola is responsible for downy mildew, a severe grapevine disease. In infected grapevine leaves, we have observed an abnormal starch accumulation at the end of the dark period, suggesting modifications in starch metabolism. Therefore, several complementary approaches, including transcriptomic analyses, measurements of enzyme activities, and sugar quantification, were performed in order to investigate and to understand the effects of P.

Measurement of carbon flux through the MEP pathway for isoprenoid synthesis by (31)P-NMR spectroscopy after specific inhibition of 2-C-methyl-d-erythritol 2,4-cyclodiphosphate reductase. Effect of light and temperature.

The methylerythritol 4-phosphate (MEP) and the mevalonate pathways are the unique synthesis routes for the precursors of all isoprenoids. An original mean to measure the carbon flux through the MEP pathway in plants is proposed by using cadmium as a total short-term inhibitor of 2-C-methyl-d-erythritol 2,4-cyclodiphosphate (MEcDP) reductase (GcpE) and measuring the accumulation rate of its substrate MEcDP by (31) P-NMR spectroscopy. The MEP pathway metabolic flux was determined in spinach (Spinacia oleracea), pea (Pisum sativum), Oregon grape (Mahonia aquifolium) and boxwood (Buxus sempervirens) leaves.

Over-expression of PHO1 in Arabidopsis leaves reveals its role in mediating phosphate efflux.

Inorganic phosphate (Pi) homeostasis in multi-cellular eukaryotes depends not only on Pi influx into cells, but also on Pi efflux. Examples in plants for which Pi efflux is crucial are transfer of Pi into the xylem of roots and release of Pi at the peri-arbuscular interface of mycorrhizal roots. Despite its importance, no protein has been identified that specifically mediates phosphate efflux either in animals or plants.

Uncoupling phosphate deficiency from its major effects on growth and transcriptome via PHO1 expression in Arabidopsis.

Inorganic phosphate (Pi) is one of the most limiting nutrients for plant growth in both natural and agricultural contexts. Pi-deficiency leads to a strong decrease in shoot growth, and triggers extensive changes at the developmental, biochemical and gene expression levels that are presumably aimed at improving the acquisition of this nutrient and sustaining growth. The Arabidopsis thaliana PHO1 gene has previously been shown to participate in the transport of Pi from roots to shoots, and the null pho1 mutant has all the hallmarks associated with shoot Pi deficiency.

Early response of plant cell to carbon deprivation: in vivo 31P-NMR spectroscopy shows a quasi-instantaneous disruption on cytosolic sugars, phosphorylated intermediates of energy metabolism, phosphate partitioning, and intracellular pHs.

• In plant cells, sugar starvation triggers a cascade of effects at the scale of 1-2 days. However, very early metabolic response has not yet been investigated. • Soluble phosphorus (P) compounds and intracellular pHs were analysed each 2.

Metabolic and structural rearrangement during dark-induced autophagy in soybean (Glycine max L.) nodules: an electron microscopy and 31P and 13C nuclear magnetic resonance study.

The effects of dark-induced stress on the evolution of the soluble metabolites present in senescent soybean (Glycine max L.) nodules were analysed in vitro using (13)C- and (31)P-NMR spectroscopy. Sucrose and trehalose were the predominant soluble storage carbons.

Novel insights into mannitol metabolism in the fungal plant pathogen Botrytis cinerea.

In order to redefine the mannitol pathway in the necrotrophic plant pathogen Botrytis cinerea, we used a targeted deletion strategy of genes encoding two proteins of mannitol metabolism, BcMTDH (B. cinerea mannitol dehydrogenase) and BcMPD (B. cinerea mannitol-1-phosphate dehydrogenase).

In folio isotopic tracing demonstrates that nitrogen assimilation into glutamate is mostly independent from current CO2 assimilation in illuminated leaves of Brassica napus.

*Nitrogen assimilation in leaves requires primary NH(2) acceptors that, in turn, originate from primary carbon metabolism. Respiratory metabolism is believed to provide such acceptors (such as 2-oxoglutarate), so that day respiration is commonly seen as a cornerstone for nitrogen assimilation into glutamate in illuminated leaves. However, both glycolysis and day respiratory CO(2) evolution are known to be inhibited by light, thereby compromising the input of recent photosynthetic carbon for glutamate production.

Effects of copper on the photosynthesis of intact chloroplasts: interaction with manganese.

Highly purified, intact chloroplasts were prepared from pea (Pisum sativum L.) and spinach (Spinacia oleracea L.) following an identical procedure, and were used to investigate the cupric cation inhibition on the photosynthetic activity.