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Thiamin diphosphate (TPP, vitamin B1 ) is an essential coenzyme present in all organisms. Animals obtain TPP from their diets, but plants synthesize TPPde novo. We isolated and characterized an Arabidopsis pale green1 (pale1) mutant that contained higher concentrations of thiamin monophosphate (TMP) and less thiamin and TPP than the wild type. Supplementation with thiamin, but not the thiazole and pyrimidine precursors, rescued the mutant phenotype, indicating that the pale1 mutant is a thiamin-deficient mutant. Map-based cloning and whole-genome sequencing revealed that the pale1 mutant has a mutation in At5g32470 encoding a TMP phosphatase of the TPP biosynthesis pathway. We further confirmed that the mutation of At5g32470 is responsible for the mutant phenotypes by complementing the pale1 mutant with constructs overexpressing full-length At5g32470. Most plant TPP biosynthetic enzymes are located in the chloroplasts and cytosol, but At5g32470-GFP localized to the mitochondrion of the root, hypocotyl, mesophyll and guard cells of the 35S:At5g32470-GFP complemented plants. The subcellular localization of a functional TMP phosphatase suggests that the complete vitamin B1 biosynthesis pathway may involve the chloroplasts, mitochondria and cytosol in plants. Analysis of PALE1 promoter-uidA activity revealed that PALE1 is mainly expressed in vascular tissues of Arabidopsis seedlings. Quantitative RT-PCR analysis of TPP biosynthesis genes and genes encoding the TPP-dependent enzymes pyruvate dehydrogenase, α-ketoglutarate dehydrogenase and transketolase revealed that the transcript levels of these genes were upregulated in the pale1 mutant. These results suggest that endogenous levels of TPP may affect the expression of genes involved in TPP biosynthesis and TPP-dependent enzymes.

The ACT domain (aspartate kinase, chorismate mutase and TyrA), an allosteric effector binding domain, is commonly found in amino acid metabolic enzymes. In addition to ACT domain-containing enzymes, plants have a novel family of ACT domain repeat (ACR) proteins, which do not contain any recognizable catalytic domain. Arabidopsis has 12 ACR proteins, whose functions are largely unknown. To study the functions of Arabidopsis ACR11, we have characterized two independent T-DNA insertion mutants, acr11-2 and acr11-3. RNA gel-blot analysis revealed that the expression of wild-type ACR11 transcripts was not detectable in the acr11 mutants. Interestingly, a lesion-mimic phenotype occurs in some rosette leaves of the acr11 mutants. In addition, high levels of reactive oxygen species (ROS), salicylic acid (SA), and callose accumulate in the mutant leaves when grown under normal conditions. The expression of several SA marker genes and the key SA biosynthetic gene ISOCHORISMATE SYNTHASE1 is up-regulated in the acr11 mutants. Furthermore, the acr11 mutants are more resistant to the infection of bacterial pathogen Pseudomonas syringae pathovar tomato DC3000. These results suggest that ACR11 may be directly or indirectly involved in the regulation of ROS and SA accumulation, which in turn modulates SA-associated defense responses and disease resistance in Arabidopsis.

In this study a two-dimensional graphene sheet (GS) doped with palladium (Pd) nanoparticles was physically mixed with a superactivated carbon (AC) receptor and used as a hydrogen adsorbent. The hydrogen adsorption/desorption isotherm of the Pd-doped GS catalyst/AC composite (Pd-GS/AC) is determined using a static volumetric measurement at room temperature (RT) and pressure up to 8 MPa. The experiments show that the H 2 uptake capacity of 0.82wt.% for Pd-GS/AC is obviously enhanced, measuring 49% more than the 0.55wt.% for Pd-free GS/AC at RT and 8 MPa. Highly reversible behavior of Pd-GS/AC is also observed. Moreover, the isosteric heat of adsorption for Pd-GS/AC (−14 to −10 kJ/mol) is higher than that for pristine AC (−8 kJ/mol). An increase in H 2 uptake in the Pd-GS/AC suggests the occurrence of a relatively strong interaction between the spilt-over H and the receptor sites due to the spillover effect.

This study demonstrates that the hydrogen storage rate (HSR) of nanoporous carbon supported platinum nanocatalysts (NC) is determined by their heterojunction and geometric configurations. The present NC is synthesized in an average particle size of ~1.5 nm by incipient wetness impregnation of Pt4+ at carbon support followed by annealing in H2 ambient at 102–105 °C. Among the steps in hydrogen storage, decomposition of H2 molecule into 2 H atoms on Pt NC surface is the deciding factor in HSR that is controlled by the thickness of Pt NC. For the best condition, HSR of Pt NC in 1~2 atomic layers thick (4.7 μg/g min) is 2.6 times faster than that (1.3 μg/g min) of Pt NC with higher than 3 atomic layers thick.

Thiamin diphosphate (TPP, vitamin B

Glutamate is a precursor for many important molecules in plants. Figure S2. Amino acid contents of 17-day-old rice seedlings. Figure S3. Regulation of glutamate-responsive genes by different concentrations of glutamate. Figure S4. Effects of different nitrogen treatments on the expression of glutamate-responsive genes. Table S1. Effects of exogenous glutamate treatment on endogenous amino acid content in rice roots. Table S2. List of glutamate up-regulated genes in representative functional categories derived from gene ontology (GO) enrichment analysis. Table S3. KEGG analysis of glutamate up-regulated genes in rice roots. Table S4. KEGG pathway enrichment analysis of glutamate up-regulated genes in rice root. Table S5. Effects of glutamate on the expression of glutamate receptor genes in rice roots. Table S6. Sequences of primers used for quantitative RT-PCR analysis. (PDF 2009Â kb)

Background Glutamate is an active amino acid. In addition to protein synthesis and metabolism, increasing evidence indicates that glutamate may also function as a signaling molecule in plants. Still, little is known about the nutritional role of glutamate and genes that are directly regulated by glutamate in rice. Results Exogenous glutamate could serve as a nitrogen nutrient to support the growth of rice seedlings, but it was not as effective as ammonium nitrate or glutamine. In nitrogen-starved rice seedlings, glutamate was the most abundant free amino acid and feeding of glutamate rapidly and significantly increased the endogenous levels of glutamine, but not glutamate. These results indicated that glutamate was quickly metabolized and converted to the other nitrogen-containing compounds in rice. Transcriptome analysis revealed that at least 122 genes involved in metabolism, transport, signal transduction, and stress responses in the roots were rapidly induced by 2.5 mM glutamate within 30 min. Many of these genes were also up-regulated by glutamine and ammonium nitrate. Still, we were able to identify some transcription factor, kinase/phosphatase, and elicitor-responsive genes that were specifically or preferentially induced by glutamate. Conclusions Glutamate is a functional amino acid that plays important roles in plant nutrition, metabolism, and signal transduction. The rapid and specific induction of transcription factor, kinase/phosphatase and elicitor-responsive genes suggests that glutamate may efficiently amplify its signal and interact with other signaling pathways to regulate metabolism, growth and defense responses in rice. Electronic supplementary material The online version of this article (doi:10.1186/s12864-017-3588-7) contains supplementary material, which is available to authorized users.

Hydrogen uptake was effectively enhanced by platinum impregnated activated carbon (Pt/AC) prepared in an improved vacuum treatment process. Under high vacuum condition, the precursor of Pt could be infused into deep pores of AC. The fine Pt nanoparticles (

The effect of the catalytic property of platinum (Pt) on the hydrogen adsorption of activated carbon (AC) via spillover was investigated. The catalytic effect on the hydrogen adsorption via spillover was clearly identified from both adsorption isotherms and adsorption kinetics. Factors, including Pt particle size, Pt loading content and AC nature, in the platinum-doped activated carbon (Pt/AC) were considered in this study. The hydrogen adsorption experiments were performed using a volumetric apparatus at room temperature (RT) and low pressure (∼0.1 MPa). In this study, enhancement factors of 16–145% due to spillover were obtained for the Pt/AC samples because of the difference in the textural properties of AC receptors. The adsorption rate of spilt-over hydrogen is strongly dominated by the Pt surface sites as functions of both crystallite size and deposition type (with or without aggregation). When the Pt surface sites amounted to below 0.011 mmol/g, an insignificant spillover effect was observed in the hydrogen adsorption of Pt/AC.

A novel, facile and low temperature process for activated carbon-platinum (AC-Pt) composites has been developed in the absence of additive reducing agents. By varying the pH value and heating approach, the size and amounts of loading Pt nanoparticles could be tuned. According to the results of nitrogen adsorption analysis, small angle X-ray scattering profiles, X-ray diffractometer spectrometer patterns, inductively coupled plasma mass spectrometry and field emission scanning electron microscope images, it was indicated that lower pH value and higher reaction temperature would conduce to larger Pt nanoparticles as well as greater amounts. Attributing to the results of nitrogen adsorption analysis, the impregnating condition of Pt nanocrystals also obviously influenced the specific surface area and the pore structure of AC-Pt composites, which evidently resulted in dissimilar hydrogen adsorption behavior. In this research, the hydrogen storage rate was measured using high pressure thermo-gravimetric analyzer under flow condition. It was discovered that small Pt nanoparticles uniformly distributed in pores might aid gas diffusion of hydrogen molecules and surface diffusion of atomic hydrogen in pores of AC via the so-called hydrogen spillover phenomenon and enhance higher adsorption rate, even at lower Pt contents. © 2011 Curtin University of Technology and John Wiley & Sons, Ltd.

The spatial distribution of hydrogen physically adsorbed in a nanoporous carbon at room temperature (RT) as a function of H2 gas pressure is investigated for the first time using small-angle neutron scattering (SANS). A hierarchical pore structure consisting of micropores and a fractal mesopore network of the used activated carbon is also studied to correlate the relationship between the spatial distribution of hydrogen and the pore confinement. The cylinder-like cluster of aggregated hydrogen is formed and is confined in the disklike micropore. The evolution of spatial structures of adsorbed hydrogen with hydrogen pressure is elucidated. A direct experimental observation of the spatial distribution and the behavior of hydrogen adsorbed in the porous materials at RT is still scarce to date. The analysis results obtained by SANS provide new information for the future investigations of the RT storage mechanism of hydrogen in the nanoporous materials developed for the purpose of on-board hydrogen storage.

Metal−organic framework-5 (MOF-5) with high surface area was synthesized in this study. The complete picture of pore structure in the crystal from the locally perfect micropore channels to the global mesopore network distributed along the constituent micrograins was revealed by small-angle X-ray scattering (SAXS). The in situ SAXS measurement was conducted to investigate the concurrent evolution of mesopore structure and micrograin boundary during heating and thermal activation at 200 °C. During the pore evacuation and formation of micrograin boundary, the flexible mesopores shrink, swell, and realign, while the micropores remain stably rigid. The result shows the role of the tunable mesopore network in the MOF-5 crystal governing the migration of gas molecules. This new finding will be useful for guiding the rational crystal design and the synthetic modification for improving the crystal quality in potential applications.

There are two regimes that exhibit two distinctive behaviors of spillover. The present study used small-angle X-ray scattering (SAXS) to measure size distribution of Pt nanoparticles in the bulk Pt-impregnated active carbon sample. The peak position of the size distribution as determined by SAXS turns out to be at ∼1 nm, which is rarely discussed in this field. SAXS technique is complementary to the other characterization methods. The experimental clue coming from SAXS measurement and our hydrogen storage capacity study shows that the impregnated Pt nanoparticles of ∼1 nm in size can enhance the hydrogen spillover effect. It can significantly increase the room temperature hydrogen uptake compared to currently studied similar systems. The mass loading of catalyst is not a critical factor. Tuning the pore-confined Pt sizes (

The present study established a time-saving technique for hydrogen uptake measurements using a high-pressure thermo-gravimetric analyzer (HPTGA). The critical buoyancy effects were considered in the analysis model. The HPTGA technique developed here for metal–organic frameworks (MOFs) was validated through independent experiments. The room temperature (RT) hydrogen uptake of MOFs via spillover was significantly enhanced by use of a bridge-building treatment. MOF samples with different structural parameters and RT hydrogen uptake performance can be prepared and manipulated through various factors affecting their synthesis. The structural evolution of MOFs within various steps during the synthesis and bridge-building processes were investigated by electron microscopy, nitrogen sorption isotherm analysis, and powder X-ray diffraction.

MOF-5-like crystals were studied by small-angle X-ray scattering (SAXS) to reveal, both quantitatively and qualitatively, their real structural details, including pore surface characteristics, pore shape, size distribution, specific surface area (SSA), spatial distribution, and pore-network structure. A combined SAXS and wide-angle X-ray scattering (WAXS) experiment was conducted to investigate the variation of the pore structure with the MOF-5 crystalline phase produced at different cooling rates. The SSA of the MOF-5 crystals synthesized herein spanned a broad range from approximately 3100 to 800 m2/g. The real pore structures were divided into two regimes. In regime I the material consisted mainly of micropores of radius approximately 8 A as well as mesopores of radius 120 approximately 80 A. The structure in regime II was a fractal network of aggregated mesopores with radiusor=32 A as the monomer, reducing SSA and hydrogen uptake capacity at room temperature. The two regimes can be manipulated by controlling the synthesis parameters. The concurrent evolution of pore structure and crystalline phase during heating for solvent removal was also revealed by the in-situ SAXS/WAXS measurement. The understanding of the impact of the real pore structure on the properties is important to establish a favorable synthetic approach for markedly improving the hydrogen storage capacity of MOF-5.

Background Glutamine is a major amino donor for the synthesis of amino acids, nucleotides, and other nitrogen-containing compounds in all organisms. In addition to its role in nutrition and metabolism, glutamine can also function as a signaling molecule in bacteria, yeast, and humans. By contrast, the functions of glutamine in nutrition and as a signaling molecule remain unclear in plants. Results We demonstrated that glutamine could effectively support the growth of rice seedlings. In glutamine-treated rice roots, the glutamine contents increased dramatically, whereas levels of glutamate remained relatively constant. Transcriptome analysis of rice roots revealed that glutamine induced the expression of at least 35 genes involved in metabolism, transport, signal transduction, and stress responses within 30 min. Interestingly, 10 of the 35 early glutamine responsive genes encode putative transcription factors, including two LBD37-like genes that are involved in the regulation of nitrogen metabolism. Glutamine also rapidly induced the expression of the DREB1A, IRO2, and NAC5 transcription factor genes, which are involved in the regulation of stress responses. Conclusions In addition to its role as a metabolic fuel, glutamine may also function as a signaling molecule to regulate gene expression in plants. The rapid induction of transcription factor genes suggests that glutamine may efficiently amplify its signal and interact with the other signal transduction pathways to regulate plant growth and stress responses. Thus, glutamine is a functional amino acid that plays important roles in plant nutrition and signal transduction. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1892-7) contains supplementary material, which is available to authorized users.

Primers used for RT-PCR analysis of glutamine-responsive genes. Table S2. Primers used for quantitative RT-PCR analysis of glutamine-responsive transcription factor genes. Figure S1. Effects of alanine and glycine on the growth of rice seedlings. Figure S2. Amino acid sequence alignment of Arabidopsis LBD37 and its rice orthologs Os03g0445700 and Os07g0589000. (PDF 2445Â kb)

The metal-organic frameworks (MOF) with low and medium specific surface areas (SSA) were shown to be able to adsorb hydrogen via bridged spillover at room temperature (RT) up to an amount of full coverage of hydrogen in the MOF. Anomalous small-angle X-ray scattering was employed to investigate the key relationship between the structures and storage properties of the involved materials. It was found that the tunable imperfect lattice defects and the 3D pore network in the MOF crystal are the most critical structures for RT hydrogen uptake rather than the known micropores in the crystal, SSA, and Pt catalyst structure.

Background The ACT domain, named after bacterial aspartate kinase, chorismate mutase and TyrA (prephenate dehydrogenase), is a regulatory domain that serves as an amino acid-binding site in feedback-regulated amino acid metabolic enzymes. We have previously identified a novel type of ACT domain-containing protein family, the ACT domain repeat (ACR) protein family, in Arabidopsis. Members of the ACR family, ACR1 to ACR8, contain four copies of the ACT domain that extend throughout the entire polypeptide. Here, we describe the identification of four novel ACT domain-containing proteins, namely ACR9 to ACR12, in Arabidopsis. The ACR9 and ACR10 proteins contain three copies of the ACT domain, whereas the ACR11 and ACR12 proteins have a putative transit peptide followed by two copies of the ACT domain. The functions of these plant ACR proteins are largely unknown. Results The ACR11 and ACR12 proteins are predicted to target to chloroplasts. We used protoplast transient expression assay to demonstrate that the Arabidopsis ACR11- and ACR12-green fluorescent fusion proteins are localized to the chloroplast. Analysis of an ACR11 promoter-β-glucuronidase (GUS) fusion in transgenic Arabidopsis revealed that the GUS activity was mainly detected in mature leaves and sepals. Interestingly, coexpression analysis revealed that the GLN2, which encodes a chloroplastic glutamine synthetase, has the highest mutual rank in the coexpressed gene network connected to ACR11. We used RNA gel blot analysis to confirm that the expression pattern of ACR11 is similar to that of GLN2 in various organs from 6-week-old Arabidopsis. Moreover, the expression of ACR11 and GLN2 is highly co-regulated by sucrose and light/dark treatments in 2-week-old Arabidopsis seedlings. Conclusions This study reports the identification of four novel ACT domain repeat proteins, ACR9 to ACR12, in Arabidopsis. The ACR11 and ACR12 proteins are localized to the chloroplast, and the expression of ACR11 and GLN2 is highly coordinated. These results suggest that the ACR11 and GLN2 genes may belong to the same functional module. The Arabidopsis ACR11 protein may function as a regulatory protein that is related to glutamine metabolism or signaling in the chloroplast.