scholarly journals Overexpression of the chloroplastic 2-oxoglutarate/malate transporter disturbs carbon and nitrogen homeostasis in rice

2020 ◽  
Author(s):  
Shirin Zamani-Nour ◽  
Hsiang-Chun Lin ◽  
Berkley J Walker ◽  
Tabea Mettler-Altmann ◽  
Roxana Khoshravesh ◽  
...  
Keyword(s):  
C4 Photosynthesis ◽  
Tricarboxylic Acid Cycle ◽  
Carbon Assimilation ◽  
Amino Acid Content ◽  
Glutamate Synthase ◽  
Co2 Assimilation ◽  
Bundle Sheath Cells ◽  
Redox Poise ◽  
High Level ◽  
Malate Transporter

Abstract The chloroplastic 2-oxaloacetate (OAA)/malate transporter (OMT1 or DiT1) takes part in the malate valve that protects chloroplasts from excessive redox poise through export of malate and import of OAA. Together with the glutamate/malate transporter (DCT1 or DiT2), it connects carbon with nitrogen assimilation, by providing 2-oxoglutarate for the GS/GOGAT (glutamine synthetase/glutamate synthase) reaction and exporting glutamate to the cytoplasm. OMT1 further plays a prominent role in C4 photosynthesis: OAA resulting from phosphoenolpyruvate carboxylation is imported into the chloroplast, reduced to malate by plastidic NADP-malate dehydrogenase, and then exported for transport to bundle sheath cells. Both transport steps are catalyzed by OMT1, at the rate of net carbon assimilation. To engineer C4 photosynthesis into C3 crops, OMT1 must be expressed in high amounts on top of core C4 metabolic enzymes. We report here high-level expression of ZmOMT1 from maize in rice (Oryza sativa ssp. indica IR64). Increased activity of the transporter in transgenic rice was confirmed by reconstitution of transporter activity into proteoliposomes. Unexpectedly, overexpression of ZmOMT1 in rice negatively affected growth, CO2 assimilation rate, total free amino acid content, tricarboxylic acid cycle metabolites, as well as sucrose and starch contents. Accumulation of high amounts of aspartate and the impaired growth phenotype of OMT1 rice lines could be suppressed by simultaneous overexpression of ZmDiT2. Implications for engineering C4 rice are discussed.

scholarly journals Overexpression of the chloroplastic 2-oxoglutarate/malate transporter in rice disturbs carbon and nitrogen homeostasis

2020 ◽  
Author(s):  
Shirin Zamani-Nour ◽  
Hsiang-Chun Lin ◽  
Berkley J. Walker ◽  
Tabea Mettler-Altmann ◽  
Roxana Khoshravesh ◽  
...  
Keyword(s):  
Carbon Assimilation ◽  
Tca Cycle ◽  
Over Expression ◽  
Carbon And Nitrogen ◽  
Bundle Sheath Cells ◽  
Redox Poise ◽  
Amino Acid Contents ◽  
High Level ◽  
Increased Activity ◽  
Malate Transporter

AbstractThe chloroplastic oxaloacetate/malate transporter (OMT1 or DiT1) takes part in the malate valve that protects chloroplasts from excessive redox poise through export of malate and import of oxaloacetate (OAA). Together with the glutamate/malate transporter (DCT1 or DiT2), it connects carbon with nitrogen assimilation, by providing α-ketoglutarate for the GS/GOGAT reaction and exporting glutamate to the cytoplasm. OMT1 further plays a prominent role in C4 photosynthesis. OAA resulting from PEP-carboxylation is imported into the chloroplast, reduced to malate by plastidic NADP-MDH, and then exported for transport to bundle sheath cells. Both transport steps are catalyzed by OMT1, at the rate of net carbon assimilation. Therefore, to engineer C4 photosynthesis into C3 crops, OMT1 must be expressed in high amounts on top of core C4 metabolic enzymes. We report here high-level expression of ZmOMT1 from maize in rice (Oryza sativa ssp. indica IR64). Increased activity of the transporter in transgenic rice was confirmed by reconstitution of transporter activity into proteoliposomes. Unexpectedly, over-expression of ZmOMT1 in rice negatively affected growth, CO2 assimilation rate, total free amino acid contents, TCA cycle metabolites, as well as sucrose and starch contents. Accumulation of high amounts of aspartate and the impaired growth phenotype of OMT1 rice lines could be suppressed by simultaneous over-expression of ZmDiT2. Implications for engineering C4-rice are discussed.

Analysis of Bundle Sheath Conductance and C4 Photosynthesis using a PEP-Carboxylase Inhibitor

1997 ◽  
Vol 24 (4) ◽  
pp. 549 ◽  
Author(s):  
R. Harold Brown
Keyword(s):  
C4 Photosynthesis ◽  
Co2 Assimilation ◽  
Co2 Exchange ◽  
Bundle Sheath ◽  
Panicum Maximum ◽  
Panicum Miliaceum ◽  
Pep Carboxylase ◽  
C4 Species ◽  
Bundle Sheath Cells ◽  
Sorghum Bicolor L

High [CO2] in bundle sheath cells (BSC) allows high rates of CO2 assimilation (A) and minimises photorespiration in C4 leaves. The [CO2] in BSC is likely to be low when PEPcase is inhibited by 3,3-dichloro-2-dihydroxyphosphinoylmethyl-2-propenoate (DCDP), but Rubisco is still functional. The degree of C4 photosynthesis can be assessed by decreased A and the conductance of BSC walls by the slope of A versus [CO2] during application of DCDP. Inhibition of A by 4.0 mM DCDP was 87-100% in C4 species and was overcome by increasing [CO2] to 2.0-2.5 kPa. In C3 -C4 species in Moricandia, Panicum and Neurachne, A and its inhibition by O2 were unchanged by DCDP, but in C3 -C4 and C4 -like species and interspecific hybrids of Flaveria, A was reduced and its inhibition by O2 was increased. Conductance of BSC walls was 1.13, 1.96, and 2.35 mmol m-2 s-1 in the C4 species, Sorghum bicolor (L.) Moench, Panicum miliaceum L., and Panicum maximum Jacq., respectively. There was no effect of O2 on A in DCDP-treated C4 leaves, apparently because the low conductance of BSC walls masks the influence of O2 on CO2 exchange in these cells.

scholarly journals Measurement of the Leakage of CO2 from Bundle-Sheath Cells of Leaves during C4 Photosynthesis

1995 ◽  
Vol 108 (1) ◽  
pp. 173-181 ◽  
Author(s):  
M. D. Hatch ◽  
A. Agostino ◽  
CLD. Jenkins
Keyword(s):  
C4 Photosynthesis ◽  
Bundle Sheath ◽  
Bundle Sheath Cells ◽  
Sheath Cells

Electrocatalytic reduction of nitrate and selenate by NapAB

2011 ◽  
Vol 39 (1) ◽  
pp. 236-242 ◽  
Author(s):  
Andrew J. Gates ◽  
Clive S. Butler ◽  
David J. Richardson ◽  
Julea N. Butt
Keyword(s):  
Cytoplasmic Membrane ◽  
Current Knowledge ◽  
Reductase Activity ◽  
Protonmotive Force ◽  
Metabolic Diversity ◽  
Protein Film ◽  
Carbon Substrates ◽  
Redox Poise ◽  
Paracoccus Pantotrophus ◽  
High Level

Bacterial cellular metabolism is renowned for its metabolic diversity and adaptability. However, certain environments present particular challenges. Aerobic metabolism of highly reduced carbon substrates by soil bacteria such as Paracoccus pantotrophus presents one such challenge since it may result in excessive electron delivery to the respiratory redox chain when compared with the availability of terminal oxidant, O2. The level of a periplasmic ubiquinol-dependent nitrate reductase, NAP, is up-regulated in the presence of highly reduced carbon substrates. NAP oxidizes ubiquinol at the periplasmic face of the cytoplasmic membrane and reduces nitrate in the periplasm. Thus its activity counteracts the accumulation of excess reducing equivalents in ubiquinol, thereby maintaining the redox poise of the ubiquinone/ubiquinol pool without contributing to the protonmotive force across the cytoplasmic membrane. Although P. pantotrophus NapAB shows a high level of substrate specificity towards nitrate, the enzyme has also been reported to reduce selenate in spectrophotometric solution assays. This transaction draws on our current knowledge concerning the bacterial respiratory nitrate reductases and extends the application of PFE (protein film electrochemistry) to resolve and quantify the selenate reductase activity of NapAB.

Photosynthetic Pathway-Related Ultrastructure of C3, C4 and C3-Like C3-C4 Intermediate Sedges (Cyperaceae), With Special Reference to Eleocharis

1995 ◽  
Vol 22 (4) ◽  
pp. 521 ◽  
Author(s):  
JJ Bruhl ◽  
S Perry
Keyword(s):  
Carbon Assimilation ◽  
Mestome Sheath ◽  
Carbon Reduction ◽  
Peripheral Reticulum ◽  
Δ13c Value ◽  
Bundle Sheath Cells ◽  
Photosynthetic Carbon ◽  
Ultrastructural Characteristics ◽  
Photosynthetic Carbon Assimilation ◽  
Photosynthetic Carbon Reduction

The ultrastructure of photosynthetic organs (leaf blades and culms) was investigated in eight species from four genera of sedges: Fimbristylis (C, fimbristyloid anatomy), Pycreus (C4 chlorocyperoid anatomy), Rhynchospora (C4 rhynchosporoid anatomy) - all NADP-ME (malic enzyme) type, and uninvestigated C3, C4 (eleocharoid anatomy, NAD-ME type) and C3-like C3-C4 intermediate species of Eleocharis. Ultrastructural characteristics previously reported for the former anatomical types are largely confirmed, though some evidence of poorly developed peripheral reticulum in C4 rhynchosporoid sedges is presented. Sedges, regardless of anatomical and biochemical type, possess a suberised lamella in photosynthetic organs which is invariably present in and confined to the mestome sheath cell walls, though it is often incomplete in the radial walls. By contrast with other C4 sedges, NAD-ME Eleocharis species and the C3-like C3-C4 intermediate E. pusilla possess abundant mitochondria and chloroplasts with well-stacked grana in the photosynthetic carbon reduction (PCR) (Kranz)/bundle sheath cells. Peripheral reticulum is well developed in NAD-ME species in both PCR and photosynthetic carbon assimilation (PCA) (C4 mesophyll) chloroplasts, but differs from that seen in chlorocyperoid and fimbristyloid type sedges. The suberised lamella and starch grains (well preserved), and granal stacks (poorly preserved) are identifiable in dried herbarium material (Eleocharis). Prediction of C4 biochemical type of sedges should be possible by combining anatomical, ultrastructural and δ13C value data. The significance of the ultrastructural similarities between the C4 NAD-ME and C3-C4 intermediate Eleocharis species is discussed.

Quantum Yield of Photosystem II and Efficiency of CO2 Fixation in Flaveria (Asteraceae) Species under Varying Light and CO2

1991 ◽  
Vol 18 (4) ◽  
pp. 369 ◽  
Author(s):  
JP Krall ◽  
GE Edwards ◽  
MSB Ku
Keyword(s):  
Quantum Yield ◽  
Photosystem Ii ◽  
Co2 Fixation ◽  
C4 Photosynthesis ◽  
Co2 Assimilation ◽  
Quantum Yields ◽  
Progressive Development ◽  
Psii Activity ◽  
C3 And C4 Photosynthesis

The quantum yields of electron transport from photosystem II (PSII) (Φe, determined from chlorophyll a fluorescence), and CO2 assimilation (ΦCO2, photosynthetic rate/light intensity) were measured simultaneously in vivo with representative species of Flaveria which show a progression in development between C3 and C4 photosynthesis and in reduction of photorespiration. These were F. pringlei (C3), F. sonorensis (C3-C4, but lacking a C4 cycle), F. floridana (C3-C4, with partially functional C4 cycle), F. brownii (C4-like) and F. bidentis (C4). The level of PSII activity with varying CI under 210 mbar O2 was very similar in all species. However, the progressive development of C4 characteristics among the species produced an increased efficiency in utilisation of PSII derived energy for CO2 assimilation under 210 mbar O2, due to reduced photorespiratory losses at low CO2 levels. In all species, when photorespiration was limited by low O2 (20 mbar), there was a linear or near linear relationship between the quantum yield of PSII v. the quantum yield of CO2 fixation with varying intercellular levels of CO2 (Ci) indicating that CO2 fixation in this case is linked to PSII activity. When switching from 20 to 210 mbar O2 at atmosphere levels of CO2, there was a similar decrease in the efficiency in utilising PSII activity for CO2 assimilation at different light intensities, but the degree of sensitivity to O2 progressively decreased among the species concomitant with the development of C4 photosynthesis. These results may help explain why there is an advantage to evolution of C4 photosynthesis in environments where Ci becomes limiting.

scholarly journals Metabolomics of Escherichia coli Treated with the Antimicrobial Carbon Monoxide-Releasing Molecule CORM-3 Reveals Tricarboxylic Acid Cycle as Major Target

2019 ◽  
Vol 63 (10) ◽  
Author(s):  
Sandra M. Carvalho ◽  
Joana Marques ◽  
Carlos C. Romão ◽  
Lígia M. Saraiva
Keyword(s):  
Escherichia Coli ◽  
Carbon Monoxide ◽  
Tricarboxylic Acid Cycle ◽  
Redox Homeostasis ◽  
Glutamate Synthase ◽  
Tca Cycle ◽  
Tricarboxylic Acid ◽  
Bacterial Cells ◽  
Content Type ◽  
Iron Sulfur

ABSTRACT In the last decade, carbon monoxide-releasing molecules (CORMs) have been shown to act against several pathogens and to be promising antimicrobials. However, the understanding of the mode of action and reactivity of these compounds on bacterial cells is still deficient. In this work, we used a metabolomics approach to probe the toxicity of the ruthenium(II) complex Ru(CO)3Cl(glycinate) (CORM-3) on Escherichia coli. By resorting to 1H nuclear magnetic resonance, mass spectrometry, and enzymatic activities, we show that CORM-3-treated E. coli accumulates larger amounts of glycolytic intermediates, independently of the oxygen growth conditions. The work provides several evidences that CORM-3 inhibits glutamate synthesis and the iron-sulfur enzymes of the tricarboxylic acid (TCA) cycle and that the glycolysis pathway is triggered in order to establish an energy and redox homeostasis balance. Accordingly, supplementation of the growth medium with fumarate, α-ketoglutarate, glutamate, and amino acids cancels the toxicity of CORM-3. Importantly, inhibition of the iron-sulfur enzymes glutamate synthase, aconitase, and fumarase is only observed for compounds that liberate carbon monoxide. Altogether, this work reveals that the antimicrobial action of CORM-3 results from intracellular glutamate deficiency and inhibition of nitrogen and TCA cycles.

scholarly journals Genomic Insights into the Carbon and Energy Metabolism of a Thermophilic Deep-Sea Bacterium Deferribacter autotrophicus Revealed New Metabolic Traits in the Phylum Deferribacteres

Genes ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 849 ◽  
Author(s):  
Alexander Slobodkin ◽  
Galina Slobodkina ◽  
Maxime Allioux ◽  
Karine Alain ◽  
Mohamed Jebbar ◽  
...  
Keyword(s):  
Energy Metabolism ◽  
Co Oxidation ◽  
Co2 Fixation ◽  
Tricarboxylic Acid Cycle ◽  
Draft Genome ◽  
Genomic Analysis ◽  
Co2 Assimilation ◽  
Co Dehydrogenase ◽  
Hydroxylamine Oxidoreductase ◽  
Type Complex

Information on the biochemical pathways of carbon and energy metabolism in representatives of the deep lineage bacterial phylum Deferribacteres are scarce. Here, we report the results of the sequencing and analysis of the high-quality draft genome of the thermophilic chemolithoautotrophic anaerobe Deferribacter autotrophicus. Genomic data suggest that CO2 assimilation is carried out by recently proposed reversible tricarboxylic acid cycle (“roTCA cycle”). The predicted genomic ability of D. autotrophicus to grow due to the oxidation of carbon monoxide was experimentally proven. CO oxidation was coupled with the reduction of nitrate to ammonium. Utilization of CO most likely involves anaerobic [Ni, Fe]-containing CO dehydrogenase. This is the first evidence of CO oxidation in the phylum Deferribacteres. The genome of D. autotrophicus encodes a Nap-type complex of nitrate reduction. However, the conversion of produced nitrite to ammonium proceeds via a non-canonical pathway with the participation of hydroxylamine oxidoreductase (Hao) and hydroxylamine reductase. The genome contains 17 genes of putative multiheme c-type cytochromes and “e-pilin” genes, some of which are probably involved in Fe(III) reduction. Genomic analysis indicates that the roTCA cycle of CO2 fixation and putative Hao-enabled ammonification may occur in several members of the phylum Deferribacteres.

scholarly journals The Arabidopsis Transcription Factor CDF3 Is Involved in Nitrogen Responses and Improves Nitrogen Use Efficiency in Tomato

2020 ◽  
Vol 11 ◽  
Author(s):  
José Domínguez-Figueroa ◽  
Laura Carrillo ◽  
Begoña Renau-Morata ◽  
Lu Yang ◽  
Rosa-V Molina ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Primary Root ◽  
Carbon Assimilation ◽  
Glutamate Synthase ◽  
N Availability ◽  
Signal Molecule ◽  
N Accumulation ◽  
Yield Efficiency ◽  
Use Efficiency ◽  
Nitrate Transporters

Nitrate is an essential macronutrient and a signal molecule that regulates the expression of multiple genes involved in plant growth and development. Here, we describe the participation of Arabidopsis DNA binding with one finger (DOF) transcription factor CDF3 in nitrate responses and shows that CDF3 gene is induced under nitrate starvation. Moreover, knockout cdf3 mutant plants exhibit nitrate-dependent lateral and primary root modifications, whereas CDF3 overexpression plants show increased biomass and enhanced root development under both nitrogen poor and rich conditions. Expression analyses of 35S::CDF3 lines reveled that CDF3 regulates the expression of an important set of nitrate responsive genes including, glutamine synthetase-1, glutamate synthase-2, nitrate reductase-1, and nitrate transporters NRT2.1, NRT2.4, and NRT2.5 as well as carbon assimilation genes like PK1 and PEPC1 in response to N availability. Consistently, metabolite profiling disclosed that the total amount of key N metabolites like glutamate, glutamine, and asparagine were higher in CDF3-overexpressing plants, but lower in cdf3-1 in N limiting conditions. Moreover, overexpression of CDF3 in tomato increased N accumulation and yield efficiency under both optimum and limiting N supply. These results highlight CDF3 as an important regulatory factor for the nitrate response, and its potential for improving N use efficiency in crops.

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