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Peter Westhoff - One of the best experts on this subject based on the ideXlab platform.
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efficient 2 phosphoglycolate degradation is required to maintain carbon assimilation and allocation in the C4 Plant flaveria bidentis
Journal of Experimental Botany, 2019Co-Authors: Myles Levey, Stefan Timm, Tabea Mettleraltmann, Gian Luca Borghi, Maria Koczor, Stephanie Arrivault, Andreas P M Weber, Hermann Bauwe, Udo Gowik, Peter WesthoffAbstract:Photorespiration is indispensable for oxygenic photosynthesis since it detoxifies and recycles 2-phosphoglycolate (2PG), which is the primary oxygenation product of Rubisco. However, C4 Plant species typically display very low rates of photorespiration due to their efficient biochemical carbon-concentrating mechanism. Thus, the broader relevance of photorespiration in these organisms remains unclear. In this study, we assessed the importance of a functional photorespiratory pathway in the C4 Plant Flaveria bidentis using knockdown of the first enzymatic step, namely 2PG phosphatase (PGLP). The isolated RNAi lines showed strongly reduced amounts of PGLP protein, but distinct signs of the photorespiratory phenotype only emerged below 5% residual PGLP protein. Lines with this characteristic were stunted in growth, had strongly increased 2PG content, exhibited accelerated leaf senescence, and accumulated high amounts of branched-chain and aromatic amino acids, which are both characteristics of incipient carbon starvation. Oxygen-dependent gas-exchange measurements consistently suggested the cumulative impairment of ribulose-1,5-bisphosphate regeneration with increased photorespiratory pressure. Our results indicate that photorespiration is essential for maintaining high rates of C4 photosynthesis by preventing the 2PG-mediated inhibition of carbon utilization efficiency. However, considerably higher 2PG accumulation can be tolerated compared to equivalent lines of C3 Plants due to the differential distribution of specific enzymatic steps between the mesophyll and bundle sheath cells.
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differential expression of plastome encoded ndh genes in mesophyll and bundle sheath chloroplasts of the C4 Plant sorghum bicolor indicates that the complex i homologous nad p h plastoquinone oxidoreductase is involved in cyclic electron transport
Planta, 1996Co-Authors: Andreas Kubicki, Peter Westhoff, Edgar Funk, Klaus SteinmüllerAbstract:Cyanobacteria and plastids harbor a putative NAD(P)H- or ferredoxin-plastoquinone oxidoreductase that is homologous to the NADH-ubiquinone oxidoreductase (complex I) of mitochondria and eubacteria. The enzyme is a multimeric protein complex that consists of at least 11 subunits (NDH-A-K) and is localized in the stroma lamellae of the thylakoid membrane system. We investigated the expression of the different subunits of the enzyme in mesophyll and bundle-sheath chloroplasts of Sorghum bicolor [L.] Moench, a C4 Plant of the NADP-malic enzyme type. The relative amounts of the subunits NDH-H, -J and -K were strongly increased in bundle-sheath plastids as compared to mesophyll plastids. This increase was accompanied by enhanced transcript levels for all subunits except NDH-I. Because the main function of the protein complexes in the thylakoid membranes of bundle-sheath chloroplasts (photosystem I, cytochrome b6/f-complex and ATPase) is the generation of ATP for CO2 fixation via cyclic electron transport, we conclude that the NAD(P)H/ferredoxin-plastoquinone oxidoreductase is an essential component of the cyclic electron-transport pathway in chloroplasts.
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genomic structure and expression of the pyruvate orthophosphate dikinase gene of the dicotyledonous C4 Plant flaveria trinervia asteraceae
Plant Molecular Biology, 1995Co-Authors: Elke Rosche, Peter WesthoffAbstract:Pyruvate orthophosphate dikinase (PPDK) is a key enzyme of C4 photosynthesis providing the acceptor molecule for the primary CO2 fixation in the mesophyll cells. Here we present the isolation and characterisation of the corresponding gene (termed pdk) from the C4 Plant Flaveria trinervia (Asteraceae). Southern analysis indicates that in contrast to maize pdk sequences in F. trinervia are present as single copy. Sequence analysis of the entire gene reveals that its coding sequence is identical to the previous isolated PPDK-cDNA from this species. The gene spans about 13 kb and consists of 21 exons, it thus contains two additional exons compared to the maize gene. As in maize, a long intervening sequence of 6.1 kb is positioned at the boundary of the transit peptide segment and the mature protein region. Pdk transcripts accumulate abundantly in leaves, but are also detectable in stems and roots. While the leaf and stem transcripts are 3.4 kb in size and encode the chloroplastic PPDK isoform, a 3.0 kb transcript lacking the region encoding the plastidic transit peptide accumulates in roots. Thus two different transcripts can be produced from a single pdk gene most likely by use of alternative promoters and not by alternative splicing. The accumulation of the 3.4 kb transcript is under light control. Darkening leads to a drastic depletion of this transcript in both leaves and stems. Instead, the 3.0 kb transit peptide-lacking pdk transcript accumulates, but only in stems and roots, not in leaves.
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The C3 Plant Flaveria pringlei contains a plastidic NADP-malic enzyme which is orthologous to the C4 isoform of the C4 Plant F. trinervia.
Plant molecular biology, 1994Co-Authors: Bärbel Lipka, Klaus Steinmüller, Elke Rosche, Dagmar Börsch, Peter WesthoffAbstract:To study the molecular evolution of NADP-dependent malic enzyme (NADP-ME) in the genus Flaveria a leaf-specific cDNA library of the C3 Plant F. pringlei was screened for the presence of sequences homologous to the C4 isoform gene (named modA) of the C4 Plant F. trinervia. The cDNAs isolated contained varying numbers of identical restriction fragments suggesting that they were derived from a single gene. This was supported by Southern hybridisation experiments with genomic DNA from F. trinervia and F. pringlei. Nucleotide sequence analysis of a full-size clone identified the presence of a typical plastidic transit peptide and revealed that the mature modA proteins of F. trinervia (C4) and F. pringlei (C3) are 90% similar. These findings indicate that C3 Plants, like C4 species, possess a plastidic isoform of NADP-ME and that the modA genes of the two species represent orthologous genes. Northern analyses showed that modA transcripts accumulate to similar levels in leaves, stems and roots of F. pringlei. The expression of this gene in F. pringlei thus appears to be rather constitutive. In contrast, the modA gene of F. trinervia is abundantly expressed in leaves, but maintains its expression in stems and roots. It has to be concluded from these data that the leaf-specific increase in the expression level was a key step which was taken during the evolution of the C4 isoform modA gene starting from a C3 ancestral gene.
Eric Lichtfouse - One of the best experts on this subject based on the ideXlab platform.
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Mild hydrolysis and alcohol compounds of humic acids
Chinese Journal of Soil Science, 2002Co-Authors: Dou Sen, Eric Lichtfouse, André MariottiAbstract:Alcohol compounds of humic acid (HA) hydrolyzed products were studied by using alkaline mild hydrolysis, thin layer chromatography (TLC) and GC—MC. The results showed that the alcohols content in HA hydrolyzed products were saturated alcohol＞sterol＞unsaturated linear alcohol. Saturated alcohols were mainly even-number carbon of C20～30 and C15; Unsaturated linear alcohols were mainly C20-1π, C20-2πand C19-4π. HAs from soils under C3 and C4 Plant cultivation were different in some aspects. C3-HA contained more unsaturated alcohol, whereas C4-HA contained more saturated alcohol (especially C12 and C26).
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13C Labelling of soil n-hentriacontane (C31) by maize cultivation
Tetrahedron Letters, 1995Co-Authors: Eric LichtfouseAbstract:The fate of Plant carbon into molecular organic substances from soils can be followed by stable carbon analysis. Soil organic matter has thus been progressively labelled with 13C at natural abundance by cultivation of Zea mays, a C4 Plant, on a soil which was previously under isotopically distinct C3 vegetation. The molar carbon percentage of maize n-hentriacontane within soil n-hentriacontane has been calculated by isotopic means and amounts to around 50% after 23 years of maize cultivation.
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Isotope evidence for soil organic carbon pools with distinct turnover rates—II. Humic substances
Organic Geochemistry, 1995Co-Authors: Eric Lichtfouse, Sen Dou, Sabine Houot, Enrique BarriusoAbstract:Two experiments using 13C-enriched substrates have been undertaken to evaluate the relative turnover rates of the main pools of soil organic carbon namely bulk organic carbon, humin and humic acids. Firstly, soil organic matter was labelled naturally during a 5 year field experiment by cultivating Zea mays, a C4 Plant, on a soil that had previously grown isotopically distincts C3 Plants, e.g. wheat. Secondly, soil organic matter was labelled artificially with either Image-glucose of 13C-enriched Image-glucose during a 21 day laboratory experiment. Isotopic variations observed during both experiments demonstrated the existence of soil carbon pools of decreasing turnover rates: humic acids > bulk organic carbon > humin.
Zhuo Wang - One of the best experts on this subject based on the ideXlab platform.
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Systematic comparison of C3 and C4 Plants based on metabolic network analysis.
BMC systems biology, 2012Co-Authors: Chuanli Wang, Longyun Guo, Zhuo WangAbstract:The C4 photosynthetic cycle supercharges photosynthesis by concentrating CO2 around ribulose-1,5-bisphosphate carboxylase and significantly reduces the oxygenation reaction. Therefore engineering C4 feature into C3 Plants has been suggested as a feasible way to increase photosynthesis and yield of C3 Plants, such as rice, wheat, and potato. To identify the possible transition from C3 to C4 Plants, the systematic comparison of C3 and C4 metabolism is necessary. We compared C3 and C4 metabolic networks using the improved constraint-based models for Arabidopsis and maize. By graph theory, we found the C3 network exhibit more dense topology structure than C4. The simulation of enzyme knockouts demonstrated that both C3 and C4 networks are very robust, especially when optimizing CO2 fixation. Moreover, C4 Plant has better robustness no matter the objective function is biomass synthesis or CO2 fixation. In addition, all the essential reactions in C3 network are also essential for C4, while there are some other reactions specifically essential for C4, which validated that the basic metabolism of C4 Plant is similar to C3, but C4 is more complex. We also identified more correlated reaction sets in C4, and demonstrated C4 Plants have better modularity with complex mechanism coordinates the reactions and pathways than that of C3 Plants. We also found the increase of both biomass production and CO2 fixation with light intensity and CO2 concentration in C4 is faster than that in C3, which reflected more efficient use of light and CO2 in C4 Plant. Finally, we explored the contribution of different C4 subtypes to biomass production by setting specific constraints. All results are consistent with the actual situation, which indicate that Flux Balance Analysis is a powerful method to study Plant metabolism at systems level. We demonstrated that in contrast to C3, C4 Plants have less dense topology, higher robustness, better modularity, and higher CO2 and radiation use efficiency. In addition, preliminary analysis indicated that the rate of CO2 fixation and biomass production in PCK subtype are superior to NADP-ME and NAD-ME subtypes under enough supply of water and nitrogen.
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Comparative analysis of C3 and C4 Plants using constraint-based model
2012 IEEE 4th International Symposium on Plant Growth Modeling Simulation Visualization and Applications, 2012Co-Authors: Chuanli Wang, Longyun Guo, Zhuo WangAbstract:To realize the transition from C3 to C4 Plants, the systematic comparison of C3 and C4 metabolism is necessary. In this study, we detected their differences using the improved constraint-based models by setting the ratio between carboxylation and oxygenation by Rubisco. We found the C3 model exhibit more dense topology structure than C4. The simulation of enzyme knockouts demonstrated that both C3 and C4 models are very robust, especially when optimizing CO2 fixation. Moreover, C4 Plant has better robustness no matter the objective function is biomass or CO2 fixation. In addition, all the essential reactions in C3 model are also essential for C4, while there are some other reactions specifically essential for C4, which validated that the basic metabolism of C4 Plant is similar to C3, but C4 is more complex. We also identified more correlated reaction sets in C4, and demonstrated C4 Plants have better modularity with complex mechanism coordinates the reactions and pathways than that of C3 Plants. Finally, the increase of both biomass and CO2 fixation with light intensity and CO2 concentration in C4 is faster than that in C3, which reflect more efficient use of light and CO2 in C4 Plant. All results are consistent with the actual situation, which indicate that constraint-based modeling is a powerful method to study Plant metabolism at systems level.
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Systematic Comparison of C3 and C4 Plants Based on Metabolic Network Analysis
BMC Systems Biology, 2012Co-Authors: Chuanli Wang, Longyun Guo, Zhuo WangAbstract:Abstract Background The C4 photosynthetic cycle supercharges photosynthesis by concentrating CO2 around ribulose-1,5-bisphosphate carboxylase and significantly reduces the oxygenation reaction. Therefore engineering C4 feature into C3 Plants has been suggested as a feasible way to increase photosynthesis and yield of C3 Plants, such as rice, wheat, and potato. To identify the possible transition from C3 to C4 Plants, the systematic comparison of C3 and C4 metabolism is necessary. Results We compared C3 and C4 metabolic networks using the improved constraint-based models for Arabidopsis and maize. By graph theory, we found the C3 network exhibit more dense topology structure than C4. The simulation of enzyme knockouts demonstrated that both C3 and C4 networks are very robust, especially when optimizing CO2 fixation. Moreover, C4 Plant has better robustness no matter the objective function is biomass synthesis or CO2 fixation. In addition, all the essential reactions in C3 network are also essential for C4, while there are some other reactions specifically essential for C4, which validated that the basic metabolism of C4 Plant is similar to C3, but C4 is more complex. We also identified more correlated reaction sets in C4, and demonstrated C4 Plants have better modularity with complex mechanism coordinates the reactions and pathways than that of C3 Plants. We also found the increase of both biomass production and CO2 fixation with light intensity and CO2 concentration in C4 is faster than that in C3, which reflected more efficient use of light and CO2 in C4 Plant. Finally, we explored the contribution of different C4 subtypes to biomass production by setting specific constraints. Conclusions All results are consistent with the actual situation, which indicate that Flux Balance Analysis is a powerful method to study Plant metabolism at systems level. We demonstrated that in contrast to C3, C4 Plants have more dense topology, higher robustness, better modularity, and higher CO2 and radiation use efficiency. In addition, preliminary analysis indicated that the rate of CO2 fixation and biomass production in PCK subtype are superior to NADP-ME and NAD-ME subtypes under enough supply of water and nitrogen.
Enrique Barriuso - One of the best experts on this subject based on the ideXlab platform.
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Isotope evidence for soil organic carbon pools with distinct turnover rates—II. Humic substances
Organic Geochemistry, 1995Co-Authors: Eric Lichtfouse, Sen Dou, Sabine Houot, Enrique BarriusoAbstract:Two experiments using 13C-enriched substrates have been undertaken to evaluate the relative turnover rates of the main pools of soil organic carbon namely bulk organic carbon, humin and humic acids. Firstly, soil organic matter was labelled naturally during a 5 year field experiment by cultivating Zea mays, a C4 Plant, on a soil that had previously grown isotopically distincts C3 Plants, e.g. wheat. Secondly, soil organic matter was labelled artificially with either Image-glucose of 13C-enriched Image-glucose during a 21 day laboratory experiment. Isotopic variations observed during both experiments demonstrated the existence of soil carbon pools of decreasing turnover rates: humic acids > bulk organic carbon > humin.
Z Matinzadeh - One of the best experts on this subject based on the ideXlab platform.
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a new species of bienertia chenopodiaceae from iranian salt deserts a third species of the genus and discovery of a fourth terrestrial C4 Plant without kranz anatomy
Plant Biosystems, 2012Co-Authors: Hossein Akhani, T Chatrenoor, M Dehghani, R Khoshravesh, P Mahdavi, Z MatinzadehAbstract:Abstract Bienertia is a very interesting genus with its unique C4 photosynthesis in a single cell. Recent investigations on the taxonomy of the genus using a multidisciplinary approach revealed the existence a third species of this genus from the margin of Dasht-e Kavir (desert plain) in central Iran, thus adding a fourth terrestrial C4 Plant lacking Kranz anatomy. The flattened leaves, the semi-inferior ovary resulting from adnation of the perianth with the ovary, in addition to cotyledon morphology and hypocotyl length, provide evidence for the existence of a new species. The new species is here described as Bienertia kavirense Akhani spec. nov., after its locality at the margin of the Kavir. The gametic chromosome complement of the new species is n = 9. The carbon isotope values (δ13C) showed a C4 photosynthesis which is remarkably less negative than in the two other species of Bienertia. Detailed information on the morphology, leaf anatomy, and ecology of the new species is provided, and the new assoc...
