| 1. |
- Betti, Marco, et al.
(författare)
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Manipulating photorespiration to increase plant productivity : recent advances and perspectives for crop improvement
- 2016
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Ingår i: Journal of Experimental Botany. - : Oxford University Press (OUP). - 0022-0957 .- 1460-2431. ; 67:10, s. 2977-2988
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Forskningsöversikt (refereegranskat)abstract
- Recycling of the 2-phosphoglycolate generated by the oxygenase reaction of Rubisco requires a complex and energy-consuming set of reactions collectively known as the photorespiratory cycle. Several approaches aimed at reducing the rates of photorespiratory energy or carbon loss have been proposed, based either on screening for natural variation or by means of genetic engineering. Recent work indicates that plant yield can be substantially improved by the alteration of photorespiratory fluxes or by engineering artificial bypasses to photorespiration. However, there is also evidence indicating that, under certain environmental and/or nutritional conditions, reduced photorespiratory capacity may be detrimental to plant performance. Here we summarize recent advances obtained in photorespiratory engineering and discuss prospects for these advances to be transferred to major crops to help address the globally increasing demand for food and biomass production.
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| 2. |
- Bykova, Natalia V, et al.
(författare)
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Interaction between photorespiration and respiration in transgenic potato plants with antisense reduction in glycine decarboxylase.
- 2005
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Ingår i: Planta. - : Springer Science and Business Media LLC. - 0032-0935 .- 1432-2048. ; 222:1, s. 130-40
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Potato (Solanum tuberosum L. cv. Désirée) plants with an antisense reduction in the P-protein of the glycine decarboxylase complex (GDC) were used to study the interaction between respiration and photorespiration. Mitochondria isolated from transgenic plants had a decreased capacity for glycine oxidation and glycine accumulated in the leaves. Malate consumption increased in leaves of GDC deficient plants and the capacity for malate and NADH oxidation increased in isolated mitochondria. A lower level of alternative oxidase protein and decreased partitioning of electrons to the alternative pathway was found in these plants. The adenylate status was altered in protoplasts from transgenic plants, most notably the chloroplastic ATP/ADP ratio increased. The lower capacity for photorespiration in leaves of GDC deficient plants was compensated for by increased respiratory decarboxylations in the light. This is interpreted as a decreased light suppression of the tricarboxylic acid cycle in GDC deficient plants in comparison to wild-type plants. The results support the view that respiratory decarboxylations in the light are restricted at the level of the pyruvate dehydrogenase complex and/or isocitrate dehydrogenase and that this effect is likely to be mediated by mitochondrial photorespiratory products.
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| 3. |
- Eisenhut, Marion, et al.
(författare)
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The plant-like C2 glycolate cycle and the bacterial-like glycerate pathway cooperate in phosphoglycolate metabolism in cyanobacteria.
- 2006
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 142:1
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Tidskriftsartikel (refereegranskat)abstract
- The occurrence of a photorespiratory 2-phosphoglycolate metabolism in cyanobacteria is not clear. In the genome of the cyanobacterium Synechocystis sp. strain PCC 6803, we have identified open reading frames encoding enzymes homologous to those forming the plant-like C2 cycle and the bacterial-type glycerate pathway. To study the route and importance of 2-phosphoglycolate metabolism, the identified genes were systematically inactivated by mutagenesis. With a few exceptions, most of these genes could be inactivated without leading to a high-CO(2)-requiring phenotype. Biochemical characterization of recombinant proteins verified that Synechocystis harbors an active serine hydroxymethyltransferase, and, contrary to higher plants, expresses a glycolate dehydrogenase instead of an oxidase to convert glycolate to glyoxylate. The mutation of this enzymatic step, located prior to the branching of phosphoglycolate metabolism into the plant-like C2 cycle and the bacterial-like glycerate pathway, resulted in glycolate accumulation and a growth depression already at high CO(2). Similar growth inhibitions were found for a single mutant in the plant-type C2 cycle and more pronounced for a double mutant affected in both the C2 cycle and the glycerate pathway after cultivation at low CO(2). These results suggested that cyanobacteria metabolize phosphoglycolate by the cooperative action of the C2 cycle and the glycerate pathway. When exposed to low CO(2), glycine decarboxylase knockout mutants accumulated far more glycine and lysine than wild-type cells or mutants with inactivated glycerate pathway. This finding and the growth data imply a dominant, although not exclusive, role of the C2 route in cyanobacterial phosphoglycolate metabolism.
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| 4. |
- Hasse, Dirk, et al.
(författare)
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Alternative splicing produces an H-protein with better substrate properties for the P-protein of glycine decarboxylase.
- 2009
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 276:23
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Tidskriftsartikel (refereegranskat)abstract
- Several thousand plant genes are known to produce multiple transcripts, but the precise function of most of the alternatively encoded proteins is not known. Alternative splicing has been reported for the H-protein subunit of glycine decarboxylase in the genus Flaveria. H-protein has no catalytic activity itself but is a substrate of the three enzymatically active subunits, P-, T- and L-protein. In C(4) species of Flaveria, two H-proteins originate from single genes in an organ-dependent manner. Here, we report on differences between the two alternative H-protein variants with respect to their interaction with the glycine-decarboxylating subunit, P-protein. Steady-state kinetic analyses of the alternative Flaveria H-proteins and artificially produced 'alternative' Arabidopsis H-proteins, using either pea mitochondrial matrix extracts or recombinant cyanobacterial P-protein, consistently demonstrate that the alternative insertion of two alanine residues at the N-terminus of the H-protein elevates the activity of P-protein by 20%in vitro, and could promote glycine decarboxylase activity in vivo.
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| 5. |
- Hasse, Dirk, et al.
(författare)
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Crystallization and preliminary X-ray diffraction analyses of the homodimeric glycine decarboxylase (P-protein) from the cyanobacterium Synechocystis sp. PCC 6803.
- 2010
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Ingår i: Acta Crystallographica. Section F. - 1744-3091 .- 1744-3091. ; 66:Pt 2, s. 187-191
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Tidskriftsartikel (refereegranskat)abstract
- Glycine decarboxylase, or P-protein, is a major enzyme that is involved in the C(1) metabolism of all organisms and in the photorespiratory pathway of plants and cyanobacteria. The protein from Synechocystis sp. PCC 6803 is a homodimer with a mass of 215 kDa. Recombinant glycine decarboxylase was expressed in Escherichia coli and purified by metal-affinity, ion-exchange and gel-filtration chromatography. Crystals of P-protein that diffracted to a resolution of 2.1 A were obtained using the hanging-drop vapour-diffusion method at 291 K. X-ray diffraction data were collected from cryocooled crystals using synchrotron radiation. The crystals belonged to space group P2(1)2(1)2(1), with unit-cell parameters a = 96.30, b = 135.81, c = 179.08 A.
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| 6. |
- Hasse, Dirk, et al.
(författare)
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Properties of recombinant glycine decarboxylase P- and H-protein subunits from the cyanobacterium Synechocystis sp. strain PCC 6803.
- 2007
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793 .- 1873-3468. ; 581:7
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Tidskriftsartikel (refereegranskat)abstract
- The multi-enzyme complex glycine decarboxylase is important for one-carbon metabolism, essential for the photorespiratory glycolate cycle of plants, and comprises four different polypeptides, P-, H-, T-, and L-protein. We report on the production and properties of recombinant P-protein from the cyanobacterium Synechocystis and also describe features of recombinant H-protein from the same organism. The P-protein shows enzymatic activity with lipoylated H-protein and very low activity with H-apoprotein or lipoate as artificial cofactors. Its affinity towards glycine is unaffected by the presence and nature of the methyleneamine acceptor molecule. The cyanobacterial H-protein apparently forms stable dimers.
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| 7. |
- Hasse, Dirk, et al.
(författare)
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Structure of the Homodimeric Glycine Decarboxylase P-protein from Synechocystis sp PCC 6803 Suggests a Mechanism for Redox Regulation
- 2013
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 288:49, s. 35333-35345
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Tidskriftsartikel (refereegranskat)abstract
- Glycine decarboxylase, or P-protein, is a pyridoxal 5-phosphate (PLP)-dependent enzyme in one-carbon metabolism of all organisms, in the glycine and serine catabolism of vertebrates, and in the photorespiratory pathway of oxygenic phototrophs. P-protein from the cyanobacterium Synechocystis sp. PCC 6803 is an (2) homodimer with high homology to eukaryotic P-proteins. The crystal structure of the apoenzyme shows the C terminus locked in a closed conformation by a disulfide bond between Cys(972) in the C terminus and Cys(353) located in the active site. The presence of the disulfide bridge isolates the active site from solvent and hinders the binding of PLP and glycine in the active site. Variants produced by substitution of Cys(972) and Cys(353) by Ser using site-directed mutagenesis have distinctly lower specific activities, supporting the crucial role of these highly conserved redox-sensitive amino acid residues for P-protein activity. Reduction of the 353-972 disulfide releases the C terminus and allows access to the active site. PLP and the substrate glycine bind in the active site of this reduced enzyme and appear to cause further conformational changes involving a flexible surface loop. The observation of the disulfide bond that acts to stabilize the closed form suggests a molecular mechanism for the redox-dependent activation of glycine decarboxylase observed earlier.
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| 8. |
- Timm, Stefan, et al.
(författare)
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A Cytosolic Pathway for the Conversion of Hydroxypyruvate to Glycerate during Photorespiration in Arabidopsis.
- 2008
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Ingår i: The Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 20, s. 2848-2859
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Tidskriftsartikel (refereegranskat)abstract
- Deletion of any of the core enzymes of the photorespiratory cycle, one of the major pathways of plant primary metabolism, results in severe air-sensitivity of the respective mutants. The peroxisomal enzyme hydroxypyruvate reductase (HPR1) represents the only exception to this rule. This indicates the presence of extraperoxisomal reactions of photorespiratory hydroxypyruvate metabolism. We have identified a second hydroxypyruvate reductase, HPR2, and present genetic and biochemical evidence that the enzyme provides a cytosolic bypass to the photorespiratory core cycle in Arabidopsis thaliana. Deletion of HPR2 results in elevated levels of hydroxypyruvate and other metabolites in leaves. Photosynthetic gas exchange is slightly altered, especially under long-day conditions. Otherwise, the mutant closely resembles wild-type plants. The combined deletion of both HPR1 and HPR2, however, results in distinct air-sensitivity and a dramatic reduction in photosynthetic performance. These results suggest that photorespiratory metabolism is not confined to chloroplasts, peroxisomes, and mitochondria but also extends to the cytosol. The extent to which cytosolic reactions contribute to the operation of the photorespiratory cycle in varying natural environments is not yet known, but it might be dynamically regulated by the availability of NADH in the context of peroxisomal redox homeostasis.
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