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  • 1
    Electronic Resource
    Electronic Resource
    Development of a strategy for transgenic studies and monitoring of transgene expression in two closely related Moricandia species possessing a C3 or C3–C4 intermediate photosynthetic phenotype (2003)
    Oxford, UK : Munksgaard International Publishers
    Physiologia plantarum 119 (2003), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In order to establish a model system for comparative studies of C3 and C3–C4 intermediate photosynthesis, the development of efficient transformation systems and the monitoring of transgene behaviour and stability were carried out in two closely related Moricandia species (Brassicaceae): the C3–C4 photosynthetic intermediate species M. arvensis and the C3 species M. moricandioides. In this study the green fluorescent protein (gfp) reporter gene was used as a vital marker gene while the use of the β-glucuronidase (gusA) gene was based on the highly sensitive detection of its activity. For Agrobacterium-mediated transformation of leaf explants, a cauliflower mosaic virus 35S promoter-driven, modified version of gfp, the mgfp5-ER gene and the gusA gene, respectively, were introduced into the new dual binary transformation vector system pGreen/pSoup (Hellens et al. 2000, Plant Mol Bio 42: 819–832). GFP5 produced bright-green fluorescence in transformed tissues that was distinctly detected 5–12 days following transformation in developing calli of the two species. Visual screening, combined with antibiotic selection, enabled early and easy identification of transformation events and contributed to improvements in the transformation strategies. Transgene integration studies demonstrated that mgfp5-ER was inserted with low copy number in the M. arvensis plant lines and the transgene was transmitted in a Mendelian fashion to T1 and T2 progenies. GFP5 expression levels in a population of 100 independent primary transformed M. arvensis plant lines (T0) showed great variation between transformation events (coefficient of variation of 108%). The mgfp5-ER or gusA reporter genes were expressed in 90–95% of the kanamycin-resistant M. arvensis plant lines and in up to 98% of the independent M. moricandioides plant lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2003.00135.x
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  • 2
    Electronic Resource
    Electronic Resource
    Metabolism of glucose-6-phosphate and utilization of multiple metabolites for fatty acid synthesis by plastids from developing oilseed rape embryos (1996)
    Springer
    Planta 199 (1996), S. 321-327 
    Details
    ISSN: 1432-2048
    Keywords: Brassica ; Embryo ; Carbon partitioning ; Fatty acid synthesis ; Plastid ; Starch synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aim of this work was to investigate the partitioning of imported glucose 6-phosphate (Glc6P) to starch and fatty acids, and to CO2 via the oxidative pentose phosphate pathway (OPPP) in plastids isolated from developing embryos of oilseed rape (Brassica napus L.). The ability of the isolated plastids to utilize concurrently supplied substrates and the effects of these substrate combinations on the Glc6P partitioning were also assessed. The relative fluxes of carbon from Glc6P to starch, fatty acids, and to CO2 via the OPPP were close to 2∶1∶1 when Glc6P was supplied alone. Under these conditions NADPH generated via the OPPP was greater than that required by the concurrent rate of fatty acid synthesis. Fatty acid synthesis was unaffected by the presence or absence of exogenous NADH and/or NADPH and the requirement of fatty acid synthesis for reducing power is therefore met entirely by intraplastidial metabolism. When Glc6P was supplied in the presence of either pyruvate or pyruvate and acetate, the total flux from these metabolites to fatty acids was up to threefold greater than that from either Glc6P or pyruvate when they were supplied singly. In these experiments there was little competition between Glc6P and pyruvate in fatty acid synthesis and the flux to starch was unchanged. This implies that the starch and fatty acid biosynthesis pathways did not compete for the exogenously supplied ATP on which they were strongly dependent. When Glc6P and pyruvate were provided together, the NADPH generated by the OPPP pathway was less than that required by the concurrent rate of fatty acid synthesis. This suggests that the metabolism of exogenous Glc6P via the OPPP can contribute to the NADPH demand created during fatty acid synthesis but it also indicates that other intraplastidial sources of reducing power must be available under the in-vitro conditions used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196575
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  • 3
    Electronic Resource
    Electronic Resource
    The activity of acetyl-CoA carboxylase is not correlated with the rate of lipid synthesis during development of oilseed rape (Brassica napus L.) embryos (1994)
    Springer
    Planta 193 (1994), S. 320-325 
    Details
    ISSN: 1432-2048
    Keywords: Acetyl-CoA carboxylase ; Brassica ; Embryo (development) ; Fatty acid synthesis ; Pisum ; Ricinus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Acetyl-CoA carboxylase (ACCase; EC 6.4.1.2) activity has been determined in seed tissues of oilseed rape (Brassica napus L.), pea (Pisum sativum L.) and castor bean (Ricinus communis L.). A new method is described which leads to significantly higher measurable activities of the enzyme in tissue homogenates than previously reported. This method does not involve either Triton X-100 or centrifugation treatments which have been used previously in the study of the enzyme. In the case of oilseed rape the activity was also increased by removal of the testa from the seed. The activity of ACCase was determined throughout the development of oilseed rape embryos. Enzyme activity increased 3.5-fold as the embryo fresh weight increased from 0.3 to 2.0 mg and then reached a plateau at 1.1 nmol malonyl-CoA-min−1 · embryo−1. The main period of lipid accumulation commenced at an embryo fresh weight of 2.3 mg, which was after the plateau in ACCase activity had been reached. Activity of the enzyme declined after an embryo fresh weight of 3.5 mg, which was before lipid accumulation in the embryo had been completed. Comparison of the activity of ACCase and the apparent in-vivo rate of lipid synthesis on an embryo-fresh-weight basis (i.e. nmol malonyl-CoA formed or utilized·min−1·mg−1 fresh weight) revealed that ACCase activity declines relative to the rate of lipid synthesis throughout development. The negative correlation between these two rates is discussed in relation to the role of ACCase in the regulation of accumulation of storage lipid during embryo development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201808
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  • 4
    Electronic Resource
    Electronic Resource
    Starch metabolism in developing embryos of oilseed rape (1997)
    Springer
    Planta 203 (1997), S. 480-487 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Amylase (isoforms) ; Brassica (starch metabolism) ; Embryo (developing) ; Plastid ; Starch phosphorylase (isoforms) ; Starch (synthesis/degradation)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The aim of this work was to characterise the metabolism of starch in developing embryos of oilseed rape (Brassica napus L. cv. Topaz). The accumulation of starch in embryos in siliques which were darkened or had been exposed to the light was similar, suggesting that the starch is synthesised from imported sucrose rather than via photosynthesis in the embryo. Starch content and the activities of plastidial enzymes required for synthesis of starch from glucose 6-phosphate (Glc6P) both peaked during the early-mid stage of cotyledon development (i.e. during the early part of oil accumulation) and then declined. The mature embryo contained almost no starch. The starch-degrading enzymes α-(EC 3.2.1.1) and β-amylase (EC 3.2.1.2) and phosphorylase (EC 2.4.1.1) were present throughout development. Most of the activity of these three enzymes was extraplastidial and therefore unlikely to be involved in starch degradation, but there were distinct plastidial and extraplastidial isoforms of all three enzymes. Activity gels indicated that distinct plastidial isoforms increase during the change from net synthesis to net degradation of starch. Plastids isolated from embryos at stages both before and after the maximum starch content could convert Glc6P to starch although the rate was lower at the later stage. The results are consistent with the idea that starch synthesis and degradation occur simultaneously during embryo development. The possible roles of transient starch accumulation during embryo development are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050217
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  • 5
    Electronic Resource
    Electronic Resource
    T-protein of the glycine decarboxylase multienzyme complex: evidence for partial similarity to formyltetrahydrofolate synthetase (1995)
    Springer
    Plant molecular biology 27 (1995), S. 1215-1220 
    Details
    ISSN: 1573-5028
    Keywords: glycine cleavage system ; T-protein ; THF binding site
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have isolated and sequenced cDNA clones encoding T-protein of the glycine decarboxylase complex from three plant species, Flaveria pringlei, Solanum tuberosum and Pisum sativum. The predicted amino acid sequences of these clones are at least 87% identical and all are similar to the predicted sequences of the bovine, human, chicken and Escherichia coli T-proteins. Alignment of all these sequences revealed conserved domains, one of which showed a significant similarity to a part of the formyltetrahydrofolate synthetases from procaryotes and eucaryotes. This suggests that the T-protein sequence is not as unique as previously thought.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00020895
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  • 6
    Electronic Resource
    Electronic Resource
    Photorespiratory metabolism and immunogold localization of photorespiratory enzymes in leaves of C3 and C3-C4 intermediate species of Moricandia (1988)
    Springer
    Planta 173 (1988), S. 298-308 
    Details
    ISSN: 1432-2048
    Keywords: C3-C4 intermediate plants ; Glycine decarboxylase (localization) ; Moricandia (photorespiration) ; Photorespiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photorespiratory metabolism of the C3-C4 intermediate species Moricandia arvensis (L.) DC has been compared with that of the C3 species, Moricandia moricandioides (Boiss.) Heywood. Assays of glycollate oxidase (EC 1.1.3.1), glyoxylate aminotransferases (EC 2.6.1.4, EC 2.6.1.45) and hydroxypyruvate reductase (EC 1.1.1.29) indicate that the capacity for flux through the photorespiratory cycle is similar in both species. Immunogold labelling with monospecific antibodies was used to investigate the cellular locations of ribulose 1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39), glycollate oxidase, and glycine decarboxylase (EC 2.1.2.10) in leaves of the two species. Ribulose 1,5-bisphosphate carboxylase/oxygenase was confined to the stroma of chloroplasts and glycollate oxidase to the peroxisomes of all photosynthetic cells in leaves of both species. However, whereas glycine decarboxylase was present in the mitochondria of all photosynthetic cells in M. moricandioides, it was only found in the mitochondria of bundle-sheath cells in M. arvensis. We suggest that localized decarboxylation of glycine in the leaves of M. arvensis will lead to improved recapture of photorespired CO2 and hence a lower rate of photorespiration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00401016
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  • 7
    Electronic Resource
    Electronic Resource
    Distribution of photorespiratory enzymes between bundle-sheath and mesophyll cells in leaves of the C3−C4 intermediate species Moricandia arvensis (L.) DC (1988)
    Springer
    Planta 176 (1988), S. 527-532 
    Details
    ISSN: 1432-2048
    Keywords: C3−C4 intermediate plant ; Glycine decarboxylation ; Moricandia (photorespiration) ; Photorespiratory enzymes (localization) ; Protoplast isolation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to study the location of enzymes of photorespiration in leaves of the C3−C4 intermediate species Moricandia arvensis (L.). DC, protoplast fractions enriched in mesophyll or bundlesheath cells have been prepared by a combination of mechanical and enzymic techniques. The activities of the mitochondrial enzymes fumarase (EC 4.2.1.2) and glycine decarboxylase (EC 2.1.2.10) were enriched by 3.0- and 7.5-fold, respectively, in the bundle-sheath relative to the mesophyll fraction. Enrichment of fumarase is consistent with the larger number of mitochondria in bundle-sheath cells relative to mesophyll cells. The greater enrichment of glycine decarboxylase indicates that the activity is considerably higher on a mitochondrial basis in bundle-sheath than in mesophyll cells. Serine hydroxymethyltransferase (EC 2.1.2.1) activity was enriched by 5.3-fold and glutamate-dependent glyoxylate-aminotransferase (EC 2.6.1.4) activity by 2.6-fold in the bundle-sheath relative to the mesophyll fraction. Activities of serine- and alanine-dependent glyoxylate aminotransferase (EC 2.6.1.45 and EC 2.6.1.4), glycollate oxidase (EC 1.1.3.1), hydroxypyruvate reductase (EC 1.1.1.81), glutamine synthetase (EC 6.3.1.2) and phosphoribulokinase (EC 2.7.1.19) were not significantly different in the two fractions. These data provide further independent evidence to complement earlier immunocytochemical studies of the distribution of photorespiratory enzymes in the leaves of this species, and indicate that while mesophyll cells of M. arvensis have the capacity to synthesize glycine during photorespiration, they have only a low capacity to metabolize it. We suggest that glycine produced by photorespiratory metabolism in the mesophyll is decarboxylated predominantly by the mitochondria in the bundle sheath.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397660
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  • 8
    Electronic Resource
    Electronic Resource
    Subcellular distribution of multiple forms of glutathione reductase in leaves of pea (Pisum sativum L.) (1990)
    Springer
    Planta 180 (1990), S. 278-284 
    Details
    ISSN: 1432-2048
    Keywords: Chloroplast ; Glutathione reductase (isoforms, localization) ; Mitochondrion ; Pisum (glutathione reductase)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract On sodium-dodecyl-sulfate polyacrylamide gels, purified glutathione reductase (GR; EC 1.6.4.2) from the leaves of two- to three-week-old pea (Pisum sativum L. cv. Birte) seedlings was represented by a single band with an apparent molecular weight of 55 kilodaltons. This polypeptide was resolved to multiple isoforms by two-dimensional electrophoresis. Fractionation of protoplasts and purification of subcellular organelles has shown that enzyme activity is associated with the chloroplasts, mitochondria and cytosol (in this order, approx. 77%, 3%, and 20% of the total activity). Distinct multiple isoforms of the enzyme, which differed in isoelectric point and were compartment-specific, were resolved from purified mitochondria and chloroplasts. The latency of the glutathione reductase activity which co-purified on Percoll gradients with the mitochondrial marker enzyme, cytochrome-c oxidase (EC 1.9.3.1.), indicated that this enzyme was within the mitochondrion. The mitochondrial glutathione reductase activity was strongly dependent on NADPH and not NADH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194008
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  • 9
    Electronic Resource
    Electronic Resource
    Glycine decarboxylase is confined to the bundle-sheath cells of leaves of C3−C4 intermediate species (1988)
    Springer
    Planta 175 (1988), S. 452-459 
    Details
    ISSN: 1432-2048
    Keywords: C4 evolution ; C3−C4 intermediate plants ; Flaveria ; Glycine decarboxylase (localization) ; Photosynthesis (C3−C4 intermediate) ; Photorespiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Immunogold labelling has been used to determine the cellular distribution of glycine decarboxylase in leaves of C3, C3−C4 intermediate and C4 species in the genera Moricandia, Panicum, Flaveria and Mollugo. In the C3 species Moricandia foleyi and Panicum laxum, glycine decarboxylase was present in the mitochondria of both mesophyll and bundle-sheath cells. However, in all the C3−C4 intermediate (M. arvensis var. garamatum, M. nitens, M. sinaica, M. spinosa, M. suffruticosa, P. milioides, Flaveria floridana, F. linearis, Mollugo verticillata) and C4 (P. prionitis, F. trinervia) species studied glycine decarboxylase was present in the mitochondria of only the bundle-sheath cells. The bundle-sheath cells of all the C3−C4 intermediate species have on their centripetal faces numerous mitochondria which are larger in profile area than those in mesophyll cells and are in close association with chloroplasts and peroxisomes. Confinement of glycine decarboxylase to the bundle-sheath cells is likely to improve the potential for recapture of photorespired CO2 via the Calvin cycle and could account for the low rate of photorespiration in all C3−C4 intermediate species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393064
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  • 10
    Electronic Resource
    Electronic Resource
    The relationship between the post-illumination CO2 burst and glycine metabolism in leaves of C3 and C3-C4 intermediate species of Moricandia (1991)
    Springer
    Planta 186 (1991), S. 122-126 
    Details
    ISSN: 1432-2048
    Keywords: Amino acid metabolism ; C3-C4 intermediate plant ; Carbon dioxide (post-illumination burst) ; Glycine metabolism ; Moricandia ; Photorespiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The free-pool sizes of amino acids involved in photorespiratory metabolism have been determined in leaves of Moricandia species during the post-illumination CO2 burst. The kinetics of the burst and the time to attainment of steady-state rates of dark respiration were much slower in the C3-C4 intermediate species Moricandia arvensis (L.) DC than in the C3 species Moricandia moricandioides (Boiss.) Heywood. When plants were equilibrated at a high photon flux density (PFD; 1200 μmol · m−2 · s−1 PAR) the glycine and serine pool sizes in leaves of M. arvensis were 1.9 and 1.4 μmol · mg−1 phaeophytin, respectively, values which were twice those in leaves of M. moricandioides. Amounts of glycine and serine were smaller at a lower PFD (150 μmol · m−2 · s−1) but were still twice as large in M. arvensis. Amounts of other amino acids involved in photorespiration or background cell metabolism (glutamate/glutamine, alanine, valine and threonine) were comparable in both species and did not respond to irradiance or change markedly during the dark burst. In contrast, during the first minute of the post-illumination burst the glycine pool in the leaves of both species had declined by at least 60%. It continued to decline, reaching 6–7 % of the level in the light by the time steady-state rates of dark respiration had been established. The rate of disappearance of glycine was comparable in both species and therefore depletion to steady-state dark levels took longer in M. arvensis than in M. moricandioides (8.4 and 4.6 min, respectively). These data indicate that almost all of the glycine pool in the leaves of C3 and C3-C4 Moricandia species is a consequence of photorespiratory metabolism. The significance of a large but readily metabolised pool of glycine in the leaves of M. arvensis is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201507
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