| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
|
First published online January 21, 2005; 10.1104/pp.104.055566 Plant Physiology 137:611-622 (2005) © 2005 American Society of Plant Biologists Enhanced Photosynthetic Performance and Growth as a Consequence of Decreasing Mitochondrial Malate Dehydrogenase Activity in Transgenic Tomato Plants1Max-Planck-Institut für Molekulare Pflanzenphysiologie, 14476 Golm, Germany (A.N.-N., F.C., A.L., A.R.F.); Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom (A.M.O.S., R.G.R., L.J.S.); and Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa–Minas Gerais, Brazil (M.E.L.)
Transgenic tomato (Solanum lycopersicum) plants expressing a fragment of the mitochondrial malate dehydrogenase gene in the antisense orientation and exhibiting reduced activity of this isoform of malate dehydrogenase show enhanced photosynthetic activity and aerial growth under atmospheric conditions (360 ppm CO2). In comparison to wild-type plants, carbon dioxide assimilation rates and total plant dry matter were up to 11% and 19% enhanced in the transgenics, when assessed on a whole-plant basis. Accumulation of carbohydrates and redox-related compounds such as ascorbate was also markedly elevated in the transgenics. Also increased in the transgenic plants was the capacity to use L-galactono-lactone, the terminal precursor of ascorbate biosynthesis, as a respiratory substrate. Experiments in which ascorbate was fed to isolated leaf discs also resulted in increased rates of photosynthesis providing strong indication for an ascorbate-mediated link between the energy-generating processes of respiration and photosynthesis. This report thus shows that the repression of this mitochondrially localized enzyme improves both carbon assimilation and aerial growth in a crop species.
Improving plant productivity is now of unprecedented importance given the twin problems of environmental deterioration and the world population explosion (Miyagawa et al., 2001  ). One of the major determinants of crop growth and yield is believed to be photosynthetic carbon metabolism (Galtier et al., 1993; Sweetlove et al., 1998; Miyagawa et al., 2001); however, to date very few molecular approaches aimed at improving the efficiency of these pathways have proven successful. Those strategies that did work generally involved expression of cyanobacterial enzymes in higher plants. The expression of Fru-1,6/sedoheptulose 1,7-bisphosphatase (Miyagawa et al., 2001) in tomato (Solanum lycopersicum); ictB, a gene involved in HCO3– accumulation; tobacco (Nicotiana tabacum); and Arabidopsis (Arabidopsis thaliana; Lieman-Hurwitz et al., 2003) resulted in increased photosynthetic rates and growth under normal and limiting carbon dioxide concentrations, respectively. A recent report showed that overexpression of the gene otsA from Escherichia coli, encoding trehalose phosphate synthase, resulted in elevated rates of photosynthesis and growth in tobacco leaves (Pellny et al., 2004). Interestingly, however, none of the successful strategies described above has been the result of alterations in the levels of the endogenous plant proteins.
As part of an ongoing project to determine the function of the TCA cycle in the illuminated leaf, we previously comprehensively phenotyped the tomato wild species (Solanum pennellii) mutant Aco1, which exhibits a deficiency in expression of one of the two isoforms of aconitase present in the tomato (Tanksley et al., 1992
In this study we turn our attention to the analysis of the importance of the mitochondrial malate dehydrogenase (mMDH) for photosynthetic metabolism. The enzyme MDH catalyses the reversible reduction of oxaloacetate to malate and is important in multiple metabolic pathways. Higher plants contain multiple forms of MDH that differ in coenzyme specificity and subcellular localization (Gietl et al., 1996
Cloning of a cDNA-Encoding mMDH from Tomato
Searching tomato expressed sequence tag collections (Van der Hoeven et al., 2003
Transgenic Plants Show an Elevated Growth Rate But Not an Accelerated Developmental Phenotype A 996-bp fragment of the cDNA-encoding mMDH was cloned either in the antisense orientation into the transformation vector pBINAR between the cauliflower mosaic virus (CaMV) promoter and the ocs terminator (Fig. 1B, subsection i) or using the RNAi design (Fig. 1B, subsection ii). We then transferred 60 transgenic tomato plants obtained by Agrobacterium tumefaciens-mediated transformation to the greenhouse. Screening of the lines for a reduction of total cellular MDH activity yielded eight lines that exhibited a significant reduction in activity as determined by activity gel assays (data not shown). To demonstrate that this reduction was a consequence of a specific reduction in the mitochondrial isoform we carried out northern (data not shown) and western (Fig. 1C) analyses in addition to direct assay of total MDH activity (Fig. 1D). These preliminary studies suggested that the antisense, but not the RNAi, transformants were suitable for further study since in these lines the reduction in MDH expression was confined to the mitochondrial isoform. Subcellular fractionation studies on samples from a second harvest (Table I), provided further evidence, in addition to that provided by zymogram and northern analysis, that the reduction in activity was confined to the mitochondria. It should be noted that, although the absolute values for total MDH activity are variable between the harvests, the relative degree of inhibition in the antisense lines is conserved between the harvests.
Analysis of the maximal catalytic activities of other important enzymes of photosynthetic carbohydrate metabolism revealed no changes in important enzymes of photosynthesis (Rubisco and Calvin cycle enzymes) but a mild increase in the glycolytic enzyme phosphofructokinase (PFK). In addition, no significant differences were observed in the maximal catalytic activity of L-galactono-lactone dehydrogenase (GLDH), the terminal step of ascorbic acid biosynthesis in plants (Wheeler et al., 1998 ); however, this activity was highly variable both across and within genotypes. When we grew the transgenic plants in the greenhouse side by side with wild-type controls, a clear increase in the growth of the aerial parts of the transformants was observed (Fig. 2A). Close examination of the transgenic plants revealed that they were significantly taller and appeared to have marginally bigger fruit; however, there were no difference in leaf formation or onset of senescence. These visual observations were supported by experimental measurements (Fig. 2B). Furthermore, there was a tendency of earlier flowering in the transformants (significant in the cases of lines AL7 and AL8). While the total leaf mass did not vary across the genotypes, analysis of root biomass revealed that this was somewhat restricted in the transformants (Fig. 2B). When taken together these findings imply an improved harvest index. Assessment of pigment content of leaves revealed that the photosynthetic pigment content was largely unaltered with the exception of small decreases in violaxanthin and significant increases in the level of antheraxanthin (data not shown).
Reduction in mMDH Activity Results in an Increased Chloroplastic-Electron Transport Rate and Enhanced Photosynthesis Given the increase in aerial yield in the transformants, we next analyzed whether they exhibited altered photosynthetic rates. Firstly, we studied the metabolism of 14CO2 by leaf discs excised from the wild-type and transformant plants. Notably the assimilation rate was markedly increased in plants exhibiting inhibition of MDH (Fig. 3A). Furthermore, this increased carbon fixation was coupled with an increase in the accumulation of [14C]Suc, [14C]-starch, and [14C]-organic acids. When these data are expressed as a percentage of 14CO2 metabolised, decreased mMDH activity led to a decreased partitioning into organic and amino acids, implying a reduced respiration rate in these plants.
As a second experiment, fluorescence emission was measured in vivo using a pulse amplitude modulation (PAM) fluorimeter in order to calculate relative electron transport rates (ETRs). When exposed to higher irradiance (photon flux density [PFD] of 700 µmol m–2 s–1) the mMDH plants exhibited elevated ETRs (significantly so in the case of line AL7; Fig. 3B). Finally, gas exchange was measured directly in a subset of the transformants under PFDs that ranged from 100 to 1,000 µmol m–2 s–1 (Fig. 3, C–E). The transformants exhibited assimilation rates that were higher than the wild type under all conditions except the lowest irradiance (significantly so in the case of AL21; Fig. 3C). Similar results were obtained from a second harvest. Interestingly, when data from both harvests are plotted together a clear negative correlation becomes apparent between the activity of MDH and the rate of photosynthesis (data not shown). Analysis of other parameters of gas exchange revealed that the transformants also exhibited minor changes in transpiration rate at all PFD (Fig. 3D) and that the stomatal conductance is noticeably (yet not significantly) lower in the transgenics. The lower stomatal conductance, paradoxically, suggests increased resistance to carbon dioxide uptake (Fig. 3E) and, in keeping with this, the internal carbon dioxide concentration inside the stomatal cavity was estimated to be lower (data not shown).
Analysis of the carbohydrate content of leaves from 6-week-old plants during a diurnal cycle revealed that the transformants were characterized by small, but nonsignificant, increases in Suc and starch contents (Fig. 4) and significant increases in Glc and Fru (data not shown). In all cases metabolite contents were in a similar range to those reported previously for tomato (e.g., Galtier et al., 1993
Since this method does not readily allow the determination of phosphorylated intermediates, which are important diagnostic markers for alterations in photosynthesis (Stitt, 1997 ) we assayed these by means of cycling assays, regular linear spectrophotometric assays, and HPLC methods (Table II). There were no significant differences in either the individual pools or the total phosphoester levels in the transformants, and furthermore, little change in the levels of nucleotides. The one exception to this statement is the fact that line AL9 displayed a decreased level of UTP and consequently a decreased level of total uridinylates. Interestingly, there was, however, a tendential decrease in the level of inorganic phosphate in the transgenics (significant in lines AL8 and AL9) and a consequent increase in the deduced phosphoester to inorganic phosphate ratio.
Inhibition in mMDH Activity Results in Reduced Rates of Respiration
While some of the results presented above suggest a decreased rate of respiration, they do not provide direct evidence in support of this. We therefore next directly evaluated the rate of respiration in the transformants. For this purpose we adopted two strategies. First, we recorded the evolution of 14CO2 following incubation of leaf discs in positionally labeled 14C-Glc molecules, and second, we used a combination of conventional respiratory and NMR studies of isolated mitochondria to assess flux through the TCA cycle. In the first experiment, we incubated leaf discs taken from plants in the light and supplied these with [1-14C], [2-14C], [3:4-14C], or [6-14C]Glc over a period of 6 h. During this time, we collected the 14CO2 evolved at hourly intervals. Carbon dioxide can be released from the C1 position by the action of enzymes that are not associated with mitochondrial respiration, but carbon dioxide evolution from the C3:4 positions of Glc cannot (ap Rees and Beevers, 1960
Carbon dioxide evolution from the C2 and C6 positions was relatively similar across the genotypes with the exception that evolution from the C6 position was somewhat higher, in both lines tested, and that from the C2 position was lower, in line AL21, than that observed in wild type.
Isolation of suitable quantities of leaf mitochondria for respiratory measurements was not feasible, so for the second experiment we isolated mitochondria from breaker fruits obtained from the wild type and two transgenic lines (AL7 and AL8). The mitochondria were incubated with [3-13C]pyruvate under simulated cytosolic conditions (described in detail in Smith et al., 2004
To summarize, the transgenic lines are characterized by a decreased rate of flux through the TCA cycle, a decreased rate of respiration, an increase in the cellular level of ascorbate, and an enhanced photosynthetic rate. To ascertain if the level of ascorbate has any functional significance with respect to the rate of respiration, we next incubated leaf discs isolated from wild-type plants in 50 mM ascorbate in the dark for a period of 2 h before illuminating them and measuring the assimilation of 14CO2 (Fig. 7). We chose this concentration of ascorbate since it is similar to that estimated to be present in the chloroplast (Smirnoff, 2000
The ability of plants to convert solar energy into biomass is of immense importance since the very survival of both photoauxotrophic and nonphotoautotrophic organisms depends on this process. Although the process of domestication of crop species has lead to huge increases in productivity, this has taken many generations and has come at the cost of narrowing the base of genetic diversity (Tanksley and McCouch, 1997 ; Zamir, 2001) and has generally occurred without an improvement in leaf photosynthesis (Richards, 2000). Recently, a number of biotechnology-based approaches utilizing transgenesis have been attempted. However, it is important to note that the majority of reports claiming enhanced photosynthetic rates are very much conditional; for example, the overexpression of maize (Zea mays) sucrose-phosphate synthase in tomato resulted in an increase rate of photosynthesis under saturating carbon dioxide and light but not in air (Galtier et al., 1993), whereas in contrast, plants expressing the cyanobacterial ictB gene displayed higher rates of photosynthesis only under limiting conditions (Lieman-Hurwitz et al., 2003). The mMDH antisense plants generated here were similarly characterized by elevated rates of photosynthesis over a range of light intensities; however, it seems most unlikely that a conserved mechanism underlies these observations. In both previous studies, either the initial or the total Rubisco activity was elevated in lines exhibiting enhanced assimilation, but this was not the case for the mMDH antisense plants. The reason for the increased assimilation in the AL lines is also not apparent when looking at metabolite levels that are usually considered to be diagnostic for the regulation of photosynthesis (Stitt, 1997), since, for example, the phosphate levels are repressed, which would be expected, paradoxically, to limit photosynthesis. However, the fact that the levels of carbohydrates do not accumulate dramatically in the AL lines, although they exhibit elevated shoot and fruit growth, may facilitate the high rates of photosynthesis observed.
Thus far we have discussed the elevated photosynthetic rates only in terms of the classically considered mechanisms of photosynthetic regulation rather than concentrating on the primary metabolic lesion that these plants display. That the TCA cycle could have a direct role in the regulation of the rate of photosynthesis is in keeping with current reevaluation of the role of the TCA cycle in the illuminated leaf (Ragahvendra and Padmasree, 2003
Surveying the levels of a wide range of primary metabolites suggested that these transgenic plants exhibit reduced ammonium assimilation and an increase in photorespiration. They also revealed a somewhat surprising trend in increasing succinate with decreasing mMDH activity; however, no consistent changes were observed in the levels of other Krebs cycle intermediates. Given that the evaluation of subcellular metabolite concentrations is not yet of high enough resolution to determine intracellular organic acids, the exact reason for this pattern of change remains unclear. By far the most striking feature of the metabolite data was, however, the dramatic increase in ascorbate observed in the transgenics. Intriguingly, reanalysis of GC-MS spectra revealed that the Aco1 mutant also displayed a dramatically elevated ascorbate level (F. Carrari and A.R. Fernie, unpublished data). That ascorbate levels increase following a restriction of flux through the Krebs cycle is fascinating, especially in light of recent reports suggesting that the terminal enzyme of ascorbate biosynthesis GLDH is coupled to the cytochrome pathway (Bartoli et al., 2000
The increase in ascorbate in the transformants, while interesting in its own right, may additionally be pivotal in the elevation of photosynthetic rate observed in these plants. Much is known concerning the importance of ascorbate within photosynthesis. Ascorbate acts in the Mehler peroxidase reaction with ascorbate peroxidase to regulate the redox state of photosynthetic electron carriers and as a cofactor for violaxanthin deepoxidase, an enzyme involved in xanthophyll cycle-mediated photoprotection (Smirnoff and Wheeler, 2000
Materials
Tomato (Solanum lycopersicum) L. cv Moneymaker was obtained from Meyer Beck (Berlin). Plants were handled as described in the literature (Carrari et al., 2003
The 996-bp fragment of the mitochondrial SlMDH was cloned in antisense orientation or using an RNAi approach into the vector pBINAR (Liu et al., 1999
Total RNA was isolated using the commercially available Trizol kit (Gibco BRL, Karlsruhe, Germany) according to the manufacturer's suggestions for the extraction from plant material. Hybridization using standard conditions was carried out using the expressed sequence tags for the various isoforms of MDH obtained from Clemson University (Clemson, SC) collection.
Western analysis of MDH protein was carried out on either crude protein extract or mitochondrial protein extract, exactly as previously described (Gietl et al., 1996
Enzyme extracts were prepared as described previously (Tauberger et al., 2000
Leaf samples were taken at the time point indicated, immediately frozen in liquid nitrogen, and stored at –80°C until further analysis. Extraction was performed by rapid grinding of tissue in liquid nitrogen and immediate addition of the appropriate extraction buffer. The levels of starch, Suc, Fru, and Glc in the leaf tissue were determined exactly as described previously (Fernie et al., 2001a
The determination of the levels of chlorophylls a and b,
The 14C-labeling pattern of Suc, starch, and other cellular constituents was performed by illuminating leaf discs (10-mm diameter) in a leaf-disc oxygen electrode (Hansatech, Kings Lynn, Norfolk, UK) in saturating 14CO2 at a PFD of 250 µmol m–2 s–1 of photosynthetically active radiation at 20°C for 30 min, and subsequent fractionation was performed exactly as detailed by Lytovchenko et al. (2002)
Dark respiration was measured using the same gas exchange system as defined above. Estimations of the TCA cycle flux on the basis of 14CO2 evolution were carried out following incubation of isolated leaf discs in 10 mM MES-KOH, pH 6.5, containing 2.32 KBq mL–1 of [1-14C]-, [2-14C]-, [3:4-14C]-, or [6-14C]Glc. 14CO2 evolved was trapped in KOH and quantified by liquid scintillation counting. The results were interpreted following ap Rees and Beevers (1960)
Proton-decoupled 13C NMR spectra of low-density mitochondrial suspensions were recorded at 150.9 MHz on a Varian Unity Inova 600 spectrometer (Palo Alto, CA) using a 10-mm diameter broadband probehead. The suspension was oxygenated with an air-lift (Fox et al., 1989
The t tests were performed using the algorithm embedded into Microsoft Excel (Microsoft, Seattle). The term significant is used in the text only when the change in question has been confirmed to be significant (P < 0.05) with the t test. Sequence data from this article have been deposited with the EMBL/GenBank data libraries under accession numbers AY725474 (mMDH), AY725475 (cMDH), AY725476 (gMDH), and AY725477 (chMDH).
We are very grateful to Dr. Joachim Fisahn (Max-Planck-Institut für Molekulare Pflanzenphysiologie) for help in organization of gas-exchange measurements and discussion of the results and are indebted to Helga Kulka (same institute) for excellent care of the plants. We are also most grateful to Christine Gietl (Technische Universität Munich, Germany) for the generous gift of the MDH antibodies. Received October 23, 2004; returned for revision December 3, 2004; accepted December 5, 2004.
1 This work was supported by the Max-Planck-Gesellschaft (to F.C., A.N.-N., A.L., and A.R.F.), by Conselho Nacional de Desenvolvimento Científico e Tecnológico (A.N.-N.), by Deutscher Akademischer Austauschdienst (A.N.-N.), and by the United Kingdom Biotechnology and Biological Sciences Research Council (A.M.O.S., R.G.R., and L.J.S.).  Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.104.055566. * Corresponding author; e-mail fernie{at}mpimp-golm.mpg.de; fax 49–(0)331–5678408.
Aebi H (1984) Catalase in vitro. Methods Enzymol 105: 121–126[ISI][Medline] Agius F, Gonzalez-Lamothe R, Caballero JL, Munoz-Blanco J, Botella MA, Valpuesta V (2003) Engineering increased vitamin C levels in plants by overexpression of a D-galacturonic acid reductase. Nat Biotechnol 21: 177–181[CrossRef][ISI][Medline]
ap Rees T, Beevers H (1960) Pathways of glucose dissimilation in carrot slices. Plant Physiol 35: 830–838
Aubert S, Bligny R, Douce R, Gout E, Ratcliffe RG, Roberts JKM (2001) Contribution of glutamate dehydrogenase to mitochondrial glutamate metabolism studied by 13C and 31P nuclear magnetic resonance. J Exp Bot 52: 37–45
Balmer Y, Vensel WH, Tanaka CK, Hurkman WJ, Gelhaye E, Rouhier N, Jacquot JP, Manieri W, Schuurmann P, Droux M, et al (2004) Thioredoxin links redox to the regulation of fundamental processes of plant mitochondria. Proc Natl Acad Sci USA 101: 2642–2647
Bartoli CG, Pastori GM, Foyer CH (2000) Ascorbate biosynthesis in mitochondria is linked to the electron transport chain between complexes III and IV. Plant Physiol 123: 335–343
Carrari F, Nunes-Nesi A, Gibon Y, Lytovchenko A, Ehlers Loureiro M, Fernie AR (2003) Reduced expression of aconitase results in an enhanced rate of photosynthesis and marked shifts in carbon partitioning in illuminated leaves of wild species tomato. Plant Physiol 133: 1322–1335
Chen Z, Gallie DR (2004) The ascorbic acid redox state controls guard cell signaling and stomatal movement. Plant Cell 16: 1143–1162
Danna CH, Bartoli CG, Sacco F, Ingala LR, Santa-Maria GE, Guiamet JJ, Ugalde RA (2003) Thylakoid bound ascorbate peroxidase mutant exhibits impaired electron transport and photosynthetic activity. Plant Physiol 132: 2116–2125 Farre EM, Bachmann A, Willmitzer L, Trethewey RN (2001a) Acceleration of potato tuber sprouting by the expression of a bacterial pyrophosphatase. Nat Biotechnol 19: 268–272[CrossRef][ISI][Medline]
Farre EM, Tiessen A, Roessner U, Geigenberger P, Trethewey RN, Willmitzer L (2001b) Analysis of the compartmentation of glycolytic intermediates, nucleotides, sugars, organic acids, amino acids and sugar alcohols in potato tubers using a nonaquous fractionation method. Plant Physiol 127: 685–700 Fernie AR, Carrari F, Sweetlove LJ (2004b) Respiratory metabolism: glycolysis, the TCA cycle and mitochondrial electron transport chain. Curr Opin Plant Biol 7: 254–261[CrossRef][ISI][Medline] Fernie AR, Roessner U, Trethewey RN, Willmitzer L (2001a) The contribution of plastidial phosphoglucomutase to the control of starch synthesis within the potato tuber. Planta 213: 418–426[CrossRef][ISI][Medline] Fernie AR, Roscher A, Ratcliffe RG, Kruger NJ (2001b) Fructose 2,6-bisphosphate activates pyrophosphate: fructose 6 phosphate 1-phosphotransferase and increases triose phosphate to hexose phosphate cycling in heterotrophic cells. Planta 212: 250–263[CrossRef][ISI][Medline] Fernie AR, Trethewey RN, Krotzky A, Willmitzer L (2004a) Metabolic profiling: from diagnostics to systems biology. Nat Rev Mol Cell Biol 5: 763–769[CrossRef][ISI][Medline] Fox GG, Ratcliffe RG, Southon TE (1989) Airlift systems for in vivo NMR spectroscopy of plant tissues. J Magn Reson 82: 360–366 Galtier N, Foyer CH, Huber J, Voelker TA, Huber SC (1993) Effects of elevated sucrose phosphate synthase activity on photosynthesis, assimilate partitioning, and growth in tomato (Lycoperscion esculentum var UC82B). Plant Physiol 101: 535–543[Abstract] Gibon Y, Vigeolas H, Tiessen A, Geigenberger P, Stitt M (2002) Sensitive and high throughput metabolite assays for inorganic pyrophosphate, ADPGlc, nucleotide phosphates, and glycolytic intermediates based on a novel cycling system. Plant J 30: 221–233[CrossRef][ISI][Medline] Gietl C (1992) Malate dehydrogenase isoenzymes: cellular locations and role in the flow of metabolites between the cytoplasm and cell organelles. Biochim Biophys Acta 1100: 217–234[CrossRef][Medline] Gietl C, Seidel C, Svendsen I (1996) Plant glyoxysomal but not mitochondrial malate dehydrogenase can fold without chaperone assistance. Biochim Biophys Acta 1274: 48–58[Medline] Hancock RD, Viola R (2002) Biotechnological approaches for L-ascorbic acid production. Trends Biotechnol 20: 299–305[CrossRef][Medline] Higgins DG, Sharp PM (1988) CLUSTAL: a package for performing multiple sequence alignment on a microcomputer. Gene 73: 237–244[CrossRef][ISI][Medline] Holtzapffel RC, Finnegan PM, Millar AH, Badger MR, Day DA (2002) Mitochondrial protein expression in tomato fruit during on-vine ripening and cold storage. Funct Plant Biol 29: 827–834[CrossRef] Jain AK, Nessler CL (2000) Metabolic engineering of an alternative pathway for ascorbate biosynthesis in plants. Mol Breed 6: 73–78[CrossRef]
Jenner HL, Winning BM, Millar AH, Tomlinson KM, Leaver CJ, Hill SA (2001) NAD malic enzyme and the control of carbohydrate metabolism in potato tubers. Plant Physiol 126: 1139–1149 Kiddle G, Pastori GM, Bernard S, Pignocchi C, Antoniw J, Verrier PJ, Foyer CH (2003) Effects of leaf ascorbate content on defence and photosynthesis gene expression in Arabidopsis thaliana. Antioxid Redox Signal 5: 23–32[CrossRef][ISI][Medline] Lieman-Hurwitz J, Rachmilevitch S, Mittler R, Marcus Y, Kaplan A (2003) Enhanced photosynthesis and growth of transgenic plants that express ictB, a gene involved in HCO3- accumulation in cyanobacteria. Plant Biotechnol J 1: 43–50 Liu XJ, Prat S, Willmitzer L, Frommer WB (1999) Cis-regulatory elements directing tuber specific and sucrose inducible expression of a chimeric class I patatin promoter-GUS gene fusion. Mol Gen Genet 223: 101–106 Lytovchenko A, Sweetlove LJ, Pauly M, Fernie AR (2002) The influence of cytosolic phosphoglucomutase on photosynthetic carbohydrate metabolism. Planta 215: 1013–1021[CrossRef][ISI][Medline]
Millar AH, Mittova V, Kiddle G, Heazlewood JL, Bartoli CG, Theodoulou FL, Foyer CH (2003) Control of ascorbate synthesis by respiration and its implications for stress responses. Plant Physiol 133: 443–447 Miller SS, Driscoll BT, Gregerson RG, Gantt JS, Vance CP (1998) Alfalfa malate dehydrogenase (MDH): molecular cloning and characterization of five different forms reveals a unique nodule-enhanced MDH. Plant J 15: 173–184[CrossRef][ISI][Medline] Miyagawa Y, Tamoi M, Shigeoka S (2001) Overexpression of a cyanobacterial fructose-1,6-/sedoheptulose-1,7-bisphosphatase in tobacco enhances photosynthesis and growth. Nat Biotechnol 19: 965–969[CrossRef][ISI][Medline] Neuberger M (1985) Preparation of plant mitochondria, criteria for assessment of mitochondrial integrity and impurity, survival in vitro. In R Douce, D Day, eds, Higher Plant Cell Respiration. Springer-Verlag, Berlin, pp 7–24
Pastori GM, Kiddle G, Antoniw J, Bernard S, Veljovic-Janovic S, Verrier PJ, Graham N, Foyer CH (2003) Leaf vitamin C contents modulate plant defence transcripts and regulate genes that control development through hormone signaling. Plant Cell 15: 939–951 Pellny TK, Ghannoum O, Conroy JP, Schluepmann H, Smeekens S, Andralojc J, Krause KP, Goddijn O, Paul MJ (2004) Genetic modification of photosynthesis with E. coli genes for trehalose synthesis. Plant Biotechnol J 2: 71–82[CrossRef][Medline] Raghavendra AS, Padmasree K (2003) Beneficial interactions of mitochondrial metabolism with photosynthetic carbon assimilation. Trends Plant Sci 8: 546–553[CrossRef][ISI][Medline]
Richards RA (2000) Selectable traits to increase crop photosynthesis and yield of grain crops. J Exp Bot 51: 447–458
Roessner U, Luedemann A, Brust D, Fiehn O, Linke T, Willmitzer L, Fernie AR (2001) Metabolic profiling allows comprehensive phenotyping of genetically or environmentally modified plant systems. Plant Cell 13: 11–29
Roessner-Tunali U, Hegemann B, Lytovchenko A, Carrari F, Bruedigam C, Granot D, Fernie AR (2003) Metabolic profiling of transgenic tomato plants overexpressing hexokinase reveals that the influence of hexose phosphorylation diminishes during fruit development. Plant Physiol 133: 84–99
Schauer N, Zamir D, Fernie AR (2005) Metabolic profiling of leaves and fruit of wild species tomato: a survey of the Solanum lycopersicon complex. J Exp Bot 56: 297–307 Scheibe R (2004) Malate valves to balance cellular energy supply. Physiol Plant 120: 21–26[CrossRef][Medline]
Sharkey TD, Vanderveer PJ (1989) Stromal phosphate concentration is low during feedback limited photosynthesis. Plant Physiol 91: 679–684 Shaw CR, Prasad R (1970) Starch gel electrophoresis of enzymes: a compilation of recipes. Biochem Genet 4: 297–320[CrossRef][ISI][Medline] Smirnoff N (2000) Ascorbate biosynthesis and function in photoprotection. Philos Trans R Soc Lond B Biol Sci 355: 1455–1464[CrossRef][ISI][Medline] Smirnoff N, Wheeler GL (2000) Ascorbic acid in plants: biosynthesis and function. CRC Crit Rev Plant Sci 19: 267–290[CrossRef]
Smith AMO, Ratcliffe RG, Sweetlove LJ (2004) Activation and function of plant mitochondrial uncoupling protein. J Biol Chem 279: 51944–51952 Stitt M (1997) The flux of carbon between the chloroplast and the cytoplasm. In DT Dennis, DH Turpin, DD Lefebre, DB Layzell, eds, Plant Metabolism. Longman, Harlow, UK, pp 382–400 Sweetlove LJ, Heazelwood JL, Herald V, Holtzapffel R, Day DA, Leaver CJ, Millar AH (2002) The impact of oxidative stress on Arabidopsis mitochondria. Plant J 32: 891–904[CrossRef][ISI][Medline] Sweetlove LJ, Kossmann J, Riesmeier JW, Trethewey RN, Hill SA (1998) The control of source to sink carbon flux during tuber development in potato. Plant J 15: 697–706[CrossRef] Tanksley SD, Ganal MW, Prince JP, de Vincente MC, Bonierbale MW, Broun P, Fulton TM, Giovannoni JJ, Grandillo S, Martin GB, et al (1992) High density molecular linkage maps of the tomato and potato genomes. Genetics 132: 1141–1160[Abstract]
Tanksley SD, McCouch SR (1997) Seed banks and molecular maps: unlocking genetic potential from the wild. Science 277: 1063–1066 Tauberger E, Fernie AR, Emmermann M, Renz A, Kossmann J, Willmitzer L, Trethewey RN (2000) Antisense inhibition of plastidial phosphoglucomutase provides compelling evidence that potato tuber amyloplasts import carbon from the cytosol in the form of glucose 6-phosphate. Plant J 23: 43–53[CrossRef][ISI][Medline] Thayer SS, Björkmann O (1990) Leaf xanthophyll content and composition in sun and shade determined by HPLC. Photosynth Res 23: 331–343[CrossRef] Van der Hoeven R, Ronning C, Giovannoni J, Martin G, Tanksley S (2003) Deductions about the number, organization and evolution of genes in the tomato genome based on analysis of a large expressed sequence tag collection and selective genomic sequencing. Plant Cell 14: 1441–1456 Wheeler GL, Jones MA, Smirnoff N (1998) The biosynthetic pathway of vitamin C in higher plants. Nature 393: 365–368[CrossRef][Medline] Zamir D (2001) Improving plant breeding with exotic genetic libraries. Nat Rev Genet 2: 983–989[CrossRef][ISI][Medline] This article has been cited by other articles:
|
TOP
ABSTRACT
RESULTS
-oxidation (Gietl et al., 1996
