Journal of Experimental Botany, Vol. 54, No. 384, pp. 1075-1083,
March 1, 2003
© 2003 Oxford University Press
Malate metabolism and reactions of oxidoreduction in cold-hardened winter rye (Secale cereale L.) leaves
Received 15 October 2002; Accepted 21 November 2002
1 Botanisches Institut, Goethe-Universität, PO Box 111932, D-60054 Frankfurt am Main, Germany
2 Laboratoire d’Ecophysiologie Végétale, Bâtiment 362, UFR Scientifique d’Orsay, Université Paris XI, F-91405 Orsay Cedex, France
3 To whom correspondence should be addressed. Fax: +49 69 79824822. E-mail: Feierabend{at}em.uni-frankfurt.de
Abbreviations: CHL, cold-hardened leaves; NHL, non-hardened leaves; NMR, nuclear-magnetic resonance spetroscopy; PEPCase, phosphoenolpyruvate carboxylase; PPDK, pyruvate;orthophosphate dikinase; ROS, reactive oxygen species.
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and methodsResultsDiscussionReferences |
|---|
In cold-hardened leaves (CHL) of winter rye (Secale cereale L.) much higher levels of malate were detected by 13C-NMR than in non-hardened leaves (NHL). As this was not observed previously, malate metabolism of CHL was studied in more detail by biochemical assays. The activities of several enzymes of malate metabolism, NADP-malate dehydrogenase, NAD-malate dehydrogenase, phosphoenolpyruvate carboxylase, and NADP-malic enzyme, were also increased in CHL. Short exposures to low temperature of 1–3 d did not induce increases in the malate content or in the activities of enzymes of malate metabolism in mature NHL. The malate content and the enzyme activities declined within 1–2 d after a transfer of CHL from their growing temperature of 4 °C to 22 °C. The malate content was further increased when CHL were exposed to a higher light intensity at 4 °C. In CO2-free air the malate content of CHL strongly declined at 4 °C. Malate may thus serve as an additional carbon sink and as a CO2-store in CHL. It may further function as a vacuolar osmolyte balancing increased concentrations of soluble sugars previously observed in the cytosol of CHL. Malate was not used as a source of reductants when CHL were exposed to photo-oxidative stress by treatment with paraquat. However, the activities of enzymes of the oxidative pentose phosphate pathway were markedly increased in CHL and may serve as non-photosynthetic sources of NADPH and thus contribute to the previously observed superior capacity of CHL of winter rye to maintain their antioxidants in a reduced state in the presence of paraquat.
Key words: Cold-acclimation, malate metabolism, paraquat, pentose phosphate pathway, Secale.
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Overwintering herbaceous plants or evergreen trees can only survive the winter seasons of cold climates when they are able to acclimate. Cold-acclimation is not solely restricted to freezing tolerance (Levitt, 1980; Steponkus, 1984; Pearce, 1999; Thomashow, 1999), but also requires resistance to cold-induced photodamage. Chilling temperatures enhance the risk for the production of reactive oxygen species (ROS) and aggravate photo-oxidative damage. At low temperatures, the balance between photosynthetic energy conversion and consumption is disturbed, because the dark reactions of photosynthesis are more strongly retarded than energy absorption and electron flow (Wise, 1995; Huner et al., 1998). Overreduction of the photosynthetic electron transport chain favours the transfer of excitation energy or of electrons to O2 with the production of 1O2 or of superoxide radicals O·2– (Asada, 1994; Foyer, 1997). Furthermore, low temperatures suppress protein synthesis. This also causes declines in the activities of photosystem II and the antioxidative enzyme catalase, because both are generally inactivated in light and depend on continuous concomitant repair in order to maintain constant steady-state levels (Streb et al., 1999). In cold-hardened plants, two different strategies for light utilization in photosynthesis were observed (Savitch et al., 2002). Cold-acclimated conifers reduce their chlorophyll content, down-regulate photosynthesis during the winter months, and dissipate light energy as heat. Cold-acclimated herbaceous plants, such as winter cereals acquire, however, resistance to photoinhibition (Somersalo and Krause, 1990; Hurry and Huner, 1992; Huner et al., 1993; Streb et al., 1997, 1999). They maintain a high capacity of photosynthesis, soluble sugars or fructans are accumulated and the plants continue to grow at low temperature (Hurry et al., 1995a, b; Savitch et al., 2000a, 2002). Due to the increased capacities of electron sinks overreduction of the photosynthetic electron transport chain and ROS formation can be largely avoided in cold-hardened winter cereals. In addition, cold-hardened leaves of winter rye acquire an increased capacity for the repair of photoinactivated proteins at low temperature (Shang et al., 2003).
While the contents of serveral antioxidants, such as ascorbate, glutathione or 
-tocopherol were greatly increased in cold-hardened (CHL), relative to non- hardened leaves (NHL) of winter rye (Streb et al., 1999), increased antioxidant levels alone were insufficient to prevent cold-induced photodamage (Streb and Feierabend, 1999). Soluble sugars which accumulate in cold-hardened leaves are assumed to serve as cryoprotectants, as a correlation between sugar accumulation and freezing tolerance was described (Tognetti et al., 1990; Guy et al., 1992). In addition to soluble sugars, such as sucrose and raffinose, CHL of Puma rye accumulate glycinebetaine and proline which also serve as compatible solutes in salt- or drought-stressed plants (Koster and Lynch, 1992).
A comparative screening of soluble carbon metabolites in CHL and NHL of winter rye by 13C-NMR-spectroscopy indicated remarkably increased levels of malate in CHL which had not been reported previously. Therefore, the potential role of malate and malate metabolism for CHL of rye was investigated in more detail. To this end, conditions favouring the accumulation or consumption of malate were analysed. As malate can serve as a sink for excess reducing equivalents in the chloroplasts via the ‘malate valve’ shuttle (Scheibe, 1987), it may also provide a store of reductants. Therefore, enzymes of malate metabolism and several non-photosynthetic reactions that might either accept or provide reducing equivalents under high excitation pressure or photo-oxidative conditions were also investigated for comparison.
|
Materials and methods |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Plant material and growing conditions
Experiments were performed with primary leaves of winter rye seedlings (Secale cereale L. cv. ‘Halo’, F.v. Lochow-Petkus GmbH, Bergen, Germany). Crops from 2001 (for Figs 4 and 9) or 1999 (all other figs) were used. Seedlings were grown either for 6 d at 22 °C (non-hardened leaves, NHL) or for 5 weeks at 4 °C (cold-hardened leaves, CHL) in continuous white light of 96 µmol m–2 s–1 PAR in glass-covered plastic boxes on filter paper (Macherey and Nagel MN 218, Freiburg, Germany) moistened with a modified Knop’s nutrient solution as described by Streb et al. (1999). After 6 d or 5 weeks, respectively, 22 °C-grown or 4 °C-grown leaves had reached a comparable stage of maturity, at which growth had been completed (Streb et al., 1999). For comparison, some measurements were performed with leaves of 6-week-old maize leaves (Zea mays L. cv. ‘Prinz’) grown in soil in the greenhouse at 23–25 °C.
|
|
Experimental treatments
Except for the incubations with paraquat, whole seedlings were used for the experimental treatments. Seedlings were placed in plastic boxes (22x22 cm2). The leaves lay flat on two layers of moist filter paper, containing either Knop’s solution, 0.4 M NaCl or 0.4 M mannitol, as indicated. For incubations with different CO2-concentrations, boxes with seedlings were placed in larger containers that were closed airtight with a plexiglass lid and streamed (200 cm3 min–1) either with air containing 3 kPa CO2 or with CO2-free air and kept for 24 h at 4 °C and 96 µmol m–2 s–1 PAR. For the removal of CO2 the air was passed through a washing bottle containing 0.1 M Ba(OH)2 before entering the container with the seedlings. For incubations with paraquat, segments of 4 cm were excised from the middle of the leaves and floated for 24 h at 4 °C in Petri dishes (10 cm diameter) on Knop’s solution containing 50 µM paraquat at either 96 µmol m–2 s–1 or 500 µmol m–2 s–1 PAR. Controls were incubated on Knop’s solution.
Extraction and assay of malate
Segments of 4 cm were excised from the middle of ten primary leaves and ground to a fine powder under liquid nitrogen. The powder was extracted with 0.4 ml 10% (w/v) perchloric acid with the addition of 20 mg Polyclar AT (insoluble). After centrifugation (5 min 4400 g at 4 °C) the sediment was washed with 2% (w/v) perchloric acid and recentrifuged. The combined supernatants were neutralized with 5 M KOH in 1 M ethanolamine. After adding 7% (w/v) Polyclar AT (insoluble) and 30 min incubation on a shaker at 4 °C the extract was centrifuged for 10 min at 4400 g and 4 °C and the resulting supernatant used for the malate assays. The malate content was determined enzymatically by the reduction of NAD at 340 nm. The assay mixture contained: 84.5 mM glycylglycine, pH 10.0, 43.0 mM glutamate, 0.5 mM NAD, 3.0 units malate dehydrogenase (from porcine heart), 3.0 units glutamate-oxaloacetate transaminase (from porcine heart), and 20 µl extract in a total volume of 1.0 ml.
Extraction and assay of enzyme activities
Homogenates of 5.0 ml or 2.0 ml (for PEPCase: phosphoenolpyruvate carboxylase and PPDK: pyruvate,orthophosphate dikinase) final volume were prepared by grinding sections of 4 cm from the middle of the primary leaves under ice-cold conditions with extraction buffer. Homogenates were centrifuged for 5 min (for PEPCase and PPDK) or 15 min (all other enzymes) at 7400 g and 4 °C, and the resulting supernatants used for the enzyme assays. The extraction buffer contained 0.1 M K-phosphate, pH 7.5, for the assays of NAD-malate dehydrogenase and NADP-isocitrate dehydrogenase, 0.1 M Tris/HCl, pH 7.5, 0.1 mM Na2EDTA, 5.0 mM MgCl2, 5.0 mM dithioerythritol, 0.5% (w/v) isoascorbate, and 2.5% (w/v) Polyclar AT (insoluble) for the assay of NADP-malic enzyme, 0.1 mM Tris/HCl, pH 7.5, 20 mM MgCl2, 1 mM Na2EDTA, 20% (v/v) glycerol, and 1 mM DTT for the assay of NADP-malate dehydrogenase, 0.1 M HEPES-KOH, pH 8.2, 5.0 mM MgCl2, 2.0 mM Na2EDTA, 4.0 mM amino-n-caproic acid, 2.0 mM NaH2PO4, 5.0 mM DTT, 0.14% (w/v) bovine serum albumin, and 1% (w/v) soluble polyvinylpyrrolidone for the assays of PEPCase and PPDK, 50 mM Tris/HCl, pH 7.5, for the assays of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, 50 mM Tris/HCl, pH 7.5, 1 mM Na2EDTA, and 1 mM ß-mercaptoethanol for the assay of glycerol-3- phosphate dehydrogenase.
Enzyme activities were assayed spectrophotometrically at 25 °C. The activity of NADP-malic anzyme (EC 1.1.1.40) was determined according to Asami et al. (1979), the activity of NADP-malate dehydrogenase (EC 1.1.1.82) according to Kingston-Smith et al. (1997), the activities of PEPCase (EC 4.1.1.91) and PPDK (EC 2.7.9.1) according to Pittermann and Sage (2000), the activity of glycerol-3-phosphate dehydrogenase (EC 1.1.1.8) according to White (1975). The assay mixture for NAD-malate dehydrogenase (EC 1.1.1.37) contained in a total volume of 1.0 ml 94 mM K-phosphate, pH 7.6, 0.5 mM NADH and 0.5 mM oxaloacetate. The assay mixture for NADP-isocitrate dehydrogenase (EC 1.1.1.42) contained in a total volume of 1.0 ml 45 mM K-phosphate, pH 7.6, 0.4 mM MgCl2 and 90 µM NADP and 7.5 mM isocitrate. The assay mixtures for glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (EC 1.1.1.44) contained in a total volume of 1.0 ml 45.0 mM triethanolamine-KOH, pH 8.0, 3.6 mM Na2EDTA, 0.7 mM MgCl2, 0.5 mM NADP, and 2 mM of either glucose-6-phosphate or 6-phosphogluconate.
13C-NMR spectroscopy
Ten g of primary leaves were ground to a fine powder with liquid nitrogen and extracted with perchloric acid as described by Aubert et al. (1998). The extracts were adjusted to pH 5.0, lyophilized, dissolved in 10% 2H2O and neutralized to pH 7.5 with KOH. Extracts were used for measurements in a NMR-spectrometer (AMX 400, Bruker, Bilerica, MA) in a 10 mm multinuclear tube tuned at 100.6 MH2 for 13C-NMR. The resonance signal of 2H2O was used as a lock signal. Data acquisition conditions were as described (Aubert et al., 1998), except that 13C-NMR-data were recorded with 225 scans. The peaks in the NMR-spectra were identified by comparison with standard solutions of known compounds that had previously been reported (Aubert et al., 1998).
|
Results |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Malate accumulation in cold-hardened leaves
Soluble carbon metabolites of NHL and CHL of winter rye were analysed by 13C-NMR. The carbon spectrum was dominated by the soluble sugars glucose, sucrose and fructose (Fig. 1). Cold-hardened leaves contained slightly higher sucrose and markedly lower glucose levels than NHL, as expected according to previous reports (Tognetti et al., 1990; Guy et al., 1992). A most remarkable unexpected difference was, however, that CHL contained several-fold higher levels of malate than NHL. The properties of malate accumulation were further investigated by quantitative biochemical analysis. The highest malate concentrations occurred in the basal parts and the lowest malate concentrations in the upper tip parts of CHL (Fig. 2). In order to investigate conditions for malate accumulation further, only the middle parts of the leaves were used (Fig. 3). Malate concentrations of the middle sections of CHL were more than 3-fold higher than those of NHL (Fig. 3). The range of the malate contents of CHL varied greatly between leaves of seedlings obtained from seeds of different years of harvest (compare Figs 3, 4). It was, however, always much higher in CHL than in NHL.
|
|
|
The malate content of CHL remained unchanged when the seedlings were kept in darkness for 24 h at 4 °C. It was further increased during exposure to a higher light intensity of 1000 µmol m–2 s–1 PAR at 4 °C. Exposure of the leaves to salt (0.4 M NaCl) or osmotic stress (0.4 M mannitol) at 4 °C induced minor increases. Exposure to an elevated CO2-atmosphere (3 kPa) at 4 °C did not increase the malate content. However, when CHL were kept for 24 h in CO2-free air the malate was depleted and declined nearly to the level of NHL (Fig. 3). Within 24 h the malate content declined almost to the level of NHL whenever cold-hardened seedlings were transferred from 4 °C to 22 °C, independently of the light conditions (Fig. 3). The decline of the malate content at 22 °C was relatively slow, with a half time of 5–6 h (not shown). In NHL the malate content was not increased by 1–3 d exposures to 4 °C (not shown). In the presence of 50 µM paraquat, which evokes the production of O·2– radicals (Dodge, 1994), the malate content of CHL was not markedly diminished at 4 °C. However, the increase of the malate content observed after transfer of CHL to a higher light intensity at 4 °C was prevented in the presence of paraquat (Fig. 4).
Enzymes of malate metabolism and oxidoreduction
The activity of PEPCase was assayed as a potential source of malate production. In CHL, the activity of PEPCase was twice as high as in NHL (Fig. 5). The activity of PPDK, which would be needed for the regeneration of phosphoenolpyruvate in a complete cycle of C4-metabolism did, however, not differ in CHL and NHL. Relative to leaves of a typical C4-plant, such as maize, the activities of both PEPCase and PPDK were much lower in both CHL and NHL of winter rye (Fig. 5). The enzyme activities of malate metabolism, such as NADP-malate dehydrogenase, NAD-malate dehydrogenase and NADP-malic enzyme, were significantly increased in CHL, relative to NHL (Fig. 6). Both the apparent activity observed after extraction and the maximal activity of NADP-malate dehydrogenase measured after activation in the presence of 50 mM DTT in vitro were similarly increased in CHL. In NHL as well as in CHL the apparent activity amounted to about 40% of the maximal activity at a low light intensity of 96 µmol m–2 s–1 PAR. After transfer of CHL from their growing temperature of 4 °C to 22 °C activities of both malate dehydrogenases declined. The activation state of the NADP-malate dehydrogenase declined from about 40% at 4 °C to 25–30% at 22 °C. Malic enzyme activity was almost absent in NHL and was virtually lost within 2 d after exposure of CHL to 22 °C (Fig. 6). The activities of NADP-malate dehydrogenase (Fig. 7) and of NADP-malic enzyme (not shown) did not increase when NHL were exposed for up to 2 d to 4 °C. As the maximal activity of NADP-malate dehydrogenase declined, the activation state of the enzyme increased in NHL during the cold exposure (Fig. 7). When CHL were treated with 50 µM paraquat, NADP-malate dehydrogenase was totally inactivated at both low and high light intensity, but could be reactivated in vitro by incubation with 50 mM DTT to the same high maximal activity as measured in untreated CHL (Fig. 8).
|
|
|
|
Compared with enzymes of malate metabolism, other enzyme reactions were investigated that could conceivably be either related to alternative carbon sinks or serve as non-photosynthetic sources for reducing equivalents, in particular of NADPH. Glycerolphosphate dehydrogenase which is predominantly involved in glycerolipid synthesis was hardly detected in mature NHL, but significantly increased in CHL (Fig. 9). However, in contrast to the behaviour of malic enzyme, increased activities of glycerolphosphate dehydrogenase did not correlate with cold acclimation of the leaves. Glycerolphosphate dehydrogenase did not decline during the dehardening (Streb et al., 1999) of CHL of rye after transfer to 22 °C (Fig. 9) and its activity also increased after a short-term exposure of only 1 d to low temperature which does not induce cold-hardening (Fig. 7). Increases of glycerolphosphate dehydrogenase could also be induced in NHL by an exposure to a higher light intensity (1000 µmol m–2 s–1 PAR) without low temperature treatment (Fig. 7). Among NADP- reducing reactions NADP-isocitrate dehydrogenase was slightly increased in CHL, relative to NHL (Fig. 9). Glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were quite markedly increased in CHL and their activities declined during dehardening after transfer of CHL from 4 °C to 22 °C (Fig. 9). The activities of these enzymes were not increased during up to 2 d short-term exposures of NHL to 4 °C (not shown).
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Cold-hardened leaves of winter rye were characterized by higher malate contents than NHL. The occurrence of an increased malate accumulation and of increased activities of enzymes of malate metabolism, particularly of NADP-malic enzyme, was well correlated to the state of cold-hardening of winter rye leaves. Increased malate contents and enzyme activities were observed only after prolonged growth of the plants at 4 °C, but not after short-term exposures of 1–3 d of NHL to low temperature. Resistance to cold-induced photoinhibitory damage is only acquired when winter rye leaves develop at low temperature (Huner et al., 1993; Streb et al., 1999). As previously documented, resistance to cold-induced photodamage is largely lost within 3 d when cold-hardened winter rye plants are transferred to a higher temperature of 22 °C (Streb et al., 1999). During this dehardening at 22 °C, malate contents and the activities of enzymes of malate metabolism also declined to the levels of NHL, whereas several antioxidants (ascorbate, glutathione,
-tocopherol) and activities of antioxidative enzymes retained much higher levels than in NHL (Streb et al., 1999). Interestingly, malate was also found to represent the most abundant soluble carbon compound in cold-acclimated leaves of the alpine plant Ranunculus glacialis where it also declined during deacclimation (Streb et al., 2003). The specificity of the correlation of increased activities of enzymes of malate metabolism to cold-hardening of the winter rye leaves is further underlined by a comparison with the behaviour of glycerolphosphate dehydrogenase. Glycerolphosphate dehydrogenase is involved in the biosynthesis of glycerolipids which could represent additional carbon sinks. Photodamage, as expected under high excitation pressure, may lead to membrane damage and demand an enhanced regeneration of membrane lipids. Accordingly, glycerolphosphate dehydrogenase activity was much higher in CHL than in NHL. However, the high activity did not decline during dehardening of CHL and its acitvity also increased during short exposures of NHL to low temperature and even after exposure of NHL to a higher light intensity at 22 °C. Thus glycerolphosphate dehydrogenase appeared to respond to changes of the excitation pressure (Huner et al., 1996, 1998) rather than to low temperature per se. Malate is a well-known intermediate of photosynthetic metabolism of C4- and CAM-plants. The increased acitivity of PEPCase suggests that the increased malate content of CHL of winter rye was produced via this enzyme. However, its activity in CHL was much lower than in leaves of a conventional C4-plant, such as maize. A complete C4- or CAM-cycle would, in addition, require an increased activity of PPDK which was, however, not observed in CHL of winter rye. Such observations indicate that increased malate production was not related to C4- or CAM-metabolism in CHL.
Malate is known to function as a vacuolar osmolyte, for instance in guard cells where it also appears to be synthesized via PEPCase (Asai et al., 2000). Chilling-tolerant plants were found to close their stomata at low temperature (Wilkinson et al., 2001). Stomatal closure would be accompanied by a decrease of malate, however, no information is available on the proportion of the malate content of CHL that is localized in guard cells. Malate may, nevertheless, provide an osmoticum for other leaf cells of cold-hardened rye, although its accumulation was only slightly stimulated by osmotic stress conditions in the presence of NaCl or mannitol. The major solutes that are accumulated in CHL at low temperature are soluble sugars, such as sucrose, raffinose (Guy, 1990; Koster and Lynch, 1992) or fructans (Savitch et al., 2000a). These compatible solutes are regarded as cryoprotectants. However, according to Koster and Lynch (1992) sucrose and raffinose accumulated only in the cytosolic compartments but not in the vacuole of cold-acclimated rye leaves. Therefore, increased malate accumulation in the vacuole may be necessary in order to balance the higher solute concentration of the cytoplasm.
Malate may also serve as an additional sink for carbon assimilation and reducing equivalents at low temperature and simultaneously provide a store for CO2 and reducing equivalents. In several other plants, fumaric acid was recently described as a previously overlooked photoassimilate which often exceeds the levels of soluble sugars and starch (Chia et al., 2000). Evidence was obtained that increased malate accumulation in CHL was indeed related to photosynthetic carbon assimilation, as its content was further stimulated by a higher light intensity and this increase was prevented when photosynthesis was inhibited by paraquat. The decline of malate in CO2-free air suggests that it could be used as a carbon store for the liberation of CO2 via malic enzyme, as in C4- or CAM plants. Under high excitation pressure, as expected to occur at low temperature (Savitch et al., 2000b), malate was also shown to function as a transport metabolite exporting reducing equivalents out of the chloroplasts via the so-called ‘malate valve’ (Scheibe, 1987). The increased malate formation observed after exposure of CHL to high light could thus conceivably serve as a means to avoid an overreduction of the chloroplastic electron transport chain. It is, however, not known to what extent exported malate can accumulate and also function as a store of reducing equivalents. In CHL of winter rye, malate was not utilized under the photo-oxidative stress conditions that were imposed by the paraquat treatment. Obviously this was not possible, because in paraquat-treated CHL the redox-sensitive NADP-malate dehydrogenase was totally inactivated and, therefore, malate could not be used as a source of reducing equivalents in the chloroplasts.
Cold-hardened leaves of winter rye are much more tolerant to paraquat-induced photodamage than NHL. It was previously shown that a mere increase of antioxidants, such as ascorbate and glutathione, which can be induced without cold-hardening by feeding substrates for their biosynthesis, was not sufficient to establish such a high paraquat tolerance in NHL, as observed in CHL (Streb and Feierabend, 1999). In addition to increased antioxidant contents, CHL had a much higher capacity for maintaining these antioxidants in a reduced state under the oxidative stress that was imposed by the paraquat treatment (Streb and Feierabend, 1999). Relative to NHL, CHL must therefore possess superior non-photosynthetic sources of reductants that can be utilized for the control of the redox state of antioxidants. While malate could not be utilized, the oxidative pentose phosphate pathway may serve as a major non-photosynthetic source of NADPH production which is needed for the reduction of oxidized glutathione. The observed increases of the key enzymes glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were well correlated to the state of cold-hardening of winter rye leaves and thus emphasized a potential protective role of the oxidative pentose phosphate pathway for the stress tolerance of CHL. In cold-acclimated winter rape plants the contribution of the oxidative pentose phosphate cycle to glucose catabolism was also shown to be increased in relation to glycolysis (Maciejewska and Bogatek, 2002). In non-photosynthetic organisms, such as yeast, animal or human cells the fundamental function of the pentose phosphate cycle for antioxidant defence is well established, and the activity of glucose-6-phosphate dehydrogenase was shown to correlate closely with the content of glutathione and the strength of antioxidative protection (Pandolfi et al., 1995; Juhnke et al., 1996; Kuo and Tang, 1998; Préville et al., 1999).
|
Acknowledgements |
|---|
Financial support by the Deutsche Forschungsgemeinschaft, Bonn, is greatly appreciated. We thank Professor Richard Bligny and Dr Elisabeth Gout, Grenoble, and Dr Matthias Schmidt, Frankfurt am Main, for valuable advice.
|
References |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Asada K. 1994. Production and action of active oxygen species in photosynthetic tissues. In: Foyer CH, Mullineaux PM, eds. Causes of photo-oxidative stress and amelioration of defence systems in plants. Boca Raton, FL: CRC Press, 77–104.
Asai N, Nakajima N, Tamaoki M, Kamada H, Kondo N. 2000. Role of malate synthesis mediated by phosphoenolpyruvate carboxylase in guard cells in the regulation of stomatal movement. Plant and Cell Physiology 41, 10–15.
Asami S, Inoue K, Matsumoto K, Murachi A, Akazawa T. 1979. NADP-malic enzyme from maize leaf: purification and properties. Archives of Biochemistry and Biophysics 194, 503–510.[CrossRef][Web of Science][Medline]
Aubert S, Curien G, Bligny R, Gout E, Douce R. 1998. Transport, compartmentation, and metabolism of homoserine in higher plant cells. Plant Physiology 116, 547–557.
Chia DW, Yoder TJ, Reiter W-D, Gibson SI. 2000. Fumaric acid: an overlooked form of fixed carbon in Arabidopsis and other plant species. Planta 211, 743–751.[CrossRef][Web of Science][Medline]
Dodge AD. 1994. Herbicide action and effects on detoxification processes. In: Foyer CH, Mullineaux PM, eds. Causes of photo-oxidative stress and amelioration of defense systems in plants. Boca Raton, FL: CRC Press, 220–236.
Foyer CH. 1997. Oxygen metabolism and electron transport in photosynthesis. In: Scandalios JG, ed. Oxidative stress and the molecular biology of antioxidant defenses, Monograph 34. Cold Spring Harbor: Cold Spring Harbor Laboratory Press, 587–621.
Guy CL. 1990. Cold acclimation and freezing stress tolerance: role of protein metablism. Annual Review of Plant Physiology and Plant Molecular Biology 41, 187–223.[Web of Science]
Guy CL, Huber JLA, Huber SC. 1992. Sucrose phosphate synthase and sucrose accumulation at low temperature. Plant Physiology 100, 502–503.
Huner NPA, Maxwell DP, Gray GR, Savitch LV, Krol M, Ivanov AG, Falk S. 1996. Sensing environmental temperature change through imbalances between energy supply and energy consumption: redox state of photosystem II. Physiologia Plantarum 98, 358–364.
Huner NPA, Öquist G, Hurry VM, Krol M, Falk S, Griffith M. 1993. Photosynthesis, photoinhibition and low temperature acclimation in cold-tolerant plants. Photosynthesis Research 37, 19–39.
Huner NPA, Öquist G, Sarhan F. 1998. Energy balance and acclimation to light and cold. Trends in Plant Science 3, 224–230.[CrossRef][Web of Science]
Hurry VM, Huner NPA. 1992. Effect of cold hardening on sensitivity of winter and spring wheat leaves to short-term photoinhibition and recovery of photosynthesis. Plant Physiology 100, 1283–1290.
Hurry VM, Keerberg O, Pärnik T, Gardeström P, Öquist G. 1995a. Cold-hardening results in increased activity of enzymes involved in carbon metabolism in leaves in winter rye (Secale cereale L.). Planta 195, 554–562.[Web of Science]
Hurry V, Strand Å, Tobiaeson M, Gardeström P, Öquist G. 1995b. Cold hardening of spring and winter wheat and rape results in different effects on growth, carbon metabolism, and carbohydrate content. Plant Physiology 109, 697–706.[Abstract]
Juhnke H, Krems B, Kötter P, Entian K-D. 1996. Mutants that show increased sensitivity to hydrogen peroxide reveal an important role for the pentose phosphate pathway in protection of yeast against oxidative stress. Molecular and General Genetics 252, 456–464.
Kingston-Smith AH, Harbinson J, Williams J, Foyer CH. 1997. Effect of chilling on carbon assimilation, enzyme activation, and photosynthetic electron transport in the absence of photoinhibition in maize leaves. Plant Physiology 114, 1039–1046.[Abstract]
Koster KL, Lynch DV. 1992. Solute accumulation and compartmentation during the cold acclimation of Puma rye. Plant Physiology 98, 108–113.
Kuo WY, Tang TK. 1998. Effects of G6PD overexpression in NIH3T3 cells treated with tert-butyl hydroperoxide or paraquat. Free Radical Biology and Medicine 24, 1130–1138.[CrossRef][Web of Science][Medline]
Levitt J. 1980. Responses of plants to environmental stresses, Vol. 1. Chilling, freezing, and high temperature stresses. New York: Academic Press.
Maciejewska U, Bogatek R. 2002. Glucose catabolism in leaves of cold-treated winter rape plants. Journal of Plant Physiology 159, 397–402.[CrossRef]
Pandolfi PP, Sonati F, Rivi R, Mason P, Grosveld F, Luzzatto L. 1995. Targeted disruption of the housekeeping gene encoding glucose 6-phosphate dehydrogenase (G6PD): G6PD is dispensable for pentose synthesis but essential for defense against oxidative stress. EMBO Journal 14, 5209–5215.[Web of Science][Medline]
Pearce RS. 1999. Molecular analysis of acclimation to cold. Plant Growth Regulation 29, 47–76.
Pittermann J, Sage RF. 2000. Photosynthetic performance at low temperature of Bouteloua gracilis Lag. a high-altitude C4 grass from the Rocky Mountains, USA. Plant, Cell and Environment 23, 811–823.[CrossRef]
Préville X, Salvemini F, Giraud S, Chaufour S, Paul C, Stepien G, Ursini MV, Arrigo A-P. 1999. Mammalian small stress proteins protect against oxidative stress through their ability to increase glucose-6-phosphate dehydrogenase activity and by maintaining optimal cellular detoxifying machinery. Experimental Cell Research 247, 61–78.[CrossRef][Web of Science][Medline]
Savitch LV, Harney T, Huner NPA. 2000a. Sucrose metabolism in spring and winter wheat in reponse to high irradiance, cold stress and cold acclimation. Physiologia Plantarum 108, 270–278.[CrossRef]
Savitch LV, Leonardos ED, Krol M, Jansson S, Grodzinski B, Huner NPA, Öquist G. 2002. Two different strategies for light utilization in photosynthesis in relation to growth and cold acclimation. Plant, Cell and Environment 25, 761–771.[CrossRef]
Savitch LV, Massacci A, Gray GR, Huner NPA. 2000b. Acclimation to low temperature or high light mitigates sensitivity to photoinhibition: roles of the Calvin cycle and the Mehler reaction. Australian Journal of Plant Physiology 27, 253–264.[Web of Science]
Scheibe R. 1987. NADP+-malate dehydrogenase in C3-plants: regulation and role of a light-activated enzyme. Physiologia Plantarum 71, 393–400.[CrossRef]
Shang W, Schmidt M, Feierabend J. 2003. Increased capacity for synthesis of the D1 protein and of catalase at low temperature in leaves of cold-hardened winter rye (Secale cereale L.). Planta (in press).
Somersalo S, Krause GH. 1990. Reversible photoinhibition of unhardened and cold-acclimated spinach leaves at chilling temperatures. Planta 180, 181–187.
Steponkus PL. 1984. Role of the plasma membrane in freezing injury and cold acclimation. Annual Review of Plant Physiology 35, 543–584.[CrossRef][Web of Science]
Streb P, Aubert S, Gout E, Bligny R. 2003. Reversibility of cold- and light-stress tolerance and accompanying changes of metabolite and antioxidant levels in the two high mountain plant species Soldanella alpina and Ranunculus glacialis. Journal of Experimental Botany 54, 405–418.
Streb P, Feierabend J. 1999. Significance of antioxidants and electron sinks for the cold-hardening-induced resistance of winter rye leaves to photo-oxidative stress. Plant, Cell and Environment 22, 1225–1237.
Streb P, Feierabend J, Bligny R. 1997. Resistance to photoinhibition of photosystem II and catalase and antioxidative protection in high mountain plants. Plant, Cell and Environment 20, 1030–1040.
Streb P, Shang W, Feierabend J. 1999. Resistance of cold-hardened winter rye leaves (Secale cereale L.) to photo-oxidative stress. Plant, Cell and Environment 22, 1211–1223.
Tognetti JA, Salerno GL, Crespi MD, Pontis HG. 1990. Sucrose and fructan metabolism of different wheat cultivars at chilling temperatures. Physiologia Plantarum 78, 554–559.[CrossRef]
Thomashow MF. 1999. Plant cold acclimation: freezing tolerance genes and regulatory mechanisms. Annual Review of Plant Physiology and Plant Molecular Biology 50, 571–599.[CrossRef][Web of Science][Medline]
White III HB. 1975. Glycerol phosphate dehydrogenase of chicken breast muscle. In: Wood WA, ed. Methods in enzymology. Vol. XLI B. New York: Academic Press, 245–259.
Wilkinson S, Clephan AL, Davies WJ. 2001. Rapid low temperature-induced stomatal closure occurs in cold-tolerant Commelina communis leaves but not in cold-sensitive tobacco leaves, via a mechanism that envolves apoplastic calcium but not abscisic acid. Plant Physiology 126, 1566–1578.
Wise RR. 1995. Chilling-enhanced photo-oxidation: the production, action and study of reactive oxygen species produced during chilling in the light. Photosynthesis Research 45, 79–97.[CrossRef][Web of Science]
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  S. Nogues, G. Tcherkez, P. Streb, A. Pardo, F. Baptist, R. Bligny, J. Ghashghaie, and G. Cornic Respiratory carbon metabolism in the high mountain plant species Ranunculus glacialis J. Exp. Bot., November 1, 2006; 57(14): 3837 - 3845. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y.-O. Kim and H. Kang The Role of a Zinc Finger-containing Glycine-rich RNA-binding Protein During the Cold Adaptation Process in Arabidopsis thaliana Plant Cell Physiol., June 1, 2006; 47(6): 793 - 798. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||