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1.
Xiang L Le Roy K Bolouri-Moghaddam MR Vanhaecke M Lammens W Rolland F Van den Ende W 《Journal of experimental botany》2011,62(11):3849-3862
Over the past decades, considerable advances have been made in understanding the crucial role and the regulation of sucrose metabolism in plants. Among the various sucrose-catabolizing enzymes, alkaline/neutral invertases (A/N-Invs) have long remained poorly studied. However, recent findings have demonstrated the presence of A/N-Invs in various organelles in addition to the cytosol, and their importance for plant development and stress tolerance. A cytosolic (At-A/N-InvG, At1g35580) and a mitochondrial (At-A/N-InvA, At1g56560) member of the A/N-Invs have been analysed in more detail in Arabidopsis and it was found that At-A/N-InvA knockout plants show an even more severe growth phenotype than At-A/N-InvG knockout plants. The absence of either A/N-Inv was associated with higher oxidative stress defence gene expression, while transient overexpression of At-A/N-InvA and At-A/N-InvG in leaf mesophyll protoplasts down-regulated the oxidative stress-responsive ascorbate peroxidase 2 (APX2) promoter. Moreover, up-regulation of the APX2 promoter by hydrogen peroxide or abscisic acid could be blocked by adding metabolizable sugars or ascorbate. A hypothetical model is proposed in which both mitochondrial and cytosolic A/N-Invs can generate glucose as a substrate for mitochondria-associated hexokinase, contributing to mitochondrial reactive oxygen species homeostasis. 相似文献
2.
Iron deficiency enhances the levels of ascorbate,glutathione, and related enzymes in sugar beet roots 总被引:1,自引:0,他引:1
Summary. The effects of Fe deficiency stress on the levels of ascorbate and glutathione, and on the activities of the enzymes ferric
chelate reductase, glutathione reductase (EC 1.6.4.2), ascorbate free-radical reductase (EC 1.6.5.4) and ascorbate peroxidase
(EC 1.11.1.11), have been investigated in sugar beet (Beta vulgaris L.) roots. Plasma membrane vesicles and cytosolic fractions were isolated from the roots of the plants grown in nutrient
solutions in the absence or presence of Fe for two weeks. Plants responded to Fe deficiency not only with a 20-fold increase
in root ferric chelate reductase activity, but also with moderately increased levels of the general reductants ascorbate (2-fold)
and glutathione (1.6-fold). The enzymes of the ascorbate-glutathione cycle in roots were also affected by Fe deficiency. Glutathione
reductase activity was enhanced 1.4-fold with Fe deficiency, associated to an increased ratio of reduced to oxidized glutathione,
from 3.1 to 5.2. The plasma membrane fraction from iron-deficient roots showed 1.7-fold higher ascorbate free-radical reductase
activity, whereas in the cytosolic fraction the enzyme activity was not affected by Fe deficiency. The activity of the cytosolic
hemoprotein ascorbate peroxidase decreased approximately by 50% with Fe deprivation. These results show that sugar beet responds
to Fe deficiency with metabolic changes affecting components of the ascorbate-glutathione cycle in root cells. This suggests
that the ascorbate-glutathione cycle would play certain roles in the general Fe deficiency stress responses in strategy I
plants.
Received November 19, 2001; accepted September 30, 2002; published online April 2, 2003
RID="*"
ID="*" Correspondence and reprints: Departamento de Nutrición Vegetal, Estación Experimental de Aula Dei, CSIC, Apartado 202,
50080 Zaragoza, Spain. 相似文献
3.
Double mutants deficient in cytosolic and thylakoid ascorbate peroxidase reveal a complex mode of interaction between reactive oxygen species, plant development, and response to abiotic stresses 总被引:10,自引:1,他引:9
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Miller G Suzuki N Rizhsky L Hegie A Koussevitzky S Mittler R 《Plant physiology》2007,144(4):1777-1785
Reactive oxygen species (ROS) play a key signaling role in plants and are controlled in cells by a complex network of ROS metabolizing enzymes found in several different cellular compartments. To study how different ROS signals, generated in different cellular compartments, are integrated in cells, we generated a double mutant lacking thylakoid ascorbate peroxidase (tylapx) and cytosolic ascorbate peroxidase1 (apx1). Our analysis suggests that two different signals are generated in plants lacking cytosolic APX1 or tylAPX. The lack of a chloroplastic hydrogen peroxide removal enzyme triggers a specific signal in cells that results in enhanced tolerance to heat stress, whereas the lack of a cytosolic hydrogen peroxide removal enzyme triggers a different signal, which results in stunted growth and enhanced sensitivity to oxidative stress. When the two signals are coactivated in cells (i.e. tylapx/apx1), a new response is detected, suggesting that the integration of the two different signals results in a new signal that manifests in late flowering, low protein oxidation during light stress, and enhanced accumulation of anthocyanins. Our results demonstrate a high degree of plasticity in ROS signaling in Arabidopsis (Arabidopsis thaliana) and suggest the existence of redundant pathways for ROS protection that compensate for the lack of classical ROS removal enzymes such as cytosolic and chloroplastic APXs. Further investigation of the enhanced heat tolerance in plants lacking tylAPX, using mutants deficient in chloroplast-to-nuclei retrograde signaling, suggests the existence of a chloroplast-generated stress signal that enhances basal thermotolerance in plants. 相似文献
4.
The presence of sucrose (Suc) in plastids was questioned for several decades. Although it was reported some decades ago, neither
Suc transporters nor Suc metabolizing enzymes were demonstrated to be active in those organelles. By biochemical, immunological,
molecular and genetic approaches we show that alkaline/neutral invertases (A/N-Invs) are also localized in chloroplasts of
spinach and Arabidopsis. A/N-Inv activity and polypeptide content were shown in protein extracts from intact chloroplasts. Moreover, we functionally
characterized the Arabidopsis
At-A/N-InvE gene coding for a chloroplast-targeted A/N-Inv. The At-A/N-InvE knockout plants displayed a lower total A/N-Inv activity in comparison with wild-type plants. Furthermore, neither A/N-Inv
activity nor A/N-Inv polypeptides were detected in protein extracts prepared from chloroplasts of mutant plants. Also, the
measurement of carbohydrate content, in leaves harvested either at the end of the day or at the end of the night period, revealed
that the knockout plants showed a decrease in starch accumulation but no alteration in Suc levels. These are the first results
demonstrating the presence of a functional A/N-Inv inside chloroplasts and its relation with carbon storage in Arabidopsis leaves. Taken together our data and recent reports, we conclude that the participation of A/N-Invs in the carbon flux between
the cytosol and the plastids may be a general phenomenon in plants.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
5.
Experiments were conducted to investigate the relationship between ultraviolet (UV) C-induced oxidative damage and the activity
of ascorbate peroxidase (APX), using transgenic tobacco (Nicotiana tabacum L. cv. Petit Havana) plants overexpressing cytosolic APX gene (apx1). Transgenic plants having 2.3 fold higher total APX activity, as compared to the wild type plants, showed normal morphological
characters. Exposure of 70-day-old plants to fixed intensity UV-C radiation caused an increase in the malondialdehyde (MDA)
content in wild type as well as transgenic plants. However, the wild type plants showed significantly higher (p < 0.05) lipid peroxidation as compared to the transgenic plants. Higher proline accumulation was recorded in transgenic plants
as compared to the wild type plants, after 24 hours of UV-C exposure. Although the ascorbate content decreased continuously
with increasing exposure to UV-C radiation, yet the wild type plants exhibited higher ascorbate levels than the transgenic
plants. A marked difference in H2O2 content, between the wild type and transgenic plants, was consistently observed up to 20 hours of UV-C exposure. A direct
correlation of ascorbate, MDA and H2O2 levels was recorded with the extent of oxidative stress, signifying that these could be used as potential bio-marker molecules
for oxidative stress. The results clearly demonstrate that overexpression of cytosolic APX can protect tobacco plants from
UV-C-induced oxidative damage. 相似文献
6.
Rizhsky L Hallak-Herr E Van Breusegem F Rachmilevitch S Barr JE Rodermel S Inzé D Mittler R 《The Plant journal : for cell and molecular biology》2002,32(3):329-342
The plant genome is a highly redundant and dynamic genome. Here, we show that double antisense plants lacking the two major hydrogen peroxide-detoxifying enzymes, ascorbate peroxidase (APX) and catalase (CAT), activate an alternative/redundant defense mechanism that compensates for the lack of APX and CAT. A similar mechanism was not activated in single antisense plants that lacked APX or CAT, paradoxically rendering these plants more sensitive to oxidative stress compared to double antisense plants. The reduced susceptibility of double antisense plants to oxidative stress correlated with suppressed photosynthetic activity, the induction of metabolic genes belonging to the pentose phosphate pathway, the induction of monodehydroascorbate reductase, and the induction of IMMUTANS, a chloroplastic homologue of mitochondrial alternative oxidase. Our results suggest that a co-ordinated induction of metabolic and defense genes, coupled with the suppression of photosynthetic activity, can compensate for the lack of APX and CAT. In addition, our findings demonstrate that the plant genome has a high degree of plasticity and will respond differently to different stressful conditions, namely, lack of APX, lack of CAT, or lack of both APX and CAT. 相似文献
7.
To evaluate the physiological importance of cytosolic ascorbate peroxidase (APX) in the reactive oxygen species (ROS)-scavenging system, a full-length cDNA clone, named LmAPX, encoding a cytosolic ascorbate peroxidase was isolated from Lycium chinense Mill. using homologous cloning, then the expression of LmAPX under salt stress was investigated. After sequencing and related analysis, the LmAPX cDNA sequence was 965 bp in length and had an open reading frame (ORF) of 750 bp coding for 250 amino acids. Furthermore, the LmAPX sequence was sub-cloned into prokaryotic expression vector pET28a and the recombinant proteins had a high expression level in Escherichia coli. Results from a southern blot analysis indicated that three inserts of this gene existed in the tobacco genome encoding LmAPX. Compared with the control plants (wild-type and empty vector control), the transgenic plants expressing the LmAPX gene exhibited lower amount of hydrogen peroxide (H2O2) and relatively higher values of ascorbate peroxidase activity, proline content, and net photosynthetic rate (Pn) under the same salt stress. These results suggested that overexpression of the LmAPX gene could decrease ROS production caused by salt stress and protect plants from oxidative stress. 相似文献
8.
Localization and Characterization of Peroxidases in the Mitochondria of Chilling-Acclimated Maize Seedlings 总被引:12,自引:2,他引:10
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We present evidence of two peroxidases in maize (Zea mays L.) mitochondria. One of these uses guaiacol and the other uses cytochrome c as the electron donor. Treatments of fresh mitochondria with protease(s) indicate that ascorbate and glutathione peroxidases are likely bound to the mitochondria as cytosolic contaminants, whereas guaiacol and cytochrome peroxidases are localized within the mitochondria. These two mitochondrial peroxidases are distinct from contaminant peroxidases and mitochondrial electron transport enzymes. Cytochrome peroxidase is present within the mitochondrial membranes, whereas guaiacol peroxidase is loosely bound to the mitochondrial envelope. Unlike other cellular guaiacol peroxidases, mitochondrial guaiacol peroxidase is not glycosylated. Digestion of lysed mitochondria with trypsin activated mitochondrial guaiacol peroxidase but inhibited cytochrome peroxidase. Isoelectric focusing gel analysis indicated guaiacol peroxidase as a major isozyme (isoelectric point 6.8) that is also activated by trypsin. No change in the mobility of guaiacol peroxidase due to trypsin treatment on native polyacrylamide gel electrophoresis was observed. Although both peroxidases are induced by chilling acclimation treatments (14[deg]C), only cytochrome peroxidase is also induced by chilling (4[deg]C). Because chilling induces oxidative stress in the maize seedlings and the mitochondria are a target for oxidative stress injury, we suggest that mitochondrial peroxidases play a role similar to catalase in protecting mitochondria from oxidative damage. 相似文献
9.
Antioxidative enzymes from chloroplasts, mitochondria, and peroxisomes during leaf senescence of nodulated pea plants 总被引:1,自引:0,他引:1
Palma JM Jiménez A Sandalio LM Corpas FJ Lundqvist M Gómez M Sevilla F del Río LA 《Journal of experimental botany》2006,57(8):1747-1758
In this work the influence of the nodulation of pea (Pisum sativum L.) plants on the oxidative metabolism of different leaf organelles from young and senescent plants was studied. Chloroplasts, mitochondria, and peroxisomes were purified from leaves of nitrate-fed and Rhizobium leguminosarum-nodulated pea plants at two developmental stages (young and senescent plants). In these cell organelles, the activity of the ascorbate-glutathione cycle enzymes ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR), and the ascorbate and glutathione contents were determined. In addition, the total superoxide dismutase (SOD) activity, the pattern of mitochondrial and peroxisomal NADPH-generating dehydrogenases, some of the peroxisomal photorespiratory enzymes, the glyoxylate cycle and oxidative metabolism enzymes were also analysed in these organelles. Results obtained on the metabolism of cell organelles indicate that nodulation with Rhizobium accelerates senescence in pea leaves. A considerable decrease of the ascorbate content of chloroplasts, mitochondria, and peroxisomes was found, and in these conditions a metabolic conversion of leaf peroxisomes into glyoxysomes, characteristic of leaf senescence, took place. 相似文献
10.
11.
Santina Zancan Irene Suglia Nicoletta La Rocca Rossella Ghisi 《Environmental and Experimental Botany》2008,63(1-3):71-79
Iron deficiency is a stress frequently experienced by plants, owing to the low solubility of Fe(III) salts in neutral or alcaline soils. Iron is an essential plant nutrient as it is involved in fundamental metabolic processes. Furthermore, it is a constituent of important antioxidant enzymes, which are involved in maintaining the balance of cell redox state. UV-B radiation is an environmental problem which can alter the redox state of plants through the increased production of reactive oxygen species. In order to investigate if iron deficiency influences the antioxidant response of plants to UV-B radiation, barley seedlings, Hordeum vulgare L. cv. Express, were exposed to UV-B radiation while growing in nutrient solutions with or without iron. After eight days of growth, plants were harvested and analysed. Results show that, during the 8 days of the experimental period, in neither of the two nutritional conditions considered does UV-B exposure reduce shoot weight or induce evident alterations of thylakoid membranes in respect to controls. However, different responses to UV-B radiation between iron-deficient and iron-sufficient plants were observed at the level of parameters related to oxidative stress. In fact, in iron-sufficient plants the contents of photosynthetic pigments and ascorbate, and the enzyme activities of ascorbate peroxidase (EC 1.11.1.11) and catalase (EC 1.11.1.6) were not affected by UV-B radiation. Conversely, in iron-deficient plants the contents of ascorbate and zeaxanthin and the activity of ascorbate peroxidase increased under UV-B exposure, whereas catalase activity decreased. Furthermore, UV-B radiation induced an increase of hydrogen peroxide content which was higher in iron-deprived plants than in iron-sufficient ones. This may indicate that plants growing in an environment enriched in UV-B radiation may develop a high level of oxidative stress when iron supply is limited. 相似文献
12.
Enhancement of oxidative stress tolerance in transgenic tobacco plants overproducing Fe-superoxide dismutase in chloroplasts. 总被引:23,自引:0,他引:23
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A chimeric gene consisting of the coding sequence for chloroplastic Fe superoxide dismutase (FeSOD) from Arabidopsis thaliana, coupled to the chloroplast targeting sequence from the pea ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit, was expressed in Nicotiana tabacum cv Petit Havana SR1. Expression of the transgenic FeSOD protected both the plasmalemma and photosystem II against superoxide generated during illumination of leaf discs impregnated with methyl viologen. By contrast, overproduction of a mitochondrial MnSOD from Nicotiana plumbaginifolia in the chloroplasts of cv SR1 protected only the plasmalemma, but not photosystem II, against methyl viologen (L. Slooten, K. Capiau, W. Van Camp, M. Van Montagu, C. Sybesma, D. Inzé [1995] Plant Physiol 107: 737-750). The difference in effectiveness correlates with different membrane affinities of the transgenic FeSOD and MnSOD. Overproduction of FeSOD does not confer tolerance to H2O2, singlet oxygen, chilling-induced photoinhibition in leaf disc assays, or to salt stress at the whole plant level. In nontransgenic plants, salt stress led to a 2- to 3-fold increase in activity, on a protein basis, of FeSOD, cytosolic and chloroplastic Cu/ZnSOD, ascorbate peroxidase, dehydroascorbate reductase, and glutathione reductase. In FeSOD-overproducing plants under salt stress, the induction of cytosolic and chloroplastic Cu/ZnSOD was suppressed, whereas induction of a water-soluble chloroplastic ascorbate peroxidase isozyme was promoted. 相似文献
13.
The antipsychotic phenothiazines may have other therapeutic applications because of their ability to kill bacteria, plasmids and tumor cells. They are also known to undergo a peroxidase-catalysed oxidation to form cation radicals that are stable at acid pH, but are not detected at a neutral pH. The objective of this project was to determine whether phenothiazine cation radical metabolites could cause oxidative stress at a neutral pH resulting in cytotoxicity. At a neutral pH, catalytic amounts of phenothiazines were found to be oxidised by a peroxidase/H2O2 system and also caused ascorbate, GSH and NADH cooxidation. NADH and GSH co-oxidation was accompanied by oxygen uptake and was increased by the addition of catalytic amounts of superoxide dismutase, indicating that the superoxide radical was formed. The phenothazines were different from other peroxidase substrates in that the NADH, ascorbate or GSH cooxidation was faster at pH 6.0 than pH 7.4, thereby partly reflecting the cation radical stability. The order of catalytic effectiveness found was promazine > chlorpromazine > trifluoperazine. Peroxidase/H2O2 also markedly increased phenothiazine cytotoxicity towards isolated rat hepatocytes at nontoxic phenothiazine concentrations. At both pH 6.0 and 7.4, the same order of phenothiazine catalytic effectiveness was observed as seen in the co-oxidation experiments. Cytotoxicity to hepatocytes could be attributed to oxidative stress as most hepatocyte glutathione oxidation and lipid peroxidation preceded phenothiazine induced cytotoxicity and that cytotoxicity was prevented by the antioxidant butylated hydroxyanisole. This hepatocyte/peroxidase/H2O2 system could be a useful model for studying drug induced idiosyncratic hepatic injury enhanced by inflammation. 相似文献
14.
To study the relationship between cadmium (Cd)-induced phytotoxicity and oxidative stress, we grew Cd-sensitive wild-type
(WT) and Cd-resistant type (RT) seedlings ofArabidopsis thaliana on MS media containing up to 500 μM CdCl2. The resistant seedlings showed higher biomasses and lower hydrogen peroxide and lipid peroxidation levels, the latter expressed
in terms of malondialdehyde (MDA) production. These results indicate that RT plants experience lower oxidative stress when
exposed to Cd. Furthermore, compared with the WT, RT seedlings have significantly higher activities of superoxide dismutase
(SOD) and enzymes related to hydrogen peroxide removal, e.g., guaiacol peroxidase (GPX), ascorbate peroxidase (APX), and glutathione
reductase (GR). These differential responses suggest that such phytotoxicity could be induced by oxidative stress, and that
lower accumulations of hydrogen peroxide confer Cd tolerance in seedlings. 相似文献
15.
16.
Regulation and function of ascorbate peroxidase isoenzymes 总被引:59,自引:0,他引:59
Shigeoka S Ishikawa T Tamoi M Miyagawa Y Takeda T Yabuta Y Yoshimura K 《Journal of experimental botany》2002,53(372):1305-1319
Even under optimal conditions, many metabolic processes, including the chloroplastic, mitochondrial, and plasma membrane-linked electron transport systems of higher plants, produce active oxygen species (AOS). Furthermore, the imposition of biotic and abiotic stress conditions can give rise to excess concentrations of AOS, resulting in oxidative damage at the cellular level. Therefore, antioxidants and antioxidant enzymes function to interrupt the cascades of uncontrolled oxidation in each organelle. Ascorbate peroxidase (APX) exists as isoenzymes and plays an important role in the metabolism of H(2)O(2) in higher plants. APX is also found in eukaryotic algae. The characterization of APX isoenzymes and the sequence analysis of their clones have led to a number of investigations that have yielded interesting and novel information on these enzymes. Interestingly, APX isoenzymes of chloroplasts in higher plants are encoded by only one gene, and their mRNAs are generated by alternative splicing of the gene's two 3'-terminal exons. Manipulation of the expression of the enzymes involved in the AOS-scavenging systems by gene-transfer technology has provided a powerful tool for increasing the present understanding of the potential of the defence network against oxidative damage caused by environmental stresses. Transgenic plants expressing E. coli catalase to chloroplasts with increased tolerance to oxidative stress indicate that AOS-scavenging enzymes, especially chloroplastic APX isoenzymes are sensitive under oxidative stress conditions. It is clear that a high level of endogenous ascorbate is essential effectively to maintain the antioxidant system that protects plants from oxidative damage due to biotic and abiotic stresses. 相似文献
17.
Ectopic expression of a horseradish peroxidase enhances growth rate and increases oxidative stress resistance in hybrid aspen 总被引:9,自引:0,他引:9
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Kawaoka A Matsunaga E Endo S Kondo S Yoshida K Shinmyo A Ebinuma H 《Plant physiology》2003,132(3):1177-1185
We previously demonstrated that overexpression of the horseradish (Armoracia rusticana) peroxidase prxC1a gene stimulated the growth rate of tobacco (Nicotiana tabacum) plants. Here, the cauliflower mosaic virus 35S::prxC1a construct was introduced into hybrid aspen (Populus sieboldii x Populus grandidentata). The growth rate of these transformed hybrid aspen plants was substantially increased under greenhouse conditions. The average stem length of transformed plants was 25% greater than that of control plants. There was no other obvious phenotypic difference between the transformed and control plants. Fast-growing transformed hybrid aspen showed high levels of expression of prxC1a and had elevated peroxidase activities toward guaiacol and ascorbate. However, there was no increase of the endogenous class I ascorbate peroxidase activities in the transformed plants by separate assay and activity staining of native polyacrylamide gel electrophoresis. Furthermore, calli derived from the transformed hybrid aspen grew faster than those from control plants and were resistant to the oxidative stress imposed by hydrogen peroxide. Therefore, enhanced peroxidase activity affects plant growth rate and oxidative stress resistance. 相似文献
18.
Mariana L. Martín Leandra Lechner Eduardo J. Zabaleta Graciela L. Salerno 《Planta》2013,237(3):813-822
Recent findings demonstrate that alkaline/neutral invertases (A/N-Invs), enzymes that catalyze the breakdown of sucrose into glucose and fructose, are essential proteins in plant life. The fact that different isoforms are present in multiple locations makes them candidates for the coordination of metabolic processes. In the present study, we functionally characterized the encoding gene of a novel A/N-Inv (named A/N-InvC) from Arabidopsis, which localizes in mitochondria. A/N-InvC is expressed in roots, in aerial parts (shoots and leaves) and flowers. A detailed phenotypic analysis of knockout mutant plants (invc) reveals an impaired growth phenotype. Shoot growth was severely reduced, but root development was not affected as reported for A/N-InvA mutant (inva) plants. Remarkably, germination and flowering, two energy demanding processes, were the most affected stages. The effect of exogenous growth regulators led us to suggest that A/N-InvC may be modulating hormone balance in relation to the radicle emergence. We also show that oxygen consumption is reduced in inva and invc in comparison with wild-type plants, indicating that both organelle isoenzymes may play a fundamental role in mitochondrion functionality. Taken together, our results emphasize the involvement of mitochondrial A/N-Invs in developmental processes and uncover the possibility of playing different roles for the two isoforms located in the organelle. 相似文献
19.
Tolerance to low temperature and paraquat-mediated oxidative stress in two maize genotypes 总被引:9,自引:0,他引:9
Iannelli M; van Breusegem F; van Montagu M; Inze D; Massacci A 《Journal of experimental botany》1999,50(333):523-532
Tolerance to low temperature and paraquat-mediated oxidative stress was
investigated in two Zea mays genotypes, VA36 and A619,
grown at 25/22 C and 16/14 C for 50 d after germination. VA36, the tolerant
genotype, showed an enhanced resistance to paraquat as compared to A619,
the sensitive genotype, when grown at low temperature. In VA36, superoxide
dismutase and ascorbate peroxidase activities increased during growth at
both 25/22 °C or 16/14 °C. In A619, superoxide dismutase
activity was similar in plants grown at both 16/14 °C or 25/22
°C. Ascorbate peroxidase activity was always significantly lower in
plants grown at low temperature than in plants grown at 25/22 °C.
The total ascorbate peroxidase activity was correlated with the cytosolic
ascorbate peroxidase protein content in all but A619 plants grown at low
temperature for 25 d. The isozyme pattern of SOD showed a higher abundance
of MnSOD in VA36 than in A619 and of FeSOD in A619 compared to VA36. Growth
at low temperature enhanced resistance to paraquat infiltration more in
VA36 than in A619. SOD and APX activities were generally higher and more
stable with the increase of paraquat concentration in VA36 than in A619.
Damage indicated by Fv/Fm and ion
leakage after paraquat infiltration were generally higher in plants grown
at 25/22 °C than at 16/14 °C and higher in A619 than in
VA36. However, no causal link is proved between the extent of damage and
the increase of SOD and APX activities alone. It is suggested that
tolerance to oxidative stress requires an integrated enhancement of the
antioxidant system. 相似文献
20.
Salt and oxidative stress: similar and specific responses and their relation to salt tolerance in Citrus 总被引:45,自引:0,他引:45
Salt damage to plants has been attributed to a combination of several factors including mainly osmotic stress and the accumulation
of toxic ions. Recent findings in our laboratory showed that phospholipid hydroperoxide glutathione peroxidase (PHGPX), an
enzyme active in the cellular antioxidant system, was induced by salt in citrus cells and mainly in roots of plants. Following
this observation we studied the two most important enzymes active in elimination of reactive oxygen species, namely, superoxide
dismutase (SOD) and ascorbate peroxidase (APX), to determine whether a general oxidative stress is induced by salt. While
Cu/Zn-SOD activity and cytosolic APX protein level were similarly induced by salt and methyl viologen, the response of PHGPX
and other APX isozymes was either specific to salt or methyl viologen, respectively. Unlike PHGPX, cytosolic APX and Cu/Zn-SOD
were not induced by exogenously added abscisic acid. Salt induced a significant increase in SOD activity which was not matched
by the subsequent enzyme APX. We suggest that the excess of H2O2 interacts with lipids to form hydroperoxides which in turn induce and are removed by PHGPX. Ascorbate peroxidase seems to
be a key enzyme in determining salt tolerance in citrus as its constitutive activity in salt-sensitive callus is far below
the activity observed in salt-tolerant callus, while the activities of other enzymes involved in the defence against oxidative
stress, namely SOD, glutathione reductase and PHGPX, are essentially similar.
Received: 10 January 1997 / Accepted: 28 May 1997 相似文献