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1.
Alkaline/neutral invertases (A/N-Invs) are unique to plants and photosynthetic bacteria. Although considerable advances have been made in our understanding of sucrose metabolic enzymes in plants, the function of A/N-Invs remained puzzling. In a recent study, we have analyzed the subcellullar localization of a cytosolic (At-A/N-InvG, At1g35580) and a mitochondrial (At-A/N-InvA, At1g56560) Arabidopsis A/N-Inv. Unexpectedly, At-A/N-InvA knockout plants showed a more severe growth defect than At-A/N-InvG knockout plants and a link between the two A/N-Invs and oxidative stress defense was found. Overexpression of At-A/N-InvA and At-A/N-InvG in leaf mesophyll protoplasts reduced the activity of the ascorbate peroxidase 2 (APX2) promoter, that was stimulated by hydrogen peroxide and abscisic acid. It is discussed here how sugars and ascorbate might contribute to mitochondrial reactive oxygen species homeostasis. We hypothesize that both mitochondrial and cytosolic A/N-Invs and mitochondria-associated hexokinases are key mediators, integrating metabolic and sugar signaling processes.Key words: ascorbate peroxidase, glucose, hexokinase, mitochondria, neutral invertase, oxidative stress, sucrose 相似文献
2.
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
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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
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.
Over-expression of ascorbate peroxidase in tobacco chloroplasts enhances the tolerance to salt stress and water deficit 总被引:10,自引:0,他引:10
Badawi GH Kawano N Yamauchi Y Shimada E Sasaki R Kubo A Tanaka K 《Physiologia plantarum》2004,121(2):231-238
The role of APX (ascorbate peroxidase) in protection against oxidative stress was examined using transgenic tobacco plants. The full length cDNA, coding Arabidopsis thaliana L. APX fused downstream to the chloroplast transit sequence from A. thaliana glutathione reductase, was cloned into appropriate binary vector and mobilized into Agrobacterium tumefaciens C58C2. Leaf discs were infected with the Agrobacterium and cultured on medium supplied with kanamycin. The incorporation of the gene in tobacco genome was confirmed by Southern dot blot hybridization. Transgenic lines were generated, and the line Chl-APX5 shown to have 3.8-fold the level of APX activity in the wild-type plants. The isolated chloroplasts from this line showed higher APX activity. During early investigation, this line showed enhanced tolerance to the active oxygen-generating paraquat and sodium sulphite. The first generation of this line, also, showed enhanced tolerance to salt, PEG and water stresses, as determined by net photosynthesis. The present data indicate that overproducing the cytosolic APX in tobacco chloroplasts reduces the toxicity of H2 O2 . 相似文献
8.
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
9.
Narendra S Venkataramani S Shen G Wang J Pasapula V Lin Y Kornyeyev D Holaday AS Zhang H 《Journal of experimental botany》2006,57(12):3033-3042
Ascorbate peroxidase (APX) exists as several isoforms that are found in various compartments in plant cells. The cytosolic and chloroplast APXs appear to play important roles in antioxidation metabolism in plant cells, yet the function of peroxisomal APX is not well studied. In this study, the localization of a putative peroxisomal membrane-bound ascorbate peroxidase, APX3 from Arabidopsis, was confirmed by studying the green fluorescent protein (GFP)-APX3 fusion protein in transgenic plants. GFP-APX3 was found to co-localize with a reporter protein that was targeted to peroxisomes by the peroxisomal targeting signal 1. The function of APX3 in Arabidopsis was investigated by analysing an APX3 knockout mutant under normal and several stress conditions. It was found that loss of function in APX3 does not affect Arabidopsis growth and development, suggesting that APX3 may not be an important antioxidant enzyme in Arabidopsis, at least under the conditions that were tested, or the function of APX3 could be compensated by other antioxidant enzymes in plant cells. 相似文献
10.
Raza Ahmad Yun-Hee Kim Myoung Duck Kim Minh-Ngoc Phung Won-Il Chung Haeng-Soon Lee Sang-Soo Kwak Suk-Yoon Kwon 《Journal of Plant Biology》2008,51(6):401-407
A binary vector devoid of a plant selection-marker gene (designated as pSSA-F) was constructed to overcome bio-safety concerns
about genetically modified plants. This vector carried chloroplast-targeted superoxide dismutase (SOD) and ascorbate peroxidase
(APX) genes under the control of an oxidative stress-inducible(SWPA2) promoter, and was utilized to transform potato (Solanum tuberosum L.). Integration of these foreign genes into transgenic plants was primarily performed via PCR with genomic DNA. Twelve marker-free
transgenic lines were obtained by inoculating stem explants. The maximum transformation efficiency was 6.25% and averaged
2.2%. Successful integration of the SOD and APX genes rendered transgenic plants tolerant to methyl viologen-mediated oxidative
stress at the leaf-disc and whole-plant levels. Our findings suggest that this technique for developing selection marker-free
transgenic plants is feasible and can be employed with other crop species. 相似文献
11.
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
12.
Wheat ( Triticum aestivum L.) seedlings of a drought-resistant cv. C306 were subjected to severe water deficit directly or through stress cycles of increasing intensity with intermittent recovery periods (drought acclimation). The antioxidant defense in terms of redox metabolites and enzymes in leaf cells, chloroplasts, and mitochondria was examined in relation to ROS-induced membrane damage. Drought-acclimated seedlings modulated growth by maintaining favorable turgor potential and RWC and were able to limit H2 O2 accumulation and membrane damage as compared with non-acclimated plants during severe water stress conditions. This was due to systematic upregulation of H2 O2 -metabolizing enzymes especially ascorbate peroxidase (APX, EC 1.11.1.11) and by maintaining ascorbate–glutathione redox pool in acclimated plants. By contrast, failure in the induction of APX and ascorbate–glutathione cycle enzymes makes the chloroplast susceptible to oxidative stress in non-acclimated plants. Non-acclimated plants protected the leaf mitochondria from oxidative stress by upregulating superoxide dismutase (SOD, EC 1.15.1.1), APX, and glutathione reductase (GR, EC 1.6.4.2) activities. Rewatering led to rapid enhancement in all the antioxidant defense components in non-acclimated plants, which suggested that the excess levels of H2 O2 during severe water stress conditions might have inhibited or downregulated the antioxidant enzymes. Hence, drought acclimation conferred enhanced oxidative stress tolerance by well-co-ordinated induction of antioxidant defense both at the chloroplast and at the mitochondrial level. 相似文献
13.
Ascorbate peroxidase 1 plays a key role in the response of Arabidopsis thaliana to stress combination 总被引:3,自引:0,他引:3
Koussevitzky S Suzuki N Huntington S Armijo L Sha W Cortes D Shulaev V Mittler R 《The Journal of biological chemistry》2008,283(49):34197-34203
Within their natural habitat plants are subjected to a combination of different abiotic stresses, each with the potential to exacerbate the damage caused by the others. One of the most devastating stress combinations for crop productivity, which frequently occurs in the field, is drought and heat stress. In this study we conducted proteomic and metabolic analysis of Arabidopsis thaliana plants subjected to a combination of drought and heat stress. We identified 45 different proteins that specifically accumulated in Arabidopsis in response to the stress combination. These included enzymes involved in reactive oxygen detoxification, malate metabolism, and the Calvin cycle. The accumulation of malic enzyme during the combined stress corresponded with enhanced malic enzyme activity, a decrease in malic acid, and lower amounts of oxaloacetate, suggesting that malate metabolism plays an important role in the response of Arabidopsis to the stress combination. Cytosolic ascorbate peroxidase 1 (APX1) protein and mRNA accumulated during the stress combination. When exposed to heat stress combined with drought, an APX1-deficient mutant (apx1) accumulated more hydrogen peroxide and was significantly more sensitive to the stress combination than wild type. In contrast, mutants deficient in thylakoid or stromal/mitochondrial APXs were not more sensitive to the stress combination than apx1 or wild type. Our findings suggest that cytosolic APX1 plays a key role in the acclimation of plants to a combination of drought and heat stress. 相似文献
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The response of the antioxidative systems of leaf cell mitochondria and peroxisomes of the cultivated tomato Lycopersicon esculentum (Lem) and its wild salt-tolerant related species Lycopersicon pennellii (Lpa) to NaCl 100 mM stress was investigated. Salt-dependent oxidative stress was evident in Lem mitochondria as indicated by their raised levels of lipid peroxidation and H2O2 content whereas their reduced ascorbate and reduced glutathione contents decreased. Concomitantly, SOD activity decreased whereas APX and GPX activities remained at control level. In contrast, the mitochondria of salt-treated Lpa did not exhibit salt-induced oxidative stress. In their case salinity induced an increase in the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione-dependent peroxidase (GPX). Lpa peroxisomes exhibited increased SOD, APX, MDHAR and catalase activity and their lipid peroxidation and H2O2 levels were not affected by the salt treatment. The activities of all these enzymes remained at control level in peroxisomes of salt-treated Lem plants. The salt-induced increase in the antioxidant enzyme activities in the Lpa plants conferred cross-tolerance towards enhanced mitochondrial and peroxisomal reactive oxygen species production imposed by salicylhydroxamic acid (SHAM) and 3-amino-1,2,4-triazole (3-AT), respectively. 相似文献
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Takanori Maruta Takahiro Inoue Masahiro Noshi Masahiro Tamoi Yukinori Yabuta Kazuya Yoshimura Takahiro Ishikawa Shigeru Shigeoka 《Biochimica et Biophysica Acta (BBA)/General Subjects》2012
Background
Reactive oxygen species (ROS) are not only cytotoxic compounds leading to oxidative damage, but also signaling molecules for regulating plant responses to stress and hormones. Arabidopsis cytosolic ascorbate peroxidase 1 (APX1) is thought to be a central regulator for cellular ROS levels. However, it remains unclear whether APX1 is involved in plant tolerance to wounding and methyl jasmonate (MeJA) treatment, which are known to enhance ROS production.Methods
We studied the effect of wounding and MeJA treatment on the levels of H2O2 and oxidative damage in the Arabidopsis wild-type plants and knockout mutants lacking APX1 (KO-APX1).Results
The KO-APX1 plants showed high sensitivity to wounding and MeJA treatment. In the leaves of wild-type plants, H2O2 accumulated only in the vicinity of the wound, while in the leaves of the KO-APX1 plants it accumulated extensively from damaged to undamaged regions. During MeJA treatment, the levels of H2O2 were much higher in the leaves of KO-APX1 plants. Oxidative damage in the chloroplasts and nucleus was also enhanced in the leaves of KO-APX1 plants. These findings suggest that APX1 protects organelles against oxidative stress by wounding and MeJA treatment.General significance
This is the first report demonstrating that H2O2-scavenging in the cytosol is essential for plant tolerance to wounding and MeJA treatment. 相似文献18.
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Shunsuke Hirooka Osami Misumi Masaki Yoshida Toshiyuki Mori Keiji Nishida Fumi Yagisawa Yamato Yoshida Takayuki Fujiwara Haruko Kuroiwa Tsuneyoshi Kuroiwa 《Plant cell reports》2009,28(12):1881-1893
The ability of the primitive red alga Cyanidioschyzon merolae to adapt to high temperatures was utilized to produce thermotolerant transgenic plants. C. merolae inhabits an extreme environment (42°C, pH 2.5) and the nuclear, mitochondrial, and plastid genomes have been sequenced. We analyzed expressed sequence tag (EST) data to reveal mechanisms of tolerance to high temperatures. The stromal ascorbate peroxidase (CmstAPX) that scavenges reactive oxygen species (ROS) was expressed at high levels (4th of 4,479 entries), thus, it offers clues to understanding high-temperature tolerance. CmstAPX has a chloroplast transit peptide (cTP) and a peroxidase domain. The peroxidase domain of CmstAPX has deletions and insertions when compared with that of Arabidopsis thaliana stromal APX (AtstAPX). To clarify aspects of tolerance to oxidative and high-temperature stress, we produced transgenic A. thaliana plants overexpressing CmstAPX and AtstAPX. CmstAPX plants showed higher activities of soluble APX than those of wild-type and AtstAPX plants. Fluorescence signals of a GFP fusion protein, immuno-fluorescence, and immunogold electron microscopy showed that CmstAPX was localized in the stroma of chloroplasts. Compared with wild-type plants and AtstAPX plants, CmstAPX plants were more tolerant to oxidative stress induced by methylviologen (MV, 0.4 μM) and high-temperature stress (33°C). CmstAPX plants retained the highest chlorophyll content when treated with MV and high temperature, and their stroma and chloroplasts remained intact in their chloroplasts, whereas they disintegrated in wild-type plants. Our results suggest that the increased activity of APX in the chloroplasts of CmstAPX plants increased thermotolerance by increasing ROS-scavenging capacity at high temperatures. 相似文献
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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