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Abstract
Mitochondria actively participate in oxygenic metabolism and are one of the major sources of reactive oxygen species (ROS) production in plant cells. However, instead of measuring ROS concentrations in organelles it is more worthwhile to observe active ROS generation or downstream oxidation products, because the steady state level of ROS is easily buffered. Here, we describe how to measure the in vitro production of superoxide anion radicals (O2·-) by mitochondria and the release of O2·- into the cytosol. A method to determine glutathione, which is the most abundant mitochondrial low-mass antioxidant, is presented since changes in the redox state of glutathione can be indicative of the oxidative action of ROS. The identification of oxidative damage to mitochondrial components is the ultimate symptom that ROS homeostasis is not under control. We present how to determine the extent of oxidation of membrane lipids and the carbonylation of mitochondrial proteins. In summary, oxidative stress symptoms have to be analyzed at different levels, including ROS production, scavenging capacity, and signs of destruction, which only together can be considered markers of mitochondrial ROS status.
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Affiliation(s)
- Monika Ostaszewska-Bugajska
- Department of Plant Bioenergetics, Institute of Experimental Plant Biology and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland.
| | - Anna Podgórska
- Department of Plant Bioenergetics, Institute of Experimental Plant Biology and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland
| | - Bożena Szal
- Department of Plant Bioenergetics, Institute of Experimental Plant Biology and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland.
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Zeng J, Tang J, Zhang F, Wang Y, Kang H, Chen G, Zhang Z, Yuan S, Zhou Y. Ammonium regulates redox homeostasis and photosynthetic ability to mitigate copper toxicity in wheat seedlings. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2021; 226:112825. [PMID: 34571421 DOI: 10.1016/j.ecoenv.2021.112825] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 09/18/2021] [Accepted: 09/21/2021] [Indexed: 05/28/2023]
Abstract
As an essential plant micronutrient, copper (Cu) is required as a component of several enzymes, but it can be highly toxic to plants when present in excess quantities. Nitrogen (N) application can help to alleviate the phytotoxic effects of heavy metals, including Cu, and different N forms significantly affect the uptake and accumulation of heavy metals in plants. The aim of this study was to determine the effects of different N forms, i.e., ammonium (NH4+) and nitrate (NO3-), on Cu detoxification in wheat seedlings. The inhibition of seedling growth under excess Cu was more obvious in wheat plants supplied with NO3- than in those supplied with NH4+. This growth inhibition was directly induced by excess Cu accumulation and reduced absorption of other mineral nutrients by the plants. Compared with seedlings treated with NO3-, those treated with NH4+ showed a decrease in Cu-induced toxicity as a result of increased antioxidant capacity in the leaves and a lower redox potential in the rhizosphere. Furthermore, treatment with NH4+ decreased the loss of mineral nutrients in wheat seedlings exposed to excess Cu. In conclusion, compared with supplying NO3-, supplying NH4+ to wheat seedlings under Cu stress improved their ability to maintain their nutritional and redox balance and increased their antioxidant capacity, thereby preventing a decline in photosynthesis. According to our results, NH4+ is more effective than NO3- in reducing Cu phytotoxicity in wheat seedlings.
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Affiliation(s)
- Jian Zeng
- College of Resources, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China.
| | - Jingru Tang
- College of Resources, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China
| | - Fanglin Zhang
- College of Resources, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China
| | - Yi Wang
- Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China
| | - Houyang Kang
- Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China
| | - Guangdeng Chen
- College of Resources, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China
| | - Zhongwei Zhang
- College of Resources, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China
| | - Shu Yuan
- College of Resources, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China
| | - Yonghong Zhou
- Triticeae Research Institute, Sichuan Agricultural University, Wenjiang 611130, Sichuan, China
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Podgórska A, Burian M, Rychter AM, Rasmusson AG, Szal B. Short-term ammonium supply induces cellular defence to prevent oxidative stress in Arabidopsis leaves. PHYSIOLOGIA PLANTARUM 2017; 160:65-83. [PMID: 28008622 DOI: 10.1111/ppl.12538] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 12/01/2016] [Accepted: 12/13/2016] [Indexed: 05/21/2023]
Abstract
Plants can assimilate nitrogen from soil pools of both ammonium and nitrate, and the relative levels of these two nitrogen sources are highly variable in soil. Long-term ammonium nutrition is known to cause damage to Arabidopsis that has been linked to mitochondrial oxidative stress. Using hydroponic cultures, we analysed the consequences of rapid shifts between nitrate and ammonium nutrition. This did not induce growth retardation, showing that Arabidopsis can compensate for the changes in redox metabolism associated with the variations in nitrogen redox status. During the first 3 h of ammonium treatment, we observed distinct transient shifts in reactive oxygen species (ROS), low-mass antioxidants, ROS-scavenging enzymes, and mitochondrial alternative electron transport pathways, indicating rapid but temporally separated changes in chloroplastic, mitochondrial and cytosolic ROS metabolism. The fast induction of antioxidant defences significantly lowered intracellular H2 O2 levels, and thus protected Arabidopsis leaves from oxidative stress. On the other hand elevated extracellular ROS production in response to ammonium supply may be involved in signalling. The response pattern displays an intricate plasticity of Arabidopsis redox metabolism to minimise stress in responses to nutrient changes.
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Affiliation(s)
- Anna Podgórska
- Institute of Experimental Plant Biology and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, 02-096, Poland
| | - Maria Burian
- Institute of Experimental Plant Biology and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, 02-096, Poland
| | - Anna M Rychter
- Institute of Experimental Plant Biology and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, 02-096, Poland
| | | | - Bożena Szal
- Institute of Experimental Plant Biology and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, 02-096, Poland
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Tamás L, Mistrík I, Zelinová V. Cadmium activates both diphenyleneiodonium- and rotenone-sensitive superoxide production in barley root tips. PLANTA 2016; 244:1277-1287. [PMID: 27534965 DOI: 10.1007/s00425-016-2587-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 08/11/2016] [Indexed: 06/06/2023]
Abstract
Mild Cd stress-activated diphenyleneiodonium-sensitive superoxide production is utilized in root morphogenic responses, while severe Cd stress-induced robust rotenone-sensitive superoxide generation may lead to cell and root death. In barley, even a few minute exposure of roots to Cd concentration higher than 10 µM evoked a strong superoxide generation in the root transition zone. This superoxide generation was strongly inhibited by the inhibition of mitochondrial electron flow into complex III in the presence of the mitochondrial complex I inhibitor rotenone. Similarly, the superoxide generation induced by antimycin A, an inhibitor of mitochondrial complex III, was considerably reduced by rotenone, suggesting the involvement of complex III also in the severe Cd stress-induced superoxide generation. This severe Cd stress-induced superoxide generation was followed by an extensive cell death in this part of the root tip, which similar to the superoxide generation, was eliminated by rotenone co-treatment. In turn, mild Cd stress-induced diphenyleneiodonium (DPI)-sensitive superoxide generation was observed only in the post-stressed roots, suggesting that it is not directly associated with Cd toxicity. Diphenyleneiodonium, an inhibitor of NADPH oxidase, markedly inhibited the mild Cd stress-induced radial expansion of root apex, indicating that enhanced DPI-sensitive superoxide production is required for rapid isotropic cell growth. Severe Cd stress, probably through the inhibition of complex III, caused a rapid and robust superoxide generation leading to cell and/or root death. By contrast, mild Cd stress did not evoke oxidative stress, and the enhanced DPI-sensitive superoxide generation is utilized in adaptive morphogenic responses.
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Affiliation(s)
- Ladislav Tamás
- Institute of Botany, Slovak Academy of Sciences, Dúbravská cesta 9, SK-84523, Bratislava, Slovak Republic.
| | - Igor Mistrík
- Institute of Botany, Slovak Academy of Sciences, Dúbravská cesta 9, SK-84523, Bratislava, Slovak Republic
| | - Veronika Zelinová
- Institute of Botany, Slovak Academy of Sciences, Dúbravská cesta 9, SK-84523, Bratislava, Slovak Republic
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Mattila H, Khorobrykh S, Havurinne V, Tyystjärvi E. Reactive oxygen species: Reactions and detection from photosynthetic tissues. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2015; 152:176-214. [PMID: 26498710 DOI: 10.1016/j.jphotobiol.2015.10.001] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 09/30/2015] [Accepted: 10/01/2015] [Indexed: 12/22/2022]
Abstract
Reactive oxygen species (ROS) have long been recognized as compounds with dual roles. They cause cellular damage by reacting with biomolecules but they also function as agents of cellular signaling. Several different oxygen-containing compounds are classified as ROS because they react, at least with certain partners, more rapidly than ground-state molecular oxygen or because they are known to have biological effects. The present review describes the typical reactions of the most important ROS. The reactions are the basis for both the detection methods and for prediction of reactions between ROS and biomolecules. Chemical and physical methods used for detection, visualization and quantification of ROS from plants, algae and cyanobacteria will be reviewed. The main focus will be on photosynthetic tissues, and limitations of the methods will be discussed.
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Affiliation(s)
- Heta Mattila
- Department of Biochemistry/Molecular Plant Biology, University of Turku, 20014 Turku, Finland
| | - Sergey Khorobrykh
- Department of Biochemistry/Molecular Plant Biology, University of Turku, 20014 Turku, Finland
| | - Vesa Havurinne
- Department of Biochemistry/Molecular Plant Biology, University of Turku, 20014 Turku, Finland
| | - Esa Tyystjärvi
- Department of Biochemistry/Molecular Plant Biology, University of Turku, 20014 Turku, Finland.
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Ostaszewska-Bugajska M, Rychter AM, Juszczuk IM. Antioxidative and proteolytic systems protect mitochondria from oxidative damage in S-deficient Arabidopsis thaliana. JOURNAL OF PLANT PHYSIOLOGY 2015; 186-187:25-38. [PMID: 26339750 DOI: 10.1016/j.jplph.2015.07.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 07/15/2015] [Accepted: 07/17/2015] [Indexed: 06/05/2023]
Abstract
We examined the functioning of the antioxidative defense system in Arabidopsis thaliana under sulphur (S) deficiency with an emphasis on the role of mitochondria. In tissue extracts and in isolated mitochondria from S-deficient plants, the concentration of non-protein thiols declined but protein thiols did not change. Superoxide anion and hydrogen peroxide were accumulated in leaf blades and the generation of superoxide anion by isolated mitochondria was higher. Lower abundance of reduced (GSH) plus oxidized (GSSG) glutathione in the leaf and root tissues, and leaf mitochondria from S-deficient plants was accompanied by a decrease in the level of GSH and the changes in the GSH/GSSG ratios. In the chloroplasts, the total level of glutathione decreased. Lower levels of reduced (AsA) and oxidized (DHA) ascorbate were reflected in much higher ratios of AsA/DHA. Sulphur deficiency led to an increase in the activity of cytosolic, mitochondrial and chloroplastic antioxidative enzymes, peroxidases, catalases and superoxide dismutases. The protein carbonyl level was higher in the leaves of S-deficient plants and in the chloroplasts, while in the roots, leaf and root mitochondria it remained unchanged. Protease activity in leaf extracts of S-deficient plants was higher, but in root extracts it did not differ. The proteolytic system reflected subcellular specificity. In leaf and root mitochondria the protease activity was higher, whereas in the chloroplasts it did not change. We propose that the preferential incorporation of S to protein thiols and activation of antioxidative and proteolytic systems are likely important for the survival of S-deficient plants and that the mitochondria maintain redox homeostasis.
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Affiliation(s)
- Monika Ostaszewska-Bugajska
- Institute of Experimental Plant Biology and Biotechnology, Faculty of Biology, University of Warsaw, Poland.
| | - Anna M Rychter
- Institute of Experimental Plant Biology and Biotechnology, Faculty of Biology, University of Warsaw, Poland.
| | - Izabela M Juszczuk
- Institute of Experimental Plant Biology and Biotechnology, Faculty of Biology, University of Warsaw, Poland.
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Podgórska A, Ostaszewska M, Gardeström P, Rasmusson AG, Szal B. In comparison with nitrate nutrition, ammonium nutrition increases growth of the frostbite1 Arabidopsis mutant. PLANT, CELL & ENVIRONMENT 2015; 38:224-37. [PMID: 25040883 DOI: 10.1111/pce.12404] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2013] [Revised: 06/24/2014] [Accepted: 06/26/2014] [Indexed: 05/21/2023]
Abstract
Ammonium nutrition inhibits the growth of many plant species, including Arabidopsis thaliana. The toxicity of ammonium is associated with changes in the cellular redox state. The cellular oxidant/antioxidant balance is controlled by mitochondrial electron transport chain. In this study, we analysed the redox metabolism of frostbite1 (fro1) plants, which lack mitochondrial respiratory chain complex I. Surprisingly, the growth of fro1 plants increased under ammonium nutrition. Ammonium nutrition increased the reduction level of pyridine nucleotides in the leaves of wild-type plants, but not in the leaves of fro1 mutant plants. The observed higher activities of type II NADH dehydrogenases and cytochrome c oxidase in the mitochondrial electron transport chain may improve the energy metabolism of fro1 plants grown on ammonium. Additionally, the observed changes in reactive oxygen species (ROS) metabolism in the apoplast may be important for determining the growth of fro1 under ammonium nutrition. Moreover, bioinformatic analyses showed that the gene expression changes in fro1 plants significantly overlap with the changes previously observed in plants with a modified apoplastic pH. Overall, the results suggest a pronounced connection between the mitochondrial redox system and the apoplastic pH and ROS levels, which may modify cell wall plasticity and influence growth.
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Affiliation(s)
- Anna Podgórska
- Institute of Experimental Plant Biology and Biotechnology, Faculty of Biology, University of Warsaw, I. Miecznikowa 1, 02-096, Warsaw, Poland
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Podgórska A, Gieczewska K, Łukawska-Kuźma K, Rasmusson AG, Gardeström P, Szal B. Long-term ammonium nutrition of Arabidopsis increases the extrachloroplastic NAD(P)H/NAD(P)(+) ratio and mitochondrial reactive oxygen species level in leaves but does not impair photosynthetic capacity. PLANT, CELL & ENVIRONMENT 2013; 36:2034-45. [PMID: 23574048 DOI: 10.1111/pce.12113] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Revised: 03/26/2013] [Accepted: 03/27/2013] [Indexed: 05/23/2023]
Abstract
Ammonium nutrition has been suggested to be associated with alterations in the oxidation-reduction state of leaf cells. Herein, we show that ammonium nutrition in Arabidopsis thaliana increases leaf NAD(P)H/NAD(P)(+) ratio, reactive oxygen species content and accumulation of biomolecules oxidized by free radicals. We used the method of rapid fractionation of protoplasts to analyse which cellular compartments were over-reduced under ammonium supply and revealed that observed changes in NAD(P)H/NAD(P)(+) ratio involved only the extrachloroplastic fraction. We also showed that ammonium nutrition changes mitochondrial electron transport chain activity, increasing mitochondrial reactive oxygen species production. Our results indicate that the functional impairment associated with ammonium nutrition is mainly associated with redox reactions outside the chloroplast.
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Affiliation(s)
- Anna Podgórska
- Faculty of Biology, Institute of Experimental Plant Biology and Biotechnology, University of Warsaw, I. Miecznikowa 1, 02-096, Warsaw, Poland
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Steffens B, Steffen-Heins A, Sauter M. Reactive oxygen species mediate growth and death in submerged plants. FRONTIERS IN PLANT SCIENCE 2013; 4:179. [PMID: 23761805 PMCID: PMC3671184 DOI: 10.3389/fpls.2013.00179] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Accepted: 05/17/2013] [Indexed: 05/07/2023]
Abstract
Aquatic and semi-aquatic plants are well adapted to survive partial or complete submergence which is commonly accompanied by oxygen deprivation. The gaseous hormone ethylene controls a number of adaptive responses to submergence including adventitious root growth and aerenchyma formation. Reactive oxygen species (ROS) act as signaling intermediates in ethylene-controlled submergence adaptation and possibly also independent of ethylene. ROS levels are controlled by synthesis, enzymatic metabolism, and non-enzymatic scavenging. While the actors are by and large known, we still have to learn about altered ROS at the subcellular level and how they are brought about, and the signaling cascades that trigger a specific response. This review briefly summarizes our knowledge on the contribution of ROS to submergence adaptation and describes spectrophotometrical, histochemical, and live cell imaging detection methods that have been used to study changes in ROS abundance. Electron paramagnetic resonance (EPR) spectroscopy is introduced as a method that allows identification and quantification of specific ROS in cell compartments. The use of advanced technologies such as EPR spectroscopy will be necessary to untangle the intricate and partially interwoven signaling networks of ethylene and ROS.
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Affiliation(s)
- Bianka Steffens
- Plant Developmental Biology and Plant Physiology, Kiel UniversityKiel, Germany
- *Correspondence: Bianka Steffens, Plant Developmental Biology and Plant Physiology, Kiel University, Am Botanischen Garten 5, 24118 Kiel, Germany e-mail:
| | | | - Margret Sauter
- Plant Developmental Biology and Plant Physiology, Kiel UniversityKiel, Germany
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Szal B, Lukawska K, Zdolińska I, Rychter AM. Chilling stress and mitochondrial genome rearrangement in the MSC16 cucumber mutant affect the alternative oxidase and antioxidant defense system to a similar extent. PHYSIOLOGIA PLANTARUM 2009; 137:435-45. [PMID: 19549067 DOI: 10.1111/j.1399-3054.2009.01255.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The mosaic MSC16 cucumber (Cucumis sativus L.) mutant, which houses a rearranged mitochondrial genome, has altered respiratory chain activity, with a dysfunctional Complex I, increased external NADH dehydrogenases (ND(ex)) activity, and a higher alternative oxidase (AOX) capacity and AOX protein level. In the present study, changes in oxidative defense metabolism resulting from the respiratory chain dysfunction in the MSC16 mutant were compared with those induced by chilling. Chilling increased the enzymatic and non-enzymatic antioxidant defense systems in the wild-type (WT) but not in MSC16, which displays elevated antioxidant defenses as a result of the mitochondrial mutation. The high AOX capacity and protein level in MSC16 were unchanged as a result of chilling, whereas chilling increased these parameters in WT leaves. In mitochondria isolated from WT plants, superoxide was produced to a similar extent in the matrix and the intermembrane space, but in MSC16 mitochondria superoxide was produced largely within the intermembrane space. Mitochondria isolated from both genotypes after chilling showed increased superoxide production within the intermembrane space. Cytochemical detection revealed an increased abundance of H2O2 in the mitochondrial membrane in mesophyll cells of MSC16 leaves. The mitochondrial mutation also resulted in changes in the antioxidative defense system, including AOX, which were similar to those observed following chilling. The results presented here support the hypothesis that AOX is an effective marker of the cellular reprogramming resulting from stress. Moreover, we propose a role for reactive oxygen species (ROS) generated within the mitochondria in signal transduction.
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Affiliation(s)
- Bozena Szal
- Faculty of Biology, Institute of Experimental Plant Biology, University of Warsaw, Miecznikowa 1, 02-096 Warsaw, Poland.
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Horchani F, Gallusci P, Baldet P, Cabasson C, Maucourt M, Rolin D, Aschi-Smiti S, Raymond P. Prolonged root hypoxia induces ammonium accumulation and decreases the nutritional quality of tomato fruits. JOURNAL OF PLANT PHYSIOLOGY 2008; 165:1352-1359. [PMID: 18180072 DOI: 10.1016/j.jplph.2007.10.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2007] [Revised: 10/24/2007] [Accepted: 10/24/2007] [Indexed: 05/25/2023]
Abstract
Here we examined the effects of root hypoxia (1-2% oxygen) on the physiology of the plant and on the biochemical composition of fruits in tomato (Solanum lycopersicum cv. Micro-Tom) plants submitted to gradual root hypoxia at first flower anthesis. Root hypoxia enhanced nitrate absorption with a concomitant release of nitrite and ammonium into the medium, a reduction of leaf photosynthetic activity and chlorophyll content, and an acceleration of fruit maturation, but did not affect final fruit size. Quantitative metabolic profiling of mature pericarp extracts by (1)H NMR showed that levels of major metabolites including sugars, organic acids and amino acids were not modified. However, ammonium concentration increased dramatically in fruit flesh, and ascorbate and lycopene concentrations decreased. Our data indicate that the unfavorable effects of root hypoxia on fruit quality cannot be explained by two of the well-known effects of root hypoxia on the plant, namely a decrease in photosynthesis or an excess in ethylene production, but may instead result from disturbances in the supply of either growth regulators or ammonium, by the roots.
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Affiliation(s)
- Faouzi Horchani
- Département des Sciences Biologiques, Faculté des Sciences de Tunis, UR d'Ecologie Végétale,Campus Universitaire, Tunis, Tunisia
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Garnczarska M. Response of the ascorbate-glutathione cycle to re-aeration following hypoxia in lupine roots. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2005; 43:583-90. [PMID: 15975806 DOI: 10.1016/j.plaphy.2005.05.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Accepted: 05/11/2005] [Indexed: 05/03/2023]
Abstract
The response of the enzymes and metabolites of the ascorbate-glutathione pathway to oxidative stress caused by re-aeration following hypoxia was studied in roots of hydroponically grown lupine (Lupinus luteus L. cv. Juno) seedlings. Lupine roots were deprived of oxygen by subjecting them to hypoxia for 48 and 72 h and then re-aerated for up to 4 h. An increased content of total ascorbate was observed in lupine roots immediately after hypoxia, whereas total glutathione level decreased. However, a significant increase in the reduced forms of both metabolites was found directly after hypoxia. Re-admission of oxygen caused the decrease of the ratios of reduced to oxidized forms of ascorbate and glutathione, indicating oxidative stress. While monodehydroascorbate reductase (MDHAR, EC 1.6.5.4) activity remained unaltered during re-aeration the increase in activities of ascorbate peroxidase (APX, EC 1.11.1.11) and glutathione reductase (GR, EC 1.6.4.2) was observed 30 min after transfer from hypoxic condition. Dehydroascorbate reductase (DHAR, EC 1.8.5.1) activity approached the control level during a whole re-aeration period. Native gel electrophoresis combined with specific activity staining revealed seven isoforms of APX, five isoforms of GR and three different proteins with DHA reductase activity in roots extracts. However, immediately after hypoxic treatment APX-5 isoform and GR-1 isoform were not observed in roots. This experimental system was also used to investigate superoxide anion level in roots utilizing the superoxide anion-specific indicator dihydroethidium (DHE). Intense DHE-derived fluorescence was found in re-aerated root tips as compared to control roots, indicating that re-aeration induced superoxide anion production in hypoxically pretreated roots.
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Affiliation(s)
- Małgorzata Garnczarska
- Department of Plant Physiology, Adam Mickiewicz University, al. Niepodległości 14, 61-713 Poznań, Poland.
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