ASCORBATE AND GLUTATHIONE: Keeping Active Oxygen Under Control
01 Jun 1998-Vol. 49, Iss: 1, pp 249-279
TL;DR: A detailed account of current knowledge of the biosynthesis, compartmentation, and transport of these two important antioxidants, with emphasis on the unique insights and advances gained by molecular exploration are provided.
Abstract: To cope with environmental fluctuations and to prevent invasion by pathogens, plant metabolism must be flexible and dynamic. Active oxygen species, whose formation is accelerated under stress conditions, must be rapidly processed if oxidative damage is to be averted. The lifetime of active oxygen species within the cellular environment is determined by the antioxidative system, which provides crucial protection against oxidative damage. The antioxidative system comprises numerous enzymes and compounds of low molecular weight. While research into the former has benefited greatly from advances in molecular technology, the pathways by which the latter are synthesized have received comparatively little attention. The present review emphasizes the roles of ascorbate and glutathione in plant metabolism and stress tolerance. We provide a detailed account of current knowledge of the biosynthesis, compartmentation, and transport of these two important antioxidants, with emphasis on the unique insights and advances gained by molecular exploration.
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TL;DR: Key steps of the signal transduction pathway that senses ROIs in plants have been identified and raise several intriguing questions about the relationships between ROI signaling, ROI stress and the production and scavenging ofROIs in the different cellular compartments.
9,395 citations
Cites background or methods from "ASCORBATE AND GLUTATHIONE: Keeping ..."
...Ascorbic acid Chl, Cyt, Mit, Per, Apo H2O2, O2 [3, 8 ] Glutathione Chl, Cyt, Mit, Per, Apo H2O2 [3,8] -Tocopherol Membranes ROOH, O2...
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...Antioxidants such as ascorbic acid and glutathione, which are found at high concentrations in chloroplasts and other cellular compartments (5–20 mM ascorbic acid and 1–5 mM glutathione) are crucial for plant defense against oxidative stress [ 8 ]....
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...This ratio is maintained by glutathione reductase (GR), monodehydroascorbate reductase (MDAR) and dehydroascorbate reductase (DHAR) using NADPH as reducing power (Fig. 1) [3, 8 ]....
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...Ascorbic acid Chl, Cyt, Mit, Per, Apo H2O2, O2 [3,8] Glutathione Chl, Cyt, Mit, Per, Apo H2O2 [3, 8 ] -Tocopherol Membranes ROOH, O2...
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TL;DR: In Arabidopsis, a network of at least 152 genes is involved in managing the level of ROS, and this network is highly dynamic and redundant, and encodes ROS-scavenging and ROS-producing proteins.
4,902 citations
01 Jun 2000
TL;DR: Evidence for plant stress signaling systems is summarized, some of which have components analogous to those that regulate osmotic stress responses of yeast, some that presumably function in intercellular coordination or regulation of effector genes in a cell-/tissue-specific context required for tolerance of plants.
Abstract: ▪ Abstract Plant responses to salinity stress are reviewed with emphasis on molecular mechanisms of signal transduction and on the physiological consequences of altered gene expression that affect biochemical reactions downstream of stress sensing. We make extensive use of comparisons with model organisms, halophytic plants, and yeast, which provide a paradigm for many responses to salinity exhibited by stress-sensitive plants. Among biochemical responses, we emphasize osmolyte biosynthesis and function, water flux control, and membrane transport of ions for maintenance and re-establishment of homeostasis. The advances in understanding the effectiveness of stress responses, and distinctions between pathology and adaptive advantage, are increasingly based on transgenic plant and mutant analyses, in particular the analysis of Arabidopsis mutants defective in elements of stress signal transduction pathways. We summarize evidence for plant stress signaling systems, some of which have components analogous to t...
4,596 citations
Cites background from "ASCORBATE AND GLUTATHIONE: Keeping ..."
...Among these functions a role in prevention of oxygen radical production or in the scavenging of reactive oxygen species (ROS) may be paramount (12, 185, 187)....
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...Further support comes from the study of transgenic models, which have been generated to study antioxidant defenses (5, 47, 187, 191, 244)....
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TL;DR: The generation, sites of production and role of ROS as messenger molecules as well as inducers of oxidative damage are described and the antioxidative defense mechanisms operating in the cells for scavenging of ROS overproduced under various stressful conditions of the environment are described.
Abstract: Reactive oxygen species (ROS) are produced as a normal product of plant cellular metabolism. Various environmental stresses lead to excessive production of ROS causing progressive oxidative damage and ultimately cell death. Despite their destructive activity, they are well-described second messengers in a variety of cellular processes, including conferment of tolerance to various environmental stresses. Whether ROS would serve as signaling molecules or could cause oxidative damage to the tissues depends on the delicate equilibrium between ROS production, and their scavenging. Efficient scavenging of ROS produced during various environmental stresses requires the action of several nonenzymatic as well as enzymatic antioxidants present in the tissues. In this paper, we describe the generation, sites of production and role of ROS as messenger molecules as well as inducers of oxidative damage. Further, the antioxidative defense mechanisms operating in the cells for scavenging of ROS overproduced under various stressful conditions of the environment have been discussed in detail.
4,012 citations
Cites background from "ASCORBATE AND GLUTATHIONE: Keeping ..."
...(APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) [21]....
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...It provides membrane protection by directly reacting with O2 •−, H2O2 and regenerating α-tocopherol from tocopheroxyl radical and preserves the activities of the enzymes that contain prosthetic transition metal ions [21]....
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...0 and is decomposed to tartarate and oxalate [21]....
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...Scavenging or detoxification of excess ROS is achieved by an efficient antioxidative system comprising of the nonenzymic as well as enzymic antioxidants [21]....
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...The enzymatic components of the antioxidative defense system comprise of several antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX), enzymes of ascorbateglutathione (AsA-GSH) cycle ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) [21]....
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01 Jun 1999
TL;DR: Whenever the water-water cycle operates properly for scavenging of active oxygens in chloroplasts, it also effectively dissipates excess excitation energy under environmental stress.
Abstract: Photoreduction of dioxygen in photosystem I (PSI) of chloroplasts generates superoxide radicals as the primary product. In intact chloroplasts, the superoxide and the hydrogen peroxide produced via the disproportionation of superoxide are so rapidly scavenged at the site of their generation that the active oxygens do not inactivate the PSI complex, the stromal enzymes, or the scavenging system itself. The overall reaction for scavenging of active oxygens is the photoreduction of dioxygen to water via superoxide and hydrogen peroxide in PSI by the electrons derived from water in PSII, and the water-water cycle is proposed for these sequences. An overview is given of the molecular mechanism of the water-water cycle and microcompartmentalization of the enzymes participating in it. Whenever the water-water cycle operates properly for scavenging of active oxygens in chloroplasts, it also effectively dissipates excess excitation energy under environmental stress. The dual functions of the water-water cycle for protection from photoinihibition are discussed.
3,904 citations
References
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TL;DR: It is reported here that H2O2 from this oxidative burst not only drives the cross-linking of cell wall structural proteins, but also functions as a local trigger of programmed death in challenged cells and as a diffusible signal for the induction in adjacent cells of genes encoding cellular protectants.
2,740 citations
01 Jan 1992
TL;DR: Prospects for Stress Tolerance through Genetic Engineering of SOD and MnSOD Overexpression are surveyed, and the Mechanism of Sod Regulation is studied.
Abstract: OXIDATIVE STRESS . . . . . . . . . . . . . .. . . . . .... . . . . .. . . . . .. . . . ... .. . . . . .... . . .. .. . . . . . ... . 84 RESPONSE OF SOD TO ENVIRONMENTAL STRESS . . . . . . . . . . . . . . . .. . . . .... . . .... . . . . . . 87 Photoinhibition . . . . . . . . . . .. . ... . . .. . . . .. . . . . ..... . . . , ... ", , ... ,' , ... . ,., . . . "" . .. . ,'.' . . ,' . . . . , ., 87 Paraquat and Other Herbicides . . .. , . . .... , ..... , . . . . ... . . . .. . . . . . . . . . . . . ,.. 91 Atmospheric Pollutants . . " .... , .... , " .... " , , . . , .... , ' 94 Waterlogging and Drought .. ", . . ... , . . . . . . , .. "", . . ", . . . . . ", . . . .. ", . . .. , . . . ... """", . . " 97 The Defense Response to Pathogens . ... . . . . "" ... "" .... " ...... " ,."" .... . , 98 The Phenomenon of Cross-Tolerance . . . , , .. . . . . ...... . . , . . . . . . , . . .... , .. . . . . . . . .. .. 101 The Mechanism of SOD Regulation ........ , , ...... , " 102 GENETIC ENGINEERING OF SOD IN PLANTS .. ' ...... ' . . . . . . . . . . . . . . . . . . . . . . . .. . . . , .... ' 104 Cu/ZnSOD and MnSOD Overexpression . . . . . .. . . . . . , . . . . . . .. . . . . . .. . . . . . , .... . . . . .. . . ,.... . . 105 Prospects for Stress Tolerance through Genetic Engineering of SOD . . . . ,,, .. , . . . . . . . 106
2,603 citations
TL;DR: 3,3-diaminobenzidine polymerizes instantly and locally as soon as it comes into contact with H2O2 in the presence of peroxidase, and it was found that, by allowing the leaf to take up this substrate, in-vivo and in-situ detection of H2 O2 can be made at subcellular levels.
Abstract: Active oxygen species (AOS) are believed to have important roles in plants in general and in plant—pathogen interactions in particular. They are believed to be involved in signal transduction, cell wall reinforcement, hypersensitive response (HR) and phytoalexin production, and to have direct antimicrobial effects. Since current methods are inadequate for localizing AOS in intact plant tissue, most studies have been conducted using cell suspension culture/elicitors systems. 3,3-diaminobenzidine (DAB) polymerizes instantly and locally as soon as it comes into contact with H2O2 in the presence of peroxidase, and it was found that, by allowing the leaf to take up this substrate, in-vivo and in-situ detection of H2O2 can be made at subcellular levels. This method was successfully used to detect H2O2 in developing papillae and surrounding haloes (cell wall appositions) and whole cells of barley leaves interacting with the powdery mildew fungus. Thus, H2O2 can be detected in the epidermal cell wall subjacent to the primary germ tube from 6 h after inoculation, and subjacent to the appressorium from 15 h. The earliest time point for observation of H2O2 in relation to epidermal cells undergoing HR is 15 h after inoculation, first appearing in the zones of attachment to the mesophyll cells underneath, and eventually in the entire epidermal cell. Furthermore, it was observed that proteins in papillae and HR cells are cross-linked, a process believed to be fuelled by H2O2. This cross-linking reinforces the apposition, presumably assisting the arrest of the pathogen.
2,429 citations
TL;DR: It is proposed that glutathione functions to stabilise enzymes of the Calvin cycle, and it may also act to keep ascorbic acid in chloroplasts in the reduced form.
Abstract: Both glutathione and an NADPH-dependent glutathione reductase are present in spinach (Spinacia oleracea L.) chloroplasts. It is proposed that glutathione functions to stabilise enzymes of the Calvin cycle, and it may also act to keep ascorbic acid in chloroplasts in the reduced form.
2,351 citations
TL;DR: Of the compatible solutes tested, sorbitol, mannitol, myo-inositol and proline were effective hydroxyl radical scavengers and Glycinebetaine was ineffective.
1,969 citations