Missing links in understanding redox signaling via thiol/disulfide modulation: how is glutathione oxidized in plants ? (original) (raw)
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The role of thiols in plant adaptation to environmental stress
Thiols (-SH groups) are the main form of reduced sulphur in plants present as protein thiols (Cys residues) or low molecular weight thiols, the most prominent is the tripeptide glutathione (GSH). Due to the redox properties of the thiol groups these compounds play important roles in stress responses of plants, since stress is nearly always associated with an enhanced formation of reactive oxygen species (ROS). Because of its antioxidative properties, GSH is directly involved in protection of cells from ROS damage and in regeneration of oxidized substrates. GSH is kept in the active reduced state by glutathione reductase (GR). In the following chapter, responses of GSH and GR system to natural abiotic stresses (drought, low and high temperatures, high light, UV, salinity, anoxia), biotic stresses (pathogen infection), and air pollution impact are discussed. The reviewed results show that plant resistance to stress is commonly correlated with increased GSH contents and GR activities. Damage to plant tissues is often marked by a breakdown of the GSH system. Besides its role as protectant, GSH is thought to play a role in cellular signalling and stress sensing. Apart from GSH, small protein thiols (thioredoxins) are essential for the adjustment of metabolism to environmental conditions. Most recent results suggest that thioredoxins can be directly induced by ROS stress. The role of thiols in regulation of plant stress responses, e.g. by inducing defense enzymes and compounds, is discussed.
Glutathione homeostasis in plants: implications for environmental sensing and plant development
Journal of Experimental Botany, 1998
for life (Grant and Dawes, 1996). Analysis of the an oxidative burst during elicitation of cultured plant cells. responses of existing mutants and those arising from new Plant Physiology 90, 109-16. screens to diverse stresses will allow the genetic dissection Asada K. 1994. Production and action of active oxygen species of signal transduction pathways and will permit rigorous in photosynthetic tissues. In: Foyer CH, Mullineaux PM, eds. Causes of photooxidative stress and amelioration of defence discrimination between those specific for a particular systems in plants. Boca Raton: CRC Press Inc., 77-104. stress and those common to many. The finding that Atzori L, Dypbukt PF, Hybbinette SS, Moldéus P, Grafstrom redox-regulated kinases (Link, 1996) and phosphatases RC. 1994. Modifications of cellular thiols during growth and (Haring et al., 1995) and transcription factors (Yang and squamous differentiation of cultured human bronchial epithe-Klessig, 1996; Yang and Klessig, personal communicalial cells. Experimental Cell Research 211, 115-20. Babiychuk E, Kushnir S, Belles-Boix E, Van Montagu M, Inzé tion) function in the transcription of plant genes during D. 1995. Arabidopsis thaliana NADPH oxidoreductase homostress responses underlines the ubiquity of redox in the logs confer tolerance of yeasts toward the thiol-oxidizing fine tuning and reversible activation of signal transduction drug diamide.
Glutathione in plants: an integrated overview
Plant, Cell & Environment, 2012
cannot survive without glutathione (g-glutamylcysteinylglycine) or g-glutamylcysteinecontaining homologues. The reasons why this small molecule is indispensable are not fully understood, but it can be inferred that glutathione has functions in plant development that cannot be performed by other thiols or antioxidants. The known functions of glutathione include roles in biosynthetic pathways, detoxification, antioxidant biochemistry and redox homeostasis. Glutathione can interact in multiple ways with proteins through thiol-disulphide exchange and related processes. Its strategic position between oxidants such as reactive oxygen species and cellular reductants makes the glutathione system perfectly configured for signalling functions. Recent years have witnessed considerable progress in understanding glutathione synthesis, degradation and transport, particularly in relation to cellular redox homeostasis and related signalling under optimal and stress conditions. Here we outline the key recent advances and discuss how alterations in glutathione status, such as those observed during stress, may participate in signal transduction cascades. The discussion highlights some of the issues surrounding the regulation of glutathione contents, the control of glutathione redox potential, and how the functions of glutathione and other thiols are integrated to fine-tune photorespiratory and respiratory metabolism and to modulate phytohormone signalling pathways through appropriate modification of sensitive protein cysteine residues.
Role of glutathione and glutathione-related enzymes in response of plants to environmental stress
Published in: Annals of the New York Academy of Sciences. 02/2006; 851(1):251 - 258. DOI: 10.1111/j.1749-6632.1998.tb09000.x The tripeptide glutathione (GSH, gamma-L-glutamyl-L-cysteinylglycine), and its structural analogues are the principal nonprotein thiol compounds in plants. Following the elucidation of its chemical structure, GSH was soon identified as an antioxidant and later recognized as an essential component of antioxidative and detoxification systems in plant cells. In most tissues, GSH is predominantly present in its reduced form. The regeneration of GSH from oxidized glutathione (GSSG) is catalyzed by glutathione reductase (GR, E.C. 1.6.4.2) enzyme. Elevated GSH levels, GR, and glutathione S-transferase (GST, EC 2.5.1.18) activities were found in plants exposed to a wide range of environmental stress effects2,3 and microbial infections. The physiological basis of the damage suffered by a plant during stress can often be explained as perturbations in oxygen metabolism. An increased production of reactive oxygen species (ROS) has been shown to occur in plants exposed to various abiotic and biotic stress effects. Although the adaptive significance of the elevated level of GSH in plants exposed to various stress effects has not been unequivocally established yet, this increased production of GSH seems to contribute to the antioxidative protection of plant cells against stress caused by ROS. In this paper we shall attempt to evaluate the possible roles of GSH and GSH related enzymes in the defense reactions of plants exposed to peroxidizing herbi cides, heavy metals, and biotic stress effects.
Stress-Induced Protein S-Glutathionylation in Arabidopsis
Plant Physiology, 2005
S-Glutathionylation (thiolation) is a ubiquitous redox-sensitive and reversible modification of protein cysteinyl residues that can directly regulate their activity. While well established in animals, little is known about the formation and function of these mixed disulfides in plants. After labeling the intracellular glutathione pool with [35S]cysteine, suspension cultures of Arabidopsis (Arabidopsis thaliana ecotype Columbia) were shown to undergo a large increase in protein thiolation following treatment with the oxidant tert-butylhydroperoxide. To identify proteins undergoing thiolation, a combination of in vivo and in vitro labeling methods utilizing biotinylated, oxidized glutathione (GSSG-biotin) was developed to isolate Arabidopsis proteins/protein complexes that can be reversibly glutathionylated. Following two-dimensional polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization time of flight mass spectrometry proteomics, a total of 79 polypeptide...
Plant Physiology, 2010
Glutathione is a major cellular thiol that is maintained in the reduced state by glutathione reductase (GR), which is encoded by two genes in Arabidopsis (Arabidopsis thaliana; GR1 and GR2). This study addressed the role of GR1 in hydrogen peroxide (H 2 O 2 ) responses through a combined genetic, transcriptomic, and redox profiling approach. To identify the potential role of changes in glutathione status in H 2 O 2 signaling, gr1 mutants, which show a constitutive increase in oxidized glutathione (GSSG), were compared with a catalase-deficient background (cat2), in which GSSG accumulation is conditionally driven by H 2 O 2 . Parallel transcriptomics analysis of gr1 and cat2 identified overlapping gene expression profiles that in both lines were dependent on growth daylength. Overlapping genes included phytohormone-associated genes, in particular implicating glutathione oxidation state in the regulation of jasmonic acid signaling. Direct analysis of H 2 O 2 -glutathione interactions in cat2 gr1 double mutants established that GR1-dependent glutathione status is required for multiple responses to increased H 2 O 2 availability, including limitation of lesion formation, accumulation of salicylic acid, induction of pathogenesis-related genes, and signaling through jasmonic acid pathways. Modulation of these responses in cat2 gr1 was linked to dramatic GSSG accumulation and modified expression of specific glutaredoxins and glutathione S-transferases, but there is little or no evidence of generalized oxidative stress or changes in thioredoxin-associated gene expression. We conclude that GR1 plays a crucial role in daylength-dependent redox signaling and that this function cannot be replaced by the second Arabidopsis GR gene or by thiol systems such as the thioredoxin system.
Journal of Plant Physiology, 2015
The plant glutathione peroxidase (GPX) family consists of multiple isoenzymes with distinct subcellular locations which exhibit different tissue-specific expression patterns and environmental stress responses. Contrary to most of their counterparts in animal cells, plant GPXs contain cysteine instead of selenocysteine in their active site and while some of them have both glutathione peroxidase and thioredoxin peroxidase functions, the thioredoxin regenerating system is much more efficient in vitro than the glutathione system. At present, the function of these enzymes in plants is not completely understood. The occurrence of thiol-dependent activities of plant GPX isoenzymes suggests that-besides detoxification of H 2 O 2 and organic hydroperoxides-they may be involved in regulation of the cellular redox homeostasis by maintaining the thiol/disulfide or NADPH/NADP + balance. GPXs may represent a link existing between the glutathione-and the thioredoxin-based system. The various thiol buffers, including Trx, can affect a number of redox reactions in the cells most probably via modulation of thiol status. It is still required to identify the in vivo reductant for particular GPX isoenzymes and partners that GPXs interact with specifically. Recent evidence suggests that plant GPXs does not only protect cells from stress induced oxidative damage but they can be implicated in plant growth and development. Following a more general introduction, this study summarizes present knowledge on plant GPXs, highlighting the results on gene expression analysis, regulation and signaling of Arabidopsis thaliana GPXs and also suggests some perspectives for future research.
Plant Physiology and Biochemistry, 2013
Abiotic stresses such as salinity, drought, clilling, heavy metal are the major limiting factors for crop productivity. These stresses induce the overproduction of reactive oxygen species (ROS) which are highly reactive and toxic, which must be minimized to protect the cell from oxidative damage. The cell organelles, particularly chloroplast and mitochondria are the major sites of ROS production in plants where excessive rate of electron flow takes place. Plant cells are well equipped to efficiently scavenge ROS and its reaction products by the coordinated and concerted action of antioxidant machinery constituted by vital enzymatic and non-enzymatic antioxidant components. Glutathione reductase (GR, EC 1.6.4.2) and tripeptide glutathione (GSH, g-Glutamyl-Cysteinyl-Glycine) are two major components of ascorbate eglutathione (AsAeGSH) pathway which play significant role in protecting cells against ROS and its reaction products-accrued potential anomalies. Both GR and GSH are physiologically linked together where, GR is a NAD(P)H-dependent enzymatic antioxidant and efficiently maintains the reduced pool of GSH e a cellular thiol. The differential modulation of both GR and GSH in plants has been widely implicated for the significance of these two enigmatic antioxidants as major components of plant defense operations. Considering recent informations gained through molecular-genetic studies, the current paper presents an overview of the structure, localization, biosynthesis (for GSH only), discusses GSH and GR significance in abiotic stress (such as salinity, drought, clilling, heavy metal)-exposed crop plants and also points out unexplored aspects in the current context for future studies.