Hydrogen sulfide: environmental factor or signalling molecule?
TL;DR: It appears that instead of thinking of H₂S as a phytotoxin, it needs to be considered as a signalling molecule that interacts with reactive oxygen species and NO metabolism, as well as having direct effects on the activity of proteins.
Abstract: Hydrogen sulfide (H₂S) has traditionally been thought of as a phytotoxin, having deleterious effects on the plant growth and survival. It is now recognized that plants have enzymes which generate H₂S, cysteine desulfhydrase, and remove it, O-acetylserine lyase. Therefore, it has been suggested that H₂S is considered as a signalling molecule, alongside small reactive compounds such as hydrogen peroxide (H₂O₂) and nitric oxide (NO). Exposure of plants to low of H₂S, for example from H₂S donors, is revealing that many physiological effects are seen. H₂S seems to have effects on stomatal apertures. Intracellular effects include increases in glutathione levels, alterations of enzyme activities and influences on NO and H₂O₂ metabolism. Work in animals has shown that H₂S may have direct effects on thiol modifications of cysteine groups, work that will no doubt inform future studies in plants. It appears therefore, that instead of thinking of H₂S as a phytotoxin, it needs to be considered as a signalling molecule that interacts with reactive oxygen species and NO metabolism, as well as having direct effects on the activity of proteins. The future may see H₂S being used to modulate plant physiology in the field or to protect crops from postharvest spoilage.
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TL;DR: It is argued that cytosolic K(+) content may be considered as one of the 'master switches' enabling plant transition from the normal metabolism to 'hibernated state' during first hours after the stress exposure and then to a recovery phase.
Abstract: Intracellular potassium homeostasis is a prerequisite for the optimal operation of plant metabolic machinery and plant's overall performance. It is controlled by K(+) uptake, efflux and intracellular and long-distance relocation, mediated by a large number of K(+) -selective and non-selective channels and transporters located at both plasma and vacuolar membranes. All abiotic and biotic stresses result in a significant disturbance to intracellular potassium homeostasis. In this work, we discuss molecular mechanisms and messengers mediating potassium transport and homeostasis focusing on four major environmental stresses: salinity, drought, flooding and biotic factors. We argue that cytosolic K(+) content may be considered as one of the 'master switches' enabling plant transition from the normal metabolism to 'hibernated state' during first hours after the stress exposure and then to a recovery phase. We show that all these stresses trigger substantial disturbance to K(+) homeostasis and provoke a feedback control on K(+) channels and transporters expression and post-translational regulation of their activity, optimizing K(+) absorption and usage, and, at the extreme end, assisting the programmed cell death. We discuss specific modes of regulation of the activity of K(+) channels and transporters by membrane voltage, intracellular Ca(2+) , reactive oxygen species, polyamines, phytohormones and gasotransmitters, and link this regulation with plant-adaptive responses to hostile environments.
501 citations
Cites background from "Hydrogen sulfide: environmental fac..."
...It was documented that H2S as a signaling molecule participated in plant stress responses, where it generally tends to lower nitrosylation and oxidation stress components, increasing the glutathione level and activating antioxidant enzymes (reviewed by Lisjak et al. 2013)....
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TL;DR: This review aimed at presenting an overview of defensive systems and the regulatory network involving upstream signaling molecules including stress hormones, reactive oxygen species, gasotransmitters, polyamines, phytochromes, and calcium, as well as downstream gene regulation factors, particularly transcription factors.
Abstract: Abiotic stresses, such as low or high temperature, deficient or excessive water, high salinity, heavy metals, and ultraviolet radiation, are hostile to plant growth and development, leading to great crop yield penalty worldwide. It is getting imperative to equip crops with multistress tolerance to relieve the pressure of environmental changes and to meet the demand of population growth, as different abiotic stresses usually arise together in the field. The feasibility is raised as land plants actually have established more generalized defenses against abiotic stresses, including the cuticle outside plants, together with unsaturated fatty acids, reactive species scavengers, molecular chaperones, and compatible solutes inside cells. In stress response, they are orchestrated by a complex regulatory network involving upstream signaling molecules including stress hormones, reactive oxygen species, gasotransmitters, polyamines, phytochromes, and calcium, as well as downstream gene regulation factors, particularly transcription factors. In this review, we aimed at presenting an overview of these defensive systems and the regulatory network, with an eye to their practical potential via genetic engineering and/or exogenous application.
314 citations
TL;DR: The progress in understanding the structural, physiological and molecular mechanisms underlying HM uptake, transport, sequestration and detoxification, as well as the regulation of these processes by signal transduction in response to HM exposure are reviewed.
256 citations
TL;DR: It is proposed that the outcome of the salinity response (adaptation versus cell death) depends on the timing with which these signals appear and disappear, and that the often-neglected non-selective cation channels are relevant.
Abstract: Salinity does not only stress plants but also challenges human life and the economy by posing severe constraints upon agriculture. To understand salt adaptation strategies of plants, it is central to extend agricultural production to salt-affected soils. Despite high impact and intensive research, it has been difficult to dissect the plant responses to salt stress and to define the decisive key factors for the outcome of salinity signalling. To connect the rapidly accumulating data from different systems, treatments, and organization levels (whole-plant, cellular, and molecular), and to identify the appropriate correlations among them, a clear conceptual framework is required. Similar to other stress responses, the molecular nature of the signals evoked after the onset of salt stress seems to be general, as with that observed in response to many other stimuli, and should not be considered to confer specificity per se. The focus of the current review is therefore on the temporal patterns of signals conveyed by molecules such as Ca 2+ , H + , reactive oxygen species, abscisic acid, and jasmonate. We propose that the outcome of the salinity response (adaptation versus cell death) depends on the timing with which these signals appear and disappear. In this context, the oftenneglected non-selective cation channels are relevant. We also propose that constraining a given signal is as important as its induction, as it is the temporal competence of signalling (signal on demand) that confers specificity.
216 citations
Cites background from "Hydrogen sulfide: environmental fac..."
...As an additional regulator, hydrogen sulfide (H₂S) has emerged as a signalling molecule in plants that increases GSH levels, alters enzyme activities, and interacts with NO and ROS metabolism (reviewed by Paul and Snyder, 2012; Lisjak et al., 2013)....
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TL;DR: H2S is proposed as a potential candidate for managing toxicity of cadmium, and perhaps other heavy metals, in rice and other crops by providing an insight into H2S-induced protective mechanisms of rice exposed to Cadmium stress.
Abstract: We investigated the physiological and biochemical mechanisms by which H2S mitigates the cadmium stress in rice. Results revealed that cadmium exposure resulted in growth inhibition and biomass reduction, which is correlated with the increased uptake of cadmium and depletion of the photosynthetic pigments, leaf water contents, essential minerals, water-soluble proteins, and enzymatic and non-enzymatic antioxidants. Excessive cadmium also potentiated its toxicity by inducing oxidative stress, as evidenced by increased levels of superoxide, hydrogen peroxide, methylglyoxal and malondialdehyde. However, elevating endogenous H2S level improved physiological and biochemical attributes, which was clearly observed in the growth and phenotypes of H2S-treated rice plants under cadmium stress. H2S reduced cadmium-induced oxidative stress, particularly by enhancing redox status and the activities of reactive oxygen species and methylglyoxal detoxifying enzymes. Notably, H2S maintained cadmium and mineral homeostases in roots and leaves of cadmium-stressed plants. By contrast, adding H2S-scavenger hypotaurine abolished the beneficial effect of H2S, further strengthening the clear role of H2S in alleviating cadmium toxicity in rice. Collectively, our findings provide an insight into H2S-induced protective mechanisms of rice exposed to cadmium stress, thus proposing H2S as a potential candidate for managing toxicity of cadmium, and perhaps other heavy metals, in rice and other crops.
210 citations
References
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TL;DR: In this article, a simple colorimetric determination of proline in the 0.1 to 36.0 μmoles/g range of fresh weight leaf material was presented.
Abstract: Proline, which increases proportionately faster than other amino acids in plants under water stress, has been suggested as an evaluating parameter for irrigation scheduling and for selecting drought-resistant varieties. The necessity to analyze numerous samples from multiple replications of field grown materials prompted the development of a simple, rapid colorimetric determination of proline. The method detected proline in the 0.1 to 36.0 μmoles/g range of fresh weight leaf material.
15,328 citations
TL;DR: NO released from endothelial cells is indistinguishable from EDRF in terms of biological activity, stability, and susceptibility to an inhibitor and to a potentiator.
Abstract: Endothelium-derived relaxing factor (EDRF) is a labile humoral agent which mediates the action of some vasodilators. Nitrovasodilators, which may act by releasing nitric oxide (NO), mimic the effect of EDRF and it has recently been suggested by Furchgott that EDRF may be NO. We have examined this suggestion by studying the release of EDRF and NO from endothelial cells in culture. No was determined as the chemiluminescent product of its reaction with ozone. The biological activity of EDRF and of NO was measured by bioassay. The relaxation of the bioassay tissues induced by EDRF was indistinguishable from that induced by NO. Both substances were equally unstable. Bradykinin caused concentration-dependent release of NO from the cells in amounts sufficient to account for the biological activity of EDRF. The relaxations induced by EDRF and NO were inhibited by haemoglobin and enhanced by superoxide dismutase to a similar degree. Thus NO released from endothelial cells is indistinguishable from EDRF in terms of biological activity, stability, and susceptibility to an inhibitor and to a potentiator. We suggest that EDRF and NO are identical.
10,739 citations
TL;DR: It is concluded that although there are a number of promising selection criteria, the complex physiology of salt tolerance and the variation between species make it difficult to identify single criteria.
1,946 citations
"Hydrogen sulfide: environmental fac..." refers background in this paper
...A stress that has been linked to plant growth and productivity is salt (NaCl stress: Ashraf & Harris 2004)....
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TL;DR: Stomatal morphology, distribution and behaviour respond to a spectrum of signals, from intracellular signalling to global climatic change, which results from a web of control systems reminiscent of a ‘scale-free’ network, whose untangling requires integrated approaches beyond those currently used.
Abstract: Stomata, the small pores on the surfaces of leaves and stalks, regulate the flow of gases in and out of leaves and thus plants as a whole. They adapt to local and global changes on all timescales from minutes to millennia. Recent data from diverse fields are establishing their central importance to plant physiology, evolution and global ecology. Stomatal morphology, distribution and behaviour respond to a spectrum of signals, from intracellular signalling to global climatic change. Such concerted adaptation results from a web of control systems, reminiscent of a 'scale-free' network, whose untangling requires integrated approaches beyond those currently used.
1,877 citations
"Hydrogen sulfide: environmental fac..." refers background in this paper
...Guard cell signalling is extremely complex (Hetherington & Woodward 2003) and almost certainly a balance between a large number of signals, so blasting these cells with H2S under difference conditions may give different overall results....
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TL;DR: The data indicate that ethylene and H(2)O( 2) signalling in guard cells are mediated by ETR1 via EIN2 and ARR2-dependent pathway(s), and identify AtrbohF as a key mediator of stomatal responses to ethylene.
Abstract: Ethylene is a plant hormone that regulates many aspects of growth and development. Despite the well-known association between ethylene and stress signalling, its effects on stomatal movements are largely unexplored. Here, genetic and physiological data are provided that position ethylene into the Arabidopsis guard cell signalling network, and demonstrate a functional link between ethylene and hydrogen peroxide (H(2)O(2)). In wild-type leaves, ethylene induces stomatal closure that is dependent on H(2)O(2) production in guard cells, generated by the nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) oxidase AtrbohF. Ethylene-induced closure is inhibited by the ethylene antagonists 1-MCP and silver. The ethylene receptor mutants etr1-1 and etr1-3 are insensitive to ethylene in terms of stomatal closure and H(2)O(2) production. Stomata of the ethylene signalling ein2-1 and arr2 mutants do not close in response to either ethylene or H(2)O(2) but do generate H(2)O(2) following ethylene challenge. Thus, the data indicate that ethylene and H(2)O(2) signalling in guard cells are mediated by ETR1 via EIN2 and ARR2-dependent pathway(s), and identify AtrbohF as a key mediator of stomatal responses to ethylene.
990 citations
"Hydrogen sulfide: environmental fac..." refers background in this paper
...Ethylene was shown to mediate auxin-induced opening (Levitt, Stein & Rubinstein 1987) and to cause stomatal closure (Desikan et al. 2006)....
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