Production of reactive oxygen species by freezing stress and the protective roles of antioxidant enzymes in plants
21 Sep 2012-Journal of Agricultural Chemistry and Environment (Scientific Research Publishing)-Vol. 1, Iss: 1, pp 34-40
TL;DR: More researches will be required in near future to elucidate the most effective antioxidant enzymes to induce highest freezing tolerance in a crop plant in a transformation process or a breeding program.
Abstract: As one of the most severe environmental stresses, freezing stress can determine native flora in nature and severely reduce crop production. Many mechanisms have been proposed to explain the damage induced by freezing-thawing cycle, and oxidative stress caused by uncontrollable production of harmful reactive oxygen species (ROS) are partially contributed to causing the injury. Plants in temperate regions have evolved a unique but effective metabolism of protecting themselves called cold acclimation. Cold-acclimating plants undergo a complex but orchestrated metabolic process to increase cold hardness triggered by exposure to low temperature and shortened photoperiod and achieve the maximum freezing tolerance by a concerted regulation and expression of a number of cold responsive genes. A complicated enzymatic system have been evolved in plants to scavenge the ROS to protect themselves from oxidative stress, therefore, cold-acclimating plants are expected to increase the de novo synthesis of the genes of antioxidant genes. Indeed, many antioxidant genes increase the expression levels in response to low temperature. Furthermore, the higher expression of many antioxidant enzymes are positively correlated to inducing higher tolerance levels against freezing. All the information summarized here can be applied for developing crop and horticultural plants to have more freezing tolerance for higher production with better quality. There have been extensive studies on the activities of antioxidant enzymes and the gene regulation, however, more researches will be required in near future to elucidate the most effective antioxidant enzymes to induce highest freezing tolerance in a crop plant in a transformation process or a breeding program.
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TL;DR: In this paper, potential cold-stress protectants, such as supplemented micronutrients (Zn, Mn), seaweed extracts, and rhizobacteria with plant growth-promoting potential (PGPRs), were tested in order to improve the tolerance of maize to low root zone temperatures (RZT) during early growth.
Abstract: Low soil temperature in spring is a major constraint for cultivation of tropical crops in temperate climates, associated with impaired seedling development, inhibition of root growth and root activity. In this study, potential cold-stress protectants, such as supplemented micronutrients (Zn, Mn), seaweed extracts, and rhizobacteria with plant growth-promoting potential (PGPRs) were tested in order to improve the tolerance of maize to low root zone temperatures (RZT) during early growth. Maize (v. Colisee) was cultivated in a root cooling system for adjustment of the RZT. In three independent experiments, after germination at 20 °C, the cold-stress phase (12–14 °C) started at 14 days after sowing to simulate a cold period in spring. Micronutrients, seaweed extracts, and PGPRs were supplied by fertigation (experiment 1), fertigation and seed dressing (experiment 2), and nutrient seed priming (experiment 3). At the end of the experiments, scoring of oxidative leaf damage, biomass production, chlorophyll status (SPAD), root length density, superoxide dismutase activities in leaf and root tissues, and the shoot mineral-nutritional status were determined. Positive effects on plant growth and particularly on root development at low RZT were detected exclusively for seaweed extracts with high Zn/Mn contents and similar growth promotions were induced by Zn and Mn application in comparable amounts. This finding suggests that the selected seaweed extracts were mainly acting via improved Zn and Mn supply to the plants. It was essential that the cold-stress protectants were present during seed imbibition. The beneficial effect of Zn/Mn treatments and sea weed extracts was associated with increased superoxide dismutase activity in the root and leaf tissue, with key functions in antioxidative stress defense, depending on Zn, Mn, Cu, and Fe as enzymatic co-factors. Accordingly, leaf damage, shoot and root growth inhibition in cold-stressed plants was associated with a low Zn-nutritional status, mitigated by application of the cold-stress protectants. Since micronutrients are effective already at low concentrations, starter applications of Zn/Mn or the respective seaweed extracts may offer an economic option for cold-stress prophylaxis in crops.
81 citations
Cites background from "Production of reactive oxygen speci..."
...Reduced shoot and root growth of maize plants exposed to low temperatures has been attributed to severe oxidative damage induced by cold stress [13, 29]....
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...The different isoforms of SO as key enzyme for detoxification of free radicals, strongly depend on Zn, Mn, Cu, and Fe as cofactors and have been implicated in chilling tolerance of higher plants [29]....
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TL;DR: Investigation of the contribution of the GI–CDF module to traits that depend on GI showed that GI‐mediated regulation of CDFs contributes to several processes in addition to flowering, but is not implicated in all of the traits influenced by GI.
Abstract: SUMMARY Plants monitor and integrate temperature, photoperiod and light quality signals to respond to continuous changes in their environment. The GIGANTEA (GI) protein is central in diverse signaling pathways, including photoperiodic, sugar and light signaling pathways, stress responses and circadian clock regulation. Previously, GI was shown to activate expression of the key floral regulators CONSTANS (CO) and FLOWERING LOCUS T (FT) by facilitating degradation of a family of CYCLING DOF FACTOR (CDF) transcriptional repressors. However, whether CDFs are implicated in other processes affected by GI remains unclear. We investigated the contribution of the GI–CDF module to traits that depend on GI. Transcriptome profiling indicated that mutations in GI and the CDF genes have antagonistic effects on expression of a wider set of genes than CO and FT, whilst other genes are regulated by GI independently of the CDFs. Detailed expression studies followed by phenotypic assays showed that the CDFs function downstream of GI, influencing responses to freezing temperatures and growth, but are not necessary for proper clock function. Thus GI-mediated regulation of CDFs contributes to several processes in addition to flowering, but is not implicated in all of the traits influenced by GI.
79 citations
Cites background from "Production of reactive oxygen speci..."
...Cold tolerance levels correlated with resistance to reactive oxygen species, which are produced upon freezing and contribute to membrane damage (Baek and Skinner, 2012)....
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...Freezing temperatures cause cell dehydration and membrane damage, partly through production of reactive oxygen species (Baek and Skinner, 2012)....
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TL;DR: It is suggested that mitigation of oxidative stress is a major effect of Zn, Mn, and Si applied as cold stress protectants in a soil–free culture system without external nutrient supply.
Abstract: Low soil temperature in spring is a major constraint for the cultivation of tropical and subtropical crops in temperate climates, associated with inhibition of root growth and activity, affecting early growth and frequently plant performance and final yield. This study was initiated to investigate the physiological base of cold-protective effects induced by supplementation with silicon (Si), widely recommended as a stress-protective mineral nutrient. Maize was used as a cold-sensitive model plant, exposed to chilling stress and low root-zone temperature (RZT) during early growth in a lab to field approach. In a pot experiment, 2-weeks exposure of maize seedlings to low RZT of 12-14°C, induced leaf chlorosis and necrosis, inhibition of shoot and root growth and micronutrient limitation (particularly Zn and Mn). These phenotypes were mitigated by seed treatments with the respective micronutrients, but surprisingly, also by Si application. Both, silicon and micronutrient treatments were associated with increased activity of superoxide dismutase in shoot and roots (as a key enzyme for detoxification of reactive oxygen species, depending on Zn and Mn as cofactors), increased tissue concentrations of phenolics, proline, and antioxidants, but reduced levels of H2O2. These findings suggest that mitigation of oxidative stress is a major effect of Zn, Mn, and Si applied as cold stress protectants. In a soil-free culture system without external nutrient supply, Si significantly reduced large leaching losses of Zn and Mn from germinating seeds exposed to low-temperature stress. Silicon also increased the translocation of micronutrient seed reserves to the growing seedling, especially the Zn shoot translocation. In later stages of seedling development (10 days after sowing), cold stress reduced the root and shoot contents of important hormonal growth regulators (indole acetic acid, gibberellic acid, zeatin). Silicon restored the hormonal balances to a level comparable with non-stressed plants and stimulated the production of hormones involved in stress adaptation (abscisic, salicylic, and jasmonic acids). Beneficial effects of Si seed treatments on seedling establishment and the nutritional status of Zn and Mn were also measured for a field-grown silage maize, exposed to chilling stress by early sowing. This translated into increased final biomass yield.
77 citations
Cites background from "Production of reactive oxygen speci..."
...Consequently, excessive accumulation of ROS (Table 1) resulted in oxidative damage of plant tissues (Figure 2) considered as one of the major constraints for cold-stressed plants (Baek and Skinner, 2012; Saeidnejad et al., 2012)....
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TL;DR: Thermal analysis indicates that PHB-containing cells exhibit a higher rate of transmembrane water transport, which protects cells against the formation of intracellular ice which usually has fatal consequences.
Abstract: Accumulation of polyhydroxybutyrate (PHB) seems to be a common metabolic strategy adopted by many bacteria to cope with cold environments. This work aimed at evaluating and understanding the cryoprotective effect of PHB. At first a monomer of PHB, 3-hydroxybutyrate, was identified as a potent cryoprotectant capable of protecting model enzyme (lipase), yeast (Saccharomyces cerevisiae) and bacterial cells (Cupriavidus necator) against the adverse effects of freezing-thawing cycles. Further, the viability of the frozen–thawed PHB accumulating strain of C. necator was compared to that of the PHB non-accumulating mutant. The presence of PHB granules in cells was revealed to be a significant advantage during freezing. This might be attributed to the higher intracellular level of 3-hydroxybutyrate in PHB accumulating cells (due to the action of parallel PHB synthesis and degradation, the so-called PHB cycle), but the cryoprotective effect of PHB granules seems to be more complex. Since intracellular PHB granules retain highly flexible properties even at extremely low temperatures (observed by cryo-SEM), it can be expected that PHB granules protect cells against injury from extracellular ice. Finally, thermal analysis indicates that PHB-containing cells exhibit a higher rate of transmembrane water transport, which protects cells against the formation of intracellular ice which usually has fatal consequences.
72 citations
Cites background from "Production of reactive oxygen speci..."
...Apart from the mechanisms mentioned above, reactive oxygen species (ROS), generated as a consequence of an impaired aerobic respiration chain, also significantly contribute to the injury of cells during the freezing-thawing process [6]....
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...Apart from dehydration and intracellular ice formation, cells can also be harmed by reactive oxygen species (ROS) formed in cells during freezing [6]....
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01 Jan 2016
TL;DR: The redox-dependent modification of sensitive signalling proteins is proposed as a key mode of redox signal transmission, which plays a key role in the adaptive response to the adverse environment.
Abstract: Plants are frequently exposed to different stressful factors, both of biotic or abiotic nature, which limit their growth and productivity. To survive under stress conditions, plants must activate stress-specific signalling pathways, which finally lead to morphological, physiological, and biochemical changes that allow to adapt to the adverse environment. Cellular redox homeostasis, determined by a complex interplay between pathways that produce and scavenge reactive oxygen species (ROS), plays a key role in the adaptive response. Each deviation in the cellular redox state, due to an imbalance of ROS production and/or scavenging, is indicative of environmental disturbance and works as a signal. Under stress conditions, different ROS are produced in many cell compartments. Plants have very proficient, versatile and flexible antioxidant machinery, which comprises enzymes and metabolites with distinct biochemical properties and distinct sub-cellular localization. The antioxidant systems play a key role in the control of redox homeostasis, determining either the extent or the specificity of ROS signals and the downstream redox-dependent responses. Redox signalling is responsive to a number of environmental cues, and the complex and dynamic pathways of redox regulation occur in different cell compartments. The redox-dependent modification of sensitive signalling proteins is proposed as a key mode of redox signal transmission. Each redox-dependent interaction is opportunely regulated by a restricted environment, whose change transfers the complex system of information and influences the plant response to external changes.
57 citations
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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.
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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