Stress Tolerance in Transgenic Tobacco Seedlings that Overexpress Glutathione S-Transferase/Glutathione Peroxidase (original) (raw)
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Planta, 2005
Transgenic cotton (Gossypium hirsutum L.) lines expressing the tobacco glutathione S-transferase (GST) Nt107 were evaluated for tolerance to chilling, salinity, and herbicides, antioxidant enzyme activity, antioxidant compound levels, and lipid peroxidation. Although transgenic seedlings exhibited ten-fold and five-fold higher GST activity under normal and salt-stress conditions, respectively, germinating seedlings did not show improved tolerance to salinity, chilling conditions, or herbicides. Glutathione peroxidase (GPX) activity in transgenic seedlings was 30% to 60% higher under normal conditions, but was not different than GPX activity in wild-type seedlings under salt-stress conditions. Glutathione reductase, superoxide dismutase, ascorbate peroxidase, and monodehydroascorbate reductase activities were not increased in transgenic seedlings under salt-stress conditions, while dehydroascorbate reductase activity was decreased in transgenic seedlings under salt-stress conditions. Transgenic seedlings had 50% more oxidized glutathione when exposed to salt stress. Ascorbate levels were not increased in transgenic seedlings under salt-stress conditions. Malondialdehyde content in transgenic seedlings was nearly double that of wild-type seedlings under normal conditions and did not increase under salt-stress conditions. These results show that expression of Nt107 in cotton does not provide adequate protection against oxidative stress and suggests that the endogenous antioxidant system in cotton may be disrupted by the expression of the tobacco GST.
The role of Arabidopsis glutathione transferase F9 gene under oxidative stress in seedlings
Acta Biologica Hungarica, 2015
Arabidopsis thaliana contains 54 soluble glutathione transferases (GSTs, EC 2.5.1.18), which are thought to play major roles in oxidative stress responses, but little is known about the function of individual isoenzymes. The role of AtGST phi 9 (GSTF9) in the salt-and salicylic acid response was investigated using 2-week-old Atgstf9 and wild type (Wt) plants. Atgstf9 mutants accumulated more ascorbic acid (AsA) and glutathione (GSH) and had decreased glutathione peroxidase (GPOX) activity under control conditions. Treatment of 2-week-old seedlings with 10-7 M salicylic acid (SA) for 48 h resulted in elevated H 2 O 2 level and enhanced GST activity in Atgstf9 plants, 10-5 M SA treatment enhanced the malondialdehyde and dehydroascorbate contents compared to Wt. 50 and 150 mM NaCl increased the GST activity, AsA and GSH accumulation in Atgstf9 seedlings more pronounced than in Wt plants. We found that the Atgstf9 mutants had altered redox homeostasis under control and stress conditions, in which elevated AsA and GSH levels and modified GST and GPOX activities may play significant role. The half-cell potential values calculated from the concentration of GSH and GSSG indicate that this GST isoenzyme has an important role in the salt stress response.
Plant Science, 2011
The function of selenium independent glutathione peroxidase (GPx) in response to biotic and abiotic stresses was investigated in transgenic tomato plants overexpressing an exogenous GPx and exhibiting a 50% increase in total GPx activity. GPx-overexpressing and control plants were challenged either by a mechanical stress or by infection with the biotrophic parasite Oidium neolycopersici or the necrotrophic parasite Botrytis cinerea. In mechanically stressed plants, internode growth was significantly less modified in GPx-overexpressing plants compared to controls. This stress resistant phenotype was not accompanied with any change in the global antioxidant response of the plants other than their increased GPx activity. Following infection by O. neolycopersici or by B. cinerea, lesion extension was increased in GPxoverexpressing plants compared with controls. These results showed that GPx overexpression provoked opposite effects in situations of biotic and abiotic challenges, suggesting a key role for this scavenger enzyme in controlling biotic and abiotic stress responses.
Journal of Plant Physiology, 2003
A GST (EC 2.5.1.18) gene (Gst-cr1) from cotton was introduced into Nicotiana tabacum by Agrobacterium tumefaciens-mediated transformation. Transgenic tobacco plants overexpressing Gst-cr1 were normal in growth and mature compared with control, but had much higher levels of GST and GPx activities and showed an enhanced resistance to oxidative stress induced by a low concentration of methyl viologen (MV). Six antioxidant enzymes, glutathione S-transferase, glutathione peroxidase (EC 1.11.1.9), superoxide dismutase (EC 1.15.1.1), peroxidase (EC 1.11.1.7), catalase (EC 1.11.1.6), and ascorbate peroxidase (EC 1.11.1.11) were monitored in transgenic lines and non-transgenic control during MV treatments. When they were treated with 0.03 mmol/L of MV, both transgenic lines and control showed a rapid increase in the activities of GST, GPx, SOD, POD, APx, while the activity of CAT seemed to be irregular. The percent of the increase in SOD and POD activities was much higher in control than in transgenic plants. When treated with 0.05 mmol/L of MV, both control and transgenic plants were severely damaged, and the activities of the six enzymes decreased sharply.
Response to mild water stress in transgenic Pssu-ipt tobacco
Physiologia Plantarum, 2001
where about half of glutathione reductase activity was found in The response of antioxidant enzymes to cyclic drought was studied in control non-transformed tobacco (Nicotiana tabacum older plants, both transgenic types exhibited unchanged activi-L. cv. Petit Havana SR1) and two types of transgenic Pssu-ipt ties throughout plant development and stress treatment. No differences were found in catalase activity, although the growth tobacco (grafted on wild rootstock and poorly rooted progeny of F1 generation) grown under different conditions of irradia-in the greenhouse caused a moderate increase in all older plants. tion (greenhouse, referred as high light, versus growth chamber, In contrast to non-transgenic and Pssu-ipt rooted plants, referred as low light). Water stress cycles started with plants peroxidase activities (ascorbate, guaiacol, and syringaldazine peroxidase) in older Pssu-ipt grafts were up to four times at two contrasting developmental stages, i.e., at the stage of higher, irrespective of growth and stress, nevertheless, the effect vegetative growth (young) and at the onset of flowering (old). Drought reduced the growth of SR1 plants compared with seemed to be age-dependent. Superoxide dismutase (SOD) activity was affected particularly by plant age but also by transgenic ones, particularly, when treatment started in earlier stage of plant development. Relative leaf water content was growth conditions. Unlike in older plants, water stress caused an increase of SOD activities in all younger plants. The significantly lower (below 70%) in all transgenic grafts and differences observed in activities of enzymes of intermediary plants compared with the wild type, irrespective of age, metabolism (i.e., malic enzyme and glucose-6-phosphate dehy-drought, and growth conditions. The response of antioxidant enzymes was significantly dependent on plant type and plant drogenase) revealed that transgenic grafts probably compensated differently for a decrease of ATP and NADPH than age; nevertheless, growth conditions and water stress also control and transgenic rooted plants under stress. affected enzyme activities. Contrary to non-transgenic tobacco, be catalyzed by catalases (CAT) and peroxidases (Scandalios 1993). Plants must cope with multiple abiotic and biotic stresses in the environment, and a response observed during one type of stress may in fact have a role in the amelioration of other conditions. Non-lethal water deficit often results in increased activity of SOD, glutathione reductase (GR), and monodehydroascorbate reductase (Smirnoff 1993). Resistance to drought occurs when a plant withstands the imposed stress, and this may arise from either tolerance or a mechanism that permits avoidance of the stress. The response depends on the species and genotype, the duration and severity of
Crop Science, 2015
increased stress tolerance (Mittler and Zilinskas, 1994; Pinhero et al., 1997). Because some stress-tolerant An underlying mechanism for reductions in crop yield under stress plants have higher antioxidant enzyme activities and conditions is excessive production of reactive oxygen species (ROS) because stress tolerance can result from pretreatment that can damage lipids, nucleic acids, and proteins, leading to disruption of physiological processes. The aim of this study was to determine with sublethal stress conditions (Pinhero et al., 1997; whether overexpression of the gene for a peroxisomal antioxidant Holmberg and Bü low, 1998), antioxidant enzymes apenzyme, ascorbate peroxidase 3 (APX3), could provide protection of pear to be critical components in oxidative stress dephotosynthesis during drought when the potential rises for excessive fense mechanisms. Plant stress tolerance may, therefore, photorespiratory H 2 O 2 production. Tobacco (Nicotiana tabacum L.) be improved by the enhancement of in vivo levels of plants were transformed to constitutively overexpress the Arabidopsis antioxidant enzymes (Foyer et al., 1994; Allen, 1995). thaliana gene for APX3. Following repeated water-deficit cycles, fruit In the last several years, transgenic plants that overexnumber and seed mass of transgenic plants were significantly higher press genes for enzymes involved in scavenging ROS than those of control plants. In another experiment, water deficit was have been constructed to test the above hypothesis. The developed gradually by reducing, in stages, the extent to which water results are inconsistent, which may be due to differences lost was replenished. Genotypic differences in gas-exchange parameters were observed at the 25% replenishment stage and at 5 h after in the ability of the antioxidant gene products to funcseverely stressed plants were rewatered. At these times, transgenic tion properly, the physiological target being studied, the plants exhibited greater rates of CO 2 assimilation (A), stomatal conseverity of the stresses imposed, and/or the plant systems ductance (g s), and internal CO 2 (C i) to atmospheric CO 2 (C a) concenused in those transgenic studies (Rennenberg and Polle, tration than control plants, suggesting that differences in A were 1994; Allen, 1995). For example, overexpression of SOD controlled by differences in g s. Although these data did not support the genes in plants increased tolerance against herbicide idea that overexpression of the gene for APX3 enhances protection of treatment (Allen et al., 1997; Breusegem et al., 1999), the photosynthetic apparatus during water deficit, overexpression of water deficit (McKersie et al., 1996), low temperature APX3 may affect other cellular metabolisms that result in higher A (McKersie et al., 1993; Sen Gupta et al., 1993a; Breuunder moderate water-deficit conditions and therefore higher seed segem et al., 1999; Payton et al., 2001), and ozone treatmass after repeated water-deficit treatments.
Hydrogen peroxide protects tobacco from oxidative stress by inducing a set of antioxidant enzymes
Cellular and Molecular Life Sciences (CMLS), 2002
Tolerance against oxidative stress generated by high light intensities or the catalase inhibitor aminotriazole (AT) was induced in intact tobacco plants by spraying them with hydrogen peroxide (H 2 O 2 ). Stress tolerance was concomitant with an enhanced antioxidant status as reflected by higher activity and/or protein levels of catalase, ascorbate peroxidase, guaiacol peroxidases, and glutathione peroxidase, as well as an increased glutathione pool. The induced stress tolerance was dependent on the dose of H 2 O 2 applied. Moderate doses of H 2 O 2 enhanced the antioxidant status and induced stress tolerance, while higher concentrations caused oxidative stress and symptoms resembling a hypersensitive response. In stress-tolerant plants, induction of catalase was 1.5-fold, that of ascorbate peroxidase and glutathione peroxidase was 2fold, and that of guaiacol peroxidases was approximately 3-fold. Stress resistance was monitored by measuring lev-CMLS 1277 els of malondialdehyde, an indicator of lipid peroxidation. The levels of malondialdehyde in all H 2 O 2 -treated plants exposed to subsequent high light or AT stress were similar to those of unstressed plants, whereas lipid peroxidation in H 2 O 2 -untreated plants stressed with either high light or AT was 1.5-or 2-fold higher, respectively. Although all stress factors caused increases in the levels of reduced glutathione, its levels were much higher in all H 2 O 2 -pretreated plants. Moreover, significant accumulation of oxidized glutathione was observed only in plants that were not pretreated with H 2 O 2 . Extending the AT stress period from 1 to 7 days resulted in death of tobacco plants that were not pretreated with H 2 O 2 , while all H 2 O 2pretreated plants remained little affected by the prolonged treatment. Thus, activation of the plant antioxidant system by H 2 O 2 plays an important role in the induced tolerance against oxidative stress.
Frontiers in Plant Science, 2019
Chloroplasts are organelles subjected to extreme oxidative stress conditions. Biomolecules produced in the chloroplasts act as signals guiding plant metabolism toward stress tolerance and play a major role in regulating gene expression in the nucleus. Herein, we used transplastomic plants as an alternative approach to expression of transgenes in the nucleus for conferring stress tolerance to abiotic stresses and herbicides. To investigate the morphophysiological and molecular mechanisms and the role of plastid expressed GSTs in tobacco stress detoxification and stress tolerance, we used transplastomic tobacco lines overexpressing a theta class glutathione transferase (GST) in chloroplasts. The transplastomic plants were tested under drought (0, 100, and 200 mM mannitol) and salinity (0, 150, and 300 mM NaCl) in vitro, and under herbicide stress (Diquat). Our results suggest that pt AtGSTT lines were tolerant to herbicide-induced oxidative and salinity stresses and showed enhanced response tolerance to mannitol-induced osmotic stress compared to WT plants. Overexpression of the Arabidopsis thaliana AtGSTT in the chloroplasts resulted in enhanced photo-tolerance and turgor maintenance under stress. Whole-genome transcriptome analysis revealed that genes related to stress tolerance, were upregulated in pt AtGSTT 2a line under both control and high mannitol stress conditions. Transplastomic plants overexpressing the pt AtGSTT 2a in the chloroplast showed a state of acclimation to stress, as only limited number of genes were upregulated in the pt AtGSTT 2a transplastomic line compared to WT under stress conditions while at the same time genes related to stress tolerance were upregulated in pt AtGSTT 2a plants compared to WT in stress-free conditions. In parallel, the metabolic profile indicated limited perturbations of the metabolic homeostasis in the transplastomic lines and greater accumulation of mannitol, and soluble sugars under high mannitol stress. Therefore, transplastomic lines seem to be in a state of acclimation to stress Stavridou et al. Stress Tolerant GST Transplastomic Plants under stress-free conditions, which was maintained even under high mannitol stress. The results help to elucidate the role of GSTs in plant abiotic stress tolerance and the underlying mechanisms of the GSTs expressed in the chloroplast, toward environmental resilience of cultivated crops.