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Assessment of antioxidant system and enzyme/nonenzyme regulation related to ascorbate-glutathione cycle in ferulic acid-treated Triticum aestivum L. roots under boron toxicity
(Tubitak Scientific & Technological Research Council Turkey, 2020) Ozfidan-Konakci, Ceyda; Yildiztugay, Evren; Elbasan, Fevzi; Yildiztugay, Aysegul; Kucukoduk, Mustafa
Ferulic acid (FA; 3-methoxy-4-hydroxycinnamic acid) can eliminate stress-induced damage because of its ability to induce antioxidant activity under stress. The aim of this study was to identify the effects of FA on water status, antioxidant system, and lipid peroxidation in wheat (Triticum aestivum L.) roots exposed to boron (B) stress. Plants were grown in hydroponic culture containing the combination or alone form of 25-75 mu M FA and 4-8 mM B. Stress significantly decreased growth (RGR), water content (RWC), proline content (Pro), and osmotic potential (psi(H)). However, FA alleviated the decrease in RGR, RWC, and Pro content. Compared to the control groups, stress decreased the activities of superoxide dismutase (SOD), peroxidase (POX), catalase, and ascorbate peroxidase (APX), but an increase was only observed in glutathione reductase (GR) activity. Hydrogen peroxide (H2O2) content accumulated with B stress. Besides, a notable decrease was observed in the scavenging activity of hydroxyl radical (OH center dot); thus, wheat roots had high lipid peroxidation (thiobarbituric acid reactive substance content). In response to stress, FA triggered the activities of SOD, POX, and APX. Moreover, when FA was made present in stressed wheat roots, we observed the enhanced activities of dehydroascorbate reductase, and monodehydroascorbate reductase and dehydroascorbate contents which are related to ascorbate-glutathione cycle, so FA could maintain ascorbate (AsA) regeneration. However, when wheat roots were treated with stress, FA did not induce the regeneration of glutathione because of decline in GR activity. Due to successful elimination of H2O2 content, the exogenous application of FA alleviated B-induced lipid peroxidation in wheat. Consequently, FA eliminated the damage induced by B stress via the increased POX and the enzymes related to Asada-Halliwell pathway (AsA-GSH cycle) in wheat roots.
Biochar Triggers Systemic Tolerance Against Cobalt Stress in Wheat Leaves Through Regulation of Water Status and Antioxidant Metabolism
(Springer International Publishing Ag, 2019) Yildiztugay, Aysegul; Ozfidan-Konakci, Ceyda; Yildiztugay, Evren; Kucukoduk, Mustafa
To eliminate the damages of metal toxicity by reducing metal uptake by plants, organic amendments are useful. The use of carbon-rich materials known as biochar (BC) is a strong candidate to enhance the plant tolerance against stress conditions. The current study examined the effects of BC in wheat hydroponically grown treated with BC (1 and 3 g L-1) alone or in combination with cobalt (Co, 150 and 300 mu M). Stress reduced the relative growth rate (RGR), relative water content (RWC), osmotic potential (Psi(Pi)), and increased proline content (Pro). Besides, endogenous contents of Ca2+, K+, and Mn2+ in leaves decreased under stress. In response to Co stress, a decline in the activities of peroxidase (POX), ascorbate peroxidase (APX), and glutathione reductase (GR) resulted in the induction of hydrogen peroxide (H2O2) content. BC applied with stress decreased endogenous Co2+ content and increased RGR, RWC, chlorophyll fluorescence and Pro content. Also, the activities of superoxide dismutase (SOD), catalase (CAT), APX and GR were induced and the ascorbate (AsA) and glutathione (GSH) pool and their redox state were maintained by BC application under stress condition. While, with the addition of BC, H2O2 content and lipid peroxidation displayed remarkable decreased, the scavenging activity of hydroxyl radical (OH center dot) increased as compared to Co stress-treated wheat plants. Besides, in wheat leaves, BC application triggered AsA-GSH pathway including activities of monodehydroascorbate reductase, dehydroascorbate reductase, and the contents of dehydroascorbate, GSH, and GSH/GSSG ratio. The presented results supported the view that biochar under stress could minimize the Co-induced oxidative damages through modulation of the growth, water status, photosynthetic apparatus, and antioxidant enzyme activity found in cellular compartments and ascorbate-glutathione cycle in wheat leaves.
Ex-foliar applied extremolyte ectoine improves water management, photosystem, antioxidant system and redox homeostasis in Zea mays under cadmium toxicity
(Elsevier, 2022) Ozfidan-Konakci, Ceyda; Elbasan, Fevzi; Arikan, Busra; Alp, Fatma Nur; Yildiztugay, Evren; Keles, Ramazan; Kucukoduk, Mustafa
Stress-protective osmolytes stabilize biomolecules and mediate plant defense responses, which help to remove the negative effects of stress in plants. However, the responses of ectoine (ECT, 1,4,5,6-tetrahydro-2-methyl-4-pyrimidinecarboxylic acid), as an osmolyte, need to be investigated for a better understanding of the defense pathways on water status, antioxidant system, and photosynthetic machinery against heavy metal stress. The different ECT concentrations (0.25-0.5 mM) were applied to Zea mays L. cv Karadeniz Yildizi with/without cadmium stress (100-200 mu M Cd). Stress caused an inhibition in growth (RGR), water content (RWC), and osmotic potential (Psi(pi)). After stress exposure, ECTs provided effective water management by elevating RGR, RWC and Psi(pi). The maize exposed to stress exhibited notable repression in the photosynthetic system depending on decreasing F-v/F-m, qP and, Phi(PSII) and increasing NPQ. The consumption of excess energy on photosynthetic machinery was controlled by ECTs via reversing these parameters. Cd toxicity resulted in downregulated-transcript levels of psbA, psbD, and psaB, which impaired the stability of PSI and PSII. After both Cd treatments, ECTs markedly induced the expression levels of psaA and psaB, which showed effective protection of photochemical activity. Cd-applied plants exhibited a decrease in superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), glutathione peroxidase (GPX), and glutathione reductase (GR), causing the accumulation of TBARS in lipid peroxidation. Under Cd+ECTs, SOD, glutathione S-transferase (GST) and POX had effective radical scavenging, thereby maintaining low contents of H2O2 and TBARS. ECTs alleviated the low Cd treatment-impaired redox state and participated in the ascorbate (AsA) and glutathione (GSH) regeneration. Consequently, ECT-mediated tolerance of maize was proved by increased growth, water potential, antioxidant capacity (especially SOD, POX), up-regulation of genes encoding proteins related to PSI, and PSII and AsA-GSH redox systems under Cd toxicity. (c) 2021 Published by Elsevier B.V. on behalf of SAAB.
Exogenous Nitric Oxide (as Sodium Nitroprusside) Ameliorates Polyethylene Glycol-Induced Osmotic Stress in Hydroponically Grown Maize Roots
(Springer, 2014) Yildiztugay, Evren; Ozfidan-Konakci, Ceyda; Kucukoduk, Mustafa
The present study was designed to examine whether exogenous sodium nitroprusside (SNP) supplementation has any ameliorating action against PEG-induced osmotic stress in Zea mays cv. FRB-73 roots. Twenty percent or 40 % polyethylene glycol (PEG6000; -0.5 MPa and -1.76 MPa, respectively) treatment alone or in combination with 150 and 300 mu M SNP was applied to hydroponically grown maize roots for 72 h. Although only catalase (CAT) activity increased when maize roots were exposed to PEG-induced osmotic stress, induction of this antioxidant enzyme was inadequate to detoxify the extreme levels of reactive oxygen species, as evidenced by growth, water content, superoxide anion radical (O (2) (aEuro cent a') ), hydroxyl radical (OHaEuro cent) scavenging activity, and TBARS content. However, supplementation of PEG-exposed specimens with SNP significantly alleviated stress-induced damage through effective water management and enhancement of antioxidant defense markers including the enzymatic/non-enzymatic systems. Exogenously applied SNP under stress resulted in the up-regulation of glutathione peroxidase (GPX), glutathione S-transferase (GST), ascorbate peroxidase (APX), glutathione reductase (GR), total ascorbate, and glutathione contents involved in ascorbate-glutathione cycle. On the other hand, growth rate, osmotic potential, CAT, APX, GR, and GPX increased in maize roots exposed to both concentrations of SNP alone, but activities of monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase decreased. Based on the above results, an exogenous supply of both 150 and 300 mu M SNP to maize roots was protective for PEG-induced toxicity. The present study provides new insights into the mechanisms of SNP (NO donor) amelioration of PEG-induced osmotic stress damages in hydroponically grown maize roots.
Ferulic acid confers tolerance against excess boron by regulating ROS levels and inducing antioxidant system in wheat leaves (Triticum aestivum)
(Pergamon-Elsevier Science Ltd, 2019) Yildiztugay, Evren; Ozfidan-Konakci, Ceyda; Karahan, Huseyin; Kucukoduk, Mustafa; Turkan, Ismail
Ferulic acid (FA; 3-methoxy-4-hydroxycinnamic acid) is a candidate for improving plant tolerance to stress conditions through improving water solubility and antioxidant activity. To our knowledge, no study has thus far explored the potential for exogenous FA application to improve tolerance against excess boron (B) in plants. For this purpose, wheat seedlings grown in hydroponic culture were treated with FA (25 and 75 mu M) alone or in combination with B (4 and 8 mM). The results showed that B caused a decrease in water content (RWC), osmotic potential (Psi(Pi)) and proline content (Pro). FA application prevented decreases of these parameters. 8 mM B increased superoxide dismutase (SOD) activity. Superoxide anion radical (O-2(center dot-))and hydrogen peroxide (H2O2) increased during B exposure, while catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX) and glutathione reductase (GR) activities did not. However, due to increased SOD activity, FA under stress successfully decreased O-2(center dot-) content. Additionally, exogenously applied FA under 4mM B stress increased the activities of CAT and POX. While excess B in wheat leaves did not induce activities of APX, GR, monodehydroascorbate reductase (MDHAR) or dehydroascorbate reductase (DHAR) or increase total ascorbate (tAsA) or dehydroascorbate (DHA) contents, FA with stress did. 25 mu M FA with B remarkably maintained regeneration of ascorbate and induced contents of tAsA and GSH (including the ascorbate glutathione cycle) and induced CAT activity. Taken together, stress-induced H2O2 content significantly decreased and the scavenging of OH. increased in wheat with FA application through the activation of antioxidant enzymes. Consequently, FA prevented lipid peroxidation (TBARS) caused by stress due to increased radical scavenging activity.
Flavonoid Naringenin Alleviates Short-Term Osmotic and Salinity Stresses Through Regulating Photosynthetic Machinery and Chloroplastic Antioxidant Metabolism inPhaseolus vulgaris
(Frontiers Media Sa, 2020) Yildiztugay, Evren; Ozfidan-Konakci, Ceyda; Kucukoduk, Mustafa; Turkan, Ismail
The current study was conducted to demonstrate the possible roles of exogenously applied flavonoid naringenin (Nar) on the efficiency of PSII photochemistry and the responses of chloroplastic antioxidant of salt and osmotic-stressedPhaseolus vulgaris(cv. Yunus90). For this aim, plants were grown in a hydroponic culture and were treated with Nar (0.1 mM and 0.4 mM) alone or in a combination with salt (100 mM NaCl) and/or osmotic (10% Polyethylene glycol, -0.54 MPa). Both caused a reduction in water content (RWC), osmotic potential (psi(pi)), chlorophyll fluorescence (F-v/F-m), and potential photochemical efficiency (F-v/F-o). Nar reversed the changes on these parameters. The phenomenological fluxes (TRo/CS and ETo/CS) altered by stress were induced by Nar and Nar led to a notable increase in the performance index (PIABS) and the capacity of light reaction [phi P-o/(1-phi P-o)]. Besides, Nar-applied plants exhibited higher specific fluxes values [ABS/RC, ETo/RC, and psi E-o/(1-psi E-o)] and decreasing controlled dissipation of energy (DIo/CS(o)and DIo/RC). The transcripts levels of psbA and psbD were lowered in stress-treated bean but upregulated in Nar-treated plants after stress exposure. Nar also alleviated the changes on gas exchange parameters [carbon assimilation rate (A), stomatal conductance (g(s)), intercellular CO(2)concentrations (C-i), transpiration rate (E), and stomatal limitation (L-s)]. By regulating the antioxidant metabolism of the isolated chloroplasts, Nar was able to control the toxic levels of hydrogen peroxide (H2O2) and TBARS (lipid peroxidation) produced by stresses. Chloroplastic superoxide dismutase (SOD) activity reduced by stresses was increased by Nar. In response to NaCl, Nar increased the activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR), as well as peroxidase (POX). Nar protected the bean chloroplasts by minimizing disturbances caused by NaCl exposure via the ascorbate (AsA) and glutathione (GSH) redox-based systems. Under Nar plus PEG, Nar maintained the AsA regeneration by the induction of MDHAR and DHAR, but not GSH recycling by virtue of no induction in GR activity and the reduction in GSH/GSSG and GSH redox state. Based on these advances, Nar protected in bean chloroplasts by minimizing disturbances caused by NaCl or PEG exposure via the AsA or GSH redox-based systems and POX activity.
The humic acid-induced changes in the water status, chlorophyll fluorescence and antioxidant defense systems of wheat leaves with cadmium stress
(Academic Press Inc Elsevier Science, 2018) Ozfidan-Konakci, Ceyda; Yildiztugay, Evren; Bahtiyar, Mustafa; Kucukoduk, Mustafa
The using of bio-stimulant in plants grown under stress conditions for enhancing nutrition efficiency and crop quality traits is an effective approach. One of the bio-stimulants, humus material, is defined as humic acid (HA). HA application as a promotion of plant growth to plants grown in the heavy metals-contaminated soils has promised hope in terms of effects on plants but the its limiting effect is the application dose. Therefore, the wheat seedlings were grown in hydroponic culture for 21 d and the various concentrations of humic acid (HA; 750 or 1500 mg L-1) were treated alone or in combination with cadmium (Cd) stress (100 or 200 mu M) for 7 d. The results showed that after Cd stress treatment, water content (RWC), osmotic potential (psi(Pi)) and chlorophyll fluorescence parameters decreased and proline content (Pro) increased for 7 d. In spite of activated peroxidase (PDX) and ascorbate peroxidase (APX), stress induced the toxic levels of hydrogen peroxide (H2O2) accumulation. Cd stress triggered lipid peroxidation (TBARS content). HA application successfully eliminated the negative effects of stress on RWC, psi(Pi) and photosynthetic parameters. In the presence of HA under stress, the increased activation of superoxide dismutase (SOD), catalase (CAT) and NADPH-oxidase (NOX) enzymes and ascorbate, glutathione and GSH/GSSG ratio observed. Only 750 mg L-1 HA under stress conditions induced the activities of monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR), and dehydroascorbate (DHA) content. After the combined application of HA and Cd stress, the low contents of H2O2 and TBARS maintained in wheat leaves. Hence, HA successfully eliminated the toxicity of Cd stress by modulating the water status, photosynthetic apparatus and antioxidant activity in wheat leaves.
Hydrogen sulfide (H2S) and nitric oxide (NO) alleviate cobalt toxicity in wheat (Triticum aestivum L.) by modulating photosynthesis, chloroplastic redox and antioxidant capacity
(Elsevier, 2020) Ozfidan-Konakci, Ceyda; Yildiztugay, Evren; Elbasan, Fevzi; Kucukoduk, Mustafa; Turkan, Ismail
The role of hydrogen sulfide (H2S)/nitric oxide (NO) in mitigating stress-induced damages has gained interest in the past few years. However, the protective mechanism H2S and/or NO has towards the chloroplast system through the regulation of redox status and activation of antioxidant capacity in cobalt-treated wheat remain largely unanswered. Triticum aestivum L. cv. Ekiz was treated with alone/in combination of a H2S donor (sodium hydrosulfide (NaHS,600 mu M)), a NO donor (sodium nitroprusside (SNP,100 mu M)) and a NO scavenger (rutin hydrate (RTN,50 mu M)) to assess how the donors affect growth, water relations, redox and antioxidant capacity in chloroplasts, under cobalt (Co) concentrations of 150-300 mu M. Stress decreased a number of parameters (growth, water content (RWC), osmotic potential (psi(Pi)), carbon assimilation rate, stomatal conductance, intercellular CO2 concentrations, transpiration rate and the transcript levels of rubisco, which subsequently disrupt the photosynthetic capacity). However, SNP/NaHS counteracted the negative effects of stress on these aforementioned parameters and RTN application with stress/non-stress was reversed these effects. Hydrogen peroxide (H2O2) and TBARS were induced under stress in spite of activated ascorbate peroxidase (APX). SNP/NaHS under stress increased activation of superoxide dismutase (SOD), peroxidase (POX), APX, glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), ascorbate (tAsA) and glutathione (GSH). In conclusion, NaHS/SNP are involved in the regulation and modification of growth, water content, rubisco activity and up-regulation of ascorbate-glutathione cycle (AsA-GSH) in chloroplast under stress.
Hydrogen Sulfide Protects Damage From Methyl Viologen-Mediated Oxidative Stress by Improving Gas Exchange, Fluorescence Kinetics of Photosystem II, and Antioxidant System in Arabidopsis thaliana
(Springer, 2023) Ozfidan-Konakci, Ceyda; Yildiztugay, Evren; Arikan, Busra; Elbasan, Fevzi; Alp, Fatma Nur; Kucukoduk, Mustafa
Considering the unfavorable impacts of methyl viologen-induced oxidative stress (MV1-2, 50 and 500 mu M) on growth, gas exchange (intercellular CO2 concentration, carbon assimilation rate, stomatal conductance, transpiration rate), the efficiency of PSII photochemistry and gene expressions of proteins related to photosystems, antioxidant capacity, and the content/histochemical staining of reactive oxygen species (ROS) markers, the experiment was conducted to evaluate the possible mechanisms of sodium hydrosulfide hydrate (a hydrogen sulfide donor, 500 mu M NaHS) and its scavenger/inhibitor (hypotaurine, 50 mu M and hydroxylamine, 100 mu M) in Arabidopsis thaliana for 24 h. NaHS alleviated stress-reduced growth (4.2-fold increase for MV2 + NaHS) and improved the gas exchange parameters. NaHS was capable of improving the photosynthetic ability under 50 mu M MV through sustaining photochemical activity in PSII and photochemical conversion efficiency as evident by transcript levels of psbA, psbD, psaA, and psaB. Stress-caused oxidative damage was scavenged by POX (a 90% increase). However, this action was not enough, suggested by increased ROS accumulation, lipid peroxidation (a 165% induction) and lipoxygenase activity (2.4-fold increase), and loss of membrane integrity. Meanwhile, NaHS successfully eliminated these responses against MV, evidenced by weak histochemical staining of ROS and lesser lipid peroxidation and membrane damage. The synchronized activities of both SOD and CAT triggered by NaHS were responsible for decreasing H2O2 content (by 57.4% decrease for MV2 + NaHS) in response to MV stress. After stress exposure, NaHS utilized the ascorbate-glutathione (AsA-GSH) cycle for removing H2O2. Arabidopsis subjected to MV1 plus NaHS exhibited the advanced levels of AsA regeneration (by 15.3% increase) and the redox state of GSH. Interestingly, NaHS under the high MV concentration did not maintain the re-establishment of GSH homeostasis and redox state of GSH in spite of the induced AsA/DHA (dehydroascorbate). NaHS could protect Arabidopsis from oxidative stress, likely by regulating growth, gas exchange, and photosynthetic performance, inducing expression levels of genes associated with photosystems and regulating antioxidant capacity, and redox balance for AsA and GSH.
The impact of selenium application on enzymatic and non-enzymatic antioxidant systems in Zea mays roots treated with combined osmotic and heat stress
(Taylor & Francis Ltd, 2017) Yildiztugay, Evren; Ozfidan-Konakci, Ceyda; Kucukoduk, Mustafa; Tekis, Seyit Ahmet
Selenium (Se), regarded as an antioxidant, has been found beneficial for plants growing under stressed conditions. To investigate whether the Se application helps to improve stress tolerance, sodium selenite (Na2SeO3 . 5H(2)O, 5-15 mu M)was hydroponically applied to Zea mays variety OSSK-713-roots under heat and/or PEG-induced osmotic stress (25% PEG-6000) for 8 h. The individual/combined stress caused accumulation of reactive oxygen species (ROS). While only superoxide dismutase (SOD) increased with heat stress alone, the activities of SOD, catalase (CAT) and ascorbate peroxidase (APX) increased under PEG exposure. The combination of these stresses resulted in an induction of both SOD and CAT activities. Lipid peroxidation (TBARS) levels were also high in all the stress treatments, especially under the combination treatment. Addition of Se not only improved the activities of SOD, APX and glutathione reductase (GR) in stress-treated roots, but it also changed the activities of monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR). The findings reveal that Se has a positive effect on heat and/or osmotic stress mitigation mainly by regulating the ascorbate-glutathione cycle, especially in PEG-treated plants. Under the combined stress treatment, addition of 5 mu M of exogenous Se was most effective.
Improvement of cold stress resistance via free radical scavenging ability and promoted water status and photosynthetic capacity of gallic acid in soybean leaves
(Soc Chilena Ciencia Suelo, 2017) Yildiztugay, Evren; Ozfidan-Konakci, Ceyda; Kucukoduk, Mustafa
Plant polyphenols exhibit a wide variety of biological activities such as antimutagenicity, anticarcinogenicity and antioxidative activity. There is no report whether gallic acid (GLA), a naturally occurring plant phenol, is able to activate the plant defense system under cold stress. For this purpose, after soybean (Glycine max) was hydroponically grown for 3 weeks, seedlings were treated with gallic acid (GLA; 1 and 2 mM) and cold stress (5 oC and 10 degrees C) and GLA and stress combination for 72 h. The inhibition in growth, water content (RWC), osmotic potential (Psi II) and photosynthetic activity observed under stress and was more at the lowest temperature. Stress also elicited the accumulation of proline (Pro) only at 5 degrees C. While the capacity to maintain high growth, RWC,.. and photosynthetic efficiency was observed in GLA-treated plants under stress, Pro accumulation could not achieve with GLA plus stress. Any increase in total activities of superoxide dismutase (SOD) and catalase (CAT) induced by stress treatments determined. The lower cold stress caused an increase in the activities of ascorbate peroxidase (APX), glutathione reductase (GR) and NADPH oxidase (NOX). GLA treatment under stress (especially at 5 degrees C) could supply the increased activities of SOD, CAT, APX and GR. Also, exogenous GLA application to stress-treated plants increased the enzyme activities in ascorbate-glutathione cycle such as monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) and, contents of ascorbate (AsA) and glutathione. After GLA application under stress, it is observed reduction in hydrogen peroxide (H2O2) and the levels of lipid peroxidation (TBARS), and induction of hydroxyl radical (OH.) scavenging. Our results suggest that GLA is a potent inducer for induction of the scavenging activity of radicals as well as effectively usage of water status and photosynthetic capacity.
Influences of sulfonated graphene oxide on gas exchange performance, antioxidant systems and redox states of ascorbate and glutathione in nitrate and/or ammonium stressed-wheat (Triticum aestivum L.)
(Royal Soc Chemistry, 2021) Ozfidan-Konakci, Ceyda; Yildiztugay, Evren; Cavusoglu, Halit; Arikan, Busra; Elbasan, Fevzi; Kucukoduk, Mustafa; Turkan, Ismail
Graphene oxide has unique physiochemical properties and a large surface area. After functionalization, its shape, surface, adsorption capacity, and toxicity levels can change. The potential impacts of sulfonated graphene oxide (SGO, modified with the sulfonic group) on metabolic processes and biological pathways are unanswered questions concerning NO3- or NH4+ toxicity. To fill this gap of knowledge, in the present study, SGO (50-250-500 mg L-1) was applied to Triticum aestivum cv. Ekiz with/without 140 mM nitrate (NS stress) and 5 mM ammonium (AS stress). Both stress treatments suppressed the growth, water content, osmotic potential, and photosynthetic capacity, as detected by a decrease in the carbon assimilation rate (A), stomatal conductance (g(s)), intercellular CO2 concentration (C-i), and transpiration rate (E), and an increase in stomatal limitation. After stress exposure, SGO provided positive responses to these parameters. There were different responses in the antioxidant system under stress: superoxide dismutase (SOD) and peroxidase (POX) under NS stress; SOD, catalase (CAT) and POX under AS and NS + AS stresses. However, hydrogen peroxide (H2O2) and lipid peroxidation increased because lack of effective antioxidant activation. In response to NS or AS, SGO successfully regulated SOD, CAT, glutathione peroxidase (GPX) and the enzyme/non-enzymes related to the AsA-GSH cycle, attenuating the high levels of H2O2, lipoxygenase (LOX) and TBARS-based damage. Along with the antioxidant system, SGO controlled the contents of NO3- or NH4+ by regulation of NPF6.3 and AMT1.2 genes. Interestingly, under NS plus AS, the alleviation action of SGO varied in a concentration-dependent manner: (i) low SGO concentration (50 mg L-1) protected the regeneration of ascorbate (AsA) and glutathione (GSH) and the high activities of GST and GPX; (ii) 250 mg L-1 SGO maintained the GSH redox state and the induced activity of glutathione S-transferase (GST); (iii) the highest SGO concentration (500 mg L-1) did not eliminate H2O2 accumulation, which coincided with the increased levels of TBARS and LOX. The toxicity of the high SGO concentration was further increased in wheat with non-stress or NS plus AS stresses. Our findings specified that the damage stimulated by NS and/or AS stress was removed by SGO applications through the increased antioxidant activity and gas exchange parameters, resulting in the protection of the redox state.
Modulation of osmotic adjustment and antioxidant status in salt-stressed leaves of Thermopsis turcica
(Springer Heidelberg, 2014) Yildiztugay, Evren; Ozfidan-Konakci, Ceyda; Kucukoduk, Mustafa
Thermopsis turcica is distributed naturally in saline soils. Interestingly, how T. turcica can live in harsh salt conditions is unknown. To study its defense responses under salinity, T. turcica was grown in a medium containing 100 and 200 mM NaCl for 7 and 14 days. Physiological parameters, ion contents, reactive oxygen species accumulation, activities of antioxidant enzymes/isozymes, NADPH oxidase enzyme/isozyme, lipid peroxidation (TBARS) and osmolyte contents were investigated. Stress caused a rapid decline in relative growth rate, relative water content and chlorophyll fluorescence (F (v)/F (m)) under both NaCl treatments. These traits were more suppressed at 200 mM NaCl. The decline in osmotic potential (I (I) ) with salinity increased the gradient for water flux into the cell and assisted in turgor maintenance. The increased membrane permeability under stress caused the entrance of excess Na+ and K+ into the cell. Stress decreased superoxide dismutase, catalase and peroxidase after 14 days of growth in 200 mM NaCl, whereas glutathione reductase (GR) increased throughout the experiment. While ascorbate peroxidase (APX) increased by 44 % at 7 days, it decreased after 14 days exposure to 200 mM NaCl. 200 mM NaCl caused the highest increase in TBARS at 14 days, indicating a decrease in OH center dot scavenging activity. Increasing concentrations of salinity caused an increase in glycine betaine (GB) and choline (Cho), though an increase in proline was only observed at 200 mM NaCl for 14 days. Briefly, H2O2 was more efficiently eliminated in 100 mM-treated plants by the ascorbate-glutathione cycle in which APX acts a strong catalyst together with GR. Also, Cho and GB help to maintain osmotic adjustment and cytoplasmic function.
Modulation of osmotic adjustment and enzymatic antioxidant profiling in Apera intermedia exposed to salt stress
(Tubitak Scientific & Technological Research Council Turkey, 2014) Yildiztugay, Evren; Ozfidan Konakci, Ceyda; Kucukoduk, Mustafa; Duran, Yagmur
The effects of salinity on growth, osmotic adjustment, and antioxidative responses were evaluated in Apera intermedia. For this purpose, 30-day-old plants were irrigated every other day with Hoagland nutrient solution containing 0, 150, 300, or 600 mM NaCl for 7 and 14 days. The results showed inhibition of growth, relative growth rate, relative water content, and osmotic potential with increasing NaCl concentration. Increased Na+, Cl-, and Na+/K+ ratio and decreased K+ and Ca2+ were determined with increasing NaCl concentrations. The activities of superoxide dismutase and ascorbate peroxidase were conspicuously enhanced at 150 mM NaCl, but activities of catalase, peroxidase, and NADPH oxidase were reduced in a concentration/time-dependent manner. The highest proline, choline, and glycine betaine accumulation assisted higher osmotic adjustment and maintenance of water status at 150 mM. However, the destructive effects of 300-600 mM were more severe in comparison to lower salinity, depending on the increase of hydrogen peroxide and thiobarbituric acid reactive substances for 14 days. After exposure to 300 and 600 mM, only ascorbate peroxidase and glutathione reductase were induced, but they were not sufficient to scavenge H2O2.
Multi-Walled Carbon Nanotubes Influence on Gas Exchange, Redox Reaction and Antioxidant System in Zea mays Exposed to Excessive Copper
(Springer, 2022) Alp, Fatma Nur; Ozfidan-Konakci, Ceyda; Yildiztugay, Evren; Arikan, Busra; Elbasan, Fevzi; Ozmen, Mustafa; Kucukoduk, Mustafa
The carbon nanotube is one of the most encouraging tools in nanotechnology. However, the extent and interaction with different plant systems of multi-wall carbon nanotubes (MWCNT) are not fully understood under stress conditions. The present study aimed to evaluate the potential of MWCNT to improve tolerance to copper toxicity in maize (Zea mays). For this purpose, Zea mays was grown under exposure to exogenously applied MWCNT concentrations (50-100-250 mg L-1), individually or combined, with 50 mu M copper (Cu stress) for 7 days. MWCNTs eliminated the adverse effects caused by stress on water status, gas parameters and osmotic potential state. Although stress activated the antioxidant system, reactive oxygen species (ROS) accumulation (hydrogen peroxide (H2O2) content) and lipid peroxidation (TBARS) increased because stress-applied maize was unable to perform an effective scavenging action. MWCNT applications had a strong ROS scavenging effect on maize seedlings. Under Cu stress, there were different responses on antioxidant capacity depending on MWCNT concentrations called the hormesis effect. Under stress, M50-M100 (50 and 100 mg L-1) reversed the radical accumulation by providing increased superoxide dismutase (SOD), glutathione peroxidase (GPX) and the regeneration of ascorbate (AsA) and glutathione (GSH). The MWCNT-activated enzyme system maintained the low levels of H2O2 and TBARS contents against stress. However, after the highest MWCNT concentration (250 mg L-1) plus stress exposure, this trend could not be continued, as by represented the disrupted antioxidant capacity and the reduced AsA/DHA and GSH redox state in maize seedlings. Therefore, the levels of H2O2 and TBARS were similar to the stress ones. Our findings indicated that MWCNT provided a new potential tool against Cu stress to improve the stress tolerance mechanism in maize.
Nanomaterial sulfonated graphene oxide advances the tolerance against nitrate and ammonium toxicity by regulating chloroplastic redox balance, photochemistry of photosystems and antioxidant capacity in Triticum aestivum
(Elsevier, 2022) Yildiztugay, Evren; Ozfidan-Konakci, Ceyda; Cavusoglu, Halit; Arikan, Busra; Alp, Fatma Nur; Elbasan, Fevzi; Kucukoduk, Mustafa
The current study was designed to assess nanomaterial sulfonated graphene oxide (SGO) potential in improving tolerance of wheat chloroplasts against nitrate (NS) and ammonium (AS) toxicity. Triticum aestivum cv. Ekiz was grown under SGOs (50-250-500 mg L-1) with/without 140 mM NS and 5 mM AS stress. SGOs were eliminated the adverse effects produced by stress on chlorophyll fluorescence, potential photochemical efficiency and physiological state of the photosynthetic apparatus. SGO reversed the negative effects on these parameters. Upon SGOs exposure, the induced expression levels of photosystems-related reaction center proteins were observed. SGOs reverted radical accumulation triggered by NS by enabling the increased superoxide dismutase (SOD) activity and ascorbate (AsA) regeneration. Under AS, the turnover of both AsA and glutathione (GSH) was maintained by 50-250 mg L-1 SGO by increasing the enzymes and non-enzymes related to AsA-GSH cycle. 500 mg L-1 SGO prevented the radical over-accumulation produced by AS via the regeneration of AsA and peroxidase (POX) activity rather than GSH regeneration. 50-250 mg L-1 SGO protected from the NS+AS-induced disruptions through the defense pathways connected with AsA-GSH cycle represented the high rates of AsA/DHA and, GSH/GSSG and GSH redox state. Our findings specified that SGO to NS and AS-stressed wheat provides a new potential tool to advance the tolerance mechanism.
Naringenin induces tolerance to salt/osmotic stress through the regulation of nitrogen metabolism, cellular redox and ROS scavenging capacity in bean plants
(Elsevier France-Editions Scientifiques Medicales Elsevier, 2020) Ozfidan-Konakci, Ceyda; Yildiztugay, Evren; Alp, Fatma Nur; Kucukoduk, Mustafa; Turkan, Ismail
The present study was conducted to uncover underlying possible effect mechanisms of flavonoid naringenin (Nar, 0.1-0.4 mM) in nitrogen assimilation, antioxidant response, redox status and the expression of NLP7 and DREB2A, on salt (100 mM NaCl) and osmotic-stressed (10% Polyethylene glycol, -0.54 MPa) Phaseolus vulgaris cv. Yunus 90). Nar ameliorated salt/osmotic stresses-induced growth inhibition and improved the accumulation of proline, glycine betaine and choline. In response to stress, Nar increased endogenous content of nitrate (NO3-) and nitrite (NO2-) by regulating of nitrate reductase and nitrite reductase. Stress-triggered NH4+ was eliminated with Nar through increases in glutamine synthetase and glutamate synthase. After NaCl or NaCl + PEG exposure, Nar utilized the aminating activity of glutamate dehydrogenase in the conversion of NH4+. The stress-inducible expression levels of DREB2A were increased further by Nar, which might have affected stress tolerance of bean. Nar induced effectively the relative expression of NLP7 in the presence of the combination or alone of stress. Also, the impaired redox state by stress was modulated by Nar and hydrogen peroxide (H2O2) and TBARS decreased. Nar regulated the different pathways for scavenging of H2O2 under NaCl and/or PEG treatments. When Nar + NaCl exposure, the damage was removed by superoxide dismutase (SOD), catalase (CAT), PDX (only at 0.1 mM Nar + NaCl) and AsA-GSH cycle. Under osmotic stress plus Nar, the protection was manifested by activated CAT and, glutathione 5-transferase and the regeneration of ascorbate. 0.1 mM Nar could protect bean plant against salt/osmotic stresses, likely by regulating nitrogen assimilation pathways, improving expression levels of genes associated with tolerance mechanisms and modulating the antioxidant capacity and AsA-GSH redox-based systems.
Protective roles of exogenously applied gallic acid in Oryza sativa subjected to salt and osmotic stresses: effects on the total antioxidant capacity
(Springer, 2015) Ozfidan-Konakci, Ceyda; Yildiztugay, Evren; Kucukoduk, Mustafa
The aim of our study was to examine whether exogenously applied with gallic acid (GA) enhances the tolerance of rice cultivars to polyethylene glycol (PEG)induced osmotic stress or salt (NaCl) stress. After two Oryza sativa L. cultivars, tolerant cultivar Pokkali and sensitive cultivar IR-28, were hydroponically-grown for 3 weeks, seedlings were treated with GA (0.75 and 1.5 mM), 120 mM NaCl and 20 % PEG-6000 producing the same osmotic potential (-0.5 MPa) and GA and stress combination for 72 h. PEG had greater reduction in growth rate (RGR) and water content (RWC) than that of NaCl in both cultivars. Salt and PEG decreased the maximum photochemical efficiency (F-v/F-m), the photochemical quenching coefficient (qP) and the actual quantum yield (Phi(PSII)), even more pronounced at NaCl in IR-28. Also, a notable increase in lipid peroxidation (TBARS) and hydrogen peroxide (H2O2) content was observed with PEG as compared to NaCl treatment. Activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase in Pokkali and, catalase (CAT) and peroxidase (POX) in IR-28 were induced to a greater extent by PEG. The sensitivity of plants to stress was higher in IR-28 than in Pokkali. Also, comparing the injury between the NaCl and PEG stresses, it was greater under PEG-mediated osmotic stress. However, compared with the stress-treated plants alone, GA added to NaCl-stressed Pokkali significantly decreased H2O2 and TBARS contents, and enhanced the activities of SOD, CAT, POX and APX as well as increase of RGR, osmotic potential (Psi(Pi)), F-v/F-m and proline. In PEG-treated IR-28, GA strongly suppressed H2O2 and TBARS contents, up-regulated SOD and APX activities and increased RGR, RWC and Psi(Pi). It could be concluded that the both GA concentrations alleviated NaCl and PEG toxicity by increased the level of antioxidant activity and photosynthetic efficiency in rice.
Rare-earth element scandium improves stomatal regulation and enhances salt and drought stress tolerance by up-regulating antioxidant responses of Oryza sativa
(Elsevier France-Editions Scientifiques Medicales Elsevier, 2020) Elbasan, Fevzi; Ozfidan-Konakci, Ceyda; Yildiztugay, Evren; Kucukoduk, Mustafa
Oryza sativa L. cv. Gonen grown in hydroponic culture was treated with scandium (Sc; 25 and 50 mu M) alone or in combination with salt (100 mM NaCl) and/or drought (5% PEG-6000). Stress caused a decrease in growth (RGR), water content (RWC), osmotic potential (Psi(Pi)), chlorophyll fluorescence (F-v/F-m) and potential photochemical efficiency (F-v/F-o). Sc application prevented the decreases of these parameters. Sc also alleviated the changes on gas exchange parameters (carbon assimilation rate (A), stomatal conductance (g(s)), intercellular CO2 concentrations (C-i), transpiration rate (E) and stomatal limitation (L-s)). Stress caused no increase in superoxide dismutase (SOD) activity. After induvial applied NaCl or PEG, catalase (CAT) and ascorbate peroxidase (APX) showed an enhancement in activation and tried to scavenge of hydrogen peroxide (H(2)o(2)). On the other hand, in plants with the combination form of NaCl and PEG, only CAT activity was induced. Sc applications to NaCl-treated rice led to an increase of SOD, APX, glutathione reductase (GR), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) as well as peroxidase (PDX). Sc under NaCl could be maintained both ascorbate (AsA) and glutathione (GSH) regeneration. Despite of induction of MDHAR and DHAR under Sc plus PEG, Sc did not maintain AsA redox state because of no induction in APX activity. However, GSH pool could be regenerated by induction in DHAR and GR in this group. Sc application (especially for 25 mu M) in rice exposed to NaCl + PEG resulted an enhancement in APX and MDHAR and so Sc could be partially provided AsA regeneration. Since no increases in DHAR and GR were observed, GSH pool was reduced. Due to this activation of antioxidant enzymes, stress-induced H2O2 and TBARS content (lipid peroxidation) significantly decreased in rice with Sc applications. Sc in plants with stress also increased the transcript levels of OsCDPK7 and OsBG1 related to stomatal movement and signaling pathway. Consequently, Sc protected the rice plants by minimizing disturbances caused by NaCl or PEG exposure via the AsA-GSH redox-based systems.
The role of antioxidant responses on the tolerance range of extreme halophyte Salsola crassa grown under toxic salt concentrations
(Academic Press Inc Elsevier Science, 2014) Yildiztugay, Evren; Ozfidan-Konakci, Ceyda; Kucukoduk, Mustafa
Salsola crassa (Amaranthaceae) is an annual halophytic species and naturally grows in arid soils that are toxic to most plants. In order to study the effects of salinity on their antioxidant system and to determine the tolerance range against salt stress, S. crassa seeds were grown with different concentrations of NaCl (0, 250, 500, 750, 1000, 1250 and 1500 mM) for short (15 d) and long-term (30 d). Results showed that growth (RGR), water content (RWC) and osmotic potential (Psi(Pi)) decreased and, proline content (Pro) increased at prolonged salt treatment. Unlike K+ and Ca2+ contents, S. crassa highly accumulated Na+ and Cl- contents. Chlorophyll fluorescence (F-v/F-m) only decreased in response to 1500 mM NaCl at 30 d. No salt stimulation of superoxide anion radical (O-2(center dot-)) content was observed in plants treated with the range of 0-500 mM NaCl during the experimental period. NaCl increased superoxide dismutase (SOD) activity depending on intensities of Mn-SOD and Fe-SOD isozymes except in 1500 mM NaCl-treated plants at 30 d. In contrast to catalase (CAT), peroxidase (POX) activity increased throughout the experiment. Also, salinity caused an increase in glutathione reductase (GR) and glutathione peroxidase (GPX) and decreased in ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) at 15 d. Both total ascorbate (tAsA) and glutathione (tGlut) contents significantly increased in treated plants with 1000-1500 mM NaCl at 15 d. After 0-1000 mM NaCl stress, H2O2 and TBARS contents were similar to control groups at 15 d, which were consistent with the increased antioxidant activity (PDX, GR and GPX). However, H2O2 content was more pronounced at 30 d. Therefore, S. crassa exhibited inductions in lipid peroxidation (TBARS content) in response to extreme salt concentrations. These results suggest that S. crassa is tolerant to salt-induced damage at short-term treatments as well as extreme salt concentrations. (C) 2014 Elsevier Inc. All rights reserved.

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