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    Amino-functionalized SiO2 microbeads optimize photosynthetic performance, gene expression, ROS production and antioxidant status in chromium and copper-exposed Zea mays
    (Elsevier Sci Ltd, 2023) Alp-Turgut, Fatma Nur; Yildiztugay, Evren; Ozfidan-Konakci, Ceyda; Sargin, Idris
    The objective of the current study was to assess the potential of the amino-functionalized SiO2 microbeads (S) in improving the tolerance of maize to chromium and/or copper toxicity. For this purpose, Zea mays L. cv. DKC5685 was grown by exposure at different S concentrations (100-500 mg L-1) alone and with 200 mu M chromium (Cr stress) and 100 mu M copper (Cu stress) for 7 days. The photosynthesis-related parameters (Fv/Fm, Fv/Fo), relative growth rate (RGR), and relative water content (RWC) levels were suppressed under Cr and/or Cu stresses. In addition, stress altered antioxidant activities and gas exchange parameters. S applications abolished the negative impacts of stress on the physiological state of the photosynthetic system, potential photochemical efficiency and chlorophyll fluorescence. S increased the performance index by reversing the detrimental effects on the electron flow rate through the PSII electron transport flux and electron transfer from the decreased plastoquinone pool to the PSI reaction center. Following exposure to S, the effects of stress on photosystem I-associated reaction center proteins were rearranged by induced expression levels of PsaA and PsaB genes. S treatments had potent ROS scavengers in maize leaves. In the Cr+S groups, the AsA-GSH cycle was regulated by increasing the activities of all the responsible enzymes mentioned above, such as SOD, CAT, APX and GR, and the accumulation of H2O2 and TBARS effectively removed. CAT and POX activities in Cu+S groups were not effective in these adjustments. In Cr+Cu+S applications, although H2O2 and TBARS contents were reduced as evidenced by ROS visualization using fluorescence of dye, AsA regeneration could not be achieved, and low tAsA/DHA levels were detected. Our results show that amino-functionalized SiO2 microbeads have significant promise to offer resistance to maize by minimizing oxidative damage brought on by heavy metal uptake and preserving the metabolic processes involved in photosynthesis.
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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.
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    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.
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    The biphasic responses of nanomaterial fullerene on stomatal movement, water status, chlorophyll a fluorescence transient, radical scavenging system and aquaporin-related gene expression in Zea mays under cobalt stress
    (Elsevier, 2022) Ozfidan-Konakci, Ceyda; Arikan, Busra; Elbasan, Fevzi; Cavusoglu, Halit; Yildiztugay, Evren; Alp, Fatma Nur
    Nanomaterial fullerene (FLN) has different responses called the hormesis effect against stress conditions. The favorable/adverse impacts of hormesis on crop quality and productivity are under development in agrotechnology. In this study, the effect of FLN administration (100-250-500mg L-1 for FLN1-2-3, respectively) on growth, water management, gas exchange, chlorophyll fluorescence kinetics and cobalt (Co)-induced oxidative stress in Zea mays was investigated. The negative alterations in relative growth rate (RGR), water status (relative water content, osmotic potential and proline content) and gas exchange/stomatal regulation were removed by FLNs. FLNs were shown to protect photosynthetic apparatus and preserve the photochemistry of photosystems (PSI-PSII) in photosynthesis, chlorophyll fluorescence transients and energy flux damaged under Co stress. The maize leaves exposed to Co stress exhibited a high accumulation of hydrogen peroxide (H2O2) due to insufficient scavenging activity, which was confirmed by reactive oxygen species (ROS)-specific fluorescence visualization in guard cells. FLN regulated the gene expression of ribulose-1,5-bisphosphate carboxylase large subunit (rbcL), nodulin 26-like intrinsic protein1-1 (NIP1-1) and tonoplast intrinsic protein2-1 (TIP2-1) under stress. After stress exposure, FLNs successfully eliminated H2O2 content produced by superoxide dismutase (SOD) activity of catalase (CAT) and peroxidase (POX). The ascorbate (AsA) regeneration was achieved in all FLN applications together with Co stress through the elevated monodehydroascorbate reductase (MDHAR, under all FLNs) and dehydroascorbate reductase (DHAR, only FLN1). However, dose-dependent FLNs (FLN1-2) provided the induced pool of glutathione (GSH) and GSH redox state. Hydroponically applied FLNs removed the restrictions on metabolism and biological process induced by lipid peroxidation (TBARS content) and excessive ROS production. Considering all data, the modulation of treatment practices in terms of FLN concentrations and forms of its application will provide a unique platform for improving agricultural productivity and stress resistance in crops. The current study provided the first findings on the chlorophyll a fluorescence transient and localization of ROS in guard cells of Zea mays exposed to FLN and Co stress.
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    The effects of fullerene on photosynthetic apparatus, chloroplast-encoded gene expression, and nitrogen assimilation in Zea mays under cobalt stress
    (Wiley, 2022) Ozfidan-Konakci, Ceyda; Alp, Fatma Nur; Arikan, Busra; Balci, Melike; Parmaksizoglu, Zeynep; Yildiztugay, Evren; Cavusoglu, Halit
    Carbon nanostructures, such as the water-soluble fullerene (FLN) derivatives, are considered perspective agents for agriculture. FLN can be a novel nano-agent modulating plant response against stress conditions. However, the mechanism underlying the impacts of FLN on plants in agroecosystems remains unclear. Zea mays was exposed to exogenous C-60-FLN applications (FLN1: 100; FLN2: 250; and FLN3: 500 mg L-1) with/without cobalt stress (Co, 300 mu M) for 3 days (d). In the maize chloroplasts, Co stress disrupted the photosynthetic efficiency and the expression of genes related to the photosystems (psaA and psbA). FLNs effectively improved the efficiency and photochemical reaction of photosystems. Co stress induced the accumulation of reactive oxygen species (ROS) as confirmed by ROS-specific fluorescence in guard cells. Co stress increased only chloroplastic superoxide dismutase (SOD) and peroxidase (POX). Stress triggered oxidative damages in maize chloroplasts, measured as an increase in TBARS content. In Co-stressed seedlings exposed to FLN1 and FLN2 exposures, the hydrogen peroxide (H2O2) was scavenged through the nonenzymes/enzymes-related to the AsA-GSH cycle by preserving ascorbate (AsA) conversion, as well as GSH/GSSG and glutathione (GSH) redox state. Also, the alleviation effect of FLN3 against stress could be attributed to increased glutathione S-transferase (GST) activity and AsA regeneration. FLN applications reversed the inhibitory effects of Co stress on nitrogen assimilation. In maize chloroplasts, FLN increased the activities of nitrate reductase (NR), glutamate dehydrogenase (GDH), nitrite reductase (NiR), and glutamine synthetase (GS), which provided conversion of inorganic nitrogen (N) into organic N. The ammonium (NH4+) toxicity was removed via GS and GDH but not glutamate synthase (GOGAT). The increased NAD-GDH (deaminating) and NADH-GDH (aminating) activities indicated that GDH was needed more for NH4+ detoxification. Therefore, FLN exposure to Co-stressed maize plants might play a role in N metabolism regarding the partitioning of N assimilates. Exogenous FLN conceivably removed Co toxicity by improving the expressions of genes related to reaction center proteins of photosystems, increasing the level of enzymes related to the defense system, and improving the N assimilation in maize chloroplasts.
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    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.
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    The exogenous application of naringenin and rosmarinic acid modulates functional traits in Lepidium sativum
    (Wiley, 2023) Salehi, Hajar; Zhang, Leilei; Alp-Turgut, Fatma Nur; Arikan, Busra; Elbasan, Fevzi; Ozfidan-Konakci, Ceyda; Balci, Melike
    BACKGROUND: Phenolic modulators have attracted attention for their potential in shaping functional traits in plants. This work investigated the impact of naringenin (Nar) and rosmarinic acid (RA) on the functional properties of Lepidium sativum leaves and roots.Results: Untargeted metabolomics identified a diverse phenolic profile, including flavonoids, phenolic acids, low molecular weight phenolics, lignans, and stilbenes. Cluster, analysis of variance multiblock orthogonal partial least squares (AMOPLS), and orthogonal projection to latent structures discriminant analysis (OPLS-DA) multivariate analyses confirmed tissue-specific modulation of bioactive compounds. The tissue was the hierarchically most influential factor, explaining 27% of observed variability, while the treatment and their interaction were statistically insignificant. Thereafter, various in vitro assays were employed to assess antioxidant capacity, including 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2 '-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) radical scavenging activity, cupric ion reducing antioxidant capacity (CUPRAC), and ferric ion reducing antioxidant power (FRAP), metal chelating ability, and phosphomolybdenum (PMD) assays. Extracts were also tested for inhibitory effects on cholinesterase, amylase, glucosidase, and tyrosinase enzymes. RA application positively impacted antioxidant and enzyme inhibitory activities, holding valuable implications in shaping the health-promoting properties of L. sativum.Conclusion: The untargeted metabolomics analysis showed a significant tissue-dependent modulation of bioactive compounds, determining no synergistic effect between applying phenolic compounds in combination. Specifically, the sole application of RA increased anthocyanins and hydroxyphenyl propanoic acid content on leaves, which was strictly related to enhancing the biological activities.(c) 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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    Exogenous hesperidin and chlorogenic acid alleviate oxidative damage induced by arsenic toxicity in Zea mays through regulating the water status, antioxidant capacity, redox balance and fatty acid composition
    (Elsevier Sci Ltd, 2022) Arikan, Busra; Ozfidan-Konakci, Ceyda; Yildiztugay, Evren; Zengin, Gokhan; Alp, Fatma Nur; Elbasan, Fevzi
    Arsenic (As) toxicity is a problem that needs to be solved in terms of both human health and agricultural production in the vast majority of the world. The presence of As causes biomass loss by disrupting the balance of biochemical processes in plants and preventing growth/water absorption in the roots and accumulating in the edible parts of the plant and entering the food chain. A critical method of combating As toxicity is the use of biosafe, natural, bioactive compounds such as hesperidin (HP) or chlorogenic acid (CA). To this end, in this study, the physiological and biochemical effects of HP (100 mu M) and CA (50 mu M) were investigated in Zea mays under arsenate stress (100 mu M). Relative water content, osmotic potential, photosynthesis-related parameters were suppressed under stress. It was determined that stress decreased the activities of the antioxidant system and increased the level of saturated fatty acids and, gene expression of PHT transporters involved in the uptake and translocation of arsenate. After being exposed to stress, HP and CA improved the capacity of superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), glutathione S-transferase (GST) and glutathione peroxidase (GPX) and then ROS accumulation (H2O2) and lipid peroxidation (TBARS) were effectively removed. These phenolic compounds contributed to maintaining the cellular redox status by regulating enzyme/non-enzyme activity/contents involved in the AsA-GSH cycle. HP and CA reversed the adverse effects of excessive metal ion accumulation by re-regulated expression of the PHT1.1 and PHT1.3 genes in response to stress. Exogenously applied HP and CA effectively maintained membrane integrity by regulating saturated/unsaturated fatty acid content. However, the combined application of HP and CA did not show a synergistic protective activity against As stress and had a negative effect on the antioxidant capacity of maize leaves. As a result, HP and CA have great potentials to provide tolerance to maize under As stress by reducing oxidative injury and preserving the biochemical reactions of photosynthesis.
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    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.
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    Fe2O3-modified graphene oxide mitigates nanoplastic toxicity via regulating gas exchange, photosynthesis, and antioxidant system in Triticum aestivum
    (Pergamon-Elsevier Science Ltd, 2022) Arikan, Busra; Alp, Fatma Nur; Ozfidan-Konakci, Ceyda; Balci, Melike; Elbasan, Fevzi; Yildiztugay, Evren; Cavusoglu, Halit
    The ever-increasing plastic pollution in soil and water resources raises concerns about its effects on terrestrial plants and agroecosystems. Although there are many reports about the contamination with nanoplastics on plants, the presence of magneto-assisted nanomaterials enabling the removal of their adverse impacts still re-mains unclear. Therefore, the purpose of the current study is to evaluate the potential of nanomaterial Fe2O3- modified graphene oxide (FGO, 50-250 mg L-1) to eliminate the adverse effects of nanoplastics in plants. Wheat plants exposed to polystyrene nanoplastics concentrations (PS, 10, 50 and 100 mg L-1) showed decreased growth, water content and loss of photosynthetic efficiency. PS toxicity negatively altered gas exchange, antenna structure and electron transport in photosystems. Although the antioxidant system was partially activated (only superoxide dismutase (SOD), NADPH oxidase (NOX) and glutathione reductase (GR)) in plants treated with PS, it failed to prevent PS-triggered oxidative damage, as showing lipid peroxidation and hydrogen peroxide (H2O2) levels. FGOs eliminated the adverse impacts of PS pollution on growth, water status, gas exchange and oxidative stress markers. In addition, FGOs preserve the biochemical reactions of photosynthesis by actively increasing chlorophyll fluorescence parameters in the stressed-wheat leaves. The activities of all enzymatic antioxidants increased, and the H2O2 and TBARS contents decreased. GSH-mediated detoxifying antioxidants such as gluta-thione S-transferase (GST) and glutathione peroxidase (GPX) were stimulated by FGOs against PS pollution. FGOs also triggered the enzymes and non-enzymes related to the Asada-Halliwell cycle and protected the regeneration of ascorbate (AsA) and glutathione (GSH). Our findings indicated that FGO had the potential to mitigate nanoplastic-induced damage in wheat by regulating water relations, protecting photosynthesis reactions and providing efficient ROS scavenging with high antioxidant capacity. This is the first report on removing PS -induced damage by FGO applications in wheat leaves.
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    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.
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    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.
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    Glutamate, Humic Acids and Their Combination Modulate the Phenolic Profile, Antioxidant Traits, and Enzyme-Inhibition Properties in Lettuce
    (Mdpi, 2023) De Gregorio, Marco Armando; Zengin, Gokhan; Alp-Turgut, Fatma Nur; Elbasan, Fevzi; Ozfidan-Konakci, Ceyda; Arikan, Busra; Yildiztugay, Evren
    Lettuce (Lactuca sativa L., Asteraceae) is a popular vegetable leafy crop playing a relevant role in human nutrition. Nowadays, novel strategies are required to sustainably support plant growth and elicit the biosynthesis of bioactive molecules with functional roles in crops including lettuce. In this work, the polyphenolic profile of lettuce treated with glutamic acid (GA), humic acid (HA), and their combination (GA + HA) was investigated using an untargeted metabolomics phenolic profiling approach based on high-resolution mass spectrometry. Both aerial and root organ parts were considered, and a broad and diverse phenolic profile could be highlighted. The phenolic profile included flavonoids (anthocyanins, flavones, flavanols, and flavonols), phenolic acids (both hydroxycinnamics and hydroxybenzoics), low molecular weight phenolics (tyrosol equivalents), lignans and stilbenes. Overall, GA and HA treatments significantly modulated the biosynthesis of flavanols, lignans, low molecular weight phenolics, phenolic acids, and stilbene. Thereafter, antioxidant capacity was evaluated in vitro with 2,2-diphenyln-1-picrylhydrazyl (DPPH), 2,2'-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), ferric reducing antioxidant power (FRAP), and cupric ion reducing antioxidant capacity (CUPRAC) assays. In addition, this study examined the inhibitory properties of enzymes, including acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), tyrosinase, alpha-amylase, and alpha-glucosidase. Compared to individual treatments, the combination of GA + HA showed stronger antioxidant abilities in free radical scavenging and reducing power assays in root samples. Moreover, this combination positively influenced the inhibitory effects of root samples on AChE and BChE and the tyrosinase inhibitory effect of leaf samples. Concerning Pearson's correlations, antioxidant and enzyme inhibition activities were related to phenolic compounds, and lignans in particular correlated with radical scavenging activities. Overall, the tested elicitors could offer promising insights for enhancing the functional properties of lettuce in agricultural treatments.
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    Graphene oxide-based aerogel stimulates growth, mercury accumulation, photosynthesis-related gene expression, antioxidant efficiency and redox status in wheat under mercury exposure
    (Elsevier Sci Ltd, 2024) Alp-Turgut, Fatma Nur; Ozfidan-Konakci, Ceyda; Arikan, Busra; Comak, Gurbuz; Yildiztugay, Evren
    Mercury (Hg) pollution is a global concern in cropland systems. Hg contamination causes a disruption in the growth, energy metabolism, redox balance, and photosynthetic activity of plants. In the removal of Hg toxicity, a recent critical strategy is the use of aerogels with biodegradability and biocompatibility. However, it is unknown how graphene oxide-based aerogels stimulate the defense systems in wheat plants exposed to Hg toxicity. Therefore, in this study, the photosynthetic, genetic, and biochemical effects of reduced graphene oxide aerogel treatments (gA; 50-100-250 mg L-1) were examined in wheat (Triticum aestivum) under Hg stress (50 mu M HgCl2). The relative growth rate (RGR) significantly decreased (84%) in response to Hg stress. However, the reduced RGR and water relations (RWC) of wheat were improved by gA treatments. The impaired gas exchange levels (stomatal conductance, carbon assimilation rate, intercellular CO2 concentrations, and transpiration rate) caused by stress were reversed under Hg plus gAs. Additionally, stress hampered chlorophyll fluorescence (F-v/F-o, F-v/F-m), and under Hg toxicity the expression of psaA genes was reduced (>0.4-fold), but psaB gene was significantly up-regulated (>3-fold) which are the genes involved in PSI. By increasing expression patterns of both genes relating to PSI, gAs reversed the adverse consequences on F-v/F-o and F-v/F-m in the presence of excessive Hg concentration. The activities of glutathione S-transferase (GST), glutathione reductase (GR), catalase (CAT), ascorbate peroxidase (APX) and dehydroascorbate reductase (DHAR) decreased under Hg toxicity. On the other hand, the activities of superoxide dismutase (SOD), APX, GST, and glutathione peroxidase (GPX) increased following gA treatments against stress, leading to the successful elimination of toxic levels of H2O2 and lipid peroxidation (TBARS content) by decreasing the levels by about 30%, and 40%, respectively. By modulating enzyme/non-enzyme activity/contents including the AsA-GSH cycle, gAs contributed to the protection of the cellular redox state. Most important of all, gA applications were able to reduce Hg intake by approximately 66%. Therefore, these results showed that gAs were effective in highly inhibiting Hg uptake and could significantly increase wheat tolerance to toxicity by eliminating Hg-induced oxidative damage and inhibiting metabolic processes involved in photosynthesis. The findings obtained from the study provide a new perspective on the alleviation roles of reduced graphene oxide aerogels as an effective adsorbent for decreasing damages of mercury toxicity in wheat plants.
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    Halophytes as a source of salt tolerance genes and mechanisms: a case study for the Salt Lake area, Turkey
    (Csiro Publishing, 2016) Ozfidan-Konakci, Ceyda; Uzilday, Baris; Ozgur, Rengin; Yildiztugay, Evren; Sekmen, A. Hediye; Turkan, Ismail
    The worst case scenario of global climate change predicts both drought and salinity would be the first environmental factors restricting agriculture and natural ecosystems, causing decreased crop yields and plant growth that would directly affect human population in the next decades. Therefore, it is vital to understand the biology of plants that are already adapted to these extreme conditions. In this sense, extremophiles such as the halophytes offer valuable genetic information for understanding plant salinity tolerance and to improve the stress tolerance of crop plants. Turkey has ecological importance for its rich biodiversity with up to 3700 endemic plants. Salt Lake (Lake Tuz) in Central Anatolia, one of the largest hypersaline lakes in the world, is surrounded by salty marshes, with one of the most diverse floras in Turkey, where arid and semiarid areas have increased due to low rainfall and high evaporation during the summer season. Consequently, the Salt Lake region has a large number of halophytic, xerophytic and xero-halophytic plants. One good example is Eutrema parvulum (Schrenk) Al-Shehbaz & Warwick, which originates from the Salt Lake region, can tolerate up to 600mM NaCl. In recent years, the full genome of E. parvulum was published and it has been accepted as a model halophyte due to its close relationship (sequence identity in range of 90%) with Arabidopsis thaliana (L. Heynh.). In this context, this review will focus on tolerance mechanisms involving hormone signalling, accumulation of compatible solutes, ion transporters, antioxidant defence systems, reactive oxygen species (ROS) signalling mechanism of some lesser-known extremophiles growing in the Salt Lake region. In addition, current progress on studies conducted with E. parvulum will be evaluated to shed a light on future prospects for improved crop tolerance.
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    Halotolerant plant growth-promoting bacteria, Bacillus pumilus, modulates water status, chlorophyll fluorescence kinetics and antioxidant balance in salt and/or arsenic-exposed wheat
    (Academic Press Inc Elsevier Science, 2023) Ozfidan-Konakci, Ceyda; Arikan, Busra; Alp-Turgut, Fatma Nur; Balci, Melike; Uysal, Ahmet; Yildiztugay, Evren
    Seed priming is an effective and novel technique and the use of eco-friendly biological agents improves the physiological functioning in the vegetative stage of plants. This procedure ensures productivity and acquired stress resilience in plants against adverse conditions without contaminating the environment. Though the mechanisms of bio-priming-triggered alterations have been widely explained under induvial stress conditions, the interaction of combined stress conditions on the defense system and the functionality of photosynthetic apparatus in the vegetative stage after the inoculation to seeds has not been fully elucidated. After Bacillus pumilus inoculation to wheat seeds (Triticum aestivum), three-week-old plants were hydroponically exposed to the alone and combination of salt (100 mM NaCl) and 200 mu M sodium arsenate (Na2HAsO4 center dot 7H(2O), As) for 72 h. Salinity and As pollutant resulted in a decline in growth, water content, gas exchange parameters, fluorescence kinetics and performance of photosystem II (PSII). On the other hand, the seed inoculation against stress provided the alleviation of relative growth rate (RGR), relative water content (RWC) and chlorophyll fluorescence. Since there was no effective antioxidant capacity, As and/or salinity caused the induction of H2O(2) accumulation and thiobarbituric acid reactive substances content (TBARS) in wheat. The inoculated seedlings had a high activity of superoxide dismutase (SOD) under stress. B. pumilis decreased the NaCl-induced toxic H2O2 levels by increasing peroxidase (POX) and enzymes/non-enzymes related to ascorbate-glutathione (AsA-GSH) cycle. In the presence of As exposure, the inoculated plants exhibited an induction in CAT activity. On the other hand, for H2O2 scavenging, the improvement in the AsA-GSH cycle was observed in bacterium priming plants plus the combined stress treatment. Since B. pumilus inoculation reduced H2O2 levels against all stress treatments, lipid peroxidation subsequently decreased in wheat leaves. The findings obtained from our study explained that the seed inoculation with B. pumilus provided an activation in the defense system and protection in growth, water status, and gas exchange regulation in wheat plants against the combination of salt and As.
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    The hormetic dose-risks of polymethyl methacrylate nanoplastics on chlorophyll a fluorescence transient, lipid composition and antioxidant system in Lactuca sativa
    (Elsevier Sci Ltd, 2022) Yildiztugay, Evren; Ozfidan-Konakci, Ceyda; Arikan, Busra; Alp, Fatma Nur; Elbasan, Fevzi; Zengin, Gokhan; Cavusoglu, Halit
    Nanoplastic pollution has become an increasing problem due to over-consumption and degradation in ecosystems. A little is known about ecological toxicity and the potential risks of nanoplastics on plants. To better comprehend the hormetic effects of nanoplastics, the experimental design was conducted on the impacts of polymethyl methacrylate (PMMA) on water status, growth, gas exchange, chlorophyll a fluorescence transient, reactive oxygen species (ROS) content (both content and fluorescence visualization), lipid peroxidation and antioxidant capacity (comparatively between leaves and roots). For this purpose, PMMA (10, 20, 50 and 100 mg L-1) was hydroponically applied to Lactuca sativa for 15 days(d). PMMA exposure resulted a decline in the growth, water content and osmotic potential. As based on assimilation rate (A), stomatal conductance (g(s)), and intercellular CO2 concentrations (C-i), the decreased stomatal limitation (L-s) and, A/C-i and increased intrinsic mesophyll efficiency proved low carboxylation efficiency showing impaired photosynthesis as a non-stomatal limitation. PMMA toxicity increased the trapping fluxes and absorption with a decrease in electron transport fluxes caused the disruption in reaction centers of photosystems. The leaves and roots had a similar effect against PMMA toxicity, with increased superoxide dismutase (SOD) activity. Although, catalase (CAT) and peroxidase (POX) of leaves increased under 10 mg L-1 PMMA, these defense activities failed to prevent radicals from attacking. Compared to the leaves, the lettuce roots showed an intriguing result for AsA-GSH cycle against PMMA exposure. In the roots, the lowest PMMA application provided the high ascorbate/dehydroascorbate (AsA/DHA), GSH/GSSG and the pool of AsA/glutathione (GSH) and non-suppressed GSH redox state. Also, 10 mg L-1 PMMA helped remove high hydrogen peroxide (H2O2) by both glutathione peroxidase (GPX) and glutathione S-transferase (GST). Since this improvement in the antioxidant system could not be continued in roots after higher applications than 20 mg L-1 PMMA, TBARS (Thiobarbituric acid-reactive substances), indicating the level of lipid peroxidation, and H2O2 increased. Our findings obtained from PMMA-applied lettuce provide new information to advance the tolerance mechanism against nanoplastic pollution.
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    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.
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    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.
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    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.