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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.
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.
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 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.
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.
Hormetic activation of nano-sized rare earth element terbium on growth, PSII photochemistry, antioxidant status and phytohormone regulation in Lemna minor
(Elsevier, 2023) Alp, Fatma Nur; Arıkan, Büşra; Özfidan Konakçı, Ceyda; Gülentürk, Çağrı; Yıldıztugay, Evren; Turan, Metin; Çavuşoğlu, Halit
Soils contaminated with rare earth elements (REEs) can damage agriculture by causing physiological disorders in plants which are evaluated as the main connection of the human food chain. A biphasic dose response with excitatory responses to low concentrations and inhibitory/harmful responses to high concentrations has been defined as hormesis. However, not much is clear about the ecological effects and potential risks of REEs to plants. For this purpose, here we showed the impacts of different concentrations of nano terbium (Tb) applications (510-25-50-100-250-500 mg L-1) on the accumulation of endogeneous certain ions and hormones, chlorophyll fluoresence, photochemical reaction capacity and antioxidant activity in duckweed (Lemna minor). Tb concentrations less than 100 mg L (-1) increased the contents of nitrogen (N), phosphate (P), potassium (K+), calcium (Ca2+), magnesium (Mg2+), manganese (Mn2+) and iron (Fe2+). Chlorophyll fluorescence (Fv/Fm and Fv/Fo) was suppressed under 250-500 mg L-1 Tb. In addition, Tb toxicity affected the trapped energy adversely by the active reaction center of photosystem II (PSII) and led to accumulation of inactive reaction centers, thus lowering the detected level of electron transport from photosystem II (PSII) to photosystem I (PSI). On the other hand, 5-100 mg L-1 Tb enhanced the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), NADPH oxidase (NOX), ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione S-transferase (GST). Tb (5-50 mg L-1) supported the maintenance of cellular redox status by promoting antioxidant pathways involved in the ascorbateglutathione (AsA-GSH) cycle. In addition to the antioxidant system, the contents of some hormones such as indole-3-acetic acid (IAA), gibberellic acid (GA), cytokinin (CK) and salicylic acid (SA) were also induced in the presence of 5-100 mg L-1 Tb. In addition, the levels of hydrogen peroxide (H2O2) and lipid peroxidation (TBARS) were controlled through ascorbate (AsA) regeneration and effective hormonal modulation in L. minor. However, this induction in the antioxidant system and phytohormone contents could not be resumed after applications higher than 250 mg L-1 Tb. TBARS and H2O2, which indicate the level of lipid peroxidation, increased. The results in this study showed that Tb at appropriate concentrations has great potential to confer tolerance of duckweed by supporting the antioxidant system, protecting the biochemical reactions of photosystems and improving hormonal regulation.
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.
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 impacts of nanoplastic toxicity on the accumulation, hormonal regulation and tolerance mechanisms in a potential hyperaccumulator - Lemna minor L.
(Elsevier, 2022) Arikan, Busra; Alp, Fatma Nur; Ozfidan-Konakci, Ceyda; Yildiztugay, Evren; Turan, Metin; Cavusoglu, Halit
Plastic pollution, which is currently one of the most striking problems of our time, raises concerns about the dispersal of micro and nano-sized plastic particles in ecosystems and their toxic effects on living organisms. This study was designed to reveal the toxic effects of polystyrene nanoplastic (PS NP) exposure on the freshwater macrophyte Lemna minor. In addition, elucidating the interaction of this aquatic plant, which is used extensively in the phytoremediation of water contaminants and wastewater treatment facilities, with nanoplastics will guide the development of remediation techniques. For this purpose, we examined nanoplastic accumulation, oxidative stress markers, photosynthetic efficiency, antioxidant system activity and phytohormonal changes in L. minor leaves subjected to PS NP stress (P-1, 100 mg L-1; P-2, 200 mg L-1 PS NP). Our results showed no evidence of PS NP-induced oxidative damage in P-1 group plants, although PS NP accumulation reached 56 mu g g(-1) in the leaves. Also, no significant changes in chlorophyll a fluorescence parameters were observed in this group, indicating unaffected photosynthetic efficiency. PS NP exposure triggered the antioxidant system in L. minor plants and resulted in a 3- and 4.6-fold increase in superoxide dismutase (SOD) activity in the P-1 and P-2 groups. On the other hand, high-dose PS NP treatment resulted in insufficient antioxidant activity in the P-2 group and increased hydrogen peroxide (H2O2) and lipid peroxidation (TBARS contents) by 25 % and 17 % compared to the control plants. Furthermore, PS NP exposure triggered abscisic acid biosynthesis (two-fold in the P-1 and three-fold in the P-2 group), which is also involved in regulating the stress response. In conclusion, L. minor plants tolerated NP accumulation without growth suppression, oxidative stress damage and limitations in photosynthetic capacity and have the potential to be used in remediation studies of NP-contaminated waters.
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.
Multiwalled Carbon Nanotubes Alter the PSII Photochemistry, Photosystem-Related Gene Expressions, and Chloroplastic Antioxidant System in Zea mays under Copper Toxicity
(Amer Chemical Soc, 2022) Alp, Fatma Nur; Arikan, Busra; Ozfidan-Konakci, Ceyda; Balci, Melike; Yildiztugay, Evren; Cavusoglu, Halit
A critical approach against copper (Cu) toxicity is the use of carbon nanomaterials (CNMs). However, the effect of CNMs on Cu toxicity-exposed chloroplasts is not clear. The photosynthetic, genetic, and biochemical effects of multiwalled carbon nanotubes (50-100-250 mg L-1 CNT) were investigated under Cu stress (50-100 mu M CuSO4) in Zea mays chloroplasts. F-v/F-m and F-v/F-o were suppressed under stress. Stress altered the antioxidant system and the expression of psaA, psaB, psbA, and psbD. The chloroplastic activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione S-transferase (GST), and glutathione peroxidase (GPX) increased under CNT + stress, and those of hydrogen peroxide (H2O2) and lipid peroxidation decreased. CNTs were promoted to the maintenance of the redox state by regulating enzyme/non-enzyme activity/contents involved in the AsA-GSH cycle. Furthermore, CNTs inverted the negative effects of Cu by upregulating the transcriptions of photosystem-related genes. However, the high CNT concentration had adverse effects on the antioxidant capacity. CNT has great potential to confer tolerance by reducing Cu-induced damage and protecting the biochemical reactions of photosynthesis.
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.
Polyamine Cadaverine Detoxifies Nitrate Toxicity on the Chloroplasts of Triticum aestivum Through Improved Gas Exchange, Chlorophyll a Fluorescence and Antioxidant Capacity
(Springer, 2023) Balci, Melike; Alp, Fatma Nur; Arikan, Busra; Ozfidan-Konakci, Ceyda; Yildiztugay, Evren
Nitrate (NO3-) toxicity is a serious problem that threatens the health of living organisms and especially agricultural production. The presence of NO3- leads to biomass loss by causing the imbalance of biochemical metabolism and inhibiting photosynthetic activity. A new critical approach to cope with nitrate toxicity is the use of polyamines (PAs) as an antioxidant defence system enhancer in plants. However, there is no information about the impacts of cadaverine, is one of PAs, on chloroplasts of plants exposed to NO3- toxicity. For this purpose, this study focused on the photosynthetic and biochemical process taking place in chloroplasts of Triticum aestivum under nitrate stress (100 mM and 200 mM NO3-) and/or cadaverine (100 mu M and 1 mM Cad). Gas exchange, chlorophyll fluorescence (F-v/F-m and F-v/F-o), the efficiency of the light reaction (phi P-o/(1 - phi P-o)), the performance index (PItotal), and relative water content (RWC) levels were suppressed under NO3- stress. Stress did not improve the antioxidant activities in chloroplasts such as superoxide dismutase (SOD), glutathione reductase (GR). After 100 mM NO3- exposure, Cad increased chloroplastic SOD, peroxidase (POX), ascorbate peroxidase (APX), GR, monodehydroascorbate reductase (MDHAR), and glutathione S-transferase (GST) activities. In the presence of 200 mM NO3-, Cads decreased SOD and GST activity. In NO3- + Cad-applied wheat, the high contents of hydrogen peroxide (H2O2) and lipid peroxidation (TBARS) were effectively removed through ascorbate (AsA) regeneration. Cads promoted the maintenance of cellular redox state by regulating antioxidant pathways included in the ascorbate-glutathione (AsA-GSH) cycle. Our results showed that Cad has great potential to confer tolerance to wheat by reducing oxidative damage and protecting the biochemical reactions of photosynthesis against NO3- toxicity.
Rare earth element scandium mitigates the chromium toxicity in Lemna minor by regulating photosynthetic performance, hormonal balance and antioxidant machinery
(Elsevier, 2023) Alp, Fatma Nur; Arıkan, Büşra; Özfidan Konakçı, Ceyda; Ekim, Rumeysa; Yıldıztugay, Evren; Turan, Metin
Chromium (Cr) toxicity is a serious problem that threatens the health of living organisms and especially agricultural production. The presence of excess Cr leads to biomass loss by causing the imbalance of biochemical metabolism and inhibiting photosynthetic activity. A new critical approach to cope with Cr toxicity is the use of the rare earth elements (REEs) as an antioxidant defence system enhancer in plants. However, the effect of scandium (Sc), which is one of the REEs, is not clear enough in Lemna minor exposed to Cr toxicity. For this purpose, the photosynthetic and biochemical effects of scandium (50 μM and 200 μM Sc) treatments were investigated in Lemna minor under Cr stress (100 μM, 200 μM and 500 μM Cr). Parameters related to photosynthesis (Fv/Fm, Fv/Fo) were suppressed under Cr stress. Stress altered antioxidant enzymes activities and hormone contents. Sc applications against stress increased the activities of superoxide dismutase (SOD), NADPH oxidase (NOX), ascorbate peroxidase (APX), lutathione reductase (GR), monodehydroascorbate reductase (MDHAR), and glutathione S-transferase (GST). In addition to the antioxidant system, the contents of indole-3- acetic acid (IAA), abscisic acid (ABA) and jasmonic acid (JA) were also rearranged. However, in all treatment groups, with the provision of ascorbate (AsA) regeneration and effective hormone signaling, reactive oxygen species (ROS) retention which result in high hydrogen peroxide (H2O2) content and lipid peroxidation (TBARS) were effectively removed. Sc promoted the maintenance of cellular redox state by regulating antioxidant pathways included in the AsA-GSH cycle. Our results showed that Sc has great potential to confer tolerance to duckweed by reducing Cr induced oxidative damage, protecting the biochemical reactions of photosynthesis, and improving hormone signaling.
Rosmarinic acid and hesperidin regulate gas exchange, chlorophyll fluorescence, antioxidant system and the fatty acid biosynthesis-related gene expression in Arabidopsis thaliana under heat stress
(Pergamon-Elsevier Science Ltd, 2022) Arikan, Busra; Ozfidan-Konakci, Ceyda; Alp, Fatma Nur; Zengin, Gokhan; Yildiztugay, Evren
The impacts of exogenous rosmarinic acid (RA, 100 mu M) and/or hesperidin (HP, 100 mu M) were evaluated in improving tolerance on the gas exchange, chlorophyll fluorescence and efficiencies, phenomenological fluxes of photosystems, antioxidant system and gene expression related to the lipid biosynthesis under heat stress. For this purpose, Arabidopsis thaliana was grown under RA and HP with heat stress (S, 38 ?) for 24 h(h). As shown in gas exchange parameters, heat stress caused mesophyll efficiency and non-stomatal restrictions. Both alone and combined forms of RA and HP to stress-treated A. thaliana alleviated the disturbance of carbon assimilation, transpiration rate and internal CO2 concentrations. Stress impaired the levels of energy flow reaching reaction centers of PSII and the photon capture ability of active reaction centers. RA and/or HP enhanced photosystems' structural/functional characteristics and photosynthetic performance. Histochemical staining and biochemical analyses revealed that heat stress caused the oxidation in A. thaliana. By activating several defensive mecha-nisms, RA and/or HP could reverse the harm caused by radical production. Both alone and combined forms of RA and HP removed superoxide anion radical (O-2 & BULL;-) accumulation, inducing superoxide dismutase (SOD). The common enzyme that scavenged hydrogen peroxide (H2O2) at all three applications (S + RA, S + HP and S + RA + HP) was POX. Also, only RA could utilize the ascorbate (AsA) regeneration in response to stress, suggesting increased ascorbate peroxidase (APX), monodehydroascorbate (MDHAR) and dehydroascorbate (DHAR) activ-ities. However, the regeneration/redox state of AsA and glutathione (GSH) did not maintain under S + HP and S + RA + HP. While RA had no positive influence on the saturated fatty acids under stress, HP increased the total saturated fatty acids (primarily palmitic acid). Besides, the combined application of RA + HP effectively created the stress response by increasing the expression of genes involved in fatty acid synthesis. The synergetic in-teractions of RA and HP could explain the increased levels of saturated fatty acids in combining these com-pounds. The data obtained from the study will contribute to the responses of phenolic compounds in plants to heat stress.

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