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Öğe Abscisic acid cross-talking with hydrogen peroxide and osmolyte compounds may regulate the leaf rolling mechanism under drought(Springer Heidelberg, 2018) Sezgin, Asiye; Altuntaş, Cansu; Sağlam, Aykut; Terzi, Rabiye; Demiralay, Mehmet; Kadıoğlu, AsımLeaf rolling observed in some crops such as maize, rice, wheat and sorghum is an indicator of decreased water status. Moderate leaf rolling not tightly or early increases the photosynthesis and grain yield of crop cultivars under environmental stresses. Moreover, the effects of exogenous abscisic acid (ABA) on stomatal conductance, water status and synthesis of osmotic compounds are a well-known issue in plants subjected to water deficit. However, it is not clear how the cross-talk of ABA with H2O2 and osmolyte compounds affects the leaf rolling mechanism. Regulation mechanism of leaf rolling by ABA has been first studied in maize seedlings under drought stress induced by polyethylene glycol 6000 (PEG 6000) in this study. ABA treatment under drought stress reduced hydrogen peroxide (H2O2) content and the degree of leaf rolling (%) while the treatment-induced ABA synthesis, osmolyte levels (proline, polyamine and total soluble sugars) and some antioxidant enzyme activities in comparison to the plants that were not treated with ABA. Furthermore, exogenous ABA up-regulated the expression levels of arginine decarboxylase (ADC) and pyrroline-5-carboxylate synthase (P5CS) genes and down-regulated polyamine oxidase (PAO), diamine oxidase (DAO) and proline dehydrogenase (ProDH) gene expressions. When endogenous ABA content was decreased by the treatment of fluoridone (FLU) that is an ABA inhibitor, leaf rolling degree (%), H2O2 content and antioxidant enzyme activities increased, but osmolyte levels, ADC and P5CS gene expressions decreased. Finally, the treatment of ABA to maize seedlings exposed to drought stress resulted in the stimulation of the antioxidant system, osmotic adjustment and reduction of leaf rolling. We concluded that ABA can be a signal compound cross-talking H2O2, proline and polyamines and thus involved in the leaf rolling mechanism by providing osmotic adjustment. The results of this study can be used to provide data for the molecular breeding of maize hybrids with high grain yield by means of moderately rolled leaves.Öğe Application of sucrose modulates the expressions of genes involved in proline and polyamine metabolism in maize seedlings exposed to drought(ACAD Sciences Czech Republic, 2019) Altuntaş, Cansu; Sezgin, Asiye; Demiralay, Mehmet; Terzi, Rabiye; Sağlam, Aykut; Kadıoğlu, AsımSucrose, proline, and polyamines are compatible solutes accumulating in plant tissues and increasing cellular osmolarity under environmental stresses. These compatible solutes and hydrogen peroxide can function as signaling molecules in plants. There has been very little evidence how the supply of sucrose changes the biosynthesis of compatible solutes. This study aimed to assess the cross-talk among sucrose, H2O2, and compatible solutes on the expression of genes encoding key enzymes in the pathways of proline and polyamine metabolism in drought stressed maize seedlings. Drought stress (induced by polyethylene glycol solution) increased the expressions of genes encoding pyrroline-5-carboxylate synthetase (P5CS), arginine decarboxylase (ADC), and S-adenosylmethionine decarboxylase (SAMDC), while decreased proline dehydrogenase (ProDH), diamine oxidase (DAO), and polyamine oxidase (PAO) expressions. Addition of sucrose to the stressed seedlings increased the P5CS, ADC and SAMDC expressions more than drought stress alone and reduced more the ProDH, DAO, and PAO expressions. Moreover, exogenous sucrose increased leaf water potential and the content of proline, polyamines, and total soluble sugars, whereas decreased H2O2 content and membrane damages under the drought stress conditions. Consequently, exogenous sucrose contributed to the preservation of water status and the amelioration of damage in maize seedlings under the drought stress.Öğe Copper stress and responses in plants(Elsevier Science BV, 2016) Sağlam, Aykut; Yetişsin, Fuat; Demiralay, Mehmet; Terzi, RabiyeNo abstract availableÖğe Exogenous ascorbic acid mitigates accumulation of abscisic acid, proline and polyamine under osmotic stress in maize leaves(Springer Heidelberg, 2015) Terzi, Rabiye; Kalaycıoğlu, Ebru; Demiralay, Mehmet; Sağlam, Aykut; Kadıoğlu, AsımThe effects of osmotic stress (polyethylene glycol, PEG 6000) and exogenous ascorbic acid (ASC) on abscisic acid (ABA), some osmolytes (proline and polyamine), and gene expression of polyamine metabolic enzymes arginine decarboxylase (ADC), S-adenosylmethionine decarboxylase (SAMDC) and polyamine oxidase (PAO1) were assessed in the leaves of Zea mays L. seedlings. ASC (0.1 mM) was hydroponically applied to detached maize seedlings. ASC application scavenged endogenous hydrogen peroxide level and ameliorated leaf water status and stomatal conductance under osmotic stress. Lipid peroxidation, ABA and osmolyte accumulation were mitigated by ASC treatment. For osmolytes, the alleviation of polyamine accumulation was more obvious than that of the proline. Therefore, gene expressions of polyamine metabolic enzymes were investigated. Compared to control seedlings, down-regulation of SAMDC and ADC gene expressions were determined in ASC ? PEG-applied seedlings while PAO1 gene expression increased. These results indicated that exogenous ASC influenced polyamine metabolism. ASC application under the osmotic stress ameliorated osmotic solute levels and ABA concentration in maize.Öğe Heliotropium thermophilum, an extreme heat tolerant species,promises plants about adaptation to high soil temperature conditions(Springer, 2020) Öztürk, Kamil; Sağlam, Aykut; Kadıoğlu, AsımTo understand high temperature tolerance, Heliotropium thermophilum, a flowering plant thriving in a geothermal field with a soil temperature ranging between 55 and 65 °C, was grown in controlled laboratory conditions and two different soil temperatures were applied to the plants. One of them was the control group (CT 25 ± 3 °C) and the other was the high temperature group (HT 60 ± 4 °C). Water potential, dry weight, cell membrane injury (CMI), lipid peroxidation, hydrogen peroxide, chlorophylls, carotenoids, flavonoids, anthocyanins, proline and total soluble sugar contents were measured. Contents of total soluble sugars, phenolics, flavonoids, anthocyanins, proline were found to be higher in HT group than CT while CMI was opposite. Moreover, no difference was determined in water potential, dry weight, lipid peroxidation, total chlorophyll and carotenoids between CT and HT. H. thermophilum plants adapted to high temperature under laboratory conditions through changing membrane lipid saturation, accumulating osmotically active compounds to save water or increase its uptake and inducing antioxidants such as phenolic compounds to keep reactive oxygen species under control. In conclusion, this study showed that H. thermophilum plant was highly resistant to high soil temperature under optimized laboratory conditions. Moreover, a plant that can withstand 60 °C for a long period of time up to 60 days under laboratory conditions was reported for the first time.Öğe Hydrogen peroxide extends postharvest life of Ctenanthe setosa leaf cuts under osmotic stress by reducing leaf rolling(Korean Soc Horticultural Science, 2014) Sağlam, Aykut; Kalaycıoğlu, Ebru; Güven, Funda Gül; Saruhan, Neslihan; Kadıoğlu, Asım; Demiralay, MehmetReducing effects of exogenous hydrogen peroxide on leaf rolling in detached leaves of Ctenanthe setosa were studied. The leaves were kept in H2O2 solutions ranging from 0 to 1 mM for 48 h and then, osmotic stress was applied for 4 h by polyethylene glycol (PEG). Degree of leaf rolling, loss of leaf water, and malondialdehyde (MDA) content were reduced by 0.2 mM H2O2. Antioxidant enzymes were induced by 0.2 mM H2O2. Endogenous H2O2 content was increased after the 0.5 and 1 mM H2O2 treatments but was decreased after 0.2 mM H2O2 treatment. Proline was decreased after exogenous H2O2 applications. Total soluble sugar content was increased as compared to the control after 0.2 mM H2O2 treatment. In conclusion, low-dose exogenous H2O2 treatment could delay leaf rolling by inducing tolerance to osmotic stress due to modulation of the antioxidant system, soluble sugar accumulation, and maintenance of leaf hydration. Therefore, postharvest life of C. setosa cut foliage could be extended by 0.2 mM H2O2 treatments.Öğe Investigation of the roles of hydrogen peroxide and NADPH oxidase in the regulation of polyamine metabolism in maize plants under Drought Stress Conditions(Ankara Üniversitesi, 2022) Demiralay, Mehmet; Sağlam, Aykut; Yetişsin, Fuat; Kadıoğlu, AsimThe relationship between hydrogen peroxide and the metabolism of polyamines and the role of NADPH oxidase (NOX) in that relationship under drought conditions remains unclear. To reveal the relationship, expression levels of the genes in polyamine metabolism, such as arginine decarboxylase, agmatine aminohydrolase, spermidine synthase, S-adenosyl methionine decarboxylase, diamine oxidase, and polyamine oxidase were determined by RT PCR under drought stress combined with exogenous hydrogen peroxide (H2O2) and diphenyleneiodonium chloride (DPI) treatments in maize seedlings. In addition, some basic stress parameters (leaf water potential, lipid peroxidation), levels of polyamines (putrescine, spermidine, and spermine), and gene expression of NOX were measured under drought stress. Exogenous H2O2 induced the polyamine content by up-regulating polyamine-synthesizing genes and downregulating polyamine oxidizing genes. When the NOX enzyme was inhibited by DPI, the polyamine pathway tended towards degradation instead of production. Exogenous H2O2 regulated the metabolism of polyamines to promote their synthesis, and NOX played a key role in that regulationÖğe Leaf rolling reduces photosynthetic loss in maize under severe drought(Univ Zagreb, 2014) Sağlam, Aykut; Kadıoğlu, Asım; Demiralay, Mehmet; Terzi, RabiyeEffects of leaf rolling (LR) on maize photosynthesis under severe drought stress were studied in two cultivars with opposite drought responses, Batem 56-55 (drought tolerant) and Batem 51-52 (drought sensitive). Drought stress and artificial prevention of leaf rolling (PLR) were applied at grain filling stage for 30 days. LR in Batem 56-55 occurred later than in Batem 51-52. Leaf water potential (Psi(leaf)) did not change in Batem 56-55 but decreased in Batem 51-52 at LR. Maximum quantum yield of photosystem II (F-v/F-m), effective quantum yield of photosystem II (Phi(PSII)) and electron transport rate (ETR) of the cultivars decreased during LR more significantly in Batem 56-55 in comparison to Batem 51-52. The same was observed for the decrease in net photosynthetic rate (P-N), stomatal conductance (g(s)), transpiration (E) and intracellular level of CO2 (C-1) Rubisco activity and content were reduced at LR, but were less affected in Batem 56-55 than in Batem 51-52. Ear and kernel weights also decreased at LR. All parameters at PLR were more reduced than those of LR. These results implied that LR was an important and necessary mechanism protecting photosynthesis and reducing yield loss under drought stress by maintaining the leaf hydration, preventing loss of the photosynthetic pigments, sustaining the activity of PSII, keeping the stomata open, and conserving the activity of Rubisco.Öğe Osmotik Stres Koşullarında Dıştan Uygulanan Osmolitlerin Hücresel Poliamin, Prolin, Sakkaroz ve Absisik Asit Metabolizması İle İlgili Gen İfadeleri Üzerine Etkisi(TUBITAK, 2018) Kadıoğlu, Asım; Sağlam, Aykut; Demiralay, MehmetBitkilerde osmotik stres nedeniyle meydana gelen ürün kayıplarını azaltmak için çeşitli uygulamaların yapıldığı bilinmektedir. Dışarıdan gerçekleştirilen osmolit uygulamaları bu çözümlerden birisidir. Bitkilere dıştan yapılan uygulamalardan en önemlileri prolin, glisinbetain, şeker ve poliamindir. Mevcut projenin amacı, osmotik stres koşulları altında dıştan uygulanan osmolitler (prolin, sakkaroz ve spermidin) ile hücresel osmolitler (prolin, poliamin, şeker) ve ABA metabolizması arasındaki olası etkileşimin hangi genlerle ilişkili olduğu hakkında veriler elde etmektir. Bu amaca ulaşmak için dıştan uygulanan osmolitlerin ve bazı osmolit inhibitörlerinin, prolin, sakkaroz, poliamin ve ABA ile ilgili gen ifadeleri üzerine etkisinin belirlenmesi hedeflenmiştir.Öğe Pseudomonas putida KT2440 induces drought tolerance during fruit ripening in tomato(Universidad Centroccidental Lisandro Alvarado (UCLA), 2022) Sağlam, Aykut; Demiralay, Mehmet; Çolak, Dilsat Nigar; Gedik, Necla Pehlivan; Başok, Oğuz; Kadioğlu, AsımThe current study investigated the effects of Pseudomonas putida strain KT2440 on the drought tolerance of tomato plants during fruit maturation. Plants at the ripening stage of the mature-green were not watered for 20 days to promote drought stress. Concentrations of photosynthetic pigments were determined. Bacteria-soaked tomato plants (BSS) had higher levels of chlorophyll and carotenoids than non-soaked plants (DWS) under stress conditions. Compared to the DWS, stomatal conductance, lipid peroxidation, and hydrogen peroxide content in the BSS plants decreased under drought stress. The ascorbate peroxidase (APX), catalase (CAT), and peroxidase (POD) activities increased in BSS plants compared to DWS under drought stress. Furthermore, the number and weight of fruits in both DWS and BSS plants was reduced by the stress, but the reduction in BSS plants was lower than in DWS plants. These results showed that bacteria treatment conferred tolerance to drought stress in tomato plants by reducing the peroxidation extent of polar lipids (PLs), increasing photosynthetic pigment content, and activities of the antioxidant enzymes in the leaves. Therefore, P. putida KT2440 has supported high fruit yield under drought stress as a biotic tolerance elicitor for this plant stress.
