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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 proline to root medium is more effective for amelioration of photosynthetic damages as compared to foliar spraying or seed soaking in maize seedlings under short-term drought(TUBITAK Scientific & Technical Research Council Turkey, 2017) Demiralay, Mehmet; Altuntaş, Cansu; Sezgin, Asiye; Terzi, Rabiye; Kadıoğlu, AsımExogenous proline (PRO) at low concentrations can enhance drought stress tolerance in different application modes such as application to rooting medium, foliar spray, and seed soaking. However, there is no information about which application mode is more effective for increasing the drought tolerance. Comparative effects of 1, 10, and 20 mM PRO applications through three application modes to hydroponically grown seedlings were examined under short-term drought stress in maize seedlings. Effects on leaf water potential, membrane damage, chlorophyll content, proline level, and gas exchange parameters such as net photosynthetic rate (Pn), transpiration rate (E), stomatal conductance (gs), and substomatal CO2 concentration (Ci) were compared. Results indicated that PRO pretreatments raised the water potential, chlorophyll content, Pn, E, gs, and Ci but lowered the malondialdehyde content in the three application modes as compared to the untreated plants. Of the three different modes of PRO pretreatment, rooting medium treatment at 1 mM concentration was also more effective in alleviating stress-induced damages in maize seedlings. Moreover, effectively applied PRO increased the maximum quantum efficiency of PS II, quantum yield of PS II photochemistry, photochemical quenching, and electron transport rate but decreased nonphotochemical quenching of chlorophyll fluorescence under short-term drought stress. In conclusion, exogenous PRO was markedly more effective in the root-treated mode than in foliar spray or seed soaking mode, suggesting that PRO had a different ameliorating effect in different application modes. Proline application in an effective mode can induce photochemical efficiency under short-term drought in maize.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 alpha lipoic acid can stimulate photosystem II activity and the gene expressions of carbon fixation and chlorophyll metabolism enzymes in maize seedlings under drought(Elsevier GMBH, 2019) Sezgin, Asiye; Altuntaş, Cansu; Demiralay, Mehmet; Cinemre, Salih; Terzi, RabiyeProtective compounds such as non-enzymatic antioxidants, osmolytes and signal molecules have been applied to plants exposed to various environmental stresses to increase their stress tolerance. However, there are not enough records about the response of plants to alpha lipoic acid (ALA) application with antioxidant properties. Therefore, this study was designed to evaluate the function of exogenous ALA on the photosynthetic performance of maize seedlings grown in hydroponic conditions under drought stress. Three weeks old seedlings were treated with or without ALA (12 ?M) and they were subjected to drought stress induced by 10% polyethylene glycol (PEG6000) for 24 h. Chlorophyll content, gas exchange parameters, chlorophyll fluorescence and the expression levels of genes involved in CO2 fixation (ribulose-1,5-bisphosphate carboxylase (rubisco), phosphoenolpyruvate carboxylase (PEPc), Rubisco activase (RCA)) and chlorophyll metabolism (magnesium chelatase (MgCHLI) and chlorophyllase (Chlase)) were determined. The application of ALA increased chlorophyll content and the activity of photosystem II in comparison to the untreated seedlings under drought stress. The relative expression levels of Rubisco, PEPc, RCA and Mg-CHLI significantly increased while the Chlase gene expression decreased in seedlings to which ALA was applied in comparison those to which it was not applied under the stress. These results suggest that exogenous ALA can enhance the photosynthetic performance of maize seedlings exposed to drought by inducing photosystem II activity and the gene expressions of carbon fixation and chlorophyll metabolism enzymes.Öğe 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 Increased dehydrin level decreases leaf rolling grade by altering the reactive oxygen species homeostasis and abscisic acid content in maize subjected to osmotic stress(Springer Nature, 2022) Saruhan Güler, Neslihan; Terzi, Rabiye; Demiralay, Mehmet; Öztürk, Kamil; Kadıoğlu, AsımAbstract Dehydrins (DHNs) are stress proteins involved in the development of protective reactions in plants against dehydration. The relationship between DHNs and morphological responses such as leaf rolling in plants exposed to water defcit is not well known. In this study, we detected how variations in DHN levels afect the leaf rolling response in maize exposed to osmotic stress in relation to the antioxidant system and ABA level. In this context, we altered the DHN levels in maize seedlings by treatment with bio-regulators (salicylic acid and abscisic acid) under PEG6000-free and PEG6000-induced osmotic stress. When the DHN levels were increased by the bio-regulators (25 µM SA and 100 µM ABA), the relative expression level of the Zea mays dehydrin COR410 gene increased in the seedlings, while reactive oxygen species (ROS) and leaf rolling grade decreased. Moreover, induction of DHNs caused increases in the antioxidant enzyme activity and content of antioxidant substances, and very high amounts of endogenous abscisic acid. When DHN level was suppressed by a bio-regulator (200 µM SA) in the maize seedlings, dehydrin COR410 expression level decreased, while ROS and the leaf rolling grade increased. Moreover, the antioxidant enzyme activity and content of antioxidant substances decreased in the seedlings, while the amount of abscisic acid increased. Taken all together, an increase in DHN level by bio-regulator treatment can stimulate the antioxidant system, enable abscisic acid regulation, and thus reduce leaf rolling through decreased ROS levels. The results also indicated that DHNs may be involved in the signal pathways inducing expression of some genes related to leaf rolling response, possibly by modulating ROS levels, in maize seedlings exposed to osmotic stress.Öğe 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 Proline-stimulated signaling primarily targets the chlorophyll degradation pathway and photosynthesis associated processes to cope with short-term water deficit in maize(Springer, 2020) Altuntaş, Cansu; Demiralay, Mehmet; Muslu, Asiye Sezgin; Terzi, RabiyeIncreased photosynthetic efficiencies in genotypes with greater proline level and in crops treated with proline under water deficit have been reported in recent years, but the biochemical and molecular mechanisms of this process are still not known. We examined photosystem II (PSII) activity, photosynthetic enzymes, ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco), phosphoenolpyruvate carboxylase (PEPc), rubisco activase (RCA), and chlorophyll metabolic enzymes, magne-sium chelatase (Mg-CHLI), and chlorophyllase (Chlase), which would be the primary targets of exogenous proline to provide photosynthetic protection to plants under PEG-induced short-term water deficit. Two maize genotypes W23/M14 with greater proline content and Şafak with low proline content were hydroponically grown for 21–23 days, and then the seedlings were subjected to water deficit (? 0.75 MPa) induced by PEG6000 for 0, 4, and 8 h. Before the seedlings were exposed to the water deficit, proline (1 mM) was applied to the rooting medium of the Şafak genotype for 2 days. The time course effects of the applications showed that exogenous proline significantly enhanced PSII efficiency, PEPc activity, rubisco activity, and the relative expression levels of PEPc, rubisco large subunit, rubisco small subunit, and RCA genes at 0, 4, and 8 h. The W23/M14 genotype had higher rubisco quantity than the Şafak genotype at all time periods. Proline pre-treatment under the stress-free and PEG conditions reduced the activity of Chlase and the gene expressions of Chlase, while it enhanced Mg-CHLIgene expression at 0, 4, and 8 h. Taken together, the results indicated that the primary target of proline-stimulated signaling in maize seedlings exposed to short-term severe water deficit may be to induce PSII efficiency, activities of carbon dioxide fixation enzymes and chlorophyll metabolism and mitigate chlorophyll degradation.
