Differential responses of antioxidative enzymes and lipid peroxidation to salt stress in salt-tolerant Plantago maritima and salt-sensitive Plantago media

WOS: 000249827100005PubMed ID: 18251879The changes in plant growth, relative water content (RWC), stomatal conductance, lipid peroxidation and antioxidant system in relation to the tolerance to salt stress were investigated in salt-tolerant Plantago maritima and salt-sensitive Plantago media. The 60 days old P. maritima and P. media seedlings were subjected to 0, 100 and 200 mM NaCl for 7 days. Reduction in shoot length was higher in P. media than in P. maritima after exposure to 200 mM NaCl, but 100 mM NaCl treatment did not show any effect on shoot length of P. maritima. Shoot dry weight decreased in P. media and did not change in P. maritima. Two hundred millimolar NaCl treatment had no effect on leaf RWC in P. maritima, but it was reduced in P. media. Salt stress caused reduction in stomatal conductance being more pronounced in P. media than in P. maritima. Activities of superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6), glutathione reductase (GR; EC 1.6.4.2) decreased in P. media with increasing salinity. Ascorbate peroxidase (APX; EC 1.11.1.11) activity in leaves of P. media was increased and showed no change under 100 and 200 mM NaCl, respectively. However, activities of CAT, APX and GR increased under 200 mM NaCl while their activities did not change under 100 mM NaCl in P. maritima. SOD activity in leaves of P. maritima increased with increasing salinity. Concomitant with this, four SOD activity bands were identified in leaves of P. maritima, two bands only were observed in P. media. Peroxidase (POX; EC 1.11.1.7) activity increased under both salt concentrations in P. maritima, but only under 200 mM NaCl in P. media. Confirming this, five POX activity bands were identified in leaves of P. maritima, but only two bands were determined in P. media. Malondialdehyde levels in the leaves increased under salt stress in P. media but showed no change and decreased in P. maritima at 100 and 200 mM NaCl, respectively. These results suggest that the salt-tolerant P. maritima showed a better protection mechanism against oxidative damage caused by salt stress by its higher induced activities of antioxidant enzymes than the salt-sensitive P. media

Effect of Coronatine on Antioxidant Enzyme Response of Chickpea Roots to Combination of PEG-Induced Osmotic Stress and Heat Stress

WOS: 000314295600007Abiotic stresses, such as high temperature and drought, are major limiting factors of crop production and growth. Coronatine (COR), a structural and functional analog of jasmonates, is suggested to have a role in abiotic stress tolerance. The aim of our study was to examine whether pretreatment with COR enhances the tolerance of chickpea (Cicer arietinum L. cv ICC 4958) roots to PEG-induced osmotic stress, heat stress, and their combination. Therefore, seedlings raised hydroponically in a growth chamber for 15 days were pretreated with or without COR at 0.01 mu M for 24 h and then exposed to 6 % PEG 6000-induced osmotic stress or heat (starting at 35 A degrees C and then gradually increased 1 A degrees C every 15 min and kept at 44 A degrees C for 1 h) stress for 3 days. After different treatment periods, the changes in relative growth rate (RGR); malondialdehyde (MDA), proline (Pro), and hydrogen peroxide (H2O2) contents; and the activities of antioxidant enzymes/isoenzymes in roots of chickpea seedlings with or without 0.01 mu M COR application were studied. RGR in roots was increased by COR application. Under all stress conditions, H2O2, MDA, and Pro levels increased sharply, but pretreatment with COR significantly reduced them. Moreover, COR increased the activities of H2O2 scavenger enzymes such as catalase (CAT) under heat stress, ascorbate peroxidase (POX) under PEG stress, and CAT and POX under combined stresses. Therefore, COR might alleviate adverse effects of PEG stress and heat stress and combined stresses on roots of chickpea by reduction of H2O2 production, enhancing or keeping the existent activity of antioxidant enzymes, thereby preventing membrane peroxidation.Ege University Research FoundationEge University [2009-FEN-014]This work was supported by Ege University Research Foundation (2009-FEN-014). The authors thank Dr. Carol Bender of Oklahoma State University for kindly providing pure coronatine and Prof. Dr. Cengiz Toker of Akdeniz University for providing Cicer arietinum ICC 4958 seeds

Reactive oxygen species regulation and antioxidant defence in halophytes

WOS: 000322672000007Production of reactive oxygen species (ROS), which are a by-product of normal cell metabolism in living organisms, is an inevitable consequence of aerobic life on Earth, and halophytes are no exception to this rule. The accumulation of ROS is elevated under different stress conditions, including salinity, due to a serious imbalance between their production and elimination. These ROS are highly toxic and, in the absence of protective mechanisms, can cause oxidative damage to lipids, proteins and DNA, leading to alterations in the redox state and further damage to the cell. Besides functioning as toxic by-products of stress metabolism, ROS are also important signal transduction molecules in controlling growth, development and responses to stress. Plants control the concentrations of ROS by an array of enzymatic and nonenzymatic antioxidants. Although a relation between enzymatic and non-enzymatic antioxidant defence mechanisms and tolerance to salt stress has been reported, little information is available on ROS-mediated signalling, perception and specificity in different halophytic species. Hence, in this review, we describe recent advances in ROS homeostasis and signalling in response to salt, and discuss current understanding of ROS involvement in stress sensing, stress signalling and regulation of acclimation responses in halophytes. We also highlight the role of genetic, proteomic and metabolic approaches for the successful study of the complex relationship among antioxidants and their functions in halophytes, which would be critical in increasing salt tolerance in crop plants

Endoplasmic reticulum stress regulates glutathione metabolism and activities of glutathione related enzymes in Arabidopsis

WOS: 000419097200026Stress conditions generate an extra load on protein folding machinery in the endoplasmic reticulum (ER) and if the ER cannot overcome this load, unfolded proteins accumulate in the ER lumen, causing ER stress. ER lumen localised protein disulfide isomerase (PDI) catalyses the generation of disulfide bonds in conjugation with ER oxidoreductase1 (ERO1) during protein folding. Mismatched disulfide bonds are reduced by the conversion of GSH to GSSG. Under prolonged ER stress, GSH pool is oxidised and H2O2 is produced via increased activity of PDI-ERO1. However, it is not known how glutathione metabolism is regulated under ER stress in plants. So, in this study, ER stress was induced with tunicamycin (0.15, 0.3, 0.45 mu g mL(-1) Tm) in Arabidopsis thaliana (L.) Heynh. Glutathione content was increased by ER stress, which was accompanied by induction of glutathione biosynthesis genes (GSH1, GSH2). Also, the apoplastic glutathione degradation pathway (GGT1) was induced. Further, the activities of glutathione reductase (GR), dehydroascorbate reductase (DHAR), glutathione peroxidase (GPX) and glutathione S-transferase (GST) were increased under ER stress. Results also showed that chloroplastic GPX genes were specifically downregulated with ER stress. This is the first report on regulation of glutathione metabolism and glutathione related enzymes in response to ER stress in plants.Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [212T018]This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK, grant no. 212T018)

Reactive oxygen species scavenging capacities of cotton (Gossypium hirsutum) cultivars under combined drought and heat induced oxidative stress

WOS: 000333513600016Crop losses due to combined drought and heat is predicted be greater in the future especially due to climate change. Understanding underlying mechanisms under drought and heat combination will be crucial for the selection and breeding of tolerant varieties. The objective of this study was to assess the physiological and biochemical responses of two cotton cultivars (84-S and M-503) differing in drought tolerance to the combined effects of drought and heat. The relative growth rate (RGR) of the cultivars was decreased by 62.9% in drought sensitive 84-S and reduced by 34.58% in drought tolerant M-503 due to the combined drought and heat stresses. Combined stress also enhanced lipid peroxidation (TBARS) by 170.24% and 21.9% in 84-S and M-503, respectively which suggest that drought sensitive 84-S is more sensitive to combined stress than M-503. This sensitivity to combined stress of 84-S was associated with decreased activities of catalase (CAT) and peroxidase (POX) as compared to its control, resulting in higher H2O2 accumulation and oxidative stress induced lipid peroxidation. On the other hand, a higher combined stress tolerance of M-503 was associated with its ability to maintain constitutive activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) and induced CAT and POX. The proline content of drought resistant M-503 was greatly enhanced under drought and the combination of drought and heat treatments as compared to 84-S. To the best of our knowledge, this is the first study conducted on the activities of antioxidant enzymes of cotton under drought and heat combination. (C) 2013 Elsevier B.V. All rights reserved.Ege University Research FoundationEge University [2010-FEN-067]This work was supported by Ege University Research Foundation (2010-FEN-067). The authors thank to Prof. Dr. Stephen T. Astley for proofreading of the article