Salt and oxidative stress: similar and specific responses and their relation to salt tolerance in Citrus

Abstract

Salt damage to plants has been attributed to a combination of several factors including mainly osmotic stress and the accumulation of toxic ions. Recent findings in our laboratory showed that phospholipid hydroperoxide glutathione peroxidase (PHGPX), an enzyme active in the cellular antioxidant system, was induced by salt in citrus cells and mainly in roots of plants. Following this observation we studied the two most important enzymes active in elimination of reactive oxygen species, namely, superoxide dismutase (SOD) and ascorbate peroxidase (APX), to determine whether a general oxidative stress is induced by salt. While Cu/Zn-SOD activity and cytosolic APX protein level were similarly induced by salt and methyl viologen, the response of PHGPX and other APX isozymes was either specific to salt or methyl viologen, respectively. Unlike PHGPX, cytosolic APX and Cu/Zn-SOD were not induced by exogenously added abscisic acid. Salt induced a significant increase in SOD activity which was not matched by the subsequent enzyme APX. We suggest that the excess of H2O2 interacts with lipids to form hydroperoxides which in turn induce and are removed by PHGPX. Ascorbate peroxidase seems to be a key enzyme in determining salt tolerance in citrus as its constitutive activity in salt-sensitive callus is far below the activity observed in salt-tolerant callus, while the activities of other enzymes involved in the defence against oxidative stress, namely SOD, glutathione reductase and PHGPX, are essentially similar.

Induction and Functional Analysis of Two Reduced Nicotinamide Adenine Dinucleotide Phosphate-Dependent Glutathione Peroxidase-Like Proteins in Synechocystis PCC 6803 during the Progression of Oxidative Stress

“…Lipid hydroperoxides are generated by the enzymatic catalysis of lipooxygenase or the chemical reaction of AOS (Gueta-Dahan et al, 1997). The rate of lipid peroxidation was clearly increased in both types of gpxD mutant cells compared with wild-type and tpxD mutant cells (Fig.…”

Galactinol and Raffinose Constitute a Novel Function to Protect Plants from Oxidative Damage

“…The MDA content was estimated by measuring absorbance from A 532 to A 600 using a molar absorption coefficient of 1.56 3 10 5 (Gueta-Dahan et al, 1997). All measurements were repeated at least three times for extracts from three batches of plants.…”

Physiological adaptive mechanisms of plants grown in saline soil and implications for sustainable saline agriculture in coastal zone

“…Consequently, a degree of cellular oxidative damage in plants resulting from abiotic stress is mediated . It has been reported that salinity tolerance is closely related to antioxidant capacity in many plant species (Gossett et al 1994;Hernandez et al 1995;GuetaDahan et al 1997;Dionisio-Sese and Tobita 1998;Meneguzzo et al 1999;Hernandez et al 2000;Sreenivasulu et al 2000;Shalata et al 2001;Bor et al 2003;Mittova et al 2003;Turkan 2004, 2005;Koca et al 2006Koca et al , 2007Sekmen et al 2007;Yazici et al 2007;). In addition, transgenic plants overexpressing ROS-scavenging enzymes such as SOD (Badawi et al 2004;Tseng et al 2007), CAT (Tseng et al 2007), APX (Wang et al 1999) and GR (Foyer et al 1995) showed enhanced tolerance to the oxidative stresses in plants under adverse conditions.…”