Salt and oxidative stress: similar and specific responses and their relation to salt tolerance in Citrus |
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Authors: | Yardena Gueta-Dahan Zohara Yaniv Barbara A Zilinskas Gozal Ben-Hayyim |
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Institution: | (1) Institute of Horticulture, ARO, The Volcani Center, Bet Dagan, Israel, IL;(2) Institute of Field and Garden Crops, ARO, The Volcani Center, Bet Dagan, Israel, IL;(3) Plant Science Department, Rutgers University, New Brunswick, New Jersey 08903-0231 USA, US |
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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.
Received: 10 January 1997 / Accepted: 28 May 1997 |
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Keywords: | : Antioxidant (enzyme complex) Citrus Fatty acid Phospholipid hydroperoxide glutathione peroxidase Oxidative stress Salt stress |
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