PLANT PHYSIOLOGY , Vol 110, Issue 2 583-588, Copyright © 1996 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Overexpression of Copper/Zinc Superoxide Dismutase in the Cytosol of Transgenic Tobacco Confers Partial Resistance to Ozone-Induced Foliar Necrosis
L. H. Pitcher and B. A. Zilinskas
Plant Science Department, Cook College, Rutgers University, New Brunswick, New Jersey 08903-0231
Ozone damage to plants has been attributed to the action of oxygen
free-radicals and other ozone degradation products against which cellular
antioxidant systems have been considered to be a front-line defense. The
activity of superoxide dismutase (SOD), one such antioxidant, has been
shown to increase in ozonated plants. Past work with pea (Pisum sativum L.)
in our laboratory showed that the cytosolic Cu/Zn-SOD isoform and its
transcript were most responsive to ozone, compared to chloroplastic
Cu/Zn-SOD. In the current work we tested the hypothesis that plants that
constitutively overexpress cytosolic SOD are more tolerant of ozone. Pea
cytosolic Cu/Zn-SOD was overproduced in the cytosol of two cultivars of
transformed tobacco (Nicotiana tabacum), Bel W3 and Wisconsin 38. Young and
recently expanded leaves of transgenic plants of both cultivars showed less
foliar necrosis than nontransformed controls when exposed to acute doses of
ozone. We suggest that this may demonstrate the importance of Cu/Zn-SOD in
the cytosol as a protector of the integrity of the plasma membrane and
possibly other cellular constituents.