ELEVATED LEVELS OF SUPEROXIDE-DISMUTASE PROTECT TRANSGENIC PLANTS AGAINST OZONE DAMAGE

To evaluate the feasibility of using engineered antioxidant enzymes as an approach to improve the tolerance of plants to ambient stress, we have constructed transgenic tobacco plants that overproduce superoxide dismutase (SOD), an enzyme which converts superoxide radicals into hy drogen peroxide and oxygen, and is believed to play a crucial role in antioxidant defense. We have targeted the MnSOD from Nicotiana plumbag inifolia either to the chloroplasts or to the mitochondria, and evalua ted the ozone tolerance of transgenic and control plants. Enhanced SOD activity in the mitochondria had only a minor effect on ozone toleran ce. However overproduction of SOD in the chloroplasts resulted in a 3- 4 fold reduction of visible ozone injury.