Alteration in protein accumulation, gene expression and ascorbate-glutathione pathway in tomato (Lycopersicon esculentum) under paraquat and ozone stress

External factors such as herbicides and air pollutants can cause damage to plant cells. Paraquat-induced injury arises from the generation of active oxygen species as indicated by the alteration of enzymes and cellular antioxidants in plant tissues. Ozone-induced damage has been reported but, unlike paraquat, the target of ozone damage has never been established. We report here the first comparison of protein and in vitro translation product accumulation in tomato (Lycopersicon esculentum Mill. cv Rutgers) exposed to paraquat and ozone stress. Two sets of polypeptides were distinguished: those that decreased and those that increased during stress treatments. There was no overlap in polypeptide accumulation under ozone and paraquat stress, but an in vitro translation product that increased significantly during paraquat stress was identical with one that increased during ozone stress. The glutathione content and activities of superoxide dismutase, ascorbate peroxidase and glutathione reductase in paraquat-treated and ozone-treated plants fluctuate differently suggesting that the major targets of-ozone action in cells are not chloroplasts.