OVEREXPRESSION OF GLUTATHIONE-S-TRANSFERASE GLUTATHIONE-PEROXIDASE ENHANCES THE GROWTH OF TRANSGENIC TOBACCO SEEDLINGS DURING STRESS

Transgenic tobacco seedlings that overexpress a cDNA encoding an enzym e with both glutathione S-transferase (GST) and glutathione peroxidase (GPX) activity had GST- and GPX-specific activities approximately two fold higher than wild-type seedlings. These GST/GPX overexpressing see dlings grew significantly faster than control seedlings when exposed t o chilling or salt stress, During chilling stress, levels of oxidized glutathione (GSSG) were significantly higher in transgenic seedlings t han in wild-types. Growth of wild-type seedlings was accelerated by tr eatment with GSSG, while treatment with reduced glutathione or other s ulfhydryl-reducing agents inhibited growth, Therefore, overexpression of GST/GPX can stimulate seedling growth under chilling and salt stres s, and this effect could be caused by oxidation of the glutathione poo l.