The nopaline synthase (nos) promoter is inducible by UV-B radiation through a pathway dependent on reactive oxygen species

Abstract

The molecular mechanism of plant response to UV-B radiation was studied using the nopaline synthase (nos) promoter, which has been shown to be inducible by methyl jasmonate (MJ) and reactive oxygen species (ROS). In the leaves of transgenic tobacco (Nicotiana tabacum L.) plants that carried a fusion between the nos promoter and the chloramphenicol acetyltransferase (cat) gene, 2 h of UV-B treatment resulted in a transient increase in the level of cat mRNA, a maximum being reached at 6 h after the UV-B treatment. It was also found that MJ and UV-B enhance nos promoter expression via separate pathways. Diethyldithiocarbamic acid, a potent inhibitor of jasmonate production, had little effect on UV-B stimulation of the nos promoter In contrast, antioxidants, such as dimethylthiourea, reduced glutathione, cysteine, N-acetylcysteine and DTT, blocked UV-B induction of the nos promoter, but did not affect MJ induction of the nos promoter, These results suggest that UV-B induction of the nos promoter is mediated via a pathway that requires reactive oxygen species and is distinct from the jasmonate or MJ mediating pathway.