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

The molecular mechanism of plant response to UV-B radiation was studied usi ng the nopaline synthase (nos) promoter, which has been shown to be inducib le by methyl jasmonate (MJ) and reactive oxygen species (ROS). In the leave s of transgenic tobacco (Nicotiana tabacum L.) plants that carried a fusion between the nos promoter and the chloramphenicol acetyltransferase (cat) g ene, 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 pa thways. Diethyldithiocarbamic acid, a potent inhibitor of jasmonate product ion, had little effect on UV-B stimulation of the nos promoter In contrast, antioxidants, such as dimethylthiourea, reduced glutathione, cysteine, N-a cetylcysteine 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 rea ctive oxygen species and is distinct from the jasmonate or MJ mediating pat hway.