The promoter of the Tnt1A retrotransposon is activated by ozone air pollution in tomato, but not in its natural host tobacco

The tobacco retrotransposon Tnt1A is one of the few active plant retrotransposon and is known to be transcriptionally activated in tobacco (Nicotiana tabacum ) and in heterologous species by biotic and abiotic stress factors. It has been previously reported that Tnt1A expression is linked with the early steps of metabolic pathways leading to the activation of plant defence genes. As ozone is known to generate an oxidative stress in plant and activate the defence system, we have investigated, using LTR-GUS constructs, the effect of ozone on the Tnt1A promoter activation in its natural host tobacco and in an heterologous species, tomato (Lycopersicon esculentum ). Plants cultivated in open top chambers (OTC) were exposed to different ozone concentrations in order to simulate either different range of a realistic chronic ozone stress or an acute ozone stress. The results show that the Tnt1A promoter is not activated by ozone in tobacco, whereas dose-dependant and cumulative effects are observed in tomato. This difference observed between tobacco and tomato is discussed. Moreover the use of such a construct to study both early response to ozone stress and regulation of the retrotransoposon is examined. # 2003 Elsevier Ireland Ltd. All rights reserved.