Specific plant DNA adducts as molecular biomarkers of genotoxic atmospheric environments

The general purpose of this study was to determine whether the formation of DNA addition products ('adducts') in plants could be a valuable biomarker of genotoxic air pollution. Plants from several species were exposed to ambient atmosphere at urban and suburban sites representative of different environmental conditions. The levels of NO2 and of the quantitatively major genotoxic air pollutants benzene, toluene, and xylene were monitored in parallel with plant exposure. DNA adducts were measured in bean (Phaseolus vulgaris), rye-grass (Lolium perenne), and tobacco (Nicotiana tabacum) seedlings by means of the [32P]-postlabeling method. Whereas, no correlation was found between the levels of the major genotoxic air pollutants and the total amounts of DNA adducts, individual analyses revealed site-specific and plant species-specific adduct responses, both at the qualitative and quantitative level. Among these, the amount of a specific rye-grass DNA adduct (rgs1) correlated with benzene/toluene/xylene levels above a threshold. For further characterization, rye-grass seedlings were treated in controlled conditions with benzene, toluene, xylene or their derivatives. On the other hand, in vitro DNA adduct formation assays were developed involving benzene, toluene, xylene, or their derivatives, and plant microsomes or purified peroxidase. Although in some cases, these approaches produced specific adduct responses, they failed to generate the rgs1 DNA adduct, which appeared to be characteristic for on-site test-plant exposure. Our studies have thus identified an interesting candidate for further analysis of environmental biomarkers of genotoxicity.