Specific plant DNA adducts as molecular biomarkers of genotoxic atmospheric environments

Unambiguous identification of γ-aminobutyric acid adducts as novel plant biomarkers and their ultra-sensitive detection by UPLC-MS/MS for retrospective analyses of nitrogen mustards exposure

Plants are widely existing in the environments and have been considered as potential sentinel species of toxic chemicals' exposure. In this study, the deadly toxic chemicals of three nitrogen mustards (NMs, including NH1, NH2 and NH3) were selected as the investigated targets. First, the reactivities of common endogenous plant components with NMs were examined in vitro. Then, the model plant Nicotiana benthamiana Domin was exposed to NMs. Three γ-aminobutyric acid-nitrogen mustard adducts (GABA-NMs) were identified in the living plant by high resolution mass spectrometry and comparison with the synthesized references. A sensitive detection method with the limits of quantification of 0.0500 ng mL-1 was developed using ultrahigh performance liquid chromatography-triple quadrupole mass spectrometry. The GABA-NMs could be detected after 120 days of the exposure and even in the dead leaves without obvious decrease. Furthermore, 20 different plant species grown in diverse climate zones were exposed to HN1, and the adduct of GABA-HN1 was identified in all the leaves. The results showed the good universality and specificity of GABA-NMs as plant biomarkers for NMs exposure. This work provides a new approach for the pollution investigation of toxic chemicals through analysing biomarkers in plant materials.

Root response in Pisum sativum and Zea mays under fluoranthene stress: morphological and anatomical traits

Introduced organic pollutants in all ecosystem compartments can cause stress resulting in a wide range of responses including different root development. In this study, the effects of a polycyclic aromatic hydrocarbon-fluoranthene (FLT; 0.1, 1 and 7 mg L(-1)) on the growth, morphology and anatomical structure of roots of pea and maize was evaluated. In comparison with pea, significant stimulation of root system growth of maize caused by 0.1 mg L(-1) (total length longer by 25%, number of lateral roots by 35%) and its reduction (total length by 34%) already by 1 mg L(-1) FLT is the proof of different interspecies sensitivity to low and higher environmental loading. Nevertheless in both plant species a high loading 7 mg L(-1) FLT significantly reduced both growth (total length by 95% in pea, 94% in maize) and the number of lateral roots (by 78% in pea, 94% in maize). Significantly increased thickness of root of both maize and pea was caused by 7 mg L(-1) FLT and in maize already by 0.1 mg L(-1) FLT. It may be mainly connected with an enlargement of stele area (up to 50% in pea and 25% in maize). Increased xylem area in root tip (by up to 385% in pea, 167% in maize) and zone of maturation (up to 584% in pea, 70% in maize) and its higher portion in stele area of root tip (by 9% in pea, 21% in maize), mainly in roots exposed 7 mg L(-1) FLT, are a proof of an early differentiation of vascular tissue and a shortening of root elongation zone. Moreover in both plant species exposed to this treatment, the decline of rhizodermis cells and external layers of primary cortex was found and also significant deformation of primordia of lateral roots was recorded.

DNA adducts as biomarkers for oxidative and genotoxic stress from pesticides in crop plants

Plant studies have been carried out to identify the nature and extent of the formation of adducts with DNA bases when treated with pesticide formulations. DNA extracted from crop plants after treatment with pesticide formulations has yielded evidence of adduct formation. The extent of DNA modification has been established by (32)P postlabeling studies. The radiochromatograms from (32)P postlabeling of isolated plant DNA from grapes, bush beans, soybeans, pumpkins, and cucumbers show elevated adduct levels in treated vegetable plants as compared with untreated controls. A number of different adduct spots appear, likely indicating adduct formation with pesticide molecules or their metabolites. The DNA adducts from hexenal and 4-hydroxy-2-nonenal were clearly observed, indicating oxidative stress and lipid peroxidation in the plant.