Cadmium-Induced Cyto- and Genotoxicity are Organ-Dependent in Lettuce

Abstract

Cadmium is a priority pollutant. Its mechanisms and effects within different plant organs remain unclear. Here, cyto-genotoxicity biomarkers were evaluated in roots and leaves after Cd exposure (0, 1, 10, and 50 μM) of the model crop Lactuca sativa L. (cv. "Reine de Mai"). Overall, superoxide dismutase (SOD) and catalase (CAT) activities were stimulated in leaves, where Cd accumulation was lower in comparison to that in roots. In roots, SOD and peroxidase (POX, APX) activities were stimulated. Moreover, in both organs glutathione reductase (GR) was not affected by Cd. Overall, the H(2)O(2) content increased in both organs, while the total antioxidant capacity decreased in leaves and increased in roots with Cd concentrations. In both organs, lipid and protein oxidation rose with consequent increase of membrane permeability. Simultaneously, the comet assay showed that tail moment, tail length, and % tail DNA were maximum for 1 μM. For 10 μM, shorter tails were found suggesting induced Cd-DNA adducts that lead to DNA-DNA/DNA-protein cross-links, and/or formation of longer DNA fragments, and/or impairment of DNA repair mechanisms, while at 50 μM, nucleoids sensitivity to the technique was evident. This result was consistent with the maximum micronuclei frequency found for the 10 μM Cd dose in roots, suggesting that the surviving cells in this organ had an increase of mitotic catastrophe and that DNA repair systems for blocking cell cycle were dysfunctional. In lower Cd concentrations, root cells might have developed strategies to repair damaged DNA by blocking the cell cycle at specific checkpoints, thus avoiding mitotic catastrophe. Roots at 1 μM showed a cell cycle blockage trend at the G(2) checkpoint, while those at higher concentrations presented S phase delay. We finally discuss a general model of Cd-organ interaction covering these cyto- and genotoxic effects and the potential use of this cultivar in phytoremediation strategies.

Phenylalanine ammonia-lyase activity and anthocyanin content in different varieties of lettuce under the cadmium influence

“…However, its significant increase throughout the experiment could obviously testify to developed chelator metabolism and non-plastid pigment active participation in the negative impact of this heavy metal neutralization. The consistently high anthocyanin content during prolonged stressor exposure may also indicate the activation of its synthesis at the time of the previous reserves depletion and is consistent with scientist assertions about the antioxidant role of phenolic compounds in oxidative stress combating [3,9].…”

“…This statement necessitates the research of its toxic effect mechanisms on plant organisms and determination of the physiological and biochemical adaptive changes in plant cell metabolism [3,4].Plants resistance ability to the high environmental concentrations of cadmium depends on: plant genotype, stage of development and metal concentration, and it is achieved by activation of the induced resistance mechanisms [5]. The support of antioxidant status appropriate level and plant cell ability to the cadmium ions chelation are considered as one of the main intracellular mechanisms of plant resistance to toxic cadmium effect [6].…”

“…This statement necessitates the research of its toxic effect mechanisms on plant organisms and determination of the physiological and biochemical adaptive changes in plant cell metabolism [3,4].…”

Bridging a Gap between Cr(VI)-Induced Oxidative Stress and Genotoxicity in Lettuce Organs after a Long-Term Exposure

“…As micronuclei and mitotic aberrations need mitotic cells, only root meristems were used. Root tips were collected and stained with propidium iodide [26]. Slide preparations were observed under 1000x magnification using a fluorescence microscope (Nikon Eclipse 80i; excitation filter of 510-560 nm; barrier filter of 590 nm).…”

“…Slide preparations were observed under 1000x magnification using a fluorescence microscope (Nikon Eclipse 80i; excitation filter of 510-560 nm; barrier filter of 590 nm). To calculate the micronuclei (%MN), 200 cells were scored [26]. For mitotic aberrations, meristematic tissues were collected and stained with 2% acetic orcein.…”