Cytogenetic damage in shallot ( Allium cepa) root meristems induced by oil industry "high-density brines"

Genotoxic effects and mitosis aberrations of chromium (VI) on root cells of Vicia faba and its molecular docking analysis

Like other heavy metals, Cr (VI) is a powerful carcinogen and mutagen agent. Its toxic effects on plants are well considered. In order to elucidate its adverse effects, the present work aims to study the mitosis aberrations of Cr (VI) on the Vicia faba root-cells and its molecular docking analysis to understand the genotoxicity mechanisms. In-vivo, Vicia faba plants were exposed to 50 and 100 μM Cr (VI) for 48 h. In-silico, molecular docking and molecular dynamics simulation were used to study the interactions between dichromate and tubulin tyrosine ligase T2R-TTL (PDBID: 5XIW) with reference to Colchicine (microtubule inhibitor). According to our results, Cr (VI) affects growth and cell division and also induces many mitosis aberrations such as chromosome sticking, anaphase/telophase bridges, lagging chromosomes and fragmentation during all phases of mitosis. On the one hand, Cr (VI) reduces mitotic index and promotes micronuclei induction. The in-silico results showed that dichromate establishes very strong bonds at the binding site of the tubulin tyrosine ligase T2R-TTL, with a binding affinity of -5.17 Kcal/Mol and an inhibition constant of 163.59 μM. These interactions are similar to those of colchicine with this protein, so dichromate could be a very potent inhibitor of this protein's activity. TTL plays a fundamental role in the tyrosination/detyrosination of tubulin, which is crucial to the regulation of the microtubule cytoskeleton. Its inhibition leads to the appearance of many morphogenic abnormalities such as mitosis aberrations. In conclusion, our data confirm the highest genotoxicity effects of Cr (VI) on Vicia faba root-cells.

Toxicogenetic of tebuconazole based fungicide through Lactuca sativa bioassays

The rampant use of pesticides can cause serious environmental problems. They can be contaminating surface water and groundwater, affecting the surrounding micro and macro biota. In this sense, this work aimed to evaluate the effects of a tebuconazole-based fungicide through endpoints accessed in Lactuca sativa bioassays. Germinated-seeds with roots upon 2 mm were treated with a fungicide containing Tebuconazole (TBZ) as active compound. The final concentration of TBZ in the tested solutions were 0.025 (C1); 0.05 (C2); 0.1 (C3); 0.2 (C4) and 0.4 g/L (C5). L. sativa roots were exposed for 24 h to these solutions and Petri dishes containing the treated seeds were kept in incubation chamber at 24 °C. Two positive controls (PC,) the herbicide trifluralin (0.84 mg/L) and Methanesulfonate (4 ×10-4 mol/L), were applied. Distilled water was negative control (NC). The following endpoints were analyzed: root growth (RG), cytogenotoxic potential by cell cycle analysis, induction of DNA damage through TUNEL and comet assays. The obtained data were submitted to one-way variance analysis (ANOVA) and then to Tukey or Kruskal Wallis (P < 0.05) tests. The concentrations (C1, C2, C4 and C5) affected negatively the RG of L. sativa, in comparison with the NC. The mitotic index was reduced by 25% from NC to C1 and in the rest of treatments it did not present significant modifications. However, from C3 to C5 great amount of chromosome alterations were observed, in comparison with the NC. TBZ-based fungicide also induced DNA fragmentation as measured by TUNEL and comet assays. Thus, TBZ-based fungicide in some concentrations can have phytotoxic, cytotoxic and genotoxic effects in roots and meristematic cells of L. sativa.

Searching an auxinic herbicide to use as positive control in toxicity assays

Due to rising concerns for environmental and human health, many toxic compounds, such as auxin-based herbicides, have been tested in relation their toxicity effect. Especially cyto- and phytotoxic assays have been performed on a number monocot and eudicot plant species. In these approaches the toxicity level of the auxin is compared to a positive control - usually a commercial compound with known effects and chemical similarity to the target compound. However, many target compounds still lack an indication of an adequate positive control. Here, we evaluate the phytotoxic and cytotoxic effect of the auxins 2,4-dichlorophenoxyacetic acid, dicamba, and picloram in order test their potential use as positive controls. All tested auxinic herbicides showed clastogenic and aneugenic effect mechanisms. The results indicate 2,4-dichlorophenoxyacetic acid as the most phyto- and cytotoxic in the discontinuous method in Lactuca sativa L. and Allium cepa L., and also in the continuous method in A. cepa. Thus, we suggest 2,4-dichlorophenoxyacetic acid as a positive control for future mutagenesis studies involving new auxins. For studies with L. sativa in continuous method, we recommend the auxin picloram as positive control as this one was the only one which allowed the development of roots.

Effects of the herbicide trifluralin in the initial development of Piptadenia gonoacantha (Fabales: Fabaceae)

Trifluralin, a pre-emergent herbicide, is widely used in Brazil in the weed grass management in restoration areas. The objective was to evaluate the tolerance of Piptadenia gonoacantha to trifluralin. The treatments had three trifluralin doses (445, 890, and 1335 g a.i. ha^-1), applied in pre-sowing, as well as the control, without herbicide. Visual intoxication, seed germination, survival rate, emergence speed index (EMI), mean germination period, seedling height, and diameter, micromorphometric parameters of plant roots collected at 60 d after sowing, root length (RL) and volume, leaf area (LA), leaf numbers, root and shoot dry matter, and fluorescence of chlorophyll a at 30, 45, and 60 d after sowing were analyzed. Visual intoxication values above 50% were observed only with 1335 g a.i. ha^-1. The herbicide did not affect seed germination, EMI, average germination period, seedling height, and diameter, root micromorphometric parameters, length, dry matter or root volume, and chlorophyll a fluorescence. The dose 1335 g a.i. ha^-1 caused a reduction of 41.5% in survival, 50.3% in the LA, 36.7% in the number of leaves (LN), and 59.8% in the aerial dry mass of seedlings. The trifluralin presents potential for restoration programs of degraded areas with this forest species.

An insight into the cytotoxicity, genotoxicity, and mutagenicity of smoked cigarette butt leachate by using Allium cepa as test system

Smoked cigarette butt (SCB) discharged in the environment became an issue of unknown consequences for plants. Thus, we aim at assessing the impact of water containing SBC leachate on the meristem cells of Allium cepa roots. We defined the following experimental groups: negative control (water), positive control (cyclophosphamide); water with SCB leachate at environmental concentration (1.9 μg/L of nicotine) (EC1× group) and water with SCB leachate concentration 1000 times higher than EC1 (EC1000× group). Mitotic index, total number of abnormal cells, index of abnormal cells per mitotic/phase, relative growth index, and inhibition index were calculated after 48 exposure hours. Root meristems were used to prepare slides in order to investigate chromosomal and nuclear abnormalities. According to our data, plants exposed to SCB leachate presented low relative growth index, high inhibition index, large number of abnormal cells, and high abnormality frequency at metaphase/anaphase. The exposed A. cepa recorded a wide variety of abnormalities such as diagonal metaphase/anaphase, metaphase/anaphase presenting chromosome fragments, binucleated cells, displaced nucleus, chromosome bridges, micronuclei, necrotic cells, stick metaphase, chromosome adherence, notched nucleus, among other cell disturbances. The chemicals in the SBC leachate had aneugenic and clastogenic effect on the genetic material of the tested plants, either when they acted individually, synergistically, or additively. Thus, our study is a pioneer in reporting that the mere disposal of cigarette butts in the environment can have cytotoxic, genotoxic, and mutagenic effects on plants.

Synthesis of Novel Glycerol-Derived 1,2,3-Triazoles and Evaluation of Their Fungicide, Phytotoxic and Cytotoxic Activities

The synthesis of a series of 1,2,3-triazoles using glycerol as starting material is described. The key step in the preparation of these triazolic derivatives is the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC), also known as click reaction, between 4-(azidomethyl)-2,2-dimethyl-1,3-dioxolane (3) and different terminal alkynes. The eight prepared derivatives were evaluated with regard to their fungicide, phytotoxic and cytotoxic activities. The fungicidal activity was assessed in vitro against Colletotrichum gloeosporioides, the causative agent of papaya anthracnose. It was found that the compounds 1-(1-((2,2-dimethyl-1,3-dioxolan-4-yl)methyl)-1H-1,2,3-triazol-4-yl)-cyclo-hexanol (4g) and 2-(1-((2,2-dimethyl-1,3-dioxolan-4-yl)methyl)-1H-1,2,3-triazol-4-yl)propan-2-ol (4h) demonstrated high efficiency in controlling C. gloeosporioides when compared to the commercial fungicide tebuconazole. The triazoles did not present any phytotoxic effect when evaluated against Lactuca sativa. However, five derivatives were mitodepressive, inducing cell death detected by the presence of condensed nuclei and acted as aneugenic agents in the cell cycle of L. sativa. It is believed that glycerol derivatives bearing 1,2,3-triazole functionalities may represent a promising scaffold to be explored for the development of new agents to control C. gloeosporioides.

Genotoxicity evaluation of environmental pollutants using analysis of nucleolar alterations

Nucleolar alterations resulting from the action of either chemical or physical agents can serve as important genotoxicity biomarkers. In this study, the efficiency of AgNOR banding technique to identify the presence of nucleoli in micronucleus and assess nucleolar alterations in aberrant cells of Allium cepa was evaluated. Seeds of this plant were exposed to both water samples from a river that receives untreated urban effluent and to the trifluralin herbicide (0.84 mg/L concentration), both analyzed in two different seasons (summer and winter seasons). Samples induced significant frequencies of chromosomal and nuclear aberrations and micronuclei, as observed in cells submitted to conventional chromosomal staining. The herbicide caused a significant increase in the number of nucleoli and micronuclei, interpreted as due to the elimination of excessive nucleolar material resulting from polyploidization. The use of the AgNOR technique enabled the identification of both the presence of the nucleolus in some micronuclei and the nucleolar organizer region (NOR) behavior of aberrant cells. The NOR-banding technique showed to be an efficient tool for studying the genotoxic effects caused by a xenobiotics and a complex environmental sample.

Mutagenicity of two herbicides widely used on soybean crops by the Allium cepa test

This study evaluated the mutagenic effects of two herbicides: Clorimurom Nortox(®) and Imazaquim Ultra Nortox(®) widely used on soybean crops in Brazil. As a test system, Allium cepa assay was used, which analyzes the frequency of micronuclei (MN), chromosomal aberrations (CA) and the mitotic index (MI). Four concentrations of each herbicide (50, 75, 100 and 125 %) were tested in triplicate using distilled water (negative control) and methyl methanesulfonate (positive control) as controls. Three experimental repetitions were realized. Clorimurom Nortox(®) showed a significantly lower MI than the negative control for the concentrations of 75, 100 and 125 %, but the CA was significantly increased at all concentrations. There was no recovery for CA or MI. The 125 % concentration of Imazaquim Ultra Nortox(®) was cytotoxic and also exerted an effect on the other parameters. The concentration of 100 % showed a statistically increased MN and there was no recovery, while the 75 % concentration significantly affected CA, with recovery observed. The two herbicides showed mutagenic damage in Allium cepa cells, which implies a careful handling of these products, to minimize the risk of human and environmental contamination.

Pb-inhibited mitotic activity in onion roots involves DNA damage and disruption of oxidative metabolism

Plant responses to abiotic stress significantly affect the development of cells, tissues and organs. However, no studies correlating Pb-induced mitotic inhibition and DNA damage and the alterations in redox homeostasis during root division per se were found in the literature. Therefore, an experiment was conducted to evaluate the impact of Pb on mitotic activity and the associated changes in the oxidative metabolism in onion roots. The cytotoxic effect of Pb on cell division was assessed in the root meristems of Allium cepa (onion). The mitotic index (MI) was calculated and chromosomal abnormalities were sought. Pb-treatment induced a dose-dependent decrease in MI in the onion root tips and caused mitotic abnormalities such as distorted metaphase, fragments, sticky chromosomes, laggards, vagrant chromosomes and bridges. Single Cell Gel Electrophoresis was also performed to evaluate Pb induced genotoxicity. It was accompanied by altered oxidative metabolism in the onion root tips suggesting the interference of Pb with the redox homeostasis during cell division. There was a higher accumulation of malondialdehyde, conjugated dienes and hydrogen peroxide, and a significant increase in the activities of superoxide dismutases, ascorbate peroxidases, guaiacol peroxidases and glutathione reductases in Pb-treated onion roots, whereas catalases activity exhibited a decreasing pattern upon Pb exposure. The study concludes that Pb-induced cytotoxicity and genotoxicity in the onion roots is mediated through ROS and is also tightly linked to the cell cycle. The exposure to higher concentrations arrested cell cycle leading to cell death, whereas different repair responses are generated at lower concentrations, thereby allowing the cell to complete the cell cycle.

The effects of the anthocyanin-rich extract from red cabbage leaves on Allium cepa L. root tip cell ultrastructure

The effect of exogenously applied 250 μM anthocyanin-rich (ATH-rich) extract from red cabbage leaves on the ultrastructure of Allium cepa root meristematic cells was investigated. The tested extract slightly affected mitochondria, endoplasmic reticulum (ER), Golgi apparatus and vacuoles. In the presence of ATH, 62% of mitochondria converted to condensed type. In addition swollen, circular ER cisternae were sporadically observed. In the ATH-treated roots, one third of Golgi structures was characterized by the reduced number of vesicles. Moreover in 54% of vacuoles, the electron-dense granular and circular material appeared. Additionally, in the cytoplasm, the presence of numerous multivesicular bodies (MVB) was noticed. The observed ultrastructural modifications of mitochondria, and presumably also ER, probably resulted from the ability of an ATH to affect mitochondrial respiratory activity. The other changes in A. cepa root meristematic cell ultrastructure were connected with the transport of exogenously applied ATH into vacuoles. It seems that they are transported from the plasmolemma to the vacuole by multivesicular bodies (MVB), and there trapped by anthocyanic vacuolar inclusions (AVIs). However, none of the observed ultrastructural changes seemed to disturb cell functions, therefore the ATH-rich extract from red cabbage leaves may be regarded as cell-friendly and can be safely used as a detoxifying agent against heavy metal poisoning, as it is more and more often postulated.

Testing of the mutagenicity and genotoxicity of metolcarb by using both Ames/Salmonella and Allium test

Mutagenic and genotoxic effects of metolcarb were investigated by both bacterial reverse mutation assay in Salmonella typhimurium TA97, TA98, TA100 and TA102 strains with or without metabolic activation system (S9) and Allium cepa root meristematic cells, respectively. Metolcarb was dissolved in DMSO in Ames/Salmonella test system. 0.1, 1 and 10 microg/plate doses of metolcarb were found to be mutagenic S. typhimurium TA98 without S9. In Allium root growth inhibition test, EC50 value was determined 200 ppm and 0.5xEC50, EC50 and 2xEC50 concentrations of metolcarb were introduced to onion tuber roots and distilled water used as a negative control. Mitotic index (MI), increased in all concentrations compared to control at each exposure time. While disturbed anaphase-telophase, chromosome laggards, stickiness and bridges were observed in anaphase-telophase cells, pro-metaphase, C-mitosis, polyploidy, binuclear cells and disturbed nucleus were observed in other cells. The results were also analyzed statistically by using SPSS for Windows, Mann-Whitney test and Duncan's multiple range tests were performed respectively.

Micronucleus and chromosome aberrations induced in onion (Allium cepa) by a petroleum refinery effluent and by river water that receives this effluent

In this study, micronucleus (MN) and chromosome aberration (CA) tests in Allium cepa (onion) were carried out in order to make a preliminary characterization of the water quality of the Atibaia River in an area that is under the influence of petroleum refinery and also to evaluate the effectiveness of the treatments used by the refinery. For these evaluations, seeds of A. cepa were germinated in waters collected in five different sites related with the refinery in ultra-pure water (negative control) and in methyl methanesulfonate solution (positive control). According to our results, we can suggest that even after the treatments (physicochemical, biological and stabilization pond) the final refinery effluent could induce chromosome aberrations and micronucleus in meristematic cells of A. cepa and that the discharge of the petroleum refinery effluents in the Atibaia River can interfere in the quality of this river.

Origin of nuclear and chromosomal alterations derived from the action of an aneugenic agent--Trifluralin herbicide

Trifluralin is a herbicide capable of interfering in mitotic cell division due to either microtubule depolymerization or alteration in the concentration of calcium ions within the cell. The aim of this study was to investigate the effects of trifluralin in Allium cepa meristematic cells, evaluating the induction mechanisms of the chromosomal and nuclear aberrations. In this study, A. cepa root tips were submitted for 24h treatment to several concentrations of this herbicide and 48 h recovery post-treatment. The results showed that some concentrations of trifluralin can lead to a mitotic index inhibition, besides inducing chromosomal and nuclear alterations throughout the mitotic cycle. Some of the alterations found seem to be resulting from the herbicide action in different phases and in more than one consecutive cell cycle.