Pahs Induced Genotoxicity And Oxidative Stress In Cells Of Plant

Polycyclic aromatic hydrocarbons (PAHs) are a class of POPs that are considered potentially extremely harmful due to their teratogenic, carcinogenic, and mutagenic characteristics. A better understanding of their behaviors in the soil plant system and how they do harm to agricultural products or human health have attracted much attention.In our research mainly focus on the genotoxic effect of PAHs by using the comet assay, combining the MDA content and antioxidant enzyme activities (SOD, POD, CAT),reveal genotoxic effect and oxidative stress of PAHs on plants. At the same time, explore the possible factors which influencing genotoxic effect of PAHs, provide experimental basis for early detection and warning of PAHs pollution in soils. Main novel findings are shown as follows:(1) The DNA damage of Vicia faba root tip cells induced by phenanthrene as a representative polycyclic aromatic hydrocarbon (PAH) was investigated using the comet assay. The comet image was analyzed by software Komet Version 6.0. The Olive Tail Moment (OTM) was found to be the most preferable parameter to evaluate the DNA damages. As observed in the cellular comet assay, the DNA damage of Vicia faba root tip cells enhanced with the increase of phenanthrene concentrations (0～0.6 mg·L-1) in solution. At higher concentration(0.6 mg·L-1), OTM increased by 132.63% compared with the control. An obvious phenanthrene dose-dependent relationship was observed for DNA damage, indicating the phenanthrene induced DNA damages of Vicia faba root tip cell DNA. In addition, DNA damage by 0.1 mg·L-1 phenanthrene was time-dependent and enhanced in 0-12 h and then weakened in 12～24 h. In order to determine the pathways of phenanthrene-induced DNA damage, the direct effects of phenanthrene on Vicia faba root tip cell DNA was assessed with the acellular comet assay. It was found that phenanthrene at 0.05 mg·L-1 (corresponding OTM value 22.27±0.42) induced a significant damage to Vicia faba root tip cell DNA and the DNA damage enhanced with the increase of phenanthrene concentrations (0-0.6 mg·L-1). In solution the acellular comet assay results indicate the potential direct effects of phenanthrene on root-cell DNA of Vicia faba.(2) In order to investigate oxidative stress, DNA damage effects of PAHs on plants and the relationship between PAHs DNA damage effects and oxidative stress, experiment were studied taking phenanthrene, pyrene as representative of PAHs. In order to investigate oxidative stress, the MDA content and antioxidant enzyme activities (SOD, POD, CAT) in Vicia faba were studied under the stress of phenanthrene and pyrene; Meanwhile, the DNA damage effects of phenanthrene and pyrene were evaluated by using the comet assay; In order to investigate the relationship between PAHs DNA damage effects and oxidative stress, Vicia faba were exposed to phenanthrene or pyrene in the presence or absence of the antioxidant Vitamin E. The results indicated that phenanthrene and pyrene can enhance the antioxidant enzymes activities and MDA contents and with increasing concentrations of phenanthrene and pyrene the content of MDA gradually increased. The values of Tail Moment (TM) observed from the comet assay increased from 46.41 (negative control) to 122.04 μ.m (50 mg·kg-1 phenanthrene treatment), increased by 162.96% (P<0.01). The degree of DNA damage enhanced with the increase of pyrene concentrations(0-50 mg·kg-1). It was found that pyrene at 50 mg·kg-1 induced a significant (P<0.01) damage to Vicia faba root tip cell DNA and TM value(110.36 μm) increased by 149.21% compared to the negative control(44.30μm). The results of comet assay suggested that phenanthrene and pyrene induced the DNA damages of Vicia faba root tip cells, and the damages enhanced with the increase of phenanthrene and pyrene concentrations. With the pretreatment of antioxidant vitamin E (2,4 mg·L-1), DNA damages of Vicia faba decreased, which suggested that vitamin E can reduce damages caused by phenanthrene and pyrene. Above all, phenanthrene and pyrene can induce oxidative stress in Vicia faba as well as DNA damages, and DNA damages induced by phenanthrene and pyrene were connected with oxidative stress.(3) Using sand culture and 48 h exposure method detected the genotoxic effect of acenaphthylene, acenaphthene, fluorine, phenanthrene, fluoranthene, pyrene, benz[a]anthraene, benzo[a]pyrene (Under three concentrations-10,30,50 mg·kg-1) on Vicia faba root tip cells. The results indicated that with increasing of benzene rings quantity and molecular weight DNA damages induced by PAHs decreasesed. The result of Pearson correlation analysis among genotoxicity of 8 kinds of PAHs with benzene rings quantity, molecular weight, solubility, octanol-water partition coefficient (Kow) indicated that there was a significant negative correlation (P<0.01) among genotoxicity of 8 kinds of PAHs (Under three concentrations-10,30, 50mg·kg-1) with benzene rings quantity, molecular weight, octanol-water partition coefficient (Kow).