Mercury genotoxicity in Pisum sativum: cell cycle and DNA damage

• Autor(a) principal: Silva, Raquel Azevedo da
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/7485
• topic: Biologia molecular; Citologia; Ciclo celular; Mercúrio (Metal) - Toxicidade; Toxicologia genética; Mutagénese

Mercury (Hg) is a highly spread environmental contaminant known to cause mutagenesis and clastogenicity in animals. Hg’s deleterious effects in plants, however, are poorly understood and thus it is urgent to evaluate its genotoxicity of this metal. To determine if in vivo exposure to Hg induced genotoxic effects, the following endpoints were evaluated: ploidy level, cell cycle arrest and DNA damage. Pea seeds were germinated in distilled water and grown in modified Hoagland’s medium with increasing concentrations of HgCl2 (0, 1, 10 and 100 μM). After 14 days of exposure, plant growth was recorded and the tissues were harvested for analysis. In general, Hg exposure affected most of the endpoints assayed being that roots were more affected than shoots. Plant growth was substantially impaired in plants exposed to 100 μM. The evaluation of the ploidy level revealed that only the 2C level was observed, for any of the conditions assayed. The cell cycle dynamics of roots presented heterogeneous variations caused by Hg exposure: 1 μM of Hg caused a delay in the transition from S to G2; 10 μM had cytostatic effect at the G0/G1 checkpoint and decrease of cell proliferation index (CPI). At 100 μM, the number of cells analyzed was significantly lower than in any other condition tested but the CPI and cell cycle dynamics of the surviving cells recovered to the value presented by 1 μM roots. DNA damage assessment proved that roots exposed to 100 μM presented severe DNA degradation, nuclear distortions, micronuclei formation and an accentuated decrease in the Mitotic Index. In conclusion, our results demonstrate that Hg severally affected the parameters assessed, causing cell cycle arrest and DNA damage. Moreover, the work presented here is the first report of Hg genotoxicity analysis by Flow Cytometry and Comet Assay in plants.