Cadmium toxicity and its relationship with disturbances in the cytoskeleton, cell cycle and chromosome stability
This study aimed to investigate the mode of action of cadmium (Cd) toxicity at cell level, especially at early stages of plant exposure. Tomato seedlings were cultivated in growth media containing from 0.1 to 70 µM CdCl2 for 24 h. Mitotic index, chromosome abnormality, DNA integrity and organization of tubulin-based structures were assessed in root cells. As higher the Cd concentration in the growth media, higher was the DNA damage intensity and the occurrence of chromosomal abnormalities that included chromosome lost, bridges, stickiness, C-metaphase and polyploidy. The profile of chromosomal aberrations also varied with elevated Cd concentration, being observed increases in the frequency of chromosome stickiness. The mitotic index was reduced at the lowest Cd concentration, but such reduction was statistically similar to that detected at the highest concentration, suggesting that mitotic depression is a rapid outcome and, at same time, a Cd-induced effect that is limited at the first 24 h of direct root exposure to this metal. Under exposure to 20 µM CdCl2, heterogenous distribution of the spindle fibers, formation of two spindle complexes in both of the cell poles, absence of centrosome center, polarization of the spindle fibers during cell division, and non-uniform tubulin deposition in microtubule and phragmoplast were noticed. The results indicate that the tubulin-dependent components of cytoskeleton are Cd targets, and the sensitivity of tubulin-based structures to Cd exposure depends on cell cycle phase. Moreover, DNA damage intensity and chromosomal abnormality profile can be employed as markers of Cd toxicity level.
KeywordsComet assay Cytogenotoxicity Heavy metal Solanum lycopersicum L. Stickiness Tubulin
This work was funded in part by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP—Grant number 2009/54676-0 and scholarship number 2013/15217-5) and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES)—Finance Code 001. We also thank the National Council for Scientific and Technological Development—CNPq, Brazil and FAPESP, Brazil, for the fellowship and scholarships, respectively.
DP and FAP designed the experiment. DP and MLN carried out the experiments. MFR performed the statistical analysis of the data. DP, FAP, MLN, MM, MEAC and RAA interpreted the results and wrote the manuscript. FAP and RAA assisted during the research. All authors (except MFR, in memorium) read and approved the final manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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