Arrest of Mitotic Cycle and Induction of Chromosomal Aberrations by Aflatoxin B2 in Root Cells of Vicia faba L.
2000 年 65 巻 2 号 p. 113-122
詳細
2000 年 65 巻 2 号 p. 113-122
Image cytometric measurements demonstrated a dose-dependent effect of aflatoxin B2 (AFB2) treatments on the components of mitotic cell cycle in Vicia faba L. root meristematic cells. The most evident effect appears to be the accumulation of cells in the G0/G1 phase at the expense of other phases of the cycle (S phase, G2 phase, M phase). These results indicate that this toxin acts as an inhibitor of cell cycle progression at the G1 transition point. In addition, a dose-dependent increase in a fraction of cells having <2C DNA and >4C DNA results from the AFB2 treatments. The inhibition of mitotic activity induced by AFB2 treatments is associated with a reduction in seedling growth. Cytological examination of dividing cells revealed an abundance of dose-dependent chromosome abnormalities produced by the applied treatments of AFB2. Chromosomal abnormalities associated with stickiness of chromosomes or due to an action on the mitotic apparatus are the dominant abnormalities induced by this toxin. Some of these abnormalities, particularly chromosome lagging and multipolar ana-telophase configurations, may account for the formation of cells with <the 2C DNA value or more >4C DNA value. However, true clastogenic chromosomal aberrations including chromosome breaks and ring chromosomes at metaphase and chromosomal bridges at ana-telophase were scored in substantial proportion of cells. The induction of whole chromosome breaks at metaphase is congruent with the indication by the cytometric measurements that AFB2 acts on the G, transition point. The capacity of this toxin to induce clastogenic aberrations may be regarded as an indication of its genotoxic potential. This is also indicated by the formation of micronuclei in interphase cells.
