Effect of herbicides on the polymerization of the microtubule and induction of micronuclei in Helianthus maximiliani protoplasts
BINSFELD, PEDRO C., PETERS, JOSÉ A. and SCHNABL, HEIDE
Abstract : In order to verify the kinetics of microtubule depolymerization and dynamics of micronuclei induction, two anti-mitotic herbicides, Amiprophos-methyl (APM) and Oryzalin (ORY), were added to dividing cells of Helianthus maximiliani. The addition of both herbicides to actively dividing cells resulted in a high number of cells with micronuclei through modification of mitosis. Single chromosomes and groups of 2 or more chromosomes were scattered over the cytoplasm. After 2-3 h of herbicide application, microtubules were depolymerized and the metaphase chromosomes changed directly into micronuclei, without centromere division and chromatid separation. The most efficient concentrations were 20 µM ORY and 60 µM APM when incubated for 36 and 48 h, respectively. When the treatment duration was increased, the frequency of cells with deformed micronuclei as well as cell death increased. The presence of citochalasina-B (CB) (20 µM) after 24 h of herbicide application increased the frequency of micronucleation and stabilization of the micronuclei in the cells significantly. The control of microtubules using anti-mitotic toxins provides an efficient tool for micronuclei induction as well as representing an elegant method for partial genome transfer.
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