Figure 2
Biochemical and molecular characterization of the CPT effect on maize cultured cells. (A) Pattern of DNA fragmentation of maize cultured cells in response to CPT treatments. Maize cells were grown on MS medium supplemented with DMSO (control, 0) or with different concentrations of CPT during 30 days. Afterwards, the cells were frozen in liquid nitrogen and the genomic DNA isolated. The same amount of genomic DNA (4 μg) from each sample was fractionated on 1.5% agarose gel. The sizes of the DNA molecular markers are indicated (kb). (B) Identification of a CPT-induced nuclease in maize cultured cells. Nuclease activity assays were performed with 15 μg of total protein extracted from maize cultured cells incubated with different concentrations of CPT during 30 days. The assays were carried out in the presence of 1 mM CaCl2 and 1 mM MgCl2 in 10 mM Tris–HCl pH 7.5.