Fig. 2. Entry into mitosis is advanced by Cl-tetracycline-induced CycB2-HA expression. (A) Mitotic indices after release from aphidicolin-induced S phase block in the presence (+) or absence (-) of 0.1 mg/l Cl-tetracycline. (B) Northern blot analysis of tobacco cyclin B1, 1, histone H4, cyclin B2-HA and cnt6 mRNA levels in synchronized cells as in A. (C) Proportion of mitotic microtubule structures [pre-prophase band (PPB), spindle and phragmoplast] in synchronized cells in the same experiment.