High levels of the cytokinin BAP suppress programmed cell death in hybrid tobacco cells (Nicotiana suaveolens*N. tabacum) expressing hybrid lethality

In Nicotiana suaveolens × N. tabacum hybrid cells incubated with high levels (0.8, 4.0 or 20 μM) of BAP at 28°C, the percentage of dead cells and extent of nuclear fragmentation were suppressed and some cultured cells remained green compared with those incubated with a standard level (0.04 μM) of BAP. Though DNA ladders were detected in all hybrid cells incubated at 28°C, positive signals for TUNEL assays were detected less frequently in hybrid cells incubated with high levels of BAP than in those incubated with a standard level of BAP. The localized accumulation of formazan, indicating production of reactive oxygen species, in hybrid cells with high levels of BAP was less than that in hybrid cells with a standard level of BAP. These results suggest that high levels of BAP suppress programmed cell death in hybrid lethality.