Enhanced resistance to salt, cold and wound stresses by overproduction of animal cell death suppressors Bcl-xL and Ced-9 in tobacco cells - Their possible contribution through improved function of organella

Overproduction of animal cell death suppressors Bcl-xL and Ced-9 conferred enhanced resistance to UV-B and paraquat treatment in tobacco plants [Mitsuhara et al. (1999) Curr. Biol. 9: 775]. We report here that the progeny could germinate in 0.2 M NaCl or at 10°C under light, while control plants could not. Suspension-cultured Bcl cells resisted NaCl treatment maintaining an active mitochondrial membrane potential for longer than control cells. When intracellular pH was determined by in vivo ³¹P-NMR, immediate cytoplasmic acidification by 0.3 M NaCl treatment in control cells was found to be suppressed in transgenic cells. Monitoring of cytoplasmic and vacuolar pHs in control cells indicated the vacuole was disrupted 40 min after 0.5 M NaCl treatment, while the compartment between the cytoplasm and vacuole was likely to remain intact in Bcl cells for 100 min. Enhanced shoot regeneration from cut leaf pieces and more vigorous rooting from cut stem ends were found in transgenic plants. The Bcl protein was abundant in all subcellular fractions. Based on the results in transgenic plants carrying a mutant bcl-xL gene, Bcl-xL is thought to suppress cell death and enhance the viability of plants in stressful environments by contributing to the maintenance of the homeostasis of organella.