Abstract
Hybrid lethality, a mechanism of post-zygotic reproduction, functions as the driving force for speciation in plants, but is a major drawback for wide-cross breeding program. To analyze a role of vacuoles in death of the hybrid, we investigated the cultured cell line (GTH4) of Nicotiana gossei x N. tabacum, which starts to die at 26 C, but does nor at 37 C. Both light and fluorescence microscopic analysis of GTH4 cells indicated that vacuolar collapse plays a central role for execution of the cell death after shifting them from 37 C to 26 C, as evidenced by increases in the number of cells without cytoplasmic strings, acidification of cytoplasm, decomposition of mitochondria and chloroplasts. The activities of VPE(vacuolar processing enzyme)/legumain in the cells increased 6 h after the temperature shift at which time vacuolar collapse proceeds at the highest rate. A role of VPE/legumain will be also discussed.
