Construction of a cell-free system using extracts from apoptotic plant cells

To study the mechanism of plant apoptosis, a cell-free system has been deve loped using the extracts prepared from tobacco cells that become committed to apoptosis induced by heat shock treatment. Tobacco nuclei have displayed such characteristics of apoptosis as nucleus condensation and formation of apoptotic bodies during incubation in this system. Besides, these morpholo gical changes are accompanied by DNA fragmentation, which is detected by DN A laddering and comet assay. Furthermore, both morphological changes and DN A cleavage are not affected by pepstatin A, leupeptin or EDTA, but are part ly inhibited by iodoacetamide. This profile is consistent with Caspases, wh ich are vital to animal apoptosis, suggesting that cysteine-protease like C aspases may be involved in apoptosis in plants.