Protoplasts prepared from tobacco (Nicotiana tabacum L., cultivar BY-2) suspension cells have similar morphological characteristics to those in animal cells. The hallmarks of apoptosis such as condensation and periphe...Protoplasts prepared from tobacco (Nicotiana tabacum L., cultivar BY-2) suspension cells have similar morphological characteristics to those in animal cells. The hallmarks of apoptosis such as condensation and peripheral distribution of nuclei, TUNEL positive reaction, and DNA ladders were observed when tobacco protoplasts were treated with the hydroxyl radical generating system (1.0 mmol/L FeSO4/0.5 mmol/L H2O2). In animals, the loss of transmembrane potential (DeltaPsi(m)) and the exposure of phospholipid phosphatidylserine (PS) are believed to be the main apoptosis events. To test whether these significant processes take place in plants, flow cytometry was used to detect annexin V binding and changes in DeltaPsi(m). Results showed that the PS turned out from inner membrane and DeltaPsi(m) gradually decreased during the apoptosis. All these apoptotic characteristics proved that hydroxyl radicals can cause typical programmed cell death (PCD) in tobacco protoplasts and this design can be served as an effective experiment system to explore the mechanism of plant apoptosis.展开更多
Programmed cell death plays an important role in maintaining homeostasis during animal development, and has been conserved in animals as different as nematodes and humans. Recent studies of Drosophila have provided va...Programmed cell death plays an important role in maintaining homeostasis during animal development, and has been conserved in animals as different as nematodes and humans. Recent studies of Drosophila have provided valuable information toward our understanding of genetic regulation of death. Different signals trigger the novel death regulators rpr, hid, and grim, that utilize the evolutionarily conserved iap and ark genes to modulate caspase function. Subsequent removal of dying cells also appears to be accomplished by conserved mechanisms. The similarity between Drosophila and human in cell death signaling pathways illustrate the promise of fruit mes as a model system to elucidate the mechanisms underlying regulation of programmed cell death.展开更多
Somatic cell nuclear transfer （SCNT） and parthenogenesis are alternative forms of reproduction and development, building new life cycles on differentiated somatic cell nuclei and duplicated maternal chromatin, respe...Somatic cell nuclear transfer （SCNT） and parthenogenesis are alternative forms of reproduction and development, building new life cycles on differentiated somatic cell nuclei and duplicated maternal chromatin, respectively. In the preceding paper （Sun F, et al., Cell Res 2007; 17：117-134.）, we showed that an ＂erase-and-rebuild＂ strategy is used in normal development to transform the maternal gene expression profile to a zygotic one. Here, we investigate if the same strategy also applies to SCNT and parthenogenesis. The relationship between chromatin and chromatin factors （CFs） during SCNT and parthenogenesis was examined using immunochemical and GFP-fusion protein assays. Results from these studies indicated that soon after nuclear transfer, a majority of CFs dissociated from somatic nuclei and were redistributed to the cytoplasm of the egg. The erasure process in oogenesis is recaptured during the initial phase in SCNT. Most CFs entered pseudo-pronuclei shortly after their formation. In parthenogenesis, all parthenogenotes underwent normal oogenesis, and thus had removed most CFs from chromosomes before the initiation of development. The CFs were subsequently re-associated with female pronuclei in time and sequence similar to that in fertilized embryos. Based on these data, we conclude that the ＂erase-and-rebuild＂ process observed in normal development also occurs in SCNT and in parthenogenesis, albeit in altered fashions. The process is responsible for transcription reprogramming in these procedures. The ＂erase＂ process in SCNT is compressed and the efficiency is compromised, which likely contribute to the developmental defects often observed in nuclear transfer （nt） embryos. Furthermore, results from this study indicated that the cytoplasm of an egg contains most, if not all, essential components for assembling the zygotic program and can assemble them onto appropriate diploid chromatin of distinct origins.展开更多
文摘Protoplasts prepared from tobacco (Nicotiana tabacum L., cultivar BY-2) suspension cells have similar morphological characteristics to those in animal cells. The hallmarks of apoptosis such as condensation and peripheral distribution of nuclei, TUNEL positive reaction, and DNA ladders were observed when tobacco protoplasts were treated with the hydroxyl radical generating system (1.0 mmol/L FeSO4/0.5 mmol/L H2O2). In animals, the loss of transmembrane potential (DeltaPsi(m)) and the exposure of phospholipid phosphatidylserine (PS) are believed to be the main apoptosis events. To test whether these significant processes take place in plants, flow cytometry was used to detect annexin V binding and changes in DeltaPsi(m). Results showed that the PS turned out from inner membrane and DeltaPsi(m) gradually decreased during the apoptosis. All these apoptotic characteristics proved that hydroxyl radicals can cause typical programmed cell death (PCD) in tobacco protoplasts and this design can be served as an effective experiment system to explore the mechanism of plant apoptosis.
基金the Baehrecke laboratory for helpful discussions and comments on this manuscript. Work on this subject has been supported by NR
文摘Programmed cell death plays an important role in maintaining homeostasis during animal development, and has been conserved in animals as different as nematodes and humans. Recent studies of Drosophila have provided valuable information toward our understanding of genetic regulation of death. Different signals trigger the novel death regulators rpr, hid, and grim, that utilize the evolutionarily conserved iap and ark genes to modulate caspase function. Subsequent removal of dying cells also appears to be accomplished by conserved mechanisms. The similarity between Drosophila and human in cell death signaling pathways illustrate the promise of fruit mes as a model system to elucidate the mechanisms underlying regulation of programmed cell death.
文摘Somatic cell nuclear transfer （SCNT） and parthenogenesis are alternative forms of reproduction and development, building new life cycles on differentiated somatic cell nuclei and duplicated maternal chromatin, respectively. In the preceding paper （Sun F, et al., Cell Res 2007; 17：117-134.）, we showed that an ＂erase-and-rebuild＂ strategy is used in normal development to transform the maternal gene expression profile to a zygotic one. Here, we investigate if the same strategy also applies to SCNT and parthenogenesis. The relationship between chromatin and chromatin factors （CFs） during SCNT and parthenogenesis was examined using immunochemical and GFP-fusion protein assays. Results from these studies indicated that soon after nuclear transfer, a majority of CFs dissociated from somatic nuclei and were redistributed to the cytoplasm of the egg. The erasure process in oogenesis is recaptured during the initial phase in SCNT. Most CFs entered pseudo-pronuclei shortly after their formation. In parthenogenesis, all parthenogenotes underwent normal oogenesis, and thus had removed most CFs from chromosomes before the initiation of development. The CFs were subsequently re-associated with female pronuclei in time and sequence similar to that in fertilized embryos. Based on these data, we conclude that the ＂erase-and-rebuild＂ process observed in normal development also occurs in SCNT and in parthenogenesis, albeit in altered fashions. The process is responsible for transcription reprogramming in these procedures. The ＂erase＂ process in SCNT is compressed and the efficiency is compromised, which likely contribute to the developmental defects often observed in nuclear transfer （nt） embryos. Furthermore, results from this study indicated that the cytoplasm of an egg contains most, if not all, essential components for assembling the zygotic program and can assemble them onto appropriate diploid chromatin of distinct origins.
