Programmed cell death (PCD) of the nucellar cells at the micropylar end is involved in pollen chamber morphogenesis in Ginkgo biloba L. A development-course observation of the morphological changes in the nucellar cel...Programmed cell death (PCD) of the nucellar cells at the micropylar end is involved in pollen chamber morphogenesis in Ginkgo biloba L. A development-course observation of the morphological changes in the nucellar cells undergoing PCD to form pollen chamber was performed. During the PCD, the nucellar cells degraded their cellular components through an orderly progression. Through the vactiolation, the cytosol was engulfed by the enlarging vacuole, leaving out various organelles, which remained morphologically integrated. As the vacuolation continued, the vacuole collapsed with the breakage of the tonoplast and the cytosol disappeared completely. Organelles were subsequently destroyed. Ultimately, nucellar cells digested away all of their cytoplasm, leaving with cell walls. They became collapsed as the nucellus developed. Intracellular membranes were strikingly changed, playing a role in leading to cell death. Some of these noticeable changes were the appearance of multivesicular body, multicycle-like membranes, membrane-bounded bodies containing some organelles, tonoplast rupture and numerous vesicles. The dehiscence of the apical epidermis, resulting in the opening, appeared to have followed two different pathways with one involving a specific epidermal cell autolysis and the other by detachment from middle lamella of two neighboring epidermal cells without cell autolysis. The specific epidermal cells had been dead prior to the dehiscence of the apical epidermis, which marked the sites of the dehiscence followed. In view of the changes in the cellular morphology, a process of nucellar cell PCD in the course of the pollen chamber formation was demonstrated.展开更多
Sphinganine or dihydrosphingosine （d18：0, DHS）, one of the most abundant free sphingoid Long Chain Base （LCB） in plants, has been recently shown to induce both cytosolic and nuclear calcium transient increases an...Sphinganine or dihydrosphingosine （d18：0, DHS）, one of the most abundant free sphingoid Long Chain Base （LCB） in plants, has been recently shown to induce both cytosolic and nuclear calcium transient increases and a correlated Programmed Cell Death （PCD） in tobacco BY-2 cells. In this study, in order to get deeper insight into the LCB signaling pathway leading to cell death, the putative role of Reactive Oxygen Species （ROS） has been investigated. We show that DHS triggers a rapid dose-dependent production of H2O2 that is blocked by diphenyleniodonium （DPI）, indicating the involvement of NADPH oxidase（s） in the process. In addition, while DPI does not block DHS-induced calcium increases, the ROS production is inhibited by the broad spectrum calcium channel blocker lanthanum （La^3＋）. Therefore, ROS production occurs downstream of DHS-induced Ca^2＋ transients. Interestingly, DHS activates expression of defense-related genes that is inhibited by both La^3＋ and DPI. Since DPI does not prevent DHS-induced cell death, these results strongly indicate that DHS-induced H2O2 production is not implicated in PCD mechanisms but rather would be associated to basal cell defense mechanisms.展开更多
The spatial and temporal distributions of programmed cell death (PCD) in developing central nervous system (CNS) of human fetuses ranging from 12 to 39 weeks of gestation were investigated using techniques of flow cyt...The spatial and temporal distributions of programmed cell death (PCD) in developing central nervous system (CNS) of human fetuses ranging from 12 to 39 weeks of gestation were investigated using techniques of flow cytometry and terminal transferase-mediated nick end labeling (TUNEL). The results showed that PCD did occur in every representative brain region of all fetuses examined in different stages. It was found that there were two peaks of PCD appearing at the 12th and 39th weeks respectively, which suggested that the first peak of apoptosis may be involved in the selective elimination of neurons overproduced during the early development and the second may play an important role in establishing the correct neuronal circuitry.展开更多
The ultracytochemical localization of ATPase in the secondary xylem cells during their differentiation and dedifferentiation in the girdled Eucommia ulmoides Oliv. was carried out using a lead phosphate precipitation ...The ultracytochemical localization of ATPase in the secondary xylem cells during their differentiation and dedifferentiation in the girdled Eucommia ulmoides Oliv. was carried out using a lead phosphate precipitation technique. Throughout the differentiation, which is a typical programmed cell death (PCD) process, ATPase deposits increased in the nucleus but decreased and progressively disappeared in the cell organelles. At the same time, the distribution of ATPase increased in the inner face of the cell wall and pits with cytoplasmic degeneration. The results demonstrated that the PCD was an energy dependent active process and was controlled by nuclear genes. On the other hand, the distribution of ATPase in the intercellular spaces increased with the formation of the new cambium resulted from the dedifferentiation of the secondary xylem cells after girdling. However, ATPase was not found in the nucleus of the dividing cells, suggesting that nutrients were transported through protoplast during differentiation, and through both protoplast and apoplast during dedifferentiation. Thus, the energy required in cell division was provided mainly by intercellular spaces. These findings indicate that the dynamic distribution of ATPase reflected which cell component was actively taking part in the cell metabolism at various stages of the plant development, and its distribution was associated with the physiological state of the cell. Based on the characteristic distributions of ATPase, the critical stage of cell differentiation and the relationship between the critical stage and dedifferentiation were discussed.展开更多
文摘Programmed cell death (PCD) of the nucellar cells at the micropylar end is involved in pollen chamber morphogenesis in Ginkgo biloba L. A development-course observation of the morphological changes in the nucellar cells undergoing PCD to form pollen chamber was performed. During the PCD, the nucellar cells degraded their cellular components through an orderly progression. Through the vactiolation, the cytosol was engulfed by the enlarging vacuole, leaving out various organelles, which remained morphologically integrated. As the vacuolation continued, the vacuole collapsed with the breakage of the tonoplast and the cytosol disappeared completely. Organelles were subsequently destroyed. Ultimately, nucellar cells digested away all of their cytoplasm, leaving with cell walls. They became collapsed as the nucellus developed. Intracellular membranes were strikingly changed, playing a role in leading to cell death. Some of these noticeable changes were the appearance of multivesicular body, multicycle-like membranes, membrane-bounded bodies containing some organelles, tonoplast rupture and numerous vesicles. The dehiscence of the apical epidermis, resulting in the opening, appeared to have followed two different pathways with one involving a specific epidermal cell autolysis and the other by detachment from middle lamella of two neighboring epidermal cells without cell autolysis. The specific epidermal cells had been dead prior to the dehiscence of the apical epidermis, which marked the sites of the dehiscence followed. In view of the changes in the cellular morphology, a process of nucellar cell PCD in the course of the pollen chamber formation was demonstrated.
文摘Sphinganine or dihydrosphingosine （d18：0, DHS）, one of the most abundant free sphingoid Long Chain Base （LCB） in plants, has been recently shown to induce both cytosolic and nuclear calcium transient increases and a correlated Programmed Cell Death （PCD） in tobacco BY-2 cells. In this study, in order to get deeper insight into the LCB signaling pathway leading to cell death, the putative role of Reactive Oxygen Species （ROS） has been investigated. We show that DHS triggers a rapid dose-dependent production of H2O2 that is blocked by diphenyleniodonium （DPI）, indicating the involvement of NADPH oxidase（s） in the process. In addition, while DPI does not block DHS-induced calcium increases, the ROS production is inhibited by the broad spectrum calcium channel blocker lanthanum （La^3＋）. Therefore, ROS production occurs downstream of DHS-induced Ca^2＋ transients. Interestingly, DHS activates expression of defense-related genes that is inhibited by both La^3＋ and DPI. Since DPI does not prevent DHS-induced cell death, these results strongly indicate that DHS-induced H2O2 production is not implicated in PCD mechanisms but rather would be associated to basal cell defense mechanisms.
文摘The spatial and temporal distributions of programmed cell death (PCD) in developing central nervous system (CNS) of human fetuses ranging from 12 to 39 weeks of gestation were investigated using techniques of flow cytometry and terminal transferase-mediated nick end labeling (TUNEL). The results showed that PCD did occur in every representative brain region of all fetuses examined in different stages. It was found that there were two peaks of PCD appearing at the 12th and 39th weeks respectively, which suggested that the first peak of apoptosis may be involved in the selective elimination of neurons overproduced during the early development and the second may play an important role in establishing the correct neuronal circuitry.
文摘The ultracytochemical localization of ATPase in the secondary xylem cells during their differentiation and dedifferentiation in the girdled Eucommia ulmoides Oliv. was carried out using a lead phosphate precipitation technique. Throughout the differentiation, which is a typical programmed cell death (PCD) process, ATPase deposits increased in the nucleus but decreased and progressively disappeared in the cell organelles. At the same time, the distribution of ATPase increased in the inner face of the cell wall and pits with cytoplasmic degeneration. The results demonstrated that the PCD was an energy dependent active process and was controlled by nuclear genes. On the other hand, the distribution of ATPase in the intercellular spaces increased with the formation of the new cambium resulted from the dedifferentiation of the secondary xylem cells after girdling. However, ATPase was not found in the nucleus of the dividing cells, suggesting that nutrients were transported through protoplast during differentiation, and through both protoplast and apoplast during dedifferentiation. Thus, the energy required in cell division was provided mainly by intercellular spaces. These findings indicate that the dynamic distribution of ATPase reflected which cell component was actively taking part in the cell metabolism at various stages of the plant development, and its distribution was associated with the physiological state of the cell. Based on the characteristic distributions of ATPase, the critical stage of cell differentiation and the relationship between the critical stage and dedifferentiation were discussed.
