cytochrome-c-t and fusicoccin

The phytohormone ethylene is involved in many physiological and developmental processes of plants, as well as in stress responses and in the development of disease resistance. Fusicoccin (FC) is a well-known phytotoxin, that in sycamore (Acer pseudoplatanus L.) cultured cells, induces a set of stress responses, including synthesis of ethylene. In this study, we investigated the possible involvement of ethylene in the FC-induced stress responses of sycamore cells by means of Co(2+), a well-known specific inhibitor of ethylene biosynthesis. Co(2+) inhibited the accumulation of dead cells in the culture, the production of nitric oxide (NO) and of the molecular chaperone Binding Protein (BiP) in the endoplasmic reticulum induced by FC. By contrast, Co(2+) was ineffective on the FC-induced accumulation of cells with fragmented DNA, production of H(2)O(2) and release of cytochrome c from the mitochondrion, and only partially reduced the accumulation of regulative 14-3-3 proteins in the cytosol. In addition, we compared the effect of FC on the above parameters with that of the ethylene-releasing compound ethephon (2-chloroethane phosphonic acid). The results suggest that ethylene is involved in several stress responses induced by FC in sycamore cells, including a form of cell death that does not show apoptotic features and possibly involves NO as a signaling molecule.

Topics: 14-3-3 Proteins; Acer; Cell Death; Cell Nucleus; Cells, Cultured; Cobalt; Culture Media; Cytochromes c; Cytosol; DNA Fragmentation; Ethylenes; Glycosides; Hydrogen Peroxide; Mitochondria; Nitric Oxide; Organophosphorus Compounds; Plant Proteins; Stress, Physiological

Programmed cell death (PCD) plays a vital role in plant development and is involved in defence mechanisms against biotic and abiotic stresses. Different forms of PCD have been described in plants on the basis of the cell organelle first involved. In sycamore (Acer pseudoplatanus L.) cultured cells, the phytotoxin fusicoccin (FC) induces cell death. However, only a fraction of the dead cells shows the typical hallmarks of animal apoptosis, including cell shrinkage, chromatin condensation, DNA fragmentation and release of cytochrome c from the mitochondrion. In this work, we show that the scavenging of nitric oxide (NO), produced in the presence of FC, by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) and rutin inhibits cell death without affecting DNA fragmentation and cytochrome c release. In addition, we show that FC induces a massive depolymerization of actin filaments that is prevented by the NO scavengers. Finally, the addition of actin-depolymerizing drugs induces PCD in control cells and overcomes the inhibiting effect of cPTIO on FC-induced cell death. Vice versa, the addition of actin-stabilizing drugs to FC-treated cells partially inhibits the phytotoxin-induced PCD. These results suggest that besides an apoptotic-like form of PCD involving the release of cytochrome c, FC induces at least another form of cell death, likely mediated by NO and independent of cytochrome c release, and they make it tempting to speculate that changes in actin cytoskeleton are involved in this form of PCD.

Topics: Acer; Actin Cytoskeleton; Actins; Apoptosis; Benzoates; Cell Nucleus; Cells, Cultured; Cytochalasin D; Cytochromes c; Cytoskeleton; Depsipeptides; DNA Fragmentation; Glycosides; Hydrogen Peroxide; Imidazoles; Nitric Oxide; Rutin

Programmed cell death plays a vital role in normal plant development, response to environmental stresses, and defense against pathogen attack. Different types of programmed cell death occur in plants and the involvement of mitochondria is still under investigation. In sycamore (Acer pseudoplatanus L.) cultured cells, the phytotoxin fusicoccin induces cell death that shows apoptotic features, including chromatin condensation, DNA fragmentation, and release of cytochrome c from mitochondria. In this work, we show that cyclosporin A, an inhibitor of the permeability transition pore of animal mitochondria, inhibits the cell death, DNA fragmentation, and cytochrome c release induced by fusicoccin. In addition, we show that fusicoccin induces a change in the shape of mitochondria which is not prevented by cyclosporin A. These results suggest that the release of cytochrome c induced by fusicoccin occurs through a cyclosporin A-sensitive system that is similar to the permeability transition pore of animal mitochondria and they make it tempting to speculate that this release may be involved in the phytotoxin-induced programmed cell death of sycamore cells.

Topics: Acer; Apoptosis; Cells, Cultured; Cyclosporine; Cytochromes c; DNA Cleavage; Glycosides; Hydrogen Peroxide; Mitochondria

Programmed cell death occurs in plants during several developmental processes and during the expression of resistance to pathogen attack (i.e., the hypersensitive response). An unsolved question of plant programmed cell death is whether a unique signaling pathway or different, possibly convergent pathways exist. This problem was addressed in cultured sycamore (Acer pseudoplatanus L.) cells by comparing the effects of fusicoccin, Tunicamycin and Brefeldin A, inducers of programmed cell death with well-defined molecular and cellular targets, on some of the parameters involved in the regulation of this process. In addition to cell death, the inducers are able to stimulate the production of H2O2, the leakage of cytochrome c from mitochondria, the accumulation of cytosolic 14-3-3 proteins, and changes at the endoplasmic reticulum level, such as accumulation of the molecular chaperone binding protein and modifications in the organelle architecture. Interestingly, no additive effect on any of these parameters is observed when fusicoccin is administered in combination with Tunicamycin or Brefeldin A. Thus, these inducers seem to utilize the same or largely coincident pathways to induce programmed cell death and involvement of the endoplasmic reticulum, in addition to that of mitochondria, appears to be a common step.

Topics: 14-3-3 Proteins; Acer; Apoptosis; Arabidopsis Proteins; Blotting, Western; Brefeldin A; Carrier Proteins; Cells, Cultured; Cytochromes c; Cytosol; DNA, Plant; Endoplasmic Reticulum; Glycosides; Hydrogen Peroxide; Plant Proteins; Tunicamycin