Article Figures & Data
Figures
- Fig. 1.
A model of the general mechanism of three PCDs in plants. Cells integrate various combinations of survival and death signals to decide whether to die and subsequently how the corpse will be managed. This acquired program of death (and corpse management) begins well before cells die. How the cell corpse is managed is a function of the profile of vacuole hydrolases (and toxins) that are loaded into the vacuole and these profiles are established by the original set of signals. Death is triggered and two events are shared among most plant cell deaths: calcium flux and vacuole collapse. Collapse of the vacuole marks the beginning of corpse management. The different profiles of hydrolases loaded into the vacuole determine the manifestation of death. For tracheary elements, the protoplasm but not secondary cell walls are autolyzed. During the formation of lysigenous aerenchyma, the entire corpse is removed, whereas the corpse from the hypersensitive response is left to be crushed by expanding tissues. Not shown is death and corpse management for senescing cells which shares all these features. However, many obvious signs of cell disassembly occur before vacuole disruption in senescent cells. This skeletal model is intended to serve as a unifying theory of many, but not all, PCDs in plants and represents those features of PCD that are in common. It acknowledges the fact that many of the cytoplasmic changes that are occurring during the “preparation to die” stage differ between programs and that these changes are an integral part of the manifestation of death (corpse management). It is expected that more complex models that include the multiple signal pathways and feedback regulation will be overlaid on the model shown. With this in mind, senescence, for which much more detail of its signal transduction and cytoplasmic disassembly is known, could be integrated into the three PCDs shown above as well.
