Abstract
Plants respond to pathogenic attack by activating a variety of defense mechanisms including localized programmed cell death (PCD) known as hypersensitive response. Molecular mechanisms for execution of the PCD are largely unknown. We have developed a model system of highly synchronous PCD in tobacco BY-2 cells in which cells recognize a fungal proteinaceous elicitor (Kadota et al., Plant Cell Physiol,. in press). The dead cells were characterized by condensation of the cytoplasm but nuclei did not show morphological changes such as fragmentation. We sequentially observed dynamics of various organelles using fluorescent probes and GFP targeted into specific compartments. Cytoplasmic strands gradually decreased and vacuoles showed dynamic changes during the PCD. Fluorescence of the vacuolar lumen vanished just prior to the PCD, suggesting the change in permeability of the tonoplast. Possible significance of dynamic behavior of the vacuoles during the PCD will be discussed.
