Formation of archegonium chamber is associated with nucellar-cell programmed cell death in Ginkgo biloba

The archegonium chamber in Ginkgo biloba L. is a pathway for spermatozoids swimming towards the archegonium for fertilization. The objective of this study was to elucidate the mechanism of archegonium chamber formation. The terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay and DNA ladder demonstrated that the nucellar cell death, coordinated with the archegonium chamber formation, was a process of programmed cell death. Cytochemical localization of Ca2+ in these nucellar cells was determined by means of in situ precipitation with potassium pyroantimonate and electron microscopic visualization, in order to study the relation between Ca2+ and programmed cell death. The results showed an early uptake of the mitochondrial calcium particles in the nucellar cells undergoing programmed cell death. Together with other dynamic changes in Ca2+ subcellular distribution, this indicates that Ca2+ may play a role in the regulation of mitochondria-mediated programmed events in the nucellar cells.