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

Summary. 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. Correspondence and reprints: School of Pharmaceutical Sciences, Peking University, Beijing 100083, People’s Republic of China.