Programmed cell death induces male sterility in Actinidia deliciosa female flowers

The importance of programmed cell death (PCD) during the life cycle of plants is well established, although the underlying molecular mechanisms are still poorly defined. An emerging system for the study of PCD during development in plants is that of sex organ abortion. In this work we investigate the degeneration of microspores in the anthers of Actinidia deliciosa female flowers. The kiwifruit, A. deliciosa, is a dioecious species native to China. Pollen development in female flowers is equivalent to pollen development in the male flowers, until the microspores are released from the tetrads. At this time the first differences appear, and include the condensation and shrinkage of the cytoplasm, blebbing of the plasma membrane and of the nuclear envelope, and condensation of chromatin. However, at the time these events are occurring, all other cellular organelles, including mitochondria, have their structures well preserved. Fragmentation of DNA was detected in situ by the TUNEL procedure, which involves the end labeling of the DNA fragments by terminal deoxynucleotidyl transferase with UTP conjugated to a detectable marker. This assay confirmed the morphological characterization of PCD in this system.