title: Nuclear fragmentation and DNA degradation during programmed cell death in petals of morning glory (Ipomoea nil).
abstract: We studied DNA degradation and nuclear fragmentation during programmed cell death (PCD) in petals of Ipomoea nil (L.) Roth flowers. The DNA degradation, as observed on agarose gels, showed a large increase. Using DAPI, which stains DNA, and flow cytometry for DAPI fluorescence, we found that the number of DNA masses per petal at least doubled. This indicated chromatin fragmentation, either inside or outside the nucleus. Staining with the cationic lipophilic fluoroprobe DiOC6 indicated that each DNA mass had an external membrane. Fluorescence microscopy of the nuclei and DNA masses revealed an initial decrease in diameter together with chromatin condensation. The diameters of these condensed nuclei were about 70% of original. Two populations of nuclear diameter, one with an average diameter about half of the other, were observed at initial stages of nuclear fragmentation. The diameter of the DNA masses then gradually decreased further. The smallest observed DNA masses had a diameter less than 10% of that of the original nucleus. Cycloheximide treatment arrested the cytometrically determined changes in DNA fluorescence, indicating protein synthesis requirement. Ethylene inhibitors (AVG and 1-MCP) had no effect on the cytometrically determined DNA changes, suggesting that these processes are not controlled by endogenous ethylene.
authors.affiliation: Plant Biotechnology Institute, Ibaraki Agricultural Center, 319-0292 Ibaraki, Japan. teyamada@cc.tuat.ac.jp
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Yamada
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Takatsu
authors.forename: Masakazu
authors.initials: M
authors.lastname: Kasumi
authors.forename: Kazuo
authors.initials: K
authors.lastname: Ichimura
authors.forename: Wouter G
authors.initials: WG
authors.lastname: van  Doorn
mesh_terms: D017209:Apoptosis; D003513:Cycloheximide / Q000494:pharmacology; D053938:DNA Fragmentation; D005434:Flow Cytometry; D035264:Flowers / Q000166:cytology; D027741:Ipomoea / Q000166:cytology* / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000096:biosynthesis; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology
chemical_list: D010940:Plant Proteins; D011500:Protein Synthesis Inhibitors; D003513:Cycloheximide