title: Induction of premature mitosis in S-blocked onion cells.
abstract: Onion root-tip cells were blocked at S-phase by treating them with 5-aminouracil (5AU). These cells were then further treated with caffeine/2-aminopurine (Caf/2AP) or a combination of both in the presence of 5AU. These tyrosine kinase inhibitors were able to induce premature mitosis in the S-blocked cells as evident from the breaks and gaps in the metaphase chromosomes and the presence of laggards and fragments in anaphase. Immunofluorescence showed normal spindle formation in these cells. Immunoblotting of cyclin B revealed that the level of cyclin B was slightly higher in the recovered and treated samples than the S-blocked one. The level of p(34)was found to be almost equal in all three samples as expected. We failed to observe any significant difference in the level of p(34)containing phosphorylated tyrosine. Such premature induction of mitosis by the purine derivatives has also been reported in BHK cells. However, those cells failed to progress through mitosis. A comparative analysis indicates that the plant cells and the animal cells, perhaps, follow identical pathway for the initiation of mitosis. The possible causes for differential behaviour in mitotic progression in these cells have been discussed.
authors.affiliation: Centre of Advanced Study in Botany, University of Calcutta, Calcutta-700 019, India.
authors.forename: R
authors.initials: R
authors.lastname: Sen
authors.forename: S
authors.initials: S
authors.lastname: Ghosh
mesh_terms: D015075:2-Aminopurine / Q000494:pharmacology; D000963:Antimetabolites / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002478:Cells, Cultured; D019926:Cyclin B / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D004347:Drug Interactions / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018519:Meristem / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008938:Mitosis / Q000187:drug effects / Q000235:genetics*; D019697:Onions / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010759:Phosphorus Isotopes; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016196:S Phase / Q000187:drug effects / Q000235:genetics*; D008941:Spindle Apparatus / Q000187:drug effects / Q000235:genetics; D014498:Uracil / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D000963:Antimetabolites; D019926:Cyclin B; D004791:Enzyme Inhibitors; D010759:Phosphorus Isotopes; D002110:Caffeine; D015075:2-Aminopurine; D014498:Uracil; D003513:Cycloheximide; D011505:Protein-Tyrosine Kinases; C011166:5-aminouracil