title: Alterations in pyrimidine nucleotide metabolism as an early signal during the execution of programmed cell death in tobacco BY-2 cells.
abstract: Changes in pyrimidine metabolism were investigated during programmed cell death (PCD) of tobacco BY-2 cells, induced by a simultaneous increase in the endogenous levels of nitric oxide (NO) and hydrogen peroxide. The de novo synthesis of pyrimidine nucleotides was estimated by following the metabolic fate of the (14)C-labelled orotic acid, whereas the rates of salvage and degradation pathways were studied by measuring the respective incorporation of (14)C-labelled uridine and uracil under different treatments. Nucleic acid metabolism was also examined using labelled thymidine as a marker. The results show that specific alterations in the balance of pyrimidine nucleotide synthesis, which include a decreased rate of salvage activity of uracil and uridine and increased salvage activity of thymidine, represent a metabolic switch that establishes proper cellular conditions for the induction of PCD. In particular, a reduction in the utilization of uracil for salvage products occurs very early during PCD, before the appearance of typical cytological features of the death programme, thus representing an early metabolic marker for PCD. These changes are strictly associated with PCD, since they do not occur if NO or hydrogen peroxide are increased individually, or if actinomycin, which inhibits the death programme, is added into the medium in the presence of NO and hydrogen peroxide. The possible roles of these fluctuations in pyrimidine metabolism on the cellular nucleotide pool are discussed in relation to the induction of cell death.
authors.affiliation: Department of Plant Science, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2. stasolla@ms.umanitoba.ca
authors.forename: Claudio
authors.initials: C
authors.lastname: Stasolla
authors.forename: Natalia
authors.initials: N
authors.lastname: Loukanina
authors.forename: Edward C
authors.initials: EC
authors.lastname: Yeung
authors.forename: Trevor A
authors.initials: TA
authors.lastname: Thorpe
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D003609:Dactinomycin / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000378:metabolism; D009569:Nitric Oxide / Q000502:physiology; D009963:Orotic Acid / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D011742:Pyrimidine Nucleotides / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013936:Thymidine / Q000378:metabolism; D013997:Time Factors; D014026:Nicotiana / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D014166:Transferases / Q000378:metabolism; D014498:Uracil / Q000378:metabolism; D014529:Uridine / Q000378:metabolism
chemical_list: D011742:Pyrimidine Nucleotides; D003609:Dactinomycin; D009569:Nitric Oxide; D014498:Uracil; D009963:Orotic Acid; D006861:Hydrogen Peroxide; D014166:Transferases; D017853:Phosphotransferases (Alcohol Group Acceptor); D013936:Thymidine; D014529:Uridine