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Progression of programmed cell death in tobacco BY‐2 cells is delineated by specific changes in de novo and salvage synthesis of purine nucleotides
Author(s) -
Stasolla Claudio,
Loukanitalia,
Yeung Edward C.,
Thorpe Trevor A.
Publication year - 2005
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.2005.00461.x
Subject(s) - de novo synthesis , nucleotide , purine , adenine phosphoribosyltransferase , purine metabolism , nucleotide salvage , biochemistry , programmed cell death , adenosine , chemistry , hydrogen peroxide , inosine , biology , enzyme , apoptosis , gene
Alterations in the pattern of purine nucleotide synthesis and degradation 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 purine nucleotides was estimated by following the metabolic fate of the [8‐ 14 C]5‐aminoimidazole‐4‐carboxamide‐1‐β‐ d ‐ribofuranoside (AICAR), the salvage synthesis was investigated using [8‐ 14 C]adenine and adenosine, and the degradation pathway was studied by following the incorporation of [8‐ 14 C]inosine. The results indicated that specific changes in purine metabolism occurred during the death programme of tobacco cells. During the early phases of PCD, increases in the salvage activity of adenine and adenosine were observed, and these were related to the high activity of the two major salvage enzymes: adenine phosphoribosyltransferase (APRT) and adenosine kinase (ARK). During the following stages, a large fraction of purine nucleotide was also produced through the de novo pathway, suggesting a tight regulation between salvage and de novo synthesis. These changes were strictly associated with PCD, as they did not occur if NO or hydrogen peroxide was increased individually, or if actinomycin, which inhibits the death programme, was added to the medium in the presence of NO and hydrogen peroxide. These changes in purine nucleotide synthesis represent an early metabolic switch which may be needed to ensure the proper execution of all the high‐energy demand processes characteristic of the death programme.