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Effect of Inorganic Phosphate on the Biosynthesis of Purine and Pyrimidine Nucleotides in Suspension-Cultured Cells of Catharanthus roseus

HIROSHI ASHIHARA, XIAO-NI LI and TOSHIKO UKAJI
Annals of Botany
Vol. 61, No. 2 (February 1988), pp. 225-232
Published by: Oxford University Press
Stable URL: http://www.jstor.org/stable/42770282
Page Count: 8
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Effect of Inorganic Phosphate on the Biosynthesis of Purine and Pyrimidine Nucleotides in Suspension-Cultured Cells of Catharanthus roseus
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Abstract

The levels of purine and pyrimidine nucleotides in suspension cultures of Catharanthus roseus were determined 24 h after stationary-phase cells were transferred to fresh complete ('+Pi') or phosphatedeficient (–Pi') Murashige-Skoog medium. The levels of ATP, GTP, UTP and CTP were from approx. 3 to 5-fold greater in the cells grown in '+Pi' medium than in the cells grown in '–Pi' medium. The levels of almost all other nucleotides were slightly higher in the cells in '+Pi' medium. The rates of de novo and salvage biosynthesis of purine and pyrimidine nucleotides were estimated from the rates of incorporation of radioactivity from [¹⁴C] formate, [2-¹⁴C] glycine, NaH¹⁴CO₃, [6-¹⁴C] orotate, [8-¹⁴C] adenine, [8-¹⁴C] adenosine, [2-¹⁴C] uracil and [2-¹⁴C] uridine. The results indicated that the activity of both the de novo and the salvage pathway was higher in the cells in '+Pi' medium than in the cells in '–Pi ' medium. The rate of degradation estimated from the rate of release of ¹⁴CO₂ from labelled purines and pyrimidines indicated that degradation of uridine was significantly reduced in the cells in '+Pi' medium, but no significant difference was found in the degradation of adenine, adenosine and uracil. The possible role of Pi in the control of the biosynthesis of nucleotides and in the degradation of uridine is discussed.

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