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Title: Radiotracer computer modeling evidence that phospho-base methylation is the main route of choline synthesis in tobacco

Abstract

Among flowering plants, the synthesis of choline (Cho) from ethanolamine (EA) can potentially occur via three parallel, interconnected pathways involving methylation of free bases, phospho-bases, or phosphatidyl-bases. The authors investigated which pathways operate in tobacco (Nicotiana tabacum L.) because previous work has shown that the endogenous Cho supply limits accumulation of glycine betaine in transgenic tobacco plants engineered to convert Cho to glycine betaine. The kinetics of metabolite labeling were monitored in leaf discs supplied with [{sup 33}P]phospho-EA,[{sup 33}P]phospho-monomethylethanolamine, or [{sup 14}C]formate, and the data were subjected to computer modeling. Because partial hydrolysis of phospho-bases occurred in the apoplast, modeling of phospho-base metabolism required consideration of the re-entry of [{sup 33}P]phosphate into the network. Modeling of [{sup 14}C]formate metabolism required consideration of the labeling of the EA and methyl moieties of Cho. Results supported the following conclusions: (a) The first methylation step occurs solely at the phospho-base level; (b) the second and third methylations occur mainly (83%--92% and 65%--85%, respectively) at the phospho-base level, with the remainder occurring at the phosphatidyl-base level; and (c) free Cho originates predominantly from phosphatidylcholine rather than from phospho-Cho. This study illustrates how computer modeling of radiotracer data, in conjunction with information on chemical poolmore » sizes, can provide a coherent, quantitative picture of fluxes within a complex metabolic network.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Univ. of Florida, Gainesville, FL (US)
OSTI Identifier:
20062532
Resource Type:
Journal Article
Journal Name:
Plant Physiology (Bethesda)
Additional Journal Information:
Journal Volume: 123; Journal Issue: 1; Other Information: PBD: May 2000; Journal ID: ISSN 0032-0889
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; BIOLOGICAL PATHWAYS; CHOLINE; BIOSYNTHESIS; METHYLATION; COMPUTERIZED SIMULATION; NICOTIANA; RADIOASSAY

Citation Formats

McNeil, S.D., Nuccio, M.L., Rhodes, D., Shachar-Hill, Y., and Hanson, A.D. Radiotracer computer modeling evidence that phospho-base methylation is the main route of choline synthesis in tobacco. United States: N. p., 2000. Web. doi:10.1104/pp.123.1.371.
McNeil, S.D., Nuccio, M.L., Rhodes, D., Shachar-Hill, Y., & Hanson, A.D. Radiotracer computer modeling evidence that phospho-base methylation is the main route of choline synthesis in tobacco. United States. doi:10.1104/pp.123.1.371.
McNeil, S.D., Nuccio, M.L., Rhodes, D., Shachar-Hill, Y., and Hanson, A.D. Mon . "Radiotracer computer modeling evidence that phospho-base methylation is the main route of choline synthesis in tobacco". United States. doi:10.1104/pp.123.1.371.
@article{osti_20062532,
title = {Radiotracer computer modeling evidence that phospho-base methylation is the main route of choline synthesis in tobacco},
author = {McNeil, S.D. and Nuccio, M.L. and Rhodes, D. and Shachar-Hill, Y. and Hanson, A.D.},
abstractNote = {Among flowering plants, the synthesis of choline (Cho) from ethanolamine (EA) can potentially occur via three parallel, interconnected pathways involving methylation of free bases, phospho-bases, or phosphatidyl-bases. The authors investigated which pathways operate in tobacco (Nicotiana tabacum L.) because previous work has shown that the endogenous Cho supply limits accumulation of glycine betaine in transgenic tobacco plants engineered to convert Cho to glycine betaine. The kinetics of metabolite labeling were monitored in leaf discs supplied with [{sup 33}P]phospho-EA,[{sup 33}P]phospho-monomethylethanolamine, or [{sup 14}C]formate, and the data were subjected to computer modeling. Because partial hydrolysis of phospho-bases occurred in the apoplast, modeling of phospho-base metabolism required consideration of the re-entry of [{sup 33}P]phosphate into the network. Modeling of [{sup 14}C]formate metabolism required consideration of the labeling of the EA and methyl moieties of Cho. Results supported the following conclusions: (a) The first methylation step occurs solely at the phospho-base level; (b) the second and third methylations occur mainly (83%--92% and 65%--85%, respectively) at the phospho-base level, with the remainder occurring at the phosphatidyl-base level; and (c) free Cho originates predominantly from phosphatidylcholine rather than from phospho-Cho. This study illustrates how computer modeling of radiotracer data, in conjunction with information on chemical pool sizes, can provide a coherent, quantitative picture of fluxes within a complex metabolic network.},
doi = {10.1104/pp.123.1.371},
journal = {Plant Physiology (Bethesda)},
issn = {0032-0889},
number = 1,
volume = 123,
place = {United States},
year = {2000},
month = {5}
}