|
Plant Physiol, May 2000, Vol. 123, pp. 371-380
Radiotracer and Computer Modeling Evidence that
Phospho-Base Methylation Is the Main Route of Choline Synthesis
in Tobacco1
Scott D.
McNeil,
Michael L.
Nuccio,
David
Rhodes,
Yair
Shachar-Hill, and
Andrew D.
Hanson*
Horticultural Sciences Department, University of Florida,
Gainesville, Florida 32611 (S.D.M., M.L.N., A.D.H.); Center for Plant
Environmental Stress Physiology, Department of Horticulture and
Landscape Architecture, Purdue University, West Lafayette, Indiana
47907 (D.R.); and Department of Chemistry and Biochemistry, New Mexico
State University, Las Cruces, New Mexico 88003 (Y.S.-H.)
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. We 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
[33P]phospho-EA,
[33P]phospho-monomethylethanolamine, or
[14C]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 [33P]phosphate into the network. Modeling
of [14C]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.
1
This work was supported in part by the U.S.
Department of Agriculture National Research Initiative Competitive
Grants Program (grant no. 98-35100-6149 to A.D.H.), by the National
Science Foundation (grant no. IBN-9813999 to A.D.H.), by the
Department of Energy (grant no. DE-FG02-99ER20344 to D.R.), by a
National Institute of Science and Technology grant (to Y.S.-H.), by an
endowment from the C.V. Griffin, Sr. Foundation, and by the Florida
Agricultural Experiment Station. This paper is journal series no.
R-07256.
*
Corresponding author; e-mail adha{at}gnv.ifas.ufl.edu; fax
352-392-6479.
© 2000 American Society of Plant Physiologists
This article has been cited by other articles:
|
|
|
|
 
R. Jost, O. Berkowitz, J. Shaw, and J. Masle
Biochemical Characterization of Two Wheat Phosphoethanolamine N-Methyltransferase Isoforms with Different Sensitivities to Inhibition by Phosphatidic Acid
J. Biol. Chem.,
November 13, 2009;
284(46):
31962 - 31971.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. R. Keogh, P. D. Courtney, A. J. Kinney, and R. E. Dewey
Functional Characterization of Phospholipid N-Methyltransferases from Arabidopsis and Soybean
J. Biol. Chem.,
June 5, 2009;
284(23):
15439 - 15447.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
C. Chen and G. A. Beattie
Pseudomonas syringae BetT Is a Low-Affinity Choline Transporter That Is Responsible for Superior Osmoprotection by Choline over Glycine Betaine
J. Bacteriol.,
April 15, 2008;
190(8):
2717 - 2725.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. L. Jeong, H. Jiang, H.-S. Chen, C.-J. Tsai, and S. A. Harding
Metabolic Profiling of the Sink-to-Source Transition in Developing Leaves of Quaking Aspen
Plant Physiology,
October 1, 2004;
136(2):
3364 - 3375.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. Cruz-Ramirez, J. Lopez-Bucio, G. Ramirez-Pimentel, A. Zurita-Silva, L. Sanchez-Calderon, E. Ramirez-Chavez, E. Gonzalez-Ortega, and L. Herrera-Estrella
The xipotl Mutant of Arabidopsis Reveals a Critical Role for Phospholipid Metabolism in Root System Development and Epidermal Cell Integrity
PLANT CELL,
August 1, 2004;
16(8):
2020 - 2034.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. Boatright, F. Negre, X. Chen, C. M. Kish, B. Wood, G. Peel, I. Orlova, D. Gang, D. Rhodes, and N. Dudareva
Understanding in Vivo Benzenoid Metabolism in Petunia Petal Tissue
Plant Physiology,
August 1, 2004;
135(4):
1993 - 2011.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Z. Mou, X. Wang, Z. Fu, Y. Dai, C. Han, J. Ouyang, F. Bao, Y. Hu, and J. Li
Silencing of Phosphoethanolamine N-Methyltransferase Results in Temperature-Sensitive Male Sterility and Salt Hypersensitivity in Arabidopsis
PLANT CELL,
September 1, 2002;
14(9):
2031 - 2043.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. C. Cushman
Osmoregulation in Plants: Implications for Agriculture
Integr. Comp. Biol.,
August 1, 2001;
41(4):
758 - 769.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. D. McNeil, M. L. Nuccio, M. J. Ziemak, and A. D. Hanson
Enhanced synthesis of choline and glycine betaine in transgenic tobacco plants that overexpress phosphoethanolamine N-methyltransferase
PNAS,
July 24, 2001;
(2001)
171228998.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
C. P. Bolognese and P. McGraw
The Isolation and Characterization in Yeast of a Gene for Arabidopsis S-Adenosylmethionine:Phospho-Ethanolamine N-Methyltransferase
Plant Physiology,
December 1, 2000;
124(4):
1800 - 1813.
[Abstract]
[Full Text]
|
|
|
|
|
|
|
S. D. McNeil, D. Rhodes, B. L. Russell, M. L. Nuccio, Y. Shachar-Hill, and A. D. Hanson
Metabolic Modeling Identifies Key Constraints on an Engineered Glycine Betaine Synthesis Pathway in Tobacco
Plant Physiology,
September 1, 2000;
124(1):
153 - 162.
[Abstract]
[Full Text]
|
|
|
|
|
|
|
D. Rontein, I. Nishida, G. Tashiro, K. Yoshioka, W.-I Wu, D. R. Voelker, G. Basset, and A. D. Hanson
Plants Synthesize Ethanolamine by Direct Decarboxylation of Serine Using a Pyridoxal Phosphate Enzyme
J. Biol. Chem.,
September 14, 2001;
276(38):
35523 - 35529.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. D. McNeil, M. L. Nuccio, M. J. Ziemak, and A. D. Hanson
Enhanced synthesis of choline and glycine betaine in transgenic tobacco plants that overexpress phosphoethanolamine N-methyltransferase
PNAS,
August 14, 2001;
98(17):
10001 - 10005.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
