Document Detail


Investigating the regulation of one-carbon metabolism in Arabidopsis thaliana.
MedLine Citation:
PMID:  12668769     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Serine (Ser) biosynthesis in C(3) plants can occur via several pathways. One major route involves the tetrahydrofolate (THF)-dependent activities of the glycine decarboxylase complex (GDC, EC 2.1.1.10) and serine hydroxymethyltransferase (SHMT, EC 2.1.2.1) with glycine (Gly) as one-carbon (1-C) source. An alternative THF-dependent pathway involves the C1-THF synthase/SHMT activities with formate as 1-C source. Here, we have investigated aspects of the regulation of these two folate-mediated pathways in Arabidopsis thaliana (L.) Heynh. Columbia using two approaches. Firstly, transgenic plants overexpressing formate dehydrogenase (FDH, EC 1.2.1.2) were used to continue our previous studies on the function of FDH in formate metabolism. The formate pool size was approximately 73 nmol (g FW)(-1) in wild type (WT) Arabidopsis plants; three independent transgenic lines had similar-sized pools of formate. Transgenic plants produced more (13)CO(2) from supplied [(13)C]formate than did WT plants but were not significantly different from WT plants in their synthesis of Ser. We concluded that FDH has no direct role in the regulation of the above two pathways of Ser synthesis; the breakdown of formate to CO(2) by the FDH reaction is the primary and preferred fate of the organic acid in Arabidopsis. The ratio between the GDC/SHMT and C1-THF synthase/SHMT pathways of Ser synthesis from [alpha-(13)C]Gly and [(13)C]formate, respectively, in Arabidopsis shoots was 21 : 1; in roots, 9 : 1. In shoots, therefore, the pathway from formate plays only a small role in Ser synthesis; in the case of roots, results indicated that the 9 : 1 ratio was as a result of greater fluxes of (13)C through both pathways together with a relatively higher contribution from the C1-THF synthase/SHMT route than in shoots. We also examined the synthesis of Ser in a GDC-deficient mutant of Arabidopsis (glyD) where the GDC/SHMT pathway was impaired. Compared with WT, glyD plants accumulated 5-fold more Gly than WT after supplying [alpha-(13)C]Gly for 24 h; the accumulation of Ser from [alpha-(13)C]Gly was reduced by 25% in the same time period. On the other hand, the accumulation of Ser through the C1-THF synthase/SHMT pathway in glyD plants was 2.5-fold greater than that in WT plants. Our experiments confirmed that the GDC/SHMT and C1-THF synthase/SHMT pathways normally operate independently in Arabidopsis plants but that when the primary GDC/SHMT pathway is impaired the alternative C1-THF synthase/SHMT pathway can partially compensate for deficiencies in the synthesis of Ser.
Authors:
Rong Li; Maya Moore; John King
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Plant & cell physiology     Volume:  44     ISSN:  0032-0781     ISO Abbreviation:  Plant Cell Physiol.     Publication Date:  2003 Mar 
Date Detail:
Created Date:  2003-04-01     Completed Date:  2003-07-07     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9430925     Medline TA:  Plant Cell Physiol     Country:  Japan    
Other Details:
Languages:  eng     Pagination:  233-41     Citation Subset:  IM    
Affiliation:
Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, Saskatchewan, S7N 5E2 Canada. lirong@duke.usask.ca
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MeSH Terms
Descriptor/Qualifier:
Aminohydrolases / metabolism
Arabidopsis / enzymology,  genetics,  metabolism*
Carbon / metabolism*
Carbon Dioxide / metabolism
Carbon Isotopes
Formate Dehydrogenases / genetics,  metabolism
Formate-Tetrahydrofolate Ligase / metabolism
Formic Acids / metabolism
Gene Expression Regulation, Enzymologic
Glycine / metabolism
Glycine Hydroxymethyltransferase / metabolism
Homocysteine S-Methyltransferase
Magnetic Resonance Spectroscopy
Methylenetetrahydrofolate Dehydrogenase (NADP) / metabolism
Methyltransferases / metabolism
Multienzyme Complexes / metabolism
Mutation
Plant Shoots / metabolism
Plants, Genetically Modified
Serine / biosynthesis
Chemical
Reg. No./Substance:
0/Carbon Isotopes; 0/Formic Acids; 0/Multienzyme Complexes; 124-38-9/Carbon Dioxide; 56-40-6/Glycine; 56-45-1/Serine; 64-18-6/formic acid; 73699-18-0/formyl-methenyl-methylenetetrahydrofolate synthetase; 7440-44-0/Carbon; EC 1.2.1.2/Formate Dehydrogenases; EC 1.5.1.5/Methylenetetrahydrofolate Dehydrogenase (NADP); EC 2.1.1.-/Methyltransferases; EC 2.1.1.10/Homocysteine S-Methyltransferase; EC 2.1.2.1/Glycine Hydroxymethyltransferase; EC 3.5.4.-/Aminohydrolases; EC 6.3.4.3/Formate-Tetrahydrofolate Ligase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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