PMID- 16407450
OWN - NLM
STAT- MEDLINE
DCOM- 20060524
LR  - 20231213
IS  - 0032-0889 (Print)
IS  - 1532-2548 (Electronic)
IS  - 0032-0889 (Linking)
VI  - 140
IP  - 2
DP  - 2006 Feb
TI  - Glutamine synthetase-glutamate synthase pathway and glutamate dehydrogenase play 
      distinct roles in the sink-source nitrogen cycle in tobacco.
PG  - 444-56
AB  - Glutamate (Glu) metabolism and amino acid translocation were investigated in the 
      young and old leaves of tobacco (Nicotiana tabacum L. cv Xanthi) using 
      [15N]ammonium and [2-15N]Glu tracers. Regardless of leaf age, [15N]ammonium 
      assimilation occurred via glutamine synthetase (GS; EC 6.1.1.3) and Glu synthase 
      (ferredoxin [Fd]-GOGAT; EC 1.4.7.1; NADH-GOGAT; EC 1.4.1.14), both in the light 
      and darkness, and it did not depend on Glu dehydrogenase (GDH; EC 1.4.1.2). The 
      [15N]ammonium and ammonium accumulation patterns support the role of GDH in the 
      deamination of [2-15N]Glu to provide 2-oxoglutarate and [15N]ammonium. In the 
      dark, excess [15N]ammonium was incorporated into asparagine that served as an 
      additional detoxification molecule. The constant Glu levels in the phloem sap 
      suggested that Glu was continuously synthesized and supplied into the phloem 
      regardless of leaf age. Further study using transgenic tobacco lines, harboring 
      the promoter of the GLU1 gene (encoding Arabidopsis [Arabidopsis thaliana] 
      Fd-GOGAT) fused to a GUS reporter gene, revealed that the expression of Fd-GOGAT 
      remained higher in young leaves compared to old leaves, and higher in the veins 
      compared to the mesophyll. Confocal laser-scanning microscopy localized the 
      Fd-GOGAT protein to the phloem companion cells-sieve element complex in the leaf 
      veins. The results are consistent with a role of Fd-GOGAT in supplying Glu for 
      the synthesis and transport of amino acids. Taken together, the data provide 
      evidence that the GS-GOGAT pathway and GDH play distinct roles in the source-sink 
      nitrogen cycle of tobacco leaves.
FAU - Masclaux-Daubresse, Celine
AU  - Masclaux-Daubresse C
AD  - Unite de Nutrition Azotee des Plantes, Institut National de la Recherche 
      Agronomique, 78026 Versailles cedex, France.
FAU - Reisdorf-Cren, Michele
AU  - Reisdorf-Cren M
FAU - Pageau, Karine
AU  - Pageau K
FAU - Lelandais, Maud
AU  - Lelandais M
FAU - Grandjean, Olivier
AU  - Grandjean O
FAU - Kronenberger, Joceline
AU  - Kronenberger J
FAU - Valadier, Marie-Helene
AU  - Valadier MH
FAU - Feraud, Magali
AU  - Feraud M
FAU - Jouglet, Tiphaine
AU  - Jouglet T
FAU - Suzuki, Akira
AU  - Suzuki A
LA  - eng
SI  - GENBANK/U39287
SI  - GENBANK/U39288
SI  - GENBANK/Y09667
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20060111
PL  - United States
TA  - Plant Physiol
JT  - Plant physiology
JID - 0401224
RN  - 0 (Amides)
RN  - 0 (Plant Proteins)
RN  - 0 (Quaternary Ammonium Compounds)
RN  - 0 (Recombinant Fusion Proteins)
RN  - 3KX376GY7L (Glutamic Acid)
RN  - 87299V3Q9W (Azaserine)
RN  - EC 1.4.1.13 (Glutamate Synthase)
RN  - EC 1.4.1.2 (Glutamate Dehydrogenase)
RN  - EC 6.3.1.2 (Glutamate-Ammonia Ligase)
RN  - N762921K75 (Nitrogen)
SB  - IM
MH  - Amides/metabolism
MH  - Arabidopsis/genetics
MH  - Azaserine/pharmacology
MH  - Base Sequence
MH  - Genes, Reporter
MH  - Glutamate Dehydrogenase/*physiology
MH  - Glutamate Synthase/analysis/*metabolism
MH  - Glutamate-Ammonia Ligase/*metabolism
MH  - Glutamic Acid/metabolism/pharmacology
MH  - Kinetics
MH  - Light
MH  - Microscopy, Confocal
MH  - Models, Biological
MH  - Molecular Sequence Data
MH  - Nitrogen/*metabolism
MH  - Plant Leaves/cytology/drug effects/enzymology
MH  - Plant Proteins/*metabolism
MH  - Plants, Genetically Modified/metabolism
MH  - Quaternary Ammonium Compounds/metabolism
MH  - Recombinant Fusion Proteins/analysis/metabolism
MH  - Nicotiana/cytology/drug effects/*enzymology
PMC - PMC1361315
EDAT- 2006/01/13 09:00
MHDA- 2006/05/25 09:00
PMCR- 2007/02/01
CRDT- 2006/01/13 09:00
PHST- 2006/01/13 09:00 [pubmed]
PHST- 2006/05/25 09:00 [medline]
PHST- 2006/01/13 09:00 [entrez]
PHST- 2007/02/01 00:00 [pmc-release]
AID - pp.105.071910 [pii]
AID - 071910 [pii]
AID - 10.1104/pp.105.071910 [doi]
PST - ppublish
SO  - Plant Physiol. 2006 Feb;140(2):444-56. doi: 10.1104/pp.105.071910. Epub 2006 Jan 
      11.