| Changes in the cellular and subcellular localization of glutamine synthetase and glutamate dehydrogenase during flag leaf senescence in wheat (Triticum aestivum L.). | |
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MedLine Citation:
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PMID: 15840646 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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In order to improve our understanding of the regulation of nitrogen assimilation and recycling in wheat (Triticum aestivum L.), we studied the localization of plastidic (GS2) and cytosolic (GS1) glutamine synthetase isoenzymes and of glutamate dehydrogenase (GDH) during natural senescence of the flag leaf and in the stem. In mature flag leaves, large amounts of GS1 were detected in the connections between the mestome sheath cells and the vascular cells, suggesting an active transfer of nitrogen organic molecules within the vascular system in the mature flag leaf. Parallel to leaf senescence, an increase of a GS1 polypeptide (GS1b) was detected in the mesophyll cytosol of senescing leaves, while the GS protein content represented by another polypetide (GS1a) in the phloem companion cells remained practically constant in both leaves and stems. Both GDH aminating activity and protein content were strongly induced in senescing flag leaves. The induction occurred both in the mitochondria and in the cytosol of phloem companion cells, suggesting that the shift in GDH cellular compartmentation is important during leaf nitrogen remobilization although the metabolic or sensing role of the enzyme remains to be elucidated. Taken together, our results suggest that in wheat, nitrogen assimilation and recycling are compartmentalized between the mesophyll and the vasculature, and are shifted in different cellular compartments within these two tissues during the transition of sink leaves to source leaves. |
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Authors:
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Thomas Kichey; Jacques Le Gouis; Brigitte Sangwan; Bertrand Hirel; Frédéric Dubois |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2005-04-19 |
Journal Detail:
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Title: Plant & cell physiology Volume: 46 ISSN: 0032-0781 ISO Abbreviation: Plant Cell Physiol. Publication Date: 2005 Jun |
Date Detail:
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Created Date: 2005-07-04 Completed Date: 2005-09-14 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 9430925 Medline TA: Plant Cell Physiol Country: Japan |
Other Details:
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Languages: eng Pagination: 964-74 Citation Subset: IM |
Affiliation:
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Laboratoire d'Androgenèse et Biotechnologie Végétale, Université de Picardie Jules Verne, 33, Rue saint-Leu, 80039 Amiens Cedex, France. |
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| MeSH Terms | |
Descriptor/Qualifier:
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Cytosol
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enzymology Glutamate Dehydrogenase / metabolism* Glutamate-Ammonia Ligase / metabolism* Isoenzymes / metabolism Microscopy, Immunoelectron Nitrogen / metabolism Plant Leaves / cytology, enzymology, growth & development Plant Stems / cytology, enzymology, growth & development Plastids / enzymology Subcellular Fractions / enzymology Triticum / cytology, enzymology*, growth & development* |
| Chemical | |
Reg. No./Substance:
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0/Isoenzymes; 7727-37-9/Nitrogen; EC 1.4.1.2/Glutamate Dehydrogenase; EC 6.3.1.2/Glutamate-Ammonia Ligase |
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