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Glutamate Dehydrogenase of Tobacco Is Mainly Induced in the Cytosol of Phloem Companion Cells When Ammonia Is Provided Either Externally or Released during Photorespiration
- Source :
- Plant Physiology, Plant Physiology, American Society of Plant Biologists, 2004, 136 (4), pp.4308-4317. ⟨10.1104/pp.104.047548⟩
- Publication Year :
- 2004
- Publisher :
- HAL CCSD, 2004.
-
Abstract
- Glutamate (Glu) dehydrogenase (GDH) catalyses the reversible amination of 2-oxoglutarate for the synthesis of Glu using ammonium as a substrate. This enzyme preferentially occurs in the mitochondria of companion cells of a number of plant species grown on nitrate as the sole nitrogen source. For a better understanding of the controversial role of GDH either in ammonium assimilation or in the supply of 2-oxoglutarate (F. Dubois, T. Tercé-Laforgue, M.B. Gonzalez-Moro, M.B. Estavillo, R. Sangwan, A. Gallais, B. Hirel [2003] Plant Physiol Biochem 41: 565–576), we studied the localization of GDH in untransformed tobacco (Nicotiana tabacum) plants grown either on low nitrate or on ammonium and in ferredoxin-dependent Glu synthase antisense plants. Production of GDH and its activity were strongly induced when plants were grown on ammonium as the sole nitrogen source. The induction mainly occurred in highly vascularized organs such as stems and midribs and was likely to be due to accumulation of phloem-translocated ammonium in the sap. GDH induction occurred when ammonia was applied externally to untransformed control plants or resulted from photorespiratory activity in transgenic plants down-regulated for ferredoxin-dependent Glu synthase. GDH was increased in the mitochondria and appeared in the cytosol of companion cells. Taken together, our results suggest that the enzyme plays a dual role in companion cells, either in the mitochondria when mineral nitrogen availability is low or in the cytosol when ammonium concentration increases above a certain threshold.
- Subjects :
- 0106 biological sciences
Light
Nitrogen
Physiology
Nicotiana tabacum
[SDV]Life Sciences [q-bio]
Dehydrogenase
Plant Science
01 natural sciences
03 medical and health sciences
Ammonia
chemistry.chemical_compound
Cytosol
Oxygen Consumption
Glutamate Dehydrogenase
Gene Expression Regulation, Plant
Tobacco
Genetics
Ammonium
ComputingMilieux_MISCELLANEOUS
030304 developmental biology
0303 health sciences
Plant Stems
ATP synthase
biology
Glutamate dehydrogenase
fungi
food and beverages
Plants, Genetically Modified
biology.organism_classification
Plant Leaves
chemistry
Biochemistry
Enzyme Induction
biology.protein
Photorespiration
Phloem
Research Article
010606 plant biology & botany
Subjects
Details
- Language :
- English
- ISSN :
- 00320889 and 15322548
- Database :
- OpenAIRE
- Journal :
- Plant Physiology, Plant Physiology, American Society of Plant Biologists, 2004, 136 (4), pp.4308-4317. ⟨10.1104/pp.104.047548⟩
- Accession number :
- edsair.doi.dedup.....d6e277f68dcdef396b797bb6214f0140