Journal Article

Changes in the Cellular and Subcellular Localization of Glutamine Synthetase and Glutamate Dehydrogenase During Flag Leaf Senescence in Wheat (<i>Triticum aestivum</i> L.)

Thomas Kichey, Jacques Le Gouis, Brigitte Sangwan, Bertrand Hirel and Frédéric Dubois

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 6, pages 964-974
Published in print June 2005 | ISSN: 0032-0781
Published online June 2005 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pci105
Changes in the Cellular and Subcellular Localization of Glutamine Synthetase and Glutamate Dehydrogenase During Flag Leaf Senescence in Wheat (Triticum aestivum L.)

More Like This

Show all results sharing these subjects:

  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

GO

Show Summary Details

Preview

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.

Keywords: Cytosolic glutamine synthetase; Flag leaf; Glutamate dehydrogenase; Immunolocalization; Mestome; Senescence; Wheat; CCs, companion cells; DAF, days after flowering; GDH, glutamate dehydrogenase; GS, glutamine synthetase; GS1, cytosolic GS; GS2, chloroplastic GS; IDH, isocitrate dehydrogenase; MFL, mature flag leaf; N, nitrogen; NUE, nitrogen use efficiency; PAS-NBB, periodic acid–Schiff–naphthol blue–black; Rubisco, ribulose 1,5-bisphosphate carboxylase; SFL, senescing flag leaf

Journal Article.  7239 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

Full text: subscription required

How to subscribe Recommend to my Librarian

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.