Regulation and Functional Analysis of Glutamine Syntbetase Genes in Legumes

  • S. J. Temple
  • S. Bagga
  • C. Sengupta-Gopalan
Chapter
Part of the Current Plant Science and Biotechnology in Agriculture book series (PSBA, volume 27)

Abstract

Glutamine synthetase (GS) is the key enzyme responsible for the assimilation and reassimilation of ammonia. GS catalyzes the ATP dependent condensation of NH3 with glutamate to produce glutamine. Subsequently, glutamate synthase transfers an amido group of glutamine to ∝-ketoglutarate to produce two molecules of glutamate (Lea et al., 1990). Glutamine is one of the major nitrogen transport compounds in plants and acts as the nitrogen donor for the synthesis of most nitrogenous compounds. GS in plants, is made up of eight subunits, each subunit having a molecular weight of between 38-45kD. The GS isoenzyme localized in the plastid/chloroplast (GS2) functions in the reassimilation of NH3 produced by photorespiration, while the cytosolic isoforms of GS (GS,), depending on the organ/tissue where it is located, assimilates ammonia produced by different physiological processes (McGrath, Corruzzi, 1991). The GS1 in roots, stems and leaves is localized around the vasculature and it is believed to function in generating glutamine for nitrogen transport (Brears et al., 1991). The GS1 in the root vasculature is believed to be involved in the assimilation of ammonia produced by the reduction of nitrate obtained from the soil water. In root nodules, GS1 is localized mostly in the infected cells where it assimilates ammonia produced by the N2-fixing bacteroids.

Keywords

Glutamine Synthetase Alfalfa Plant Primary Translation Product Polypeptide Level Gene Subclass 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© Springer Science+Business Media Dordrecht 1995

Authors and Affiliations

  • S. J. Temple
    • 1
  • S. Bagga
    • 1
  • C. Sengupta-Gopalan
    • 1
  1. 1.Dept. of Agron. & Hort.New Mexico State UniversityLas CrucesUSA

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