Contributions of two cytosolic glutamine synthetase isozymes to ammonium assimilation in Arabidopsis roots

Noriyuki Konishi, Keiki Ishiyama, Marcel Pascal Beier, Eri Inoue, Keiichi Kanno, Tomoyuki Yamaya, Hideki Takahashi, Soichi Kojima

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Glutamine synthetase (GS) catalyzes a reaction that incorporates ammonium into glutamate and yields glutamine in the cytosol and chloroplasts. Although the enzymatic characteristics of the GS1 isozymes are well known, their physiological functions in ammonium assimilation and regulation in roots remain unclear. In this study we show evidence that two cytosolic GS1 isozymes (GLN1;2 and GLN1;3) contribute to ammonium assimilation in Arabidopsis roots. Arabidopsis T-DNA insertion lines for GLN1;2 and GLN1;3 (i.e. gln1;2 and gln1;3 single-mutants), the gln1;2:gln1;3 double-mutant, and the wild-type accession (Col-0) were grown in hydroponic culture with variable concentrations of ammonium to compare their growth, and their content of nitrogen, carbon, ammonium, and amino acids. GLN1;2 and GLN1;3 promoter-dependent green fluorescent protein was observed under conditions with or without ammonium supply. Loss of GLN1;2 caused significant suppression of plant growth and glutamine biosynthesis under ammonium-replete conditions. In contrast, loss of GLN1;3 caused slight defects in growth and Gln biosynthesis that were only visible based on a comparison of the gln1;2 single-and gln1;2:gln1;3 double-mutants. GLN1;2, being the most abundantly expressed GS1 isozyme, markedly increased following ammonium supply and its promoter activity was localized at the cortex and epidermis, while GLN1;3 showed only low expression at the pericycle, suggesting their different physiological contributions to ammonium assimilation in roots. The GLN1;2 promoter-deletion analysis identified regulatory sequences required for controlling ammonium-responsive gene expression of GLN1;2 in Arabidopsis roots. These results shed light on GLN1 isozyme-specific regulatory mechanisms in Arabidopsis that allow adaptation to an ammonium-replete environment.

Original languageEnglish
Pages (from-to)613-625
Number of pages13
JournalJournal of Experimental Botany
Volume68
Issue number3
DOIs
Publication statusPublished - 2017
Externally publishedYes

Fingerprint

Glutamate-Ammonia Ligase
glutamate-ammonia ligase
Ammonium Compounds
Arabidopsis
Isoenzymes
isozymes
assimilation (physiology)
promoter regions
glutamine
mutants
biosynthesis
regulatory sequences
epidermis (plant)
green fluorescent protein
hydroponics
cytosol
glutamates
nitrogen content
cortex
chloroplasts

Keywords

  • Ammonium
  • Arabidopsis
  • Glutamine
  • GS1
  • Nitrogen
  • Root

ASJC Scopus subject areas

  • Physiology
  • Plant Science

Cite this

Konishi, N., Ishiyama, K., Beier, M. P., Inoue, E., Kanno, K., Yamaya, T., ... Kojima, S. (2017). Contributions of two cytosolic glutamine synthetase isozymes to ammonium assimilation in Arabidopsis roots. Journal of Experimental Botany, 68(3), 613-625. https://doi.org/10.1093/jxb/erw454

Contributions of two cytosolic glutamine synthetase isozymes to ammonium assimilation in Arabidopsis roots. / Konishi, Noriyuki; Ishiyama, Keiki; Beier, Marcel Pascal; Inoue, Eri; Kanno, Keiichi; Yamaya, Tomoyuki; Takahashi, Hideki; Kojima, Soichi.

In: Journal of Experimental Botany, Vol. 68, No. 3, 2017, p. 613-625.

Research output: Contribution to journalArticle

Konishi, N, Ishiyama, K, Beier, MP, Inoue, E, Kanno, K, Yamaya, T, Takahashi, H & Kojima, S 2017, 'Contributions of two cytosolic glutamine synthetase isozymes to ammonium assimilation in Arabidopsis roots', Journal of Experimental Botany, vol. 68, no. 3, pp. 613-625. https://doi.org/10.1093/jxb/erw454
Konishi, Noriyuki ; Ishiyama, Keiki ; Beier, Marcel Pascal ; Inoue, Eri ; Kanno, Keiichi ; Yamaya, Tomoyuki ; Takahashi, Hideki ; Kojima, Soichi. / Contributions of two cytosolic glutamine synthetase isozymes to ammonium assimilation in Arabidopsis roots. In: Journal of Experimental Botany. 2017 ; Vol. 68, No. 3. pp. 613-625.
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