Biochemical background and compartmentalized functions of cytosolic glutamine synthetase for active ammonium assimilation in rice roots

Keiki Ishiyama, Eri Inoue, Mayumi Tabuchi, Tomoyuki Yamaya, Hideki Takahashi

研究成果: Article査読

102 被引用数 (Scopus)

抄録

Rice plants in paddy fields prefer to utilize ammonium as a major nitrogen source. Glutamine synthetase (GS) serves for assimilation of ammonium in rice root, and ameliorates the toxic effect of ammonium excess. Among the three isoenzymes of the cytosolic GS1 gene family in rice, OsGLN1;1 and OsGLN1;2 were abundantly expressed in roots. Analysis of the purified enzymes showed that OsGLN1;1 and OsGLN1;2 can be classified into high-affinity subtypes with relatively high Vmax values, as compared with the major high-affinity isoenzyme, GLN1;1, in Arabidopsis. Low-affinity forms of GS1 comparable to those in Arabidopsis (GLN1;2 and GLN1;3) were absent in rice roots. The OsGLN1;1 and OsGLN1;2 transcripts showed reciprocal responses to ammonium supply in the surface cell layers of roots. OsGLN1;1 accumulated in dermatogen, epidermis and exodermis under nitrogen-limited condition. By contrast, OsGLN1;2 was abundantly expressed in the same cell layers under nitrogen-sufficient conditions, replenishing the loss of OsGLN1;1 following ammonium treatment. Within the central cylinder of elongating zone, OsGLN1;1 and OsGLN1;2 were both induced by ammonium, which was distinguishable from the response observed in the surface cell layers. The high-capacity Gln synthetic activities of OsGLN1;1 and OsGLN1;2 facilitate active ammonium assimilation in specific cell types in rice roots.

本文言語English
ページ(範囲)1640-1647
ページ数8
ジャーナルPlant and Cell Physiology
45
11
DOI
出版ステータスPublished - 2004 11

ASJC Scopus subject areas

  • 生理学
  • 植物科学
  • 細胞生物学

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