Changes in nitrogen assimilation, metabolism, and growth in transgenic rice plants expressing a fungal NADP(H)-dependent glutamate dehydrogenase (gdhA)

Tomomi Abiko, Masataka Wakayama, Akira Kawakami, Mitsuhiro Obara, Hiroaki Kisaka, Tetsuya Miwa, Naohiro Aoki, Ryu Ohsugi

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

In plants, glutamine synthetase (GS) is the enzyme that is mainly responsible for the assimilation of ammonium. Conversely, in microorganisms such as bacteria and Ascomycota, NADP(H)-dependent glutamate dehydrogenase (GDH) and GS both have important roles in ammonium assimilation. Here, we report the changes in nitrogen assimilation, metabolism, growth, and grain yield of rice plants caused by an ectopic expression of NADP(H)-GDH (gdhA) from the fungus Aspergillus niger in the cytoplasm. An investigation of the kinetic properties of purified recombinant protein showed that the fungal gdhA had 5.4-10.2 times higher Vmax value and 15.9-43.1 times higher Km value for NH4+, compared with corresponding values for rice cytosolic GS as reported in the literature. These results suggested that the introduction of fungal GDH into rice could modify its ammonium assimilation pathway. We therefore expressed gdhA in the cytoplasm of rice plants. NADP(H)-GDH activities in the gdhA-transgenic lines were markedly higher than those in a control line. Tracer experiments by feeding with 15NH4+ showed that the introduced gdhA, together with the endogenous GS, directly assimilated NH4+ absorbed from the roots. Furthermore, in comparison with the control line, the transgenic lines showed an increase in dry weight and nitrogen content when sufficient nitrogen was present, but did not do so under low-nitrogen conditions. Under field condition, the transgenic line examined showed a significant increase in grain yield in comparison with the control line. These results suggest that the introduction of fungal gdhA into rice plants could lead to better growth and higher grain yield by enhancing the assimilation of ammonium.

Original languageEnglish
Pages (from-to)299-311
Number of pages13
JournalPlanta
Volume232
Issue number2
DOIs
Publication statusPublished - Jul 1 2010
Externally publishedYes

Fingerprint

Glutamate Dehydrogenase (NADP+)
Glutamate Dehydrogenase
glutamate dehydrogenase
Genetically Modified Plants
assimilation (physiology)
Nitrogen
genetically modified organisms
Glutamate-Ammonia Ligase
rice
metabolism
Ammonium Compounds
nitrogen
Growth
glutamate-ammonia ligase
Cytoplasm
grain yield
Ascomycota
Aspergillus niger
cytoplasm
Oryza

All Science Journal Classification (ASJC) codes

  • Genetics
  • Plant Science

Cite this

Changes in nitrogen assimilation, metabolism, and growth in transgenic rice plants expressing a fungal NADP(H)-dependent glutamate dehydrogenase (gdhA). / Abiko, Tomomi; Wakayama, Masataka; Kawakami, Akira; Obara, Mitsuhiro; Kisaka, Hiroaki; Miwa, Tetsuya; Aoki, Naohiro; Ohsugi, Ryu.

In: Planta, Vol. 232, No. 2, 01.07.2010, p. 299-311.

Research output: Contribution to journalArticle

Abiko, Tomomi ; Wakayama, Masataka ; Kawakami, Akira ; Obara, Mitsuhiro ; Kisaka, Hiroaki ; Miwa, Tetsuya ; Aoki, Naohiro ; Ohsugi, Ryu. / Changes in nitrogen assimilation, metabolism, and growth in transgenic rice plants expressing a fungal NADP(H)-dependent glutamate dehydrogenase (gdhA). In: Planta. 2010 ; Vol. 232, No. 2. pp. 299-311.
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AU - Wakayama, Masataka

AU - Kawakami, Akira

AU - Obara, Mitsuhiro

AU - Kisaka, Hiroaki

AU - Miwa, Tetsuya

AU - Aoki, Naohiro

AU - Ohsugi, Ryu

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AB - In plants, glutamine synthetase (GS) is the enzyme that is mainly responsible for the assimilation of ammonium. Conversely, in microorganisms such as bacteria and Ascomycota, NADP(H)-dependent glutamate dehydrogenase (GDH) and GS both have important roles in ammonium assimilation. Here, we report the changes in nitrogen assimilation, metabolism, growth, and grain yield of rice plants caused by an ectopic expression of NADP(H)-GDH (gdhA) from the fungus Aspergillus niger in the cytoplasm. An investigation of the kinetic properties of purified recombinant protein showed that the fungal gdhA had 5.4-10.2 times higher Vmax value and 15.9-43.1 times higher Km value for NH4+, compared with corresponding values for rice cytosolic GS as reported in the literature. These results suggested that the introduction of fungal GDH into rice could modify its ammonium assimilation pathway. We therefore expressed gdhA in the cytoplasm of rice plants. NADP(H)-GDH activities in the gdhA-transgenic lines were markedly higher than those in a control line. Tracer experiments by feeding with 15NH4+ showed that the introduced gdhA, together with the endogenous GS, directly assimilated NH4+ absorbed from the roots. Furthermore, in comparison with the control line, the transgenic lines showed an increase in dry weight and nitrogen content when sufficient nitrogen was present, but did not do so under low-nitrogen conditions. Under field condition, the transgenic line examined showed a significant increase in grain yield in comparison with the control line. These results suggest that the introduction of fungal gdhA into rice plants could lead to better growth and higher grain yield by enhancing the assimilation of ammonium.

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