Analysis of glutamate homeostasis by overexpression of Fd-GOGAT gene in Arabidopsis thaliana

作者：Ishizaki Takashi; Ohsumi Chieko; Totsuka Kazuhiko; Igarashi Daisuke^*

来源：Amino Acids, 2010, 38(3): 943-950.

DOI：10.1007/s00726-009-0303-2

• Arabidopsis
• Fd-GOGAT
• Glutamate synthase
• Photorespiration
• GLU1

Glutamate plays a central role in nitrogen flow and serves as a nitrogen donor for the production of amino acids. In plants, some amino acids work as buffers: during photorespiration, ammonium derived from the conversion of glycine to serine is promptly reassimilated into glutamate by the glutamine synthetase (GS-2)/ferredoxin-dependent glutamate synthase (Fd-GOGAT) cycle. The glutamate concentration is relatively stable compared with those of other amino acids under environmental changes. The few studies dealing with glutamate homeostasis have but all used knockouts or mutants of these enzymes. Here, we generated Fd-GOGAT (GLU1)-overexpressing Arabidopsis plants to analyze changes in the amino acid pool caused by glutamate overproduction under different ammonium conditions controlled by CO(2) concentration, light intensity and nitrate concentration. Under photorespiratory conditions with sufficient ammonium supply, aspartate increased and glutamine and glycine decreased, but glutamate barely changed. Under non-photorespiratory conditions, however, glutamate and most other amino acids increased. These results suggest that the synthesized glutamate is promptly converted into other amino acids, especially aspartate. In addition, ammonium supply by photorespiration does not limit glutamate biosynthesis, but glutamine and glycine are important. This study will contribute to the understanding of glutamate homeostasis in plants.

• 出版日期2010-3