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Identification of photorespiratory glutamate:glyoxylate aminotransferase (GGAT) gene in Arabidopsis.
- Source :
-
The Plant journal : for cell and molecular biology [Plant J] 2003 Mar; Vol. 33 (6), pp. 975-87. - Publication Year :
- 2003
-
Abstract
- In the photorespiratory process, peroxisomal glutamate:glyoxylate aminotransferase (GGAT) catalyzes the reaction of glutamate and glyoxylate to 2-oxoglutarate and glycine. Although GGAT has been assumed to play important roles for the transamination in photorespiratory carbon cycles, the gene encoding GGAT has not been identified. Here, we report that an alanine:2-oxoglutarate aminotransferase (AOAT)-like protein functions as GGAT in peroxisomes. Arabidopsis has four genes encoding AOAT-like proteins and two of them (namely AOAT1 and AOAT2) contain peroxisomal targeting signal 1 (PTS1). The expression analysis of mRNA encoding AOATs and EST information suggested that AOAT1 was the major protein in green leaves. When AOAT1 fused to green fluorescent protein (GFP) was expressed in BY-2 cells, it was found to be localized to peroxisomes depending on PTS1. By screening of Arabidopsis T-DNA insertion lines, an AOAT1 knockout line (aoat1-1) was isolated. The activity of GGAT and alanine:glyoxylate aminotransferase (AGAT) in the above-ground tissues of aoat1-1 was reduced drastically and, AOAT and glutamate:pyruvate aminotransferase (GPAT) activity also decreased. Peroxisomal GGAT was detected in the wild type but not in aoat1-1. The growth rate was repressed in aoat1-1 grown under high irradiation or without sugar, though differences were slight in aoat1-1 grown under low irradiation, high-CO2 (0.3%) or high-sugar (3% sucrose) conditions. These phenotypes resembled those of photorespiration-deficient mutants. Glutamate levels increased and serine levels decreased in aoat1-1 grown in normal air conditions. Based on these results, it was concluded that AOAT1 is targeted to peroxisomes, functions as a photorespiratory GGAT, plays a markedly important role for plant growth and the metabolism of amino acids.
- Subjects :
- Alanine Transaminase chemistry
Alanine Transaminase genetics
Alanine Transaminase metabolism
Amino Acid Sequence
Arabidopsis growth & development
Arabidopsis metabolism
Base Sequence
Carbohydrate Metabolism
Carbon Dioxide metabolism
Cell Respiration
Cloning, Molecular
Gene Deletion
Gene Expression Regulation, Plant
Genes, Plant genetics
Glutamic Acid metabolism
Glyoxylates metabolism
Light
Molecular Sequence Data
Peroxisomes enzymology
Photosynthesis
Photosynthetic Reaction Center Complex Proteins genetics
Photosynthetic Reaction Center Complex Proteins metabolism
Protein Sorting Signals physiology
Sequence Alignment
Transaminases metabolism
Arabidopsis enzymology
Arabidopsis genetics
Transaminases genetics
Subjects
Details
- Language :
- English
- ISSN :
- 0960-7412
- Volume :
- 33
- Issue :
- 6
- Database :
- MEDLINE
- Journal :
- The Plant journal : for cell and molecular biology
- Publication Type :
- Academic Journal
- Accession number :
- 12631323
- Full Text :
- https://doi.org/10.1046/j.1365-313x.2003.01688.x