The root-specific glutamate decarboxylase (GAD1) is essential for sustaining GABA levels in Arabidopsis.
In plants, as in most eukaryotes, glutamate decarboxylase catalyses the synthesis of GABA. The Arabidopsis genome contains five glutamate decarboxylase genes and one of these genes (glutamate decarboxylase1; i.e. GAD1 ) is expressed specifically in roots. By isolating and analyzing three gad1 T-DNA insertion alleles, derived from two ecotypes, we investigated the potential role of GAD1 in GABA production. We also analyzed a promoter region of the GAD1 gene and show that it confers root-specific expression when fused to reporter genes. Phenotypic analysis of the gad1 insertion mutants revealed that GABA levels in roots were drastically reduced compared with those in the wild type. The roots of the wild type contained about sevenfold more GABA than roots of the mutants. Disruption of the GAD1 gene also prevented the accumulation of GABA in roots in response to heat stress. Our results show that the root-specific calcium/calmodulin-regulated GAD1 plays a major role in GABA synthesis in plants under normal growth conditions and in response to stress.
Bouché
Nicolas
N
Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Service de Bioénergétique, Gif-sur-Yvette, France.
Fait
Aaron
A
Zik
Moriyah
M
Fromm
Hillel
H
D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D015152:Blotting, Northern; D015153:Blotting, Western; D002851:Chromatography, High Pressure Liquid; D004269:DNA, Bacterial / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism; D005968:Glutamate Decarboxylase / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D016254:Mutagenesis, Insertional; D009154:Mutation; D018517:Plant Roots / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D004269:DNA, Bacterial; D011993:Recombinant Fusion Proteins; C036483:T-DNA; D049452:Green Fluorescent Proteins; D005680:gamma-Aminobutyric Acid; D005966:Glucuronidase; D005968:Glutamate Decarboxylase