Abstract
Glutamate decarboxylase (GAD) catalyzes the conversion of L-glutamate to γ-aminobutyric acid (GABA). Interestingly, the GAD in angiosperm has a calmodulin-binding domain (CaMBD) at the C-terminus, whose enzymatic activity is regulated by a Ca2+/CaM. We have reported that rice has a novel GAD (OsGAD2) that is unable to bind to a CaM (Akama et al, 2001) and OsGAD2ΔC lacking a C-terminal region, over-expressed in E. coli, was Ca2+/CaM independent, surprisingly its enzymatic activity increased five times higher than that of wild-type OsGAD2. We report here production of rice plants where OsGAD2ΔC is over-expressed under the control of the promoter of a rice glutelin gene (GluB-1) to analyze ten transgenic rice lines. Amino acid analysis extracted from these seeds indicated more than ten-fold GABA compared with those of wild-type plants. Western blot analysis with an anti-GAD2 antibody showed high level of the enzyme expression in GABA-accumulated seeds.
