title: Cloning and characterization of a cDNA encoding calcium/calmodulin-dependent glutamate decarboxylase from Scutellaria baicalensis.
abstract: Gamma-aminobutyric acid (GABA), synthesized by glutamate decarboxylase (GAD), plays an important role in plants. To study the molecular mechanism of GAD regulation and to examine the levels of GABA in Scutellaria baicalensis, we isolated cDNA clones (SbGAD1 and 2) encoding GAD from S. baicalensis. The open reading frames of SbGADI and 2 were 1,503 and 1,494 bp long and had 450 and 497 amino acid residues, respectively. Quantitative real-time RT-PCR analysis was performed to show the variation of transcript levels among different organs of S. baicalensis. Transcript levels of SbGAD1 and 2 were highest in the root and flower, respectively. The GABA content of different parts (ranked in descending order) was as follows: leaf > flower > stem > root. We concluded that the expression pattern of SbGAD1 and 2 did not match the accumulation pattern of GABA in different organs. We presume that GABA biosynthesis might be more controlled by SbGAD2 than SbGADI. These data will aid in future studies that seek to understand the mechanisms underlying GABA biosynthesis, an important amino acid that is synthesized by the GAD enzyme. To explain adequately the GABA biosynthesis mechanisms in S. baicalensis, the enzyme activities of SbGAD1 and 2 should be determined in the near future.
authors.affiliation: Department of Crop Science, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 305-764, Korea.
authors.forename: Yeon Bok
authors.initials: YB
authors.lastname: Kim
authors.forename: Md Romij
authors.initials: MR
authors.lastname: Uddin
authors.forename: Do Yeon
authors.initials: DY
authors.lastname: Kwon
authors.forename: Min-Ki
authors.initials: MK
authors.lastname: Lee
authors.forename: Sun-Ju
authors.initials: SJ
authors.lastname: Kim
authors.forename: Chanhui
authors.initials: C
authors.lastname: Lee
authors.forename: Sang Un
authors.initials: SU
authors.lastname: Park
mesh_terms: D001483:Base Sequence; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism; D018076:DNA, Complementary / Q000737:chemistry; D005968:Glutamate Decarboxylase / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D031364:Scutellaria baicalensis / Q000201:enzymology / Q000235:genetics*; D017422:Sequence Analysis, DNA; D005680:gamma-Aminobutyric Acid / Q000096:biosynthesis*
chemical_list: D002147:Calmodulin; D018076:DNA, Complementary; D010940:Plant Proteins; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase; D002118:Calcium