title: The GA2 locus of Arabidopsis thaliana encodes ent-kaurene synthase of gibberellin biosynthesis.
abstract: The ga2 mutant of Arabidopsis thaliana is a gibberellin-deficient dwarf. Previous biochemical studies have suggested that the ga2 mutant is impaired in the conversion of copalyl diphosphate to ent-kaurene, which is catalyzed by ent-kaurene synthase (KS). Overexpression of the previously isolated KS cDNA from pumpkin (Cucurbita maxima) (CmKS) in the ga2 mutant was able to complement the mutant phenotype. A genomic clone coding for KS, AtKS, was isolated from A. thaliana using CmKS cDNA as a heterologous probe. The corresponding A. thaliana cDNA was isolated and expressed in Escherichia coli as a fusion protein. The fusion protein showed enzymatic activity that converted [3H]copalyl diphosphate to [3H]ent-kaurene. The recombinant AtKS protein derived from the ga2-1 mutant is truncated by 14 kD at the C-terminal end and does not contain significant KS activity in vitro. Sequence analysis revealed that a C-2099 to T base substitution, which converts Gln-678 codon to a stop codon, is present in the AtKS cDNA from the ga2-1 mutant. Taken together, our results show that the GA2 locus encodes KS.
authors.affiliation: Frontier Research Program, The Institute of Physical and Chemical Reasearch (RIKEN), hirosawa, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Yamaguchi
authors.forename: T p
authors.initials: Tp
authors.lastname: Sun
authors.forename: H
authors.initials: H
authors.lastname: Kawaide
authors.forename: Y
authors.initials: Y
authors.lastname: Kamiya
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000737:chemistry / Q000235:genetics*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D015152:Blotting, Northern; D015139:Blotting, Southern; D003001:Cloning, Molecular; D018076:DNA, Complementary; D004926:Escherichia coli / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D005875:Gibberellins / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid
chemical_list: D018076:DNA, Complementary; D005875:Gibberellins; D019883:Alkyl and Aryl Transferases; C105712:ent-kaurene synthetase B