title: Genetic manipulation of gibberellin metabolism in transgenic rice.
abstract: The 'green revolution' was fueled by the introduction of the semi-dwarf trait into cereal crop cultivars. The semi-dwarf cultivars--which respond abnormally to the plant growth hormone gibberellin (GA)--are more resistant to wind and rain damage and thus yield more grain when fertilized. To generate dwarf rice plants using a biotechnological approach, we modified the level of GA by overproduction of a GA catabolic enzyme, GA 2-oxidase. When the gene encoding GA 2-oxidase, OsGA2ox1, was constitutively expressed by the actin promoter, transgenic rice showed severe dwarfism but failed to set grain because GA is involved in both shoot elongation and reproductive development. In contrast, OsGA2ox1 ectopic expression at the site of bioactive GA synthesis in shoots under the control of the promoter of a GA biosynthesis gene, OsGA3ox2 (D18), resulted in a semi-dwarf phenotype that is normal in flowering and grain development. The stability and inheritance of these traits shows the feasibility of genetic improvement of cereal crops by modulation of GA catabolism and bioactive GA content.
authors.affiliation: Field Production Science Center, The University of Tokyo, 1-1-1 Midoricyo, Nishi-Tokyo 188-0002, Japan. orchardist@fm.a.u-tokyo.ac.jp
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Sakamoto
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Morinaka
authors.forename: Kanako
authors.initials: K
authors.lastname: Ishiyama
authors.forename: Masatomo
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Hironori
authors.initials: H
authors.lastname: Itoh
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Kayano
authors.forename: Shuichi
authors.initials: S
authors.lastname: Iwahori
authors.forename: Makoto
authors.initials: M
authors.lastname: Matsuoka
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tanaka
mesh_terms: D000383:Agriculture / Q000379:methods; D005240:Feasibility Studies; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D024861:Genetic Enhancement / Q000379:methods*; D005875:Gibberellins / Q000235:genetics* / Q000378:metabolism*; D012275:Oryza / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D010641:Phenotype; D030821:Plants, Genetically Modified / Q000254:growth & development / Q000378:metabolism*; D015202:Protein Engineering / Q000379:methods*
chemical_list: D005875:Gibberellins