A nucleic acid sequence is provided which encodes a gibberellin 2-oxidase gene which catalyses the 2.beta.-oxidation of a gibberellin molecule to introduce a hydroxyl group at C-2 and further catalyses the oxidation of the hydroxyl group introduced at C-2 to yield the ketone derivative. Such sequences can find application in the preparation of transgenic plants with altered levels of gibberellin 2-oxidase.