CYP714B1 and CYP714B2 encode gibberellin 13-oxidases that reduce gibberellin activity in rice

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 110; no. 5; pp. 1947 - 1952
• Main Authors: Magorne, Hiroshi, Nomura, Takahito, Hanada, Atsushi, Takeda-Kamiya, Noriko, Ohnishi, Toshiyuki, Shinma, Yuko, Katsumata, Takumi, Kawaide, Hiroshi, Kamiya, Yuji, Yamaguchi, Shinjiro
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 29.01.2013; National Acad Sciences
• Subjects: Animals; Arabidopsis - genetics; Arabidopsis - metabolism; Biological Sciences; Biosynthesis; Cytochrome P-450 Enzyme System - classification; Cytochrome P-450 Enzyme System - genetics; Cytochrome P-450 Enzyme System - metabolism; Cytochromes; Enzymes; Gene expression; Gene expression regulation; Gene Expression Regulation, Enzymologic - drug effects; Gene Expression Regulation, Plant - drug effects; Gibberellins; Gibberellins - metabolism; Gibberellins - pharmacology; Homeostasis; Hormones; Hydroxylation; Immunoblotting; Internodes; Mixed Function Oxygenases - genetics; Mixed Function Oxygenases - metabolism; Mutation; Oryza - genetics; Oryza - metabolism; Phenotype; Phenotypes; Phylogeny; Plant Growth Regulators - metabolism; Plant Growth Regulators - pharmacology; Plant Proteins - genetics; Plant Proteins - metabolism; Plants; Plants, Genetically Modified; Proteins; Reverse Transcriptase Polymerase Chain Reaction; Rice; Sf9 Cells; Transgenic plants
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1215788110

Bioactive gibberellins (GAs) control many aspects of growth and development in plants. GA ₁ has been the most frequently found bioactive GA in various tissues of flowering plants, but the enzymes responsible for GA ₁ biosynthesis have not been fully elucidated due to the enzymes catalyzing the 13-hydroxylation step not being identified. Because of the lack of mutants defective in this enzyme, biological significance of GA 13-hydroxylation has been unknown. Here, we report that two cytochrome P450 genes, CYP714B1 and CYP714B2 , encode GA 13-oxidase in rice. Transgenic Arabidopsis plants that overexpress CYP714B1 or CYP714B2 show semidwarfism. There was a trend that the levels of 13-OH GAs including GA ₁ were increased in these transgenic plants. Functional analysis using yeast or insect cells shows that recombinant CYP714B1 and CYP714B2 proteins can convert GA ₁₂ into GA ₅₃ (13-OH GA ₁₂) in vitro. Moreover, the levels of 13-OH GAs including GA ₁ were decreased, whereas those of 13-H GAs including GA ₄ (which is more active than GA ₁) were increased, in the rice cyp714b1 cyp714b2 double mutant. These results indicate that CYP714B1 and CYP714B2 play a predominant role in GA 13-hydroxylation in rice. The double mutant plants appear phenotypically normal until heading, but show elongated uppermost internode at the heading stage. Moreover, CYP714B1 and CYP714B2 expression was up-regulated by exogenous application of bioactive GAs. Our results suggest that GA 13-oxidases play a role in fine-tuning plant growth by decreasing GA bioactivity in rice and that they also participate in GA homeostasis.