shk1-D, a dwarf Arabidopsis mutant caused by activation of the CYP72C1 gene, has altered brassinosteroid levels

• Published in: The Plant journal : for cell and molecular biology Vol. 42; no. 1; pp. 13 - 22
• Main Authors: Takahashi, N, Nakazawa, M, Shibata, K, Yokota, T, Ishikawa, A, Suzuki, K, Kawashima, M, Ichikawa, T, Shimada, H, Matsui, M
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.04.2005; Blackwell Science; Blackwell Publishing Ltd
• Subjects: 6-deoxotyphasterol; 6-deoxyocastasterone; activation tagging; Amino Acid Sequence; amino acid sequences; Arabidopsis; Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis - metabolism; Arabidopsis - physiology; Arabidopsis Proteins - genetics; Arabidopsis thaliana; BAS1; Biological and medical sciences; brassinosteroid; Brassinosteroids; castasterone; Chemical agents; Cholestanols - pharmacology; CYP72C1; cytochrome P-450; Cytochrome P-450 Enzyme System - genetics; Dose-Response Relationship, Drug; dwarf; dwarf cultivars; dwarfing; Flowers & plants; Fundamental and applied biological sciences. Psychology; gene activation; Gene expression; Gene Expression Regulation, Plant - drug effects; Gene Expression Regulation, Plant - physiology; gene overexpression; Hypocotyl - drug effects; Hypocotyl - growth & development; hypocotyls; Light; Molecular Sequence Data; Mutation; nucleotide sequences; oxygenases; P450; Phenotype; Plant physiology and development; plant proteins; Plants, Genetically Modified; Steroids; Steroids, Heterocyclic - pharmacology; Time Factors; transgenic plants; Vegetative apparatus, growth and morphogenesis. Senescence; CYP72C1; Seeds; BAS1; Homeostasis; Inactivation; Genetic determinism; Arabidopsis thaliana; Brassinosteroid; Hypocotyl; Cruciferae; Dicotyledones; Angiospermae; Development; Plant growth substance; Spermatophyta; P450; dwarf; Mutation; Petiole; activation tagging
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313X.2005.02357.x

Brassinosteroids (BRs) are plant steroidal hormones that regulate plant growth and development. An Arabidopsis dwarf mutant, shrink1-D (shk1-D), was isolated and the phenotype was shown to be caused by activation of the CYP72C1 gene. CYP72C1 is a member of the cytochrome P450 monooxygenase gene family similar to BAS1/CYP734A1 that regulates BR inactivation. shk1-D has short hypocotyls in both light and dark, and short petioles and siliques. The seeds are also shortened along the longitudinal axis indicating CYP72C1 controls cell elongation. The expression of CPD, TCH4 and BAS1 were altered in CYP72C1 overexpression transgenic lines and endogenous levels of castasterone, 6-deoxocastasterone and 6-deoxotyphasterol were also altered. Unlike BAS1/CYP734A1 the expression of CYP72C1 was not changed by application of exogenous brassinolide. We propose that CYP72C1 controls BR homeostasis by modulating the concentration of BRs.