Brassinosteroids promote root growth in Arabidopsis

• Published in: Plant physiology (Bethesda) 2003-11, Vol.133 (3), p.1261-1271
• Main Authors: Mussig, C, Shin, G.H, Altmann, T
• Format: Article
• Language: English
• Subjects: 1-aminocyclopropane-1-carboxylic acid; 24-epibrassinolide; 24-epicastasterone; Agronomy. Soil science and plant productions; Amino Acids, Cyclic - pharmacology; Arabidopsis - drug effects; Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis thaliana; Auxins; Biological and medical sciences; Biosynthesis; brassinosteroid receptors; Brassinosteroids; Carboxylic acids; Chemical agents; Cholestanols - pharmacology; Development and Hormone Action; Drug Interactions - physiology; Economic plant physiology; ethylene production; Fundamental and applied biological sciences. Psychology; gene expression regulation; Gene Expression Regulation, Developmental - drug effects; Gene Expression Regulation, Plant - drug effects; Genes; gibberellins; Gibberellins - pharmacology; gravitropism; Growth and development; Growth regulators; Indoleacetic Acids - pharmacology; molecular sequence data; mutants; Mutation; nucleotide sequences; Plant growth; Plant growth promoters; Plant growth regulators; Plant Growth Regulators - pharmacology; plant hormones; Plant physiology and development; plant proteins; plant response; Plant roots; Plant Roots - drug effects; Plant Roots - growth & development; Plants; reaction inhibition; receptors; Root growth; Seedlings; signal transduction; Steroids, Heterocyclic - pharmacology; Vegetative apparatus, growth and morphogenesis. Senescence
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.103.028662

Although brassinosteroids (BRs) are known to regulate shoot growth, their role in the regulation of root growth is less clear. We show that low concentrations of BRs such as 24-epicastasterone and 24-epibrassinolide promote root elongation in Arabidopsis wild-type plants up to 50% and in BR-deficient mutants such as dwf1-6 (cbb1) and cbb3 (which is allelic to cpd) up to 150%. The growth-stimulating effect of exogenous BRs is not reduced by the auxin transport inhibitor 2,3,5-triidobenzoic acid. BR-deficient mutants show normal gravitropism, and 2,3,5-triidobenzoic acid or higher concentrations of 2,4-dichlorophenoxyacetic acid and naphtaleneacetic acid inhibit root growth in the mutants to the same extent as in wild-type plants. Simultaneous administration of 24-epibrassinolide and 2,4-dichlorophenoxyacetic acid results in largely additive effects. Exogenous gibberellins do not promote root elongation in the BR-deficient mutants, and the sensitivity to the ethylene precursor 1-aminocyclopropane-1-carboxylic acid is not altered. Thus, the root growth-stimulating effect of BRs appears to be largely independent of auxin and gibberellin action. Furthermore, we analyzed BR interactions with other phytohormones on the gene expression level. Only a limited set of auxin- and ethylene-related genes showed altered expression levels. Genes related to other phytohormones barely showed changes, providing further evidence for an autonomous stimulatory effect of BR on root growth.