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First published online August 11, 2006; 10.1104/pp.106.084871 Plant Physiology 142:553-563 (2006) © 2006 American Society of Plant Biologists Transcriptional Regulation of Gibberellin Metabolism Genes by Auxin Signaling in Arabidopsis1,[W]Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia, Consejo Superior de Investigaciones Científicas, 46022 Valencia, Spain (M.F., D.A., L.G.-C., M.A.B.); and Rothamsted Research, Harpenden, Herts AL5 2JQ, United Kingdom (J.P.-G., A.L.P., P.H.)
Auxin and gibberellins (GAs) overlap in the regulation of multiple aspects of plant development, such as root growth and organ expansion. This coincidence raises questions about whether these two hormones interact to regulate common targets and what type of interaction occurs in each case. Auxins induce GA biosynthesis in a range of plant species. We have undertaken a detailed analysis of the auxin regulation of expression of Arabidopsis (Arabidopsis thaliana) genes encoding GA 20-oxidases and GA 3-oxidases involved in GA biosynthesis, and GA 2-oxidases involved in GA inactivation. Our results show that auxin differentially up-regulates the expression of various genes involved in GA metabolism, in particular several AtGA20ox and AtGA2ox genes. Up-regulation occurred very quickly after auxin application; the response was mimicked by incubations with the protein synthesis inhibitor cycloheximide and was blocked by treatments with the proteasome inhibitor MG132. The effects of auxin treatment reflect endogenous regulation because equivalent changes in gene expression were observed in the auxin overproducer mutant yucca. The results suggest direct regulation of the expression of GA metabolism genes by Aux/IAA and ARF proteins. The physiological relevance of this regulation is supported by the observation that the phenotype of certain gain-of-function Aux/IAA alleles could be alleviated by GA application, which suggests that changes in GA metabolism mediate part of auxin action during development.
1 This work was supported by the Spanish Ministry of Education and Science (MEC; grant nos. BIO2001–1558 and BIO2004–02355); the European Molecular Biology Organization Young Investigator Programme (grant to M.A.B.); a Ramón y Cajal contract with the Spanish MEC (to D.A.); a Spanish FPI fellowship (to M.F.); the European Union Research Training Network INTEGA (J.P.-G.); and a Core Strategic Grant from the Biotechnology and Biological Sciences Research Council to Rothamsted Research (to A.L.P. and P.H.). 2 These authors contributed equally to the paper. 3 Present address: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Miguel A. Blázquez (mblazquez{at}ibmcp.upv.es). [W] The online version of this article contains Web-only data. www.plantphysiol.org/cgi/doi/10.1104/pp.106.084871 * Corresponding author; e-mail mblazquez{at}ibmcp.upv.es; fax 34–963877859. Received June 8, 2006; accepted August 3, 2006; published August 11, 2006. This article has been cited by other articles:
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