First published online October 29, 2004; 10.1104/pp.104.047266
Plant Physiology 136:3660-3669 (2004)
© 2004 American Society of Plant Biologists
DEVELOPMENT AND HORMONE ACTION
AtGA3ox2, a Key Gene Responsible for Bioactive Gibberellin Biosynthesis, Is Regulated during Embryogenesis by LEAFY COTYLEDON2 and FUSCA3 in Arabidopsis1
Julien Curaba,
Thomas Moritz,
Renaud Blervaque,
François Parcy2,
Vered Raz,
Michel Herzog and
Gilles Vachon*
Laboratoire de Plastes et Différenciation Cellulaire, Centre National de la Recherche Scientifique Unité Mixte de Recherche 5575, Université Joseph Fourier, Centre Etude et de Recherche sur les Macromolécules Organiques B.P. 53, F–38041 Grenoble cedex 9, France (J.C., R.B., M.H., G.V.); Umea Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE–901 83 Umea, Sweden (T.M.); Institut des Sciences du Végétal, UPR2355 Centre National de la Recherche Scientifique, 91190 Gif-sur-Yvette, France (F.P.); and Plant Sciences Laboratory of Molecular Biology, Wageningen University, Wageningen, The Netherlands (V.R.)
Embryonic regulators LEC2 (LEAFY COTYLEDON2) and FUS3 (FUSCA3) are involved in multiple aspects of Arabidopsis (Arabidopsis thaliana) seed development, including repression of leaf traits and premature germination and activation of seed storage protein genes. In this study, we show that gibberellin (GA) hormone biosynthesis is regulated by LEC2 and FUS3 pathways. The level of bioactive GAs is increased in immature seeds of lec2 and fus3 mutants relative to wild-type level. In addition, we show that the formation of ectopic trichome cells on lec2 and fus3 embryos is a GA-dependent process as in true leaves, suggesting that the GA pathway is misactivated in embryonic mutants. We next demonstrate that the GA-biosynthesis gene AtGA3ox2, which encodes the key enzyme AtGA3ox2 that catalyzes the conversion of inactive to bioactive GAs, is ectopically activated in embryos of the two mutants. Interestingly, both  -glucuronidase reporter gene expression and in situ hybridization indicate that FUS3 represses AtGA3ox2 expression mainly in epidermal cells of embryo axis, which is distinct from AtGA3ox2 pattern at germination. Finally, we show that the FUS3 protein physically interacts with two RY elements (CATGCATG) present in the AtGA3ox2 promoter. This work suggests that GA biosynthesis is directly controlled by embryonic regulators during Arabidopsis embryonic development.
1 This work was supported by the Région Rhône-Alpes (through the Programme Thématiques Prioritaires [2000–2003] and a doctoral fellowship to J.C.).
2 Present address: Instituto de Biologia Molecular y Celular de Plantas, Universidad Politécnica de Valencia, CSIC, Avenida de los Naranjos s/n, 46022 Valencia, Spain.
Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.104.047266.
* Corresponding author; e-mail gilles.vachon{at}ujf-grenoble.fr; fax 33–476–51–43–36.
Received May 27, 2004;
returned for revision September 16, 2004;
accepted September 16, 2004.
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