Genetic evidence for an essential role of brassinosteroids in plant development

Authors

  • Annette Kauschmann,

    1. Institut für Genbiologische Forschung Berlin GmbH, Ihnestraße 63, D-14195 Berlin, Germany
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  • Alison Jessop,

    1. Institut für Genbiologische Forschung Berlin GmbH, Ihnestraße 63, D-14195 Berlin, Germany
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    • Present address: C.I.D.-C.S.I.C., Dept. Genetica Molecular, Jordi Girona 18-26, 08034 Barcelona, Spain.

  • Csaba Koncz,

    1. Max-Planck-Institut für Züchtungsforschung, Carl-von Linné-Weg 10, D-50829 Köln, Germany
    2. Institute of Plant Biology, Biological Research Center of Hungarian Academy of Sciences, H-6701 Szeged, P.O. Box 521, Temesv ri krt. 62, Hungary
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  • Miklos Szekeres,

    1. Institute of Plant Biology, Biological Research Center of Hungarian Academy of Sciences, H-6701 Szeged, P.O. Box 521, Temesv ri krt. 62, Hungary
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  • Lotbar Willmitzer,

    1. Institut für Genbiologische Forschung Berlin GmbH, Ihnestraße 63, D-14195 Berlin, Germany
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    • Present address: Max-Planck-Institut für Molekulare Pflanzenphysiologie, Karl-Liebknecht Straße 25, Haus 20, D-14476 Golm, Germany.

  • Thomas Altmann

    Corresponding author
    1. Institut für Genbiologische Forschung Berlin GmbH, Ihnestraße 63, D-14195 Berlin, Germany
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    • Present address: Max-Planck-Institut für Molekulare Pflanzenphysiologie, Karl-Liebknecht Straße 25, Haus 20, D-14476 Golm, Germany.


*For correspondence (fax +49 331 977 2301; e-mail: altmann@mpimg-berlin-dahlem.mpg.de).

Summary

Brassinosteroids which show high structural similarity to animal steroid hormones elicit a variety of growth responses when exogeneously applied to plant tissues. Thus far however, the function of endogeneous brassinosteroids in higher plants has been unclear. This paper describes three extremely dwarfed Arabidopsis thaliana mutants, cbb1 (dwf1-6), cbb2 and cbb3, which are impared in cell elongation controlled by brassinosteroids. While cbb1 (dwf1-6) and cbb3 can be phenotypically normalized to wild-type by feeding with brassinosteroids indicating deficiencies of brassinosteroid biosynthesis, cbb2 is brassinosteroid-insensitive and defines a function required for further metabolic conversion necessary for biological activity or for perception/signal transduction of these growth-regulating plant steroid hormones. Expression of the meri5 and TCH4 genes is low in all three cbb mutants and can be restored to wild-type levels by brassinosteroid treatment in the cbb1 (dwf1-6) and cbb3 mutants but are unaffected in the cbb2 mutant. These data indicate that brassinosteroids are essential for proper plant development and play an important role in the control of cell elongation.

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