The ratio of campesterol to sitosterol that modulates growth in Arabidopsis is controlled by STEROL METHYLTRANSFERASE 2;1

Authors

  • Aurélie Schaeffer,

    1. Institut de Biologie Moléculaire des Plantes du CNRS, Département Biosynthèse et Fonctions des Isoprénoïdes, Institut de Botanique, 28 rue Goethe, 67083 Strasbourg, France
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  • Roberte Bronner,

    1. Institut de Biologie Moléculaire des Plantes du CNRS, Département Biosynthèse et Fonctions des Isoprénoïdes, Institut de Botanique, 28 rue Goethe, 67083 Strasbourg, France
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  • Pierre Benveniste,

    1. Institut de Biologie Moléculaire des Plantes du CNRS, Département Biosynthèse et Fonctions des Isoprénoïdes, Institut de Botanique, 28 rue Goethe, 67083 Strasbourg, France
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  • Hubert Schaller

    Corresponding author
      For correspondence (fax +33 3 88 35 84 84; e-mail hubert.schaller@ibmp-ulp.u-strasbg.fr).
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For correspondence (fax +33 3 88 35 84 84; e-mail hubert.schaller@ibmp-ulp.u-strasbg.fr).

Summary

The Arabidopsis genome contains three distinct genes encoding sterol-C24-methyltransferases (SMTs) involved in sterol biosynthesis. The expression of one of them, STEROL METHYLTRANSFERASE 2;1, was modulated in 35S::SMT2;1 Arabidopsis in order to study its physiological function. Plants overexpressing the transgene accumulate sitosterol, a 24-ethylsterol which is thought to be the typical plant membrane reinforcer, at the expense of campesterol. These plants displayed a reduced stature and growth that could be restored by brassinosteroid treatment. Plants showing co-suppression of SMT2;1 were characterized by a predominant 24-methylsterol biosynthetic pathway leading to a high campesterol content and a depletion in sitosterol. Pleiotropic effects on development such as reduced growth, increased branching, and low fertility of high-campesterol plants were not modified by exogenous brassinosteroids, indicating specific sterol requirements to promote normal development. Thus SMT2;1 has a crucial role in balancing the ratio of campesterol to sitosterol in order to fit both growth requirements and membrane integrity.

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