The ratio of campesterol to sitosterol that modulates growth in Arabidopsis is controlled by STEROL METHYLTRANSFERASE 2;1.
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.
Schaeffer
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A
Institut de Biologie Moléculaire des Plantes du CNRS, Département Biosynthèse et Fonctions des Isoprénoïdes, Institut de Botanique, 28 rue Goethe, 67083 Strasbourg, France.
Bronner
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R
Benveniste
P
P
Schaller
H
H
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D015152:Blotting, Northern; D060406:Brassinosteroids; D002777:Cholestanols / Q000037:antagonists & inhibitors / Q000378:metabolism; D002784:Cholesterol / Q000031:analogs & derivatives* / Q000096:biosynthesis*; D005638:Fruit / Q000254:growth & development; D018506:Gene Expression Regulation, Plant; D008780:Methyltransferases / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D010641:Phenotype; D010840:Phytosterols; D010937:Plant Growth Regulators / Q000037:antagonists & inhibitors / Q000378:metabolism; D018517:Plant Roots / Q000254:growth & development; D018547:Plant Stems / Q000254:growth & development; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000254:growth & development; D012855:Sitosterols / Q000378:metabolism*; D013260:Steroids, Heterocyclic / Q000037:antagonists & inhibitors / Q000378:metabolism; D013261:Sterols / Q000096:biosynthesis; D019076:Transgenes
D060406:Brassinosteroids; D002777:Cholestanols; D010840:Phytosterols; D010937:Plant Growth Regulators; D012855:Sitosterols; D013260:Steroids, Heterocyclic; D013261:Sterols; C021273:campesterol; C025473:gamma-sitosterol; D002784:Cholesterol; D008780:Methyltransferases; C022670:delta 24-sterol methyltransferase; C023623:brassinolide