Sterol C-24 methyltransferase type 1 controls the flux of carbon into sterol biosynthesis in tobacco seed
| Autor: | Richard Safford, Niklas Holmberg, John C. Clayton, Carl L. Gibbard, Mark Harker, Amanda Hellyer, Andrew D. Wallace, Sally Rawlins |
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| Rok vydání: | 2002 |
| Předmět: |
Physiology
Nicotiana tabacum Campesterol Coenzyme A Stigmasterol Plant Science Gene Expression Regulation Enzymologic chemistry.chemical_compound Biosynthesis Gene Expression Regulation Plant Tobacco Genetics polycyclic compounds Cloning Molecular biology Cholesterol food and beverages Phytosterols Biological Transport Methyltransferases biology.organism_classification Plants Genetically Modified Sitosterols Sterol Carbon Triterpenes Plant Leaves Metabolic pathway chemistry Biochemistry Seeds Cycloartenol lipids (amino acids peptides and proteins) Hydroxymethylglutaryl CoA Reductases Research Article |
| Zdroj: | Plant physiology. 130(1) |
| ISSN: | 0032-0889 |
| Popis: | The first committed step in the conversion of cycloartenol into Δ5 C24-alkyl sterols in plants is catalyzed by anS-adenosyl-methionine-dependent sterol-C24-methyltransferase type 1 (SMT1). We report the consequences of overexpressing SMT1 in tobacco (Nicotiana tabacum), under control of either the constitutive carnation etched ring virus promoter or the seed-specific Brassica napusacyl-carrier protein promoter, on sterol biosynthesis in seed tissue. Overexpression of SMT1 with either promoter increased the amount of total sterols in seed tissue by up to 44%. The sterol composition was also perturbed with levels of sitosterol increased by up to 50% and levels of isofucosterol and campesterol increased by up to 80%, whereas levels of cycloartenol and cholesterol were decreased by up to 53% and 34%, respectively. Concomitant with the enhanced SMT1 activity was an increase in endogenous 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, from which one can speculate that reduced levels of cycloartenol feed back to up-regulate 3-hydroxy-3-methylglutaryl coenzyme A reductase activity and thereby control the carbon flux into sterol biosynthesis. This potential regulatory role of SMT1 in seed sterol biosynthesis is discussed. |
| Databáze: | OpenAIRE |
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