Sterol C-24 Methyltransferase Type 1 Controls the Flux of Carbon into Sterol Biosynthesis in Tobacco Seed
AUTOR(ES)
Holmberg, Niklas
FONTE
American Society of Plant Physiologists
RESUMO
The first committed step in the conversion of cycloartenol into Δ5 C24-alkyl sterols in plants is catalyzed by an S-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 napus acyl-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.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=166563Documentos Relacionados
- STEROL METHYLTRANSFERASE 1 Controls the Level of Cholesterol in Plants
- Overexpression of an Arabidopsis cDNA Encoding a Sterol-C241-Methyltransferase in Tobacco Modifies the Ratio of 24-Methyl Cholesterol to Sitosterol and Is Associated with Growth Reduction
- Regulation of Squalene Synthase, a Key Enzyme of Sterol Biosynthesis, in Tobacco1
- Inhibitors of delta24(25) sterol methyltransferase block sterol synthesis and cell proliferation in Pneumocystis carinii.
- Reduction of Cholesterol and Glycoalkaloid Levels in Transgenic Potato Plants by Overexpression of a Type 1 Sterol Methyltransferase cDNA1