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First published online March 20, 2003; 10.1104/pp.102.018788 Plant Physiol, April 2003, Vol. 131, pp. 1792-1799 Reduction of Cholesterol and Glycoalkaloid Levels in Transgenic Potato Plants by Overexpression of a Type 1 Sterol Methyltransferase cDNA1Department of Plant Biology and Forest Genetics (L.A., F.S.) and Department of Food Science, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden (P.C.D.); and Södertörn University College, 14189 Huddinge, Sweden (L.J.)
Transgenic potato (Solanum tuberosum cv
Désirée) plants overexpressing a soybean (Glycine
max) type 1 sterol methyltransferase (GmSMT1)
cDNA were generated and used to study sterol biosynthesis in relation
to the production of toxic glycoalkaloids. Transgenic plants displayed
an increased total sterol level in both leaves and tubers, mainly due
to increased levels of the 24-ethyl sterols isofucosterol and
sitosterol. The higher total sterol level was due to increases in both
free and esterified sterols. However, the level of free cholesterol, a
nonalkylated sterol, was decreased. Associated with this was a
decreased glycoalkaloid level in leaves and tubers, down to 41% and
63% of wild-type levels, respectively. The results show that
glycoalkaloid biosynthesis can be down-regulated in transgenic potato
plants by reducing the content of free nonalkylated sterols, and they
support the view of cholesterol as a precursor in glycoalkaloid biosynthesis.
1 This work was supported by the Magnus Bergvall Foundation and by the C.F. Lundström Foundation. * Corresponding author; e-mail Folke.Sitbon{at}vbsg.slu.se; fax 4618-673-279. © 2003 American Society of Plant Biologists |
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