Received August 18, 2006
Accepted November 27, 2006
Saponin Biosynthesis in Saponaria vaccaria. cDNAs encoding 
-amyrin Synthase and a Triterpene Carboxylic Acid Glucosyltransferase
Dauenpen Meesapyodsuk , John Balsevich , Darwin W. Reed , and Patrick S. Covello *
Plant Biotechnology Institute, 110 Gymnasium Place, Saskatoon, SK, Canada S7N OW9
* Corresponding author; email: Patrick.Covello{at}nrc-cnrc.gc.ca.
Saponaria vaccaria (Caryophyllaceae), a soapwort, known in western Canada as cowcockle, contains bioactive oleanane type saponins similar to those found in Quillaja saponaria (Rosaceae). In order to improve our understanding of the biosynthesis of these saponins, a combined polymerase chain reaction (RT-PCR) and expressed sequence tag (EST) approach was taken to identify the genes involved. A cDNA encoding a 
-amyrin synthase (SvBS) was isolated by RT-PCR and characterized by expression in yeast. The SvBS gene is predominantly expressed in leaves. A S. vaccaria developing seed EST collection was developed and used for the isolation of a full-length cDNA bearing sequence similarity to ester-forming glycosyltransferases. The gene product of the cDNA, classified as UGT74M1, was expressed in E. coli, purified, and identified as a triterpene carboxylic acid glucosyltransferase. UGT74M1 is expressed in roots and leaves and appears to be involved in monodesmoside biosynthesis in S. vaccaria.
