title: Saponin biosynthesis in Saponaria vaccaria. cDNAs encoding beta-amyrin synthase and a triterpene carboxylic acid glucosyltransferase.
abstract: Saponaria vaccaria (Caryophyllaceae), a soapwort, known in western Canada as cowcockle, contains bioactive oleanane-type saponins similar to those found in soapbark tree (Quillaja saponaria; Rosaceae). To improve our understanding of the biosynthesis of these saponins, a combined polymerase chain reaction and expressed sequence tag approach was taken to identify the genes involved. A cDNA encoding a beta-amyrin synthase (SvBS) was isolated by reverse transcription-polymerase chain reaction and characterized by expression in yeast (Saccharomyces cerevisiae). The SvBS gene is predominantly expressed in leaves. A S. vaccaria developing seed expressed sequence tag 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 Escherichia 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.
authors.affiliation: Plant Biotechnology Institute, Saskatoon, Saskatchewan, Canada S7N OW9.
authors.forename: Dauenpen
authors.initials: D
authors.lastname: Meesapyodsuk
authors.forename: John
authors.initials: J
authors.lastname: Balsevich
authors.forename: Darwin W
authors.initials: DW
authors.lastname: Reed
authors.forename: Patrick S
authors.initials: PS
authors.lastname: Covello
mesh_terms: D000595:Amino Acid Sequence; D002264:Carboxylic Acids / Q000737:chemistry / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics*; D005964:Glucosyltransferases / Q000737:chemistry / Q000378:metabolism*; D019751:Intramolecular Transferases / Q000235:genetics / Q000378:metabolism*; D015394:Molecular Structure; D010802:Phylogeny; D029750:Saponaria / Q000378:metabolism*; D012503:Saponins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D013379:Substrate Specificity; D014315:Triterpenes / Q000737:chemistry / Q000378:metabolism
chemical_list: D002264:Carboxylic Acids; D018076:DNA, Complementary; D012503:Saponins; D014315:Triterpenes; D005964:Glucosyltransferases; D019751:Intramolecular Transferases; C039924:2,3-oxidosqualene-beta-amyrin-cyclase