title: The primary in vivo steroidal alkaloid glucosyltransferase from potato.
abstract: To provide tools for breeders to control the steroidal glycoalkaloid (SGA) pathway in potato, we have investigated the steroidal alkaloid glycosyltransferase (Sgt) gene family. The committed step in the SGA pathway is the glycosylation of solanidine by either UDP-glucose or UDP-galactose leading to alpha-chaconine or alpha-solanine, respectively. The Sgt2 gene was identified by deduced protein sequence homology to the previously identified Sgt1 gene. SGT1 has glucosyltransferase activity in vitro, but in vivo serves as the UDP-galactose:solanidine galactosyltransferase. Two alleles of the Sgt2 gene were isolated and its function was established with antisense transgenic lines and in vitro assays of recombinant protein. In tubers of transgenic potato (Solanum tuberosum) cvs. Lenape and Desirée expressing an antisense Sgt2 gene construct, accumulation of alpha-solanine was increased and alpha-chaconine was reduced. Studies with recombinant SGT2 protein purified from yeast show that SGT2 glycosylation activity is highly specific for UDP-glucose as a sugar donor. This data establishes the function of the gene product (SGT2), as the primary UDP-glucose:solanidine glucosyltransferase in vivo.
authors.affiliation: USDA, Agricultural Research Service, Crop Improvement and Utilization Research Unit, Western Regional Research Center, 800 Buchanan St., Albany, CA 94710-1105, USA.
authors.forename: Kent F
authors.initials: KF
authors.lastname: McCue
authors.forename: Paul V
authors.initials: PV
authors.lastname: Allen
authors.forename: Louise V T
authors.initials: LV
authors.lastname: Shepherd
authors.forename: Alison
authors.initials: A
authors.lastname: Blake
authors.forename: Jonathan
authors.initials: J
authors.lastname: Whitworth
authors.forename: M Malendia
authors.initials: MM
authors.lastname: Maccree
authors.forename: David R
authors.initials: DR
authors.lastname: Rockhold
authors.forename: Derek
authors.initials: D
authors.lastname: Stewart
authors.forename: Howard V
authors.initials: HV
authors.lastname: Davies
authors.forename: William R
authors.initials: WR
authors.lastname: Belknap
mesh_terms: D000470:Alkaloids / Q000378:metabolism*; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary; D005964:Glucosyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified; D011198:Solanum tuberosum / Q000201:enzymology*
chemical_list: D000470:Alkaloids; D017931:DNA Primers; D018076:DNA, Complementary; D005964:Glucosyltransferases