title: Japanese morning glory dusky mutants displaying reddish-brown or purplish-gray flowers are deficient in a novel glycosylation enzyme for anthocyanin biosynthesis, UDP-glucose:anthocyanidin 3-O-glucoside-2''-O-glucosyltransferase, due to 4-bp insertions in the gene.
abstract: Bright blue or red flowers in the Japanese morning glory (Ipomoea nil) contain anthocyanidin 3-O-sophoroside derivatives, whereas the reddish-brown or purplish-gray petals in its dusky mutants accumulate anthocyanidin 3-O-glucoside derivatives. The Dusky gene was found to encode a novel glucosyltransferase, UDP-glucose:anthocyanidin 3-O-glucoside-2''-O-glucosyltransferase (3GGT), which mediates the glucosylation of anthocyanidin 3-O-glucosides to yield anthocyanidin 3-O-sophorosides. Ipomoea nil carries one copy of the 3GGT gene that contains no intron and produces 1.6-kbp transcripts mainly in the petals and tubes of flower buds at around 24 h before flower opening. The gene products of both In3GGT in I. nil and Ip3GGT in the common morning glory (Ipomoea purpurea) comprise 459 amino acids and showed a close relationship to the petunia UDP-rhamnose:anthocyanidin 3-O-glucoside-6''-O-rhamnosyltransferase (3RT), which controls the addition of a rhamnose molecule to anthocyanidin 3-O-glucosides for conversion into anthocyanidin 3-O-rutinosides. All of the 30 dusky mutants tested were found to carry the 4-bp insertion mutations GGAT or CGAT at an identical position near the 3' end of the gene, and the insertions caused frameshift mutations. The expected 3GGT enzymatic activities were found in the crude extracts of Escherichia coli, in which the 3GGT cDNA of I. nil or I. purpurea was expressed, while no such activity was detected in the extracts expressed with the dusky mutant cDNAs containing 4-bp insertions. Moreover, the introduced Ip3GGT cDNA efficiently produced 3GGT that converted cyanidin 3-O-glucoside into cyanidin 3-O-sophoroside in transgenic petunia plants.
authors.affiliation: National Institute for Basic Biology, Okazaki 444-8585, Japan.
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Morita
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hoshino
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Kikuchi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Okuhara
authors.forename: Eiichiro
authors.initials: E
authors.lastname: Ono
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Yuko
authors.initials: Y
authors.lastname: Fukui
authors.forename: Norio
authors.initials: N
authors.lastname: Saito
authors.forename: Eiji
authors.initials: E
authors.lastname: Nitasaka
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Noguchi
authors.forename: Shigeru
authors.initials: S
authors.lastname: Iida
mesh_terms: D000595:Amino Acid Sequence; D000872:Anthocyanins / Q000096:biosynthesis* / Q000737:chemistry; D003116:Color; D035264:Flowers / Q000502:physiology; D015870:Gene Expression / Q000502:physiology; D005964:Glucosyltransferases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D027741:Ipomoea / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D015394:Molecular Structure; D016254:Mutagenesis, Insertional / Q000502:physiology; D009154:Mutation; D032306:Petunia; D010802:Phylogeny; D010940:Plant Proteins / Q000378:metabolism; D030821:Plants, Genetically Modified; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D000872:Anthocyanins; D010940:Plant Proteins; D005964:Glucosyltransferases