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Integrating Genetics and Genomics to Advance Soybean Research

Reference Report for RTN20170315.4
Title:Cloning and characterization of soybean gene Fg1 encoding flavonal 3-O-glucoside/galactoside (1-6) glucosyltransferase
Authors:Roda, F.R., Di, S., Murai, Y., Iwashina, T., Sugawara, S., Mori, T., Nakabayashi, R., Yonekura-Sakakibara, K., Saito, K., Takahashi, R.
Source:Plant Mol Biol 2016, 92:445-456
Abstract:Flavonol glycosides (FGs) are predominant in soybean leaves and they show substantial differences among genotypes. In previous studies, we identified two flavonoid glycoside glycosyltransferase genes that segregated in recombinant inbred lines developed from a cross between cultivars Nezumisaya and Harosoy; one was responsible for the attachment of glucose to the 2_-position of glucose or galactose that is bound to the 3-position of kaempferol and the other was involved in the attachment of glucose to the 6_-position. This study was conducted to clone and characterize the 6_-glucosyltransferase gene. Linkage mapping indicated that the gene was located in the molecular linkage group I (chromosome 20). Based on the genome sequence, we cloned a candidate cDNA, GmF3G6Gt from Harosoy but the corresponding cDNA could not be amplified by PCR from Nezumisaya. The coding region of GmF3G6_Gt in Harosoy is 1386 bp long encoding 462 amino acids. This gene was not expressed in leaves of Nezumisaya. The GmF3G6_Gt recombinant protein converted UDP-glucose and kaempferol 3-O-glucoside or kaempferol 3-O-galactoside to kaempferol 3-O-glucosyl-(1_6)-glucoside or kaempferol 3-O-glucosyl-(1_6)-galactoside, respectively. These results indicate that GmF3G6_Gt encodes a flavonol 3-O-glucoside/galactoside (1_6) glucosyltransferase and corresponds to the Fg1 gene. GmF3G6_Gt had an amino acid similarity of 82_% with GmF3G6_Rt encoding flavonol 3-O-glucoside/galactoside (1_6) rhamnosyltransferase, suggesting a recent evolutionary divergence of the two genes. This may be the first cloning of a sugar-sugar glucosyltransferase gene in the UGT family that attaches glucose to the 6_-position of sugar bound to a flavonol. A scheme for the control of FG biosynthesis is proposed.






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