Linkage mapping, molecular cloning and functional analysis of soybean gene Fg2 encoding flavonol 3-O-glucoside (1 → 6) rhamnosyltransferase.
There are substantial genotypic differences in the levels of flavonol glycosides (FGs) in soybean leaves. The first objective of this study was to identify and locate genes responsible for FG biosynthesis in the soybean genome. The second objective was to clone and verify the function of these candidate genes. Recombinant inbred lines (RILs) were developed by crossing the Kitakomachi and Koganejiro cultivars. The FGs were separated by high performance liquid chromatography (HPLC) and identified. The FGs of Koganejiro had rhamnose at the 6″-position of the glucose or galactose bound to the 3-position of kaempferol, whereas FGs of Kitakomachi were devoid of rhamnose. Among the 94 RILs, 53 RILs had HPLC peaks classified as Koganejiro type, and 41 RILs had peaks classified as Kitakomachi type. The segregation fitted a 1:1 ratio, suggesting that a single gene controls FG composition. SSR analysis, linkage mapping and genome database survey revealed a candidate gene in the molecular linkage group O (chromosome 10). The coding region of the gene from Koganejiro, designated as GmF3G6″Rt-a, is 1,392 bp long and encodes 464 amino acids, whereas the gene of Kitakomachi, GmF3G6″Rt-b, has a two-base deletion resulting in a truncated polypeptide consisting of 314 amino acids. The recombinant GmF3G6″Rt-a protein converted kaempferol 3-O-glucoside to kaempferol 3-O-rutinoside and utilized 3-O-glucosylated/galactosylated flavonols and UDP-rhamnose as substrates. GmF3G6″Rt-b protein had no activity. These results indicate that GmF3G6″Rt encodes a flavonol 3-O-glucoside (1 → 6) rhamnosyltransferase and it probably corresponds to the Fg2 gene. GmF3G6″Rt was designated as UGT79A6 by the UGT Nomenclature Committee.
Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8518, Japan.
Felipe
F
Rojas Rodas
Tito O
TO
Rodriguez
Yoshinori
Y
Murai
Tsukasa
T
Iwashina
Satoko
S
Sugawara
Makoto
M
Suzuki
Ryo
R
Nakabayashi
Keiko
K
Yonekura-Sakakibara
Kazuki
K
Saito
Junichi
J
Kitajima
Kyoko
K
Toda
Ryoji
R
Takahashi
D000595:Amino Acid Sequence; D001483:Base Sequence; D002851:Chromatography, High Pressure Liquid; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D006602:Hexosyltransferases / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid; D030262:Soybean Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D013025:Glycine max / Q000235:genetics*
D017931:DNA Primers; D018076:DNA, Complementary; D011994:Recombinant Proteins; D030262:Soybean Proteins; D006602:Hexosyltransferases; C586631:flavonol 3-O-glucoside (1-6) rhamnosyltransferase, soybean