NARO Western Region Agricultural Research Center , 1-3-1 Senyuu, Zentsuuji, Kagawa 765-8508, Japan.
Breed Sci. 2012 Jan;61(5):639-45. doi: 10.1270/jsbbs.61.639. Epub 2012 Feb 4.
Saponins are sterols or triterpene glycosides that are widely distributed in plants. The biosynthesis of soybean saponins is thought to involve many kinds of glycosyltransferases, which is reflected in their structural diversity. Here, we performed linkage analyses of the Sg-3 and Sg-4 loci, which may control the sugar chain composition at the C-3 sugar moieties of the soybean saponin aglycones soyasapogenols A and B. The Sg-3 locus, which controls the production of group A saponin Af, was mapped to chromosome (Chr-) 10. The Sg-4 locus, which controls the production of DDMP saponin βa, was mapped to Chr-1. To elucidate the preference of sugar chain formation at the C-3 and C-22 positions, we analyzed the F(2) population derived from a cross between a mutant variety, Kinusayaka (sg-1(0)), for the sugar chain structure at C-22 position, and Mikuriya-ao (sg-3), with respect to the segregation of the composition of the group A saponins, and found that the formation of these sugar chains was independently regulated. Furthermore, a novel saponin, predicted to be A0-γg, 3-O-[β-d-galactopyranosyl (1→2)-β-d-glucuronopyranosyl]-22-O-α-l-arabinopyranosyl-soyasapogenol A, appeared in the hypocotyl of F(2) individuals with genotype sg-1(0)/sg-1(0)sg-3/sg-3.
皂苷是甾醇或三萜糖苷，广泛分布于植物中。大豆皂苷的生物合成被认为涉及多种糖基转移酶，这反映在其结构的多样性上。在这里，我们对可能控制大豆皂苷配基 soyasapogenols A 和 B 的 C-3 糖部分的糖链组成的 Sg-3 和 Sg-4 基因座进行了连锁分析。控制 A 组皂苷 Af 产生的 Sg-3 基因座被定位在第 10 号染色体（Chr-）上。控制 DDMP 皂苷 βa 产生的 Sg-4 基因座被定位在 Chr-1 上。为了阐明 C-3 和 C-22 位糖链形成的偏好性，我们分析了源自 Kinusayaka（sg-1(0)）突变体品种和 Mikuriya-ao（sg-3）之间的 F(2)群体，该突变体品种在 C-22 位的糖链结构方面，以及 A 组皂苷的组成的分离，发现这些糖链的形成是独立调节的。此外，在基因型为 sg-1(0)/sg-1(0)sg-3/sg-3 的 F(2)个体的下胚轴中，预测出一种新的皂苷，预测为 A0-γg，3-O-[β-d-半乳糖吡喃基（1→2）-β-d-葡糖醛酸吡喃基]-22-O-α-l-阿拉伯吡喃基-soyasapogenol A，出现了。
