Analysis of Flavonoids in Flower Petals of Soybean Flower Color Variants

Abstract

We previously identified two anthocyanins, malvidin 3,5‐di‐O‐glucoside and delphinidin 3,5‐di‐O‐glucoside, in flower petals of soybean cultivars with purple flowers, ‘Harosoy’ and ‘Clark’. However, two other anthocyanins found by high performance liquid chromatography (HPLC) analysis could not be identified. We further evaluated the effects of flower color genes W1, W3, W4, and Wm on flavonoid components using near‐isogenic lines for these genes. The first objective of this study was to determine the two unidentified anthocyanins in flower petals of Clark. The second objective was to evaluate the effects of Wp for pink flower and W2 for purple‐blue flower on flavonoid biosynthesis using purple‐blue flowered cultivars Nezumisaya, Yogetsu‐1‐blue, and w2‐20, and a pink flowered line LD05–15019‐pink. Chemical analysis revealed that the two remaining anthocyanins were petunidin 3,5‐di‐O‐glucoside and delphinidin 3‐O‐glucoside. Composition and amount of flavonoids in purple‐blue flowers were generally similar to those of Clark suggesting that anthocyanin structure or copigmentation with other flavonoids may not be responsible for the color. Pink flowers contained 72% of total anthocyanins, 9% of the total flavonol glycosides, and 28% of aromadendrin 3‐O‐glucoside relative to Clark. Further, pink flowers lacked kaempferol 3‐O‐glucoside. It is uncertain whether the reduction in flavonol glycosides in combination with lower anthocyanin levels might fully explain the low intensity of pigmentation in pink flowers.

The b Gene of Pea Encodes a Defective Flavonoid 3′,5′-Hydroxylase, and Confers Pink Flower Color

“…Studies of the standard (banner) petals of purple-flowered soybean cultivars show that these have a different sugar moiety at the 3 position of the C ring of their anthocyanidins compared with pea: the primary anthocyanins detected in soybean cv Clark (W1W1 w3w3 W4W4 WmWm TT TdTd) and cv Harosoy (W1W1 w3w3 W4W4 WmWm tt TdTd) were malvidin, delphinidin, and petunidin 3,5-di-O-glucoside and delphinidin 3-O-glucoside (Iwashina et al, 2008), whereas delphinidin and petunidin-3-rhamnoside-5-glucoside were the major anthocyanins found in the wing petals of pea line JI 2822 in this study, consistent with previous studies on line L 60 of pea (Statham et al, 1972). As the intensity of coloration in pea petals indicates (Fig.…”

“…The wp allele is reported to contain a 5,722-bp CACTA transposable element in intron 2 of a F3H gene, F3H1, with down-regulated expression (Zabala and Vodkin, 2005). A null mutation would result in a lack of the substrates dihydromyricetin, dihydrokaempferol, and dihydroquercetin required for conversion into anthocyanins (Grotewold, 2006;Iwashina et al, 2008); therefore, a null mutant would be expected to have white flowers and, indeed, white-flowered mutants have been observed in other plant species (Martin et al, 1991;Britsch et al, 1992). Analysis of a wp genotype obtained by back-crossing to soybean cv Loda showed that the wp line had a low flavonoid content: 9% of the total flavonol glycosides, no detectable kaempferol 3-O-glucoside, and 28% of dihydroflavonols compared with cv Clark (Iwashina et al, 2008).…”

“…Many factors such as copigments and vacuolar pH could influence soybean flower color, but the presence of an additional defective pigmentation gene, such as the ABQ96218 allele of F3959H, for example, would also cause pink flower color. A comparison of flower color and flavonoid content in available Wp and wp near-isogenic lines (Iwashina et al, 2008) and cosegregation analysis of F3H1 and wp would help to confirm which structural genes were defective.…”

New Allelic Variant Discovered at Soybean Flower Color Locus W1 Encoding Flavonoid 3′5′‐hydroxylase

“…Plant cultivation, sampling, flavonoid extraction, and HPLC analysis were performed as previously described (Iwashina et al, 2007;Iwashina et al, 2008;Takahashi et al, 2010). Plant cultivation, sampling, flavonoid extraction, and HPLC analysis were performed as previously described (Iwashina et al, 2007;Iwashina et al, 2008;Takahashi et al, 2010).…”

“…The flavonoids in purple petals of soybean and G. soja are similar (Iwashina et al, 2007;Iwashina et al, 2008;Takahashi et al, 2010). The primary anthocyanins are malvidin 3,5-di-O-glucoside, petunidin 3,5-di-O-glucoside, delphinidin 3,5-di-O-glucoside and delphinidin 3-O-glucoside.…”