LsMybW-encoding R2R3-MYB transcription factor is responsible for a shift from black to white in lettuce seed.

KEY MESSAGE: We identified LsMybW as the allele responsible for the shift in color from black to white seeds in wild ancestors of lettuce to modern cultivars. Successfully selected white seeds are a key agronomic trait for lettuce cultivation and breeding; however, the mechanism underlying the shift from black-in its wild ancestor-to white seeds remains uncertain. We aimed to identify the gene/s responsible for white seed trait in lettuce. White seeds accumulated less proanthocyanidins than black seeds, similar to the phenotype observed in Arabidopsis TT2 mutants. Genetic mapping of a candidate gene was performed with double-digest RAD sequencing using an F2 population derived from a cross between "ShinanoPower" (white) and "Escort" (black). The white seed trait was controlled by a single recessive locus (48.055-50.197 Mbp) in linkage group 7. Using five PCR-based markers and numerous cultivars, eight candidate genes were mapped in the locus. Only the LG7_v8_49.251Mbp_HinfI marker, employing a single-nucleotide mutation in the stop codon of Lsat_1_v5_gn_7_35020.1, was completely linked to seed color phenotype. In addition, the coding region sequences for other candidate genes were identical in the resequence analysis of "ShinanoPower" and "Escort." Therefore, we proposed Lsat_1_v5_gn_7_35020.1 as the candidate gene and designated it as LsMybW (Lactuca sativa Myb White seeds), an ortholog encoding the R2R3-MYB transcription factor in Arabidopsis. When we validated the role of LsMybW through genome editing, LsMybW knockout mutants harboring an early termination codon showed a change in seed color from black to white. Therefore, LsMybW was the allele responsible for the shift in seed color. The development of a robust marker for marker-assisted selection and identification of the gene responsible for white seeds have implications for future breeding technology and physiological analysis.

Altitudinal variation of flavonoid content in the leaves of Fallopia japonica and the needles of Larix kaempferi on Mt. Fuji.

Ultraviolet-B radiation is harmful to plants, and its intensity increases at altitude. So plants growing at high altitude possess UV protection systems. Flavonoid is known as a major UV protectant because it absorbs UV radiation and scavenges UV-induced free radicals in plant tissues. Japanese knotweed (Fallopia japonica) and Japanese larch (Larix kaempferi) grow at a wide range of altitudes on Mt. Fuji, the highest mountain in Japan, while the two plants harbor a homogeneous genetic structure. In the present study, a total of 14 flavonol 3-O-glycosides were isolated from both species. Furthermore, quantitative HPLC analyses revealed that flavonoid levels in the leaves of F. japonica and the needles of L. kaempferi increased with increasing altitude of their growing sites. The altitudinal trend of UV-absorbing antioxidants of herbal and woody plants was simultaneously revealed for the first time. These results suggest that both species have chemically acclimatized to high altitude regions, in which severe environmental conditions such as higher UV radiation exist.

Flavonoids and their qualitative variation in Calystegia soldanella and related species (Convolvulaceae).

Coastal species are exposed to severe environmental stresses, e.g. salt and UV-B. The plants adapt themselves to such harsh environment by controlling morphological features and chemical defense systems. Flavonoids are known as efficient anti-stress polyphenols produced by plants. Most flavonoids show antioxidant activity, and their properties are important for plants to survive under high-stress conditions such as those in a coastal area. Among the compounds, ortho-dihydroxylated flavonoids act as strong antioxidants. In this survey, we elucidated the flavonoid composition of a seashore species Calystegia soldanella, which is distributed not only on the seashore, but also by the inland freshwater lake, Lake Biwa. Seven flavonol glycosides, i.e. quercetin 3-0- rutinoside, 3-O-glucoside, 3-O-rhamnoside and 3-O-apiosyl-(1-->2)-[rhamnosyl-(1-->6)-glucoside], and kaempferol 3-O-rutinoside, 3-O-glucoside and 3-0- rhamnoside were isolated from the leaves of C. soldanella. In addition, it was shown that the quercetin (Qu) to kaempferol (Km) ratio of coastal populations was higher than that of lakeshore populations. In general, these differences of Qu/Km ratio depend on flavonoid 3'-hydroxylase (F3'H) transcription. RT-PCR analysis suggested that F3'H of C. soldanella is regulated translationally or post-translationally, but not transcriptionally. Furthermore, quantitative and qualitative differences in flavonoid composition occurred among three Calystegia species, C. soldanella, C. japonica and C. hederacea.

Novel C-xylosylflavones from the leaves and flowers of Iris gracilipes.

Two new C-glycosylflavones, apigenin 7,4'-dimethyl ether 6-C-ß-[(4"'-acetyl-L-rhamnopyranosyl)-(1-->2)-xylopyranoside] (1) and apigenin 7,4'-dimethyl ether 6-C-ß-L-rhamnopyranosyl-(1-->2)-xylopyranoside (2) were isolated from the leaves of Iris gracilipes (Iridaceae), along with two known flavonoids, swertiajaponin (3) and swertisin (4). C-Xylosylflavones 1 and 2 were elucidated by UV and NMR spectroscopy, mass spectrometry, and acid and alkaline hydrolyses. These novel compounds were also presented in the flowers.

Anthocyanins from the flowers of Nagai line of Japanese garden Iris (Iris ensata).

Six anthocyanins were isolated from the flowers of the Nagai line of Iris ensata Thunb. They were identified as petunidin and malvidin 3-O-beta-[(4"'-Z-p-coumaroyl-alpha-rhamnopyranosyl)-(1-->6)-beta-glucopyranoside]-5-O-beta-glucopyranosides (1 and 3) and their E-forms (2 and 4), and petunidin and malvidin 3-O-rutinoside-5-O-glucosides (5 and 6). Though the E-form of petunidin 3-O-[(4"'-p-coumaroylrhamnosyl)-(1-->6)-glucoside]-5-O-glucoside has been reported, its Z-form was found for the first time. The presence of Z- and E-forms of malvidin 3-O-[(4'''-p-coumaroylrhamnosyl)-(1-->6)-glucoside]-5-O-glucoside is also reported for the first time. Fifty-one cultivars of Nagai line and their wild form (I. ensata var. spontanea) were divided into four anthocyanin patterns, i.e. 1) the presence of 1-4, 2) the presence of 2 and 4, 3) the presence of 5 and 6, and 4) no anthocyanin.

New flavonol glycosides from the leaves of Triantha japonica and Tofieldia nuda.

Two new flavonol glycosides were isolated from the leaves of Triantha japonica, together with eight known flavonols, kaempferol 3-O-sophoroside, kaempferol 3-O-sambubioside, kaempferol 3-O-glucosyl-(1 --> 2)-[glucosyl-(1 --> 6)-glucoside], quercetin 3-O-sophoroside, quercetin 3-O-sambubioside, isorhamnetin 3-O-glucoside, isorhamnetin 3-O-sophoroside and isorhamnetin 3-O-sambubioside. The new compounds were identified as kaempferol 3-O-beta-xylopyranosyl-(1 --> 2)-[beta-glucopyranosyl-(1 --> 6)-beta-glucopyranoside] (1) and isorhamnetin 3-O-beta-xylopyranosyl-(1 --> 2)-[beta-glucopyranosyl-(1 --> 6)-beta-glucopyranoside] (3) by UV, LC-MS, acid hydrolysis, and 1H and 13C NMR spectroscopy. Another two new flavonol glycosides were isolated from theleaves of Tofieldia nuda, and identified as kaempferol 3-O-beta-glucopyranosyl-(1 --> 2)-[beta-glucopyranosyl-(1 --> 6)-beta-galactopyranoside] (4) and quercetin 3-O-beta-glucopyranosyl-(1 --> 2)-[beta-glucopyranosyl-(1 --> 6)-beta-galactopyranoside] (5). Though the genera Triantha and Tofieldia were treated as Tofieldia sensu lato, they were recently divided into two genera. It was shown by this survey that their flavonoid composition were also different to each other.

New flavonol triglycosides from the leaves of soybean cultivars.

Soybean (Glycine max) is a major crop in the world. Three new flavonol 3-O-glycosides, kaempferol 3-O-alpha-L-rhamnopyranosyl-(1 --> 4)-[alpha-L-rhamnopyranosyl-(1 --> 6)-beta-D-galactopyranoside] (1), kaempferol 3-O-alpha-L-rhamnopyranosyl-(1 --> 4)-[beta-D-glucopyranosyl-(1 --> 6)-beta-D-galactopyranoside] (4) and quercetin 3-O-beta-D-glucopyranosyl-(1--> 2)-[alpha-L-rhamnopyranosyl-(1 --> 6)-beta-galactopyranoside] (5) were isolated from the leaves of soybean cultivars, together with three known compounds, kaempferol 3-O-beta-D-glucopyranosyl-(1 --> 2)-[alpha-L-rhamnopyranosyl-(1--> 6)-beta-D-galactopyranoside] (2), kaempferol 3-O-beta-D-glucopyranosyl-(1 --> 2)-[alpha-L-rhamnopyranosyl-(1 --> 6)-beta-D-glucopyranoside] (3) and quercetin 3-O-beta-D-glucopyranosyl-(1 --> 2)-[alpha-L-rhamnopyranosyl-(1 --> 6)-beta-D-glucopyranoside] (6), and also common flavonoids. The isolated compounds possess similar structures and high water solubility, and so it was hard to isolate them (in particular 5 and 6) with a normal preparative HPLC system. Their final purification was achieved by a preparative HPLC system equipped with a recycle device.