Difference in the CaMYBA genome among anthocyanin pigmented cultivars and non-pigmented cultivars in pepper (Capsicum annuum)

Anthocyanin in pepper is beneficial as a food antioxidant compound and as a pigment for ornamentals, while unexpected anthocyanin accumulation in fruit, known as black spots, reduces the commercial quality of some cultivars. Previous studies demonstrated that the Anthocyanin (A) locus determines the anthocyanin accumulation in pepper fruits, and an MYB transcription factor, CaMYBA, was found to be located near the A locus. However, the causal gene sequence of the A locus has not yet been identified. With progress regarding genome information in pepper, two other homologous MYB genes were found to be located near CaMYBA, and they are also considered to be candidate genes for the A locus. In this study, we attempted to identify the causal gene sequence of the A locus by performing linkage analysis, genomic sequence analysis, and gene expression analysis of the three candidate MYB genes. A crossing experiment between pigmented ‘Peruvian Purple’ and non-pigmented cultivars confirmed that anthocyanin accumulation in the pigmented cultivar was controlled by a single locus. Gene expression analysis demonstrated that a basic helix-loop-helix transcription factor, CaMYC, and CaMYBA were expressed abundantly in pigmented cultivars, but the other two MYB genes were not. Genotyping of the F2 population derived from the cross demonstrated that the anthocyanin accumulation phenotype was highly linked to CaMYBA, but not to CaMYC. The DNA sequence of CaMYBA in pigmented cultivars had an insertion of a 4.3 kb retrotransposable element LINE-1 in the first intron, but that of non-pigmented cultivars did not. No pigmented cultivar-specific sequence was found in the promoter region of CaMYBA. Therefore, it was suggested that CaMYBA, but not the other two homologous MYB genes, is the A locus gene, and insertion of LINE-1 in CaMYBA appeared to be important for the regulation of anthocyanin accumulation, although the mechanism by which the LINE-1 insertion induces CaMYBA expression is unknown

A Simple Screening of Flower Sensitivity to Ethylene in Several Ornamental Asteraceae Species

Generally, Asteraceae flowers such as chrysanthemums and gerberas, are low ethylene-sensitive and do not exhibit petal wilting and abscission. However, previous research found that the flowers of dahlia, an Asteraceae member belonging to the tribe Coreopsideae, are ethylene-sensitive and show abscission layer development in petal-ovary boundaries. In this study, we investigated the ethylene sensitivity of 17 ornamental Asteraceae species belonging to different tribes by measuring the petal drawing resistance and vase life after 1-3 μL·L-1 ethylene exposure for 20 h. Although more than half of the tested species did not respond to ethylene, several species showed ethylene-sensitive petal wilting and abscission of fresh ray florets. Ethylene-sensitive petal wilting occurred in only two species (Calendula officinalis L. and Osteospermum L.) of the tribe Calenduleae, while ethylene-sensitive petal abscission occurred mainly in six species (Bidens ferulifolia D.C., Coreopsis lanceolata L., Cosmos atrosanguineus (Hook) Voss., Cosmos bipinnatus Cav., Cosmos sulphureus Cav. and Dahlia Cav.) of tribe Coreopsideae and one species (Helianthus annuus L.) of the tribe Heliantheae. In these species, abscission petals maintained their turgidity, and this process could be detected by measuring the petal drawing resistance of the ray florets. The reduction in petal drawing resistance, associated with abscission layer development in the petal-ovary boundaries, was observed only in these ethylene-sensitive species. The results of this study suggest that the ethylene sensitivity and petal senescing patterns in Asteraceae flowers may be associated with the phylogenetic classification at the tribe level

Identification of Chalcones and their Contribution to Yellow Coloration in Dahlia (Dahlia variabilis) Ray Florets

Yellow color in dahlia flowers is conferred from chalcones, butein and isoliquiritigenin. The color intensity of yellow dahlia cultivars is diverse, but a detailed study on this has not yet been performed. In this study, we first identified structures of flavonoids by nuclear magnetic resonance imaging in ray florets of the red-white bicolor ‘Shukuhai’, which contains chalcones, flavones and anthocyanins. Four anthocyanins, four flavone derivatives, five isoliquiritigenin derivatives and five butein derivatives were identified. Among the identified compounds, butein 4'-malonylsophoroside is considered to be the final product for butein derivatives and the presence of chalcone 4'-glucosyltransferase, chalcone 4'-glucoside glucosyltransferase, and chalcone 4'-glucoside malonyltransferase for isoliquiritigenin and butein modification was predicted. Also, the biosynthetic pathway of butein and isoliquiritigenin derivatives in dahlia with butein 4'-malonylsophoroside as the final product was predicted from the identified compounds. Next, we used nine yellow cultivars and lines with different color intensities and analyzed the correlation between the b* value, an indicator of yellow color, and level of chalcones. There was no difference in the presence or absence of major peaks among the cultivars and lines. Peak area per fresh weight measured by HPLC was high in butein 4'-malonylglucoside, butein 4'-sophoroside and isoliquiritigenin 4'-malonylglucoside, suggesting these three compounds were accumulated abundantly. Among the identified chalcones, the highest correlation coefficient was detected between the b* value and butein 4'-malonylglucoside (r = 0.86), butein 4'-sophoroside (r = 0.82) or isoliquiritigenin 4'-malonylglucoside (r = 0.76). These results suggest that these three chalcones confer yellow color in dahlia ray florets. The findings in this study will contribute not only to efforts at breeding new yellow dahlia cultivars, but also to molecular breeding of yellow flowers in other species by introducing the butein biosynthetic pathway

<原著>落葉樹林下におけるランドスケーピング用球根植物の植栽適性の評価

景観形成のための利用を想定して, 秋植え球根37種類, 春植え球根16種類について, ケヤキZelkova serrata Mak.を主体とする落葉樹林下における植栽適性を調査・評価した。夏季の樹林下区の樹冠開空率は15%程度, 冬季は80%程度となった。夏季の樹林下での光合成有効光量子束は無遮蔽区の5%程度となり, 日平均地温は無遮蔽区と比較して3～5℃低かった。1年間の据置栽培後, 供試した1/4近くの種類の植物が無遮蔽区, 樹林下区の両条件下で生存していなかった。生存していた種類の多くで, 2年目の出芽率は, 秋植え, 春植え球根とも無遮蔽区と樹林下区でほぼ同様に高かったが, アリウム, クロッカス, フリージアなどいくつかの種類では無遮蔽区で低く樹林下区で高くなった。秋植え球根類の開花率は無遮蔽区で高く樹林下区で低くなったものが多く, 両区とも同様に高かったものも相当数認められた。また, 一部の種類では樹林下区における開花が無遮蔽区と比べて遅れた。春植え球根類の多くは樹林下区の据置き栽培で生存はしていたものの, 旺盛な生育はみられず, 開花率が低かった。これらの結果より, 秋植え球根のうち, ロドフィアラ, リコリス, ニホンスイセンなど, 出葉時期が樹冠に葉がない時期と重なる冬季出葉型の10種類の球根植物が落葉樹林下への植栽に適するものと考えられた。Adaptability of geophytes (37 fall-plantings and 16 spring-plantings) to planting under deciduous trees, which consisted mainly of Zelkova serrata Mak., was assessed for landscaping.The canopy openness of deciduous trees in summer was 15% and that in winter was 80%.In summer, photosynthetic photon flux under deciduous trees was 5% of that under clearing and the average soil temperature at the depth of 5cm was 3° -5 ℃ lower than that under clearing.One fourth of geophytes used in this experiment did not survive after one year from planting under both clearing and deciduous trees.The sprouting rate of most of the survived geophytes after one year from planting was high under both conditions, but it was higher under deciduous trees than under clearing in some geophytes such as Allium spp., Crocus spp.and Freesia.The flowering rate of most of the fall-planting geophytes was higher under clearing than under deciduous trees and that of some geophytes was high under both clearing and deciduous trees.The flowering of some geophytes delayed under deciduous trees.Most of the spring-planting geophytes survived under deciduous trees but did not grow vigorously, resulting in poor flowering.Consequently ten fall-planting geophytes including Hippeastrum bifidum, Lycoris spp.Narcissus tazetta var.chinensis were considered to be suitable for planting under deciduous trees, which hold their leaves during winter when the canopy of deciduous trees has no leaves

A basic helix-loop-helix transcription factor DvIVS determines flower color intensity in cyanic dahlia cultivars.

The study was aimed to identify the factors that regulate the intensity of flower color in cyanic dahlia (Dahlia variabilis), using fifteen cultivars with different color intensities in their petals. The cultivars were classified into three groups based on their flavonoid composition: ivory white cultivars with flavones; purple and pink cultivars with flavones and anthocyanins; and red cultivars with flavones, anthocyanins, and chalcones. Among the purple, pink, and ivory white cultivars, an inverse relationship was detected between lightness, which was used as an indicator for color intensity and anthocyanin content. A positive correlation was detected between anthocyanin contents and the expression of some structural genes in the anthocyanin synthesis pathway that are regulated by DvIVS, a basic helix-loop-helix transcription factor. A positive correlation between anthocyanin content and expression of DvIVS was also found. The promoter region of DvIVS was classified into three types, with cultivars carrying Type 1 promoter exhibited deep coloring, those carrying Type 2 and/or Type 3 exhibited pale coloring, and those carrying Type 1 and Type 2 and/or Type 3 exhibited medium coloring. The transcripts of the genes from these promoters encoded full-length predicted proteins. These results suggested that the genotype of the promoter region in DvIVS is one of the key factors determining the flower color intensity

Endogenous post-transcriptional gene silencing of flavone synthase resulting in high accumulation of anthocyanins in black dahlia cultivars.

Black color in flowers is a highly attractive trait in the floricultural industry, but its underlying mechanisms are largely unknown. This study was performed to identify the bases of the high accumulation of anthocyanidins in black cultivars and to determine whether the high accumulation of total anthocyanidins alone leads to the black appearance. Our approach was to compare black dahlia (Dahlia variabilis) cultivars with purple cultivars and a purple flowering mutant of a black cultivar, using pigment and molecular analyses. Black cultivars characteristically exhibited low lightness, high petal accumulation of cyanidin and total anthocyanidins without flavones, and marked suppression of flavone synthase (DvFNS) expression. A comparative study using black and purple cultivars revealed that neither the absence of flavones nor high accumulation of total anthocyanidins is solely sufficient for black appearance, but that cyanidin content in petals is also an important factor in the phenotype. A study comparing the black cultivar 'Kokucho' and its purple mutant showed that suppression of DvFNS abolishes the competition between anthocyanidin and flavone synthesis and leads to accumulation of cyanidin and total anthocyanidins that produce a black appearance. Surprisingly, in black cultivars the suppression of DvFNS occurred in a post-transcriptional manner, as determined by small RNA mapping

Petal Color Is Associated with Leaf Flavonoid Accumulation in a Labile Bicolor Flowering Dahlia (Dahlia variabilis) ‘Yuino’

Bicolor flowering dahlias generally produce inflorescences with bicolor petals characterized by a colored basal part and a white tip; however, they frequently produce single-colored petals. This petal color lability prevents uniform production of cut or pot flowers of bicolor dahlias and reduces the economic value of bicolor cultivars. In this study, to reveal the underlying mechanism and control color lability, the pattern of occurrence of single-colored petals was characterized in a red–white bicolor flowering cultivar ‘Yuino’. ‘Yuino’ produced inflorescences with bicolor petals, red petals, and both red and bicolor petals. Red petals occurred almost always at the outer whorls or sectorally in a mixed inflorescence, similar to a chimera or a lateral mutant. The occurrence of red petals was higher in field experiments during May to December than in greenhouse experiments during October to next July. We identified the “R-line” plant, which produced red petals with high frequency during the winter to spring cultivation; this characteristic to produce red petals with high frequency was retained through vegetative propagation. There were strong relationships between inflorescence color and leaf phenotype; red petal-producing plants accumulated flavonoids in leaves, whereas only bicolor petal-producing plants tended not to accumulate flavonoid in leaves. This suggests that petal color of ‘Yuino’ is associated with flavonoid synthetic potential in shoot. Therefore, a phenotypic difference is observed not only in petal colors but also at the whole plant level

Post-transcriptional gene silencing of CYP76AD controls betalain biosynthesis in bracts of bougainvillea

Betalain is one of four major plant pigments and shares some features with anthocyanin; however, no plant has been found to biosynthesize both pigments. Previous studies have reported that anthocyanin biosynthesis in some plants is regulated by post-transcriptional gene-silencing (PTGS), but the importance of PTGS in betalain biosynthesis remains unclear. In this study, we report the occurrence of PTGS in betalain biosynthesis in bougainvillea (Bougainvillea peruviana) ‘Thimma’, which produces bracts of three different color on the same plant, namely pink, white, and pink-white. This resembles the unstable anthocyanin pigmentation phenotype that is associated with PTGS, and hence we anticipated the presence of PTGS in the betalain biosynthetic pathway. To test this, we analysed pigments, gene expression, small RNAs, and transient overexpression. Our results demonstrated that PTGS of BpCYP76AD1, a gene encoding one of the betalain biosynthesis enzymes, is responsible for the loss of betalain biosynthesis in ‘Thimma’. Neither the genetic background nor DNA methylation in the BpCYP76AD1 sequence could explain the induction of PTGS, implying that another locus controls the unstable pigmentation. Our results indicate that naturally occurring PTGS contributes to the diversification of color patterns not only in anthocyanin biosynthesis but also in betalain biosynthesis