Floral Anthocyanin Research Articles

Unraveling the regulatory network of flower coloration in soybean: Insights into roles of GmMYBA3 and GmMYBR1

Anthocyanins play crucial roles in pollen protection and pollinator attraction in flowering plants. However, the mechanisms underlying flower color determination and whether floral anthocyanin regulators participate in other processes remain largely unresolved in soybeans (Glycine max). In this study, we investigated the genetic components and mechanisms governing anthocyanin biosynthesis in soybean flowers. Molecular and genetic studies have characterized two antagonistic regulators, the positive activator GmMYBA3 and the negative repressor GmMYBR1, that modulate the gene expression of anthocyanin biosynthesis in soybean flowers. Further findings revealed a regulatory interplay between GmMYBA3 and GmMYBR1 bridged by GmTT8a, highlighting the complexity of anthocyanin regulation in different soybean organs. Exploration of additional soybean cultivars demonstrated the universality of GmMYBA3 and GmMYBR1 in regulating floral anthocyanin biosynthesis- related genes, with GmF3′5′H identified as a crucial determinant of white flower color. This study provides a molecular mechanism underlying soybean flower color determination, paving the way for the molecular modification of soybean flowers to probably enhance their resistance to abiotic stresses and attractiveness to pollinators.

Floral scents, specialized metabolites and stress-response activities in Heritiera fomes and Bruguiera gymnorrhiza from Sundarban mangrove ecosystem.

Floral biochemistry and stress physiology is an underexplored aspect of mangroves, which should be investigated as part of preservation and restoration efforts. A thriving true mangrove tree (Bruguiera gymnorrhiza (L.) Lamk.) and a threatened mangrove-associate species (Heritiera fomes Buch. Ham.) were studied in the Sundarban region of India for seasonal variations in floral odours, non-volatile phytochemicals, antioxidant enzyme activities, and surface water chemistry in surrounding habitat. Both species were found to exhibit significant differences in floral volatilomes, protein contents, antioxidant enzyme activities, total flavonoids, and total phenolic contents between spring and autumn blooms. The bird-pollinated flowers of B. gymnorrhiza also showed considerable seasonal differences in floral anthocyanin and proline contents, indicating vulnerability of the post-anthesis open flowers to environmental factors. Contrarily to previous findings, B. gymnorrhiza floral bouquet appeared to be enriched in various classes of volatiles - dominated by sulphurous compounds in bud stage and terpenoids in open stage. Floral anthocyanins, contributing to the striking colouration of the calyx, were found to comprise cyanidin and delphinidin derivatives. Other glycosides of cyanidin and delphinidin were detected in H. fomes flowers, contributing to visual guides to potential food rewards for pollinating insects. Floral tissue in H. fomes was found to be protected by densely overlapping layers of stellate trichomes containing sesquiterpenoids as phytoprotectants. Comparison of the two floral species suggested that H. fomes flowering is optimized to oligohaline (but not freshwater) vernal conditions; whereas B. gymnorrhiza blooms are adapted for biologically enriched (including abundant herbivores and microbial growth), mesohaline forest habitats.

Natural variation in Beauty Mark is associated with UV-based geographical adaptation in Gossypium species

BackgroundAnthocyanins, a class of specialized metabolites that are ubiquitous among plant species, have attracted a great deal of attention from plant biologists due to their chemical diversity. They confer purple, pink, and blue colors that attract pollinators, protect plants from ultraviolet (UV) radiation, and scavenge reactive oxygen species (ROS) to facilitate plant survival during abiotic stress. In a previous study, we identified Beauty Mark (BM) in Gossypium barbadense as an activator of the anthocyanin biosynthesis pathway; this gene also directly led to the formation of a pollinator-attracting purple spot.ResultsHere, we found that a single nucleotide polymorphism (SNP) (C/T) within the BM coding sequence was responsible for variations in this trait. Transient expression assays of BM from G. barbadense and G. hirsutum in Nicotiana benthamiana using luciferase reporter gene also suggested that SNPs in the coding sequence could be responsible for the absent beauty mark phenotype observed in G. hirsutum. We next demonstrated that the beauty mark and UV floral patterns are associated phenotypes and that UV exposure resulted in increased ROS generation in floral tissues; BM thus contributed to ROS scavenging in G. barbadense and wild cotton plants with flowers containing the beauty mark. Furthermore, a nucleotide diversity analysis and Tajima’s D Test suggested that there have been strong selective sweeps in the GhBM locus during G. hirsutum domestication.ConclusionsTaken together, these results suggest that cotton species differ in their approaches to absorbing or reflecting UV light and thus exhibit variations in floral anthocyanin biosynthesis to scavenge reactive ROS; furthermore, these traits are related to the geographic distribution of cotton species.

Untargeted metabolites profiling of volatile and non-volatile components of Egyptian lotus (Nelumbo nucifera Gaertn.) using UHPLC/PDA/ESI-MS and solid-phase microextraction (SPME) GC/MS in relation to its antiaging and anti-inflammatory effects

Nelumbo nucifera Gaertn. is a unique member of the family Nymphaeaceae, and one of the most important industrial crops with a cultural and medicinal value, especially in the traditional herbal medicines. The beautiful scent of its pink flowers had been used in many cosmetic preparations, but rarely investigated. The goal of this study was to characterize N. nucifera flower aroma profile using solid-phase microextraction coupled with GC/MS. A total of 33 volatile compounds belonging to several classes were identified with cineole reported for the first time and likely to contribute to its aroma. Untargeted metabolites profiling of non-volatile components in leaves, flowers, and seeds was attempted using high-resolution ultra-performance liquid chromatography-mass spectrometry analysis. UPLC-MS. MS-based profiling provided an annotation of more than 60 secondary metabolites with two newly reported glycoalkaloids alongside with floral anthocyanins. Principal component analysis of the UPLC-MS dataset revealed that flowers exhibited a distinct metabolome compared to seeds and leaves. Ultimately, flower extract exhibited a promising anti-aging and anti-inflammatory activities providing a new insight into lotus flower incorporation in the industrial cosmetic formulations.

Comparative Transcriptome Analysis Identified Potential Genes and Transcription Factors for Flower Coloration in Kenaf (Hibiscus cannabinus L.)

The biochemical compounds in kenaf leaves and flowers mainly consist of flavonoids, including flavonoid glycosides and floral anthocyanins. In the present study, we performed comparative transcriptome analysis using RNA-sequencing and identified putative genes involved in flower coloration in different flower developmental stages of three kenaf mutants including Baekma (white flower), Jangdae (ivory flower), and Bora (purple flower). A total of 36.1 Gb reads were generated for two kenaf accessions and 38,601 representative transcripts with an average length of 1350 bp were yielded, of which 33,057 (85.64%) were annotated against two databases. Expression profiling of the transcripts identified 1044 and 472 differentially expressed genes (DEGs) among three mutants in the young bud and full bloom stages, respectively. KEGG enrichment analysis of these DEGs revealed that the representative pathway was “biosynthesis of secondary metabolites”, including phenylpropanoid biosynthesis and flavonoid biosynthesis. Consequently, we investigated genes related to the phenylpropanoid pathway, which included 45 DEGs from a total of 1358. Our results provide useful information for understanding gene functions of flower coloration in kenaf, which will be useful in further studies.

Major Flower Pigments Originate Different Colour Signals to Pollinators

Flower colour is mainly due to the presence and type of pigments. Pollinator preferences impose selection on flower colour that ultimately acts on flower pigments. Knowing how pollinators perceive flowers with different pigments becomes crucial for a comprehensive understanding of plant-pollinator communication and flower colour evolution. Based on colour space models, we studied whether main groups of pollinators, specifically hymenopterans, dipterans, lepidopterans and birds, differentially perceive flower colours generated by major pigment groups. We obtain reflectance data and conspicuousness to pollinators of flowers containing one of the pigment groups more frequent in flowers: chlorophylls, carotenoids and flavonoids. Flavonoids were subsequently classified in UV-absorbing flavonoids, aurones-chalcones and the anthocyanins cyanidin, pelargonidin, delphinidin, and malvidin derivatives. We found that flower colour loci of chlorophylls, carotenoids, UV-absorbing flavonoids, aurones-chalcones, and anthocyanins occupied different regions of the colour space models of these pollinators. The four groups of anthocyanins produced a unique cluster of colour loci. Interestingly, differences in colour conspicuousness among the pigment groups were almost similar in the bee, fly, butterfly, and bird visual space models. Aurones-chalcones showed the highest chromatic contrast values, carotenoids displayed intermediate values, and chlorophylls, UV-absorbing flavonoids and anthocyanins presented the lowest values. In the visual model of bees, flowers with UV-absorbing flavonoids (i.e., white flowers) generated the highest achromatic contrasts. Ours findings suggest that in spite of the almost omnipresence of floral anthocyanins in angiosperms, carotenoids and aurones-chalcones generates higher colour conspicuousness for main functional groups of pollinators.

High promoter sequence variation in subgroup 6 members of R2R3-MYB genes is involved in different floral anthocyanin color patterns in Lilium spp.

The spatially and temporally distinct expression of R2R3-MYB positive regulators is among the major mechanisms that create various anthocyanin color patterns in many flowers. However, we do not know how these positive regulators have gained different expression profiles. In the Asiatic hybrid lily 'Lollypop' (derived from the crosses of species belonging to Sinomartagon/Daurolirion section), MYB12 and MYB19S regulate the pigmentation at whole tepals and raised tepal spots, respectively. In the Oriental hybrid lily 'Sorbonne' (derived from the crosses of species belonging to the Archelirion section), MYB12 regulates both whole tepal and raised spot pigmentation. The genes have similar amino acid sequences with similar protein functions but exhibit different expression profiles in lily flowers. As promoters are among the most significant factors affecting gene expression profiles, their promoter sequences were determined in this study. The three genes had very different promoter sequences, and putative cis-regulatory elements were not conserved in numbers or order. To further confirm the promoter functions, tobacco plants were transformed with native promoter-driven MYB12 or MYB19S genes of 'Lollypop.' Expression levels of MYB12 were higher in corolla tubes than in lobes, while those of MYB19S were higher in corolla lobes than in tubes. Thus, the diverse promoter functions were likely to be the leading causes of their different expression profiles and generation of unique color patterns. Finally, the history of R2R3-MYB gene establishment during lily evolution was estimated using sequence data.

Abiotic Environment Predicts Micro- but Not Macroevolutionary Patterns of Flower Color in Monkeyflowers (Phrymaceae).

Anthocyanin pigments are responsible for many of the vivid pink, purple, red, and blue flower colors across angiosperms and frequently vary within and between closely related species. While anthocyanins are well known to influence pollinator attraction, they are also associated with tolerance to abiotic stressors such as extreme temperatures, reduced precipitation, and ultraviolet radiation. Using a comparative approach, we tested whether abiotic variables predict floral anthocyanin in monkeyflowers (Phrymaceae) across western North America. Within two polymorphic species, we found that abiotic variables predicted flower color across their geographic ranges. In Erythranthe discolor, the frequency of pink flowered (anthocyanin producing) individuals was greater in populations with reduced precipitation. In Diplacus mephiticus, the frequency of pink flowered individuals was greater at higher elevations that had reduced precipitation and lower temperatures but less ultraviolet radiation. At the macroevolutionary scale, across two parallel radiations of North American monkeyflowers, species with floral anthocyanins (pink, purple, or red corollas) occupied areas with reduced precipitation in Erythranthe but not Diplacus. However, after accounting for phylogenetic relatedness, we found no evidence for the joint evolution of flower color and environmental affinity in either clade. We conclude that although abiotic stressors may play a role in the evolution of flower color within polymorphic species, we found no evidence that these processes lead to macroevolutionary patterns across monkeyflowers.

The effects of climate change on floral anthocyanin polymorphisms.

Pigmentation affords resistance to abiotic stressors, and thus can respond adaptively or plastically to drought and extreme temperatures associated with global change. Plants frequently display variability in flower coloration that is underlain by anthocyanin pigmentation. While anthocyanin polymorphisms impact plant-animal interactions, they also impact reproductive performance under abiotic stress. We used descriptions of flower colour from over 1900 herbarium records representing 12 North American species spanning 124 years to test whether anthocyanin-based flower colour has responded to global change. Based on demonstrated abiotic associations with performance of anthocyanin colour morphs, we predicted pigmentation would increase in species experiencing increased aridity, but decline in those experiencing larger increases in temperature. We found that the frequency of reports of pigmented morphs increased temporally in some taxa but displayed subtle declines in others. Pigmentation was negatively associated with temperature and positively associated with vapour pressure deficit (a metric of aridity) across taxa. Species experiencing larger temperature increases over time displayed reductions in pigmentation, while those experiencing increases in aridity displayed increases in pigmentation. Change in anthocyanin-based floral colour was thus linked with climatic change. Altered flower coloration has the strong potential to impact plant-animal interactions and overall plant reproductive performance.

Chemical Basis of Floral Color Signals in Gesneriaceae: The Effect of Alternative Anthocyanin Pathways.

Changes in floral pigmentation can have dramatic effects on angiosperm evolution by making flowers either attractive or inconspicuous to different pollinator groups. Flower color largely depends on the type and abundance of pigments produced in the petals, but it is still unclear whether similar color signals rely on same biosynthetic pathways and to which extent the activation of certain pathways influences the course of floral color evolution. To address these questions, we investigated the physical and chemical aspects of floral color in the Neotropical Gesnerioideae (ca. 1,200 spp.), in which two types of anthocyanins, hydroxyanthocyanins, and deoxyanthocyanins, have been recorded as floral pigments. Using spectrophotometry, we measured flower reflectance for over 150 species representing different clades and pollination syndromes. We analyzed these reflectance data to estimate how the Gesnerioideae flowers are perceived by bees and hummingbirds using the visual system models of these pollinators. Floral anthocyanins were further identified using high performance liquid chromatography coupled to mass spectrometry. We found that orange/red floral colors in Gesnerioideae are produced either by deoxyanthocyanins (e.g., apigenidin, luteolinidin) or hydroxyanthocyanins (e.g., pelargonidin). The presence of deoxyanthocyanins in several lineages suggests that the activation of the deoxyanthocyanin pathway has evolved multiple times in the Gesnerioideae. The hydroxyanthocyanin-producing flowers span a wide range of colors, which enables them to be discriminated by hummingbirds or bees. By contrast, color diversity among the deoxyanthocyanin-producing species is lower and mainly represented at longer wavelengths, which is in line with the hue discrimination optima for hummingbirds. These results indicate that Gesnerioideae have evolved two different biochemical mechanisms to generate orange/red flowers, which is associated with hummingbird pollination. Our findings also suggest that the activation of the deoxyanthocyanin pathway has restricted flower color diversification to orange/red hues, supporting the potential constraining role of this alternative biosynthetic pathway on the evolutionary outcome of phenotypical and ecological diversification.

Characterization of the F Locus Responsible for Floral Anthocyanin Production in Potato

Anthocyanins are pigmented secondary metabolites produced via the flavonoid biosynthetic pathway and play important roles in plant stress responses, pollinator attraction, and consumer preference. Using RNA-sequencing analysis of a cross between diploid potato (Solanum tuberosum L.) lines segregating for flower color, we identified a homolog of the ANTHOCYANIN 2 (AN2) gene family that encodes a MYB transcription factor, herein termed StFlAN2, as the regulator of anthocyanin production in potato corollas. Transgenic introduction of StFlAN2 in white-flowered homozygous doubled-monoploid plants resulted in a recovery of purple flowers. RNA-sequencing revealed the specific anthocyanin biosynthetic genes activated by StFlAN2 as well as expression differences in genes within pathways involved in fruit ripening, senescence, and primary metabolism. Closer examination of the locus using genomic sequence analysis revealed a duplication in the StFlAN2 locus closely associated with gene expression that is likely attributable to nearby genetic elements. Taken together, this research provides insight into the regulation of anthocyanin biosynthesis in potato while also highlighting how the dynamic nature of the StFlAN2 locus may affect expression.

Genetic analysis of some morphological traits in synthetic $$\times $$ naturally polyploid cotton derivatives

Cotton has received attention of geneticists since more than a century. Gossypium hirsutum, the predominantly cultivated cotton species worldwide, has a narrow genetic base. It is important to broaden its genetic base through introgression of novel alleles from related species. Here, we report the development and characterization of a backcross population derived from the hybridization of a 'synthetic' (derived by crossing and chromosomal doubling of nonprogenitor Gossypium species) and natural tetraploid upland cotton. 'Synthetic' was observed to be male-sterile and thus, was used as the female parent. A total of 7434 flowers were pollinated to obtain 1868 BC1F1 seeds by direct and reciprocal crosses. Characterization of the experimental plant material was conducted in the field for several morphological traits such as pubescence on the stem, leaf, petiole and bract, presence/absence of petal spot, petal margin colouration and stamen filament colouration. Genetic analysis revealed that petal margin colouration phenotype was governed by a single dominant gene, whereas the petal spot and filament colouration phenotypes manifested segregation distortion. None of the BC1F1 plants was devoid of trichomes thus demonstrating that presence of trichomes is dominant over their absence. Modern upland cotton cultivars are usually devoid of petal spot, petal margin colouration and stamen filament colouration. These floral anthocyanin pigmentation characteristics, if fixed in the cotton germplasm, may serve as diagnostic features for the identification of cultivars during DUS testing as well as in the maintenance breeding programmes.

MYB repressors and MBW activation complex collaborate to fine-tune flower coloration in Freesia hybrida

Floral anthocyanin has multiple ecological and economic values, its biosynthesis largely depends on the conserved MYB-bHLH-WD40 (MBW) activation complex and MYB repressors hierarchically with the MBW complex. In contrast to eudicots, the MBW regulatory network model has not been addressed in monocots because of the lack of a suitable system, as grass plants exhibit monotonous floral pigmentation patterns. Presently, the MBW regulatory network was investigated in a non-grass monocot plant, Freesia hybrida. FhMYB27 and FhMYBx with different functional manners were confirmed to be anthocyanin related R2R3 and R3 MYB repressors, respectively. Particularly, FhMYBx could obstruct the formation of positive MBW complex by titrating bHLH proteins, whereas FhMYB27 mainly defected the activator complex into suppressor via its repression domains in C-terminus. Furthermore, the hierarchical and feedback regulatory loop was verified, indicating the synergistic and sophisticated regulatory network underlying Freesia anthocyanin biosynthesis was quite similar to that reported in eudicot plants.

Climate Predicts UV Floral Pattern Size, Anthocyanin Concentration, and Pollen Performance in Clarkia unguiculata.

Given that flower size and pigmentation can mediate plant–pollinator interactions, many studies have focused on pollinator-driven selection on these floral traits. However, abiotic factors such as precipitation, temperature, and solar radiation also contribute to geographic variation in floral color, pattern, and size within multiple species. Several studies have described an ecogeographic pattern within species in which high temperature, high ultraviolet (UV) radiation, low precipitation and/or low latitudes are associated with increased floral anthocyanin production, smaller flowers, and/or larger UV-absorbing floral patterns (nectar guides or bullseyes). However, latitude or elevation is often used as a proxy variable to study variation in floral traits associated with a wide range of climatic variables, making the proximate abiotic drivers of variation difficult to identify. In this study, we tested and corroborated several predictions for how the abiotic environment may directly or indirectly shape geographic patterns of floral color, pattern, and size in Clarkia unguiculata (Onagraceae). This study provides the first report of geographic variation in multispectral floral color and pattern in C. unguiculata, while also providing an experimental test of the putative protective role of UV absorption for pollen performance. We quantified geographic variation among greenhouse-raised populations in UV floral pattern size, mean UV petal reflectance, anthocyanin concentration, and petal area in C. unguiculata across its natural range in California and, using 30 year climate normals for each population, we identified climatic and topographic attributes that are correlated with our focal floral traits. In addition, we examined pollen performance under high and low UV light conditions to detect the protective function (if any) of UV floral patterns in this species. Contrary to our expectations, the nectar guide and the proportion of the petal occupied by the UV nectar guide were largest in low solar UV populations. Estimated floral anthocyanin concentration was highest in populations with high solar UV, which does support our predictions. The size of the UV nectar guide did not affect pollen performance in either of the light treatments used in this study. We conclude that, under the conditions examined here, UV-absorbing floral patterns do not serve a direct “pollen protection” function in C. unguiculata. Our results only partially align with expected ecogeographic patterns in these floral traits, highlighting the need for research in a wider range of taxa in order to detect and interpret broad scale patterns of floral color variation.

Cloning and Functional Characterization of a Flavonoid Transport-Related MATE Gene in Asiatic Hybrid Lilies (Lilium spp.).

Previous studies have suggested that multidrug and toxic compound extrusion (MATE) proteins might be involved in flavonoid transportation. However, whether MATE proteins are involved in anthocyanin accumulation in Lilium is unclear. Here, a flavonoid transport-related MATE candidate gene, LhDTX35, was cloned from the Asiatic hybrid lily cultivar ‘Tiny Padhye’ by rapid amplification of 5’ and 3’ cDNA ends (RACE) and found to encode 507 amino acids. BLASTx results indicated that LhDTX35 showed high homology to the DTX35 genes of other species. Bioinformatics analysis predicted that the protein encoded by LhDTX35 possessed 12 typical transmembrane segments and had functional domains typical of the MATE-like superfamily. Phylogenetic analysis grouped LhDTX35 in the same clade as the DTX35 of other species. Notably, the expression pattern of LhDTX35 was positively correlated with floral anthocyanin accumulation in ‘Tiny Padhye’. A subcellular localization assay showed that the protein encoded by LhDTX35 was plasmalemma localized but not nuclear, indicating that the LhDTX35 gene may function as a carrier protein to transport anthocyanins in Lilium. Functional complementation of the Arabidopsis DTX35 gene demonstrated that LhDTX35 could restore silique-infertility and the anthocyaninless phenotype of an Arabidopsis DTX35 mutant. These results indicated that LhDTX35 might be involved in anthocyanin accumulation in Lilium.

Stepwise evolution of floral pigmentation predicted by biochemical pathway structure.

Developmental pathways play a major role in influencing the distribution of naturally occurring phenotypes. For example, pathway structure and regulation could make some phenotypes inaccessible or restrict the routes through which phenotypes evolve. In this study, we examine floral anthocyanin pigments across the Solanaceae family and test whether patterns of phenotypic variation are consistent with predicted constraints based on the structure of the flavonoid biosynthetic pathway. We find that anthocyanin evolution occurs in a stepwise manner whereby transitions between the production of red mono hydroxylated pelargonidin pigments and blue trihydroxylated delphinidin pigments first passes through an intermediate step of producing purple dihydroxylated cyanidin pigments. Although the transitions between these three pigment types differ in frequency, we infer that these shifts are often reversible, suggesting that the functionality of the underlying biochemical pathway is generally conserved. Furthermore, our study finds that some pigment combinations are never observed, pointing to additional constraints on naturally occurring phenotypes. Overall, our findings provide insights into how the structure of an angiosperm-wide biochemical pathway has shaped macroevolutionary variation in floral pigmentation.

Evolution of floral traits and impact of reproductive mode on diversification in the phlox family (Polemoniaceae)

Pollinator-mediated selection is a major driver of evolution in flowering plants, contributing to the vast diversity of floral features. Despite long-standing interest in floral variation and the evolution of pollination syndromes in Polemoniaceae, the evolution of floral traits and known pollinators has not been investigated in an explicit phylogenetic context. Here we explore macroevolutionary patterns of both pollinator specificity and three floral traits long considered important determinants of pollinator attraction across the most comprehensive species-level phylogenetic tree yet produced for the family. The presence of floral chlorophyll is reconstructed as the ancestral character state of the family, even though the presence of floral anthocyanins is the most prevalent floral pigment in extant taxa. Mean corolla length and width of the opening of the floral tube are correlated, and both appear to vary with pollinator type. The evolution of pollination systems appears labile, with multiple gains and losses of selfing and conflicting implications for patterns of diversification. Explicit testing of diversification models rejects the hypothesis that selfing is an evolutionary dead-end. This study begins to disentangle the individual components that comprise pollination syndromes and lays the foundation for future work on the genetic mechanisms that control each trait.

Genome-scale transcriptional study of hybrid effects and regulatory divergence in an F1 hybrid Ruellia (Wild Petunias: Acanthaceae) and its parents

BackgroundNew combinations of divergent genomes can give rise to novel genetic functions in resulting hybrid progeny. Such functions may yield opportunities for ecological divergence, contributing ultimately to reproductive isolation and evolutionary longevity of nascent hybrid lineages. In plants, the degree to which transgressive genotypes contribute to floral novelty remains a question of key interest. Here, we generated an F1 hybrid plant between the red-flowered Ruellia elegans and yellow flowered R. speciosa. RNA-seq technology was used to explore differential gene expression between the hybrid and its two parents, with emphasis on genetic elements involved in the production of floral anthocyanin pigments.ResultsThe hybrid was purple flowered and produced novel floral delphinidin pigments not manufactured by either parent. We found that nearly a fifth of all 86,475 unigenes expressed were unique to the hybrid. The majority of hybrid unigenes (80.97%) showed a pattern of complete dominance to one parent or the other although this ratio was uneven, suggesting asymmetrical influence of parental genomes on the progeny transcriptome. However, 8.87% of all transcripts within the hybrid were expressed at significantly higher or lower mean levels than observed for either parent. A total of 28 unigenes coding putatively for eight core enzymes in the anthocyanin pathway were recovered, along with three candidate MYBs involved in anthocyanin regulation.ConclusionOur results suggest that models of gene evolution that explain phenotypic novelty and hybrid establishment in plants may need to include transgressive effects. Additionally, our results lend insight into the potential for floral novelty that derives from unions of divergent genomes. These findings serve as a starting point to further investigate molecular mechanisms involved in flower color transitions in Ruellia.

Acylated cyanidin 3-sophoroside-5-glucosides from the purple flowers of Raphanus sativus L. var. raphanistroides Makino (Brassicaceae)

Two novel acylated cyanidin 3-sophoroside-5-glucosides were isolated from the purple flowers of Raphanus sativus L. var. raphanistroides Makino (Family: Brassicaceae). Chemical and spectroscopic methods revealed that they were cyanidin 3-O-[2-O-(2-O-(trans-caffeoyl)-β-glucopyranosyl)-6-O-(trans-p-coumaroyl)-β-glucopyranoside]-5-O-[6-O-(malonyl)-β-glucopyranoside] and cyanidin 3-O-[2-O-(2-O-(trans-caffeoyl)-β-glucopyranosyl)-6-O-(trans-feruloyl)-β-glucopyranoside]-5-O-[6-O-(malonyl)-β-glucopyranoside], which are major floral anthocyanins. In addition, mono-hydroxycinnamoyl cyanidin 3-sophoroside-5-malonyl-glucosides, which have been identified as root peel anthocyanins of purple radishes, were identified as minor anthocyanins in the flowers of R. sativus var. raphanistroides using comparative high performance liquid chromatography with root peel anthocyanins.

Elevational divergence and clinal variation in floral color and leaf chemistry in Silene vulgaris.

Environmental heterogeneity over a species range can lead to divergent selection among populations, leading to phenotypic differences. The plant flavonoid pathway controls key reproductive and defense-related traits and responds to selection and environmental stressors, allowing for hypotheses about phenotypic divergence across environmental gradients. We hypothesized that with increasing elevation, more flavonoids would be produced as a response to increased UV radiation and that plants would be better defended against herbivores. We measured floral color, flavonoids, and herbivory in natural populations of Silene vulgaris (Caryophyllaceae) along elevational transects in the French Alps. We correlated phenotypes with environmental variables and calculated genotypic divergence (FST) to compare with phenotypic divergence (PST). We found significant phenotypic variation in S. vulgaris along elevational gradients. Strong positive correlations were observed between floral color, leaf non-anthocyanidin flavonoid concentration, and elevation. Floral anthocyanin and leaf non-anthocyanidin flavonoid phenotypes negatively covaried with temperature and precipitation seasonality. Comparisons of PST to FST provided evidence for stabilizing selection on floral color among transects and divergent selection along the elevational gradient. Flavonoid production increases along elevational gradients in S. vulgaris, with clinal variation in calyx anthocyanins and increasing leaf non-anthocyanin flavonoid concentrations. Despite the photoprotective and antiherbivore properties of some flavonoids, flavonoid production in flowers and leaves was correlated with population microclimatic variables: temperature and precipitation. Taken together, the results suggest that different flavonoid groups are targeted by selection in different tissues and provide evidence for divergent patterns of selection for flavonoids between high and low elevations.