The Genetic Basis of a Rare Flower Color Polymorphism in Mimulus lewisii Provides Insight into the Repeatability of Evolution

A long-standing question in evolutionary biology asks whether the genetic changes contributing to phenotypic evolution are predictable. Here, we identify a genetic change associated with segregating variation in flower color within a population of Mimulus lewisii. To determine whether these types of changes are predictable, we combined this information with data from other species to investigate whether the spectrum of mutations affecting flower color transitions differs based on the evolutionary time-scale since divergence. We used classic genetic techniques, along with gene expression and population genetic approaches, to identify the putative, loss-of-function mutation that generates rare, white flowers instead of the common, pink color in M. lewisii. We found that a frameshift mutation in an anthocyanin pathway gene is responsible for the white-flowered polymorphism found in this population of M. lewisii. Comparison of our results with data from other species reveals a broader spectrum of flower color mutations segregating within populations relative to those that fix between populations. These results suggest that the genetic basis of fixed differences in flower color may be predictable, but that for segregating variation is not.     

Genetic control of white flower color in scarlet rosemallow (Hibiscus coccineus Walter)

Scarlet rosemallow (Hibiscus coccineus Walter) is a diploid, perennial, erect, and woody shrub. The species is a desirable inclusion in home landscapes because it is a native plant with attractive flowers and unusual foliage. The objective of these experiments was to determine the number of loci, number of alleles, and gene action controlling flower color (red vs. white) in scarlet rosemallow. Three white-flowered and 1 red-flowered parental lines were used to create S(1) and F(1) populations, which were self-pollinated or backcrossed to generate S(2), F(2), and BC(1) populations. Evaluation of these generations showed that flower color in these populations was controlled by a single diallelic locus with red flower color completely dominant to white. I propose that this locus be named "white flower" with alleles W and w.     

梅花"粉皮宫粉"花色色素的花青苷实质和花色的动态变化

特征颜色反应和紫外-可见光谱分析初步表明梅花"粉皮宫粉"的粉红色花色色素为花青素-3-糖苷.用分光光度法检测梅花"粉皮宫粉"不同花发育时期、在树冠不同着生部位花朵花瓣的相对花青苷含量,结果表明"粉皮宫粉" 的花色主要存在着花发育时期而导致的时间变化.花色在蕾期最浓艳,花瓣展开后便逐渐变淡;在整个花发育时期,同一朵花不同层次花瓣的颜色浓淡均为外层花瓣>中层花瓣>内层花瓣,且不同层次花瓣颜色的变化趋势几乎一致.虽然树冠下部单花的花色浓于上部的、树冠内层的浓于外层的,但花朵在树冠的着生部位导致的花色差异并不显著.花青苷除了导致"粉皮宫粉"的粉红花色外,还可能增强其花的抗寒性,为花的凌寒而开创造了条件.本文可为梅花的美学鉴赏、梅花红色花色的机理探索及其色素的分子结构鉴定提供参考.     

Additional betalain accumulation by genetic engineering leads to a novel flower color in lisianthus (Eustoma grandiflorum)

Betalains, comprising violet betacyanins and yellow betaxanthins, are pigments found in plants belonging to the order Caryophyllales. In this study, we induced the accumulation of betalains in ornamental lisianthus (Eustoma grandiflorum) by genetic engineering. Three betalain biosynthetic genes encoding CYP76AD1, dihydroxyphenylalanine (DOPA) 4,5-dioxygenase (DOD), and cyclo-DOPA 5-O-glucosyltransferase (5GT) were expressed under the control of the cauliflower mosaic virus (CaMV) 35S promoter in lisianthus, in which anthocyanin pigments are responsible for the pink flower color. During the selection process on hygromycin-containing media, some shoots with red leaves were obtained. However, most red-colored shoots were suppressed root induction and incapable of further growth. Only clone #1 successfully acclimatized and bloomed, producing pinkish-red flowers, with a slightly greater intensity of red color than that in wild-type flowers. T₁ plants derived from clone #1 segregated into five typical flower color phenotypes: wine red, bright pink, pale pink, pale yellow, and salmon pink. Among these, line #1-1 showed high expression levels of all three transgenes and exhibited a novel wine-red flower color. In the flower petals of line #1-1, abundant betacyanins and low-level betaxanthins were coexistent with anthocyanins. In other lines, differences in the relative accumulation of betalain and anthocyanin pigments resulted in flower color variations, as described above. Thus, this study is the first to successfully produce novel flower color varieties in ornamental plants by controlling betalain accumulation through genetic engineering.     

POLLINATION AND SEED PRODUCTION IN IPOMOPSIS AGGREGATA: DIFFERENCES AMONG AND WITHIN FLOWER COLOR MORPHS

The pollination of red, pink, and white color morphs of Ipomopsis aggregata was evaluated to assess whether ethological isolation based on pollinator color discrimination may occur. We observed animal visitors, assessed pollen delivery, seed set per fruit, percentage of flowers setting fruit, nectar production, and timing of flower opening for different color morphs in the Front Range of Colorado. Based on traditional zoophilous flower classifications, we expected hummingbirds to pollinate red-flowered I. aggregata subsp. collina and hawkmoths to pollinate white-flowered I. aggregata subsp. Candida. However, ethological isolation does not appear to occur among color morphs of I. aggregata in the Front Range. Hummingbirds visited red-flowered plants in excess overall, and, to a lesser extent, so did hawkmoths. Both hummingbirds and hawkmoths visited all color morphs and probably transferred pollen among them. Pollen delivery data and a day-night bagging experiment also suggest that pollinators do not necessarily behave as predicted by flower classifications. In addition, there is little evidence for major differences between red, white, and pink flowers in any aspects of reproductive biology. Indeed, most variation occurs within a given color morph.     

Perspective: Evolution of flower color in the desert annual Linanthus parryae: Wright revisited

Linanthus parryae, a diminutive desert annual with white or blue flowers, has been the focus of a long-standing debate among evolutionary biologists. At issue is whether the flower color polymorphism in this species is the product of random genetic drift, as Sewall Wright argued, or of natural selection, as proposed by Carl Epling and his colleagues. Our long-term studies of three polymorphic populations in the Mojave Desert demonstrate that flower color is subject to selection that varies in both time and space in its direction and magnitude. For all sites taken together, blue-flowered plants produced more seeds than white-flowered plants in years of relatively low seed production, whereas white-flowered plants had higher fitness in years of high seed production. Evidence of selection on flower color was found in two of the three study sites. Differences in fitness between the color morphs were sometimes large, with selection coefficients as high as 0.60 in some years. Our longest period of observations was at Pearblossom site 1, where plants reached appreciable densities in seven of the 11 years of study. Here we found significant differences in the seed production of the color morphs in six years, with three years of blue advantage and three years of white advantage. For all sites taken together, total spring precipitation (March and April) was positively correlated with both absolute and relative seed production of the color morphs. At Pearblossom site 1, blue-flowered plants typically had a fitness advantage in years of low spring precipitation, whereas white-flowered plants had a fitness advantage in years of high spring precipitation. This temporal variation in selection may contribute to the maintenance of the flower-color polymorphism at Pearblossom site 1, whereas gene flow from neighboring populations is proposed as the principal factor maintaining the polymorphism at the other study sites. We found no significant differences between the color morphs in pollinator visitation rate or in their carbon isotope ratio, a measure of water-use efficiency. Although the mechanism of selection remains elusive, our results refute Wright's conclusion that the flower color polymorphism in L. parryae is an example of isolation by distance, a key component of his shifting balance theory of evolution.     

Flower color change accelerated by bee pollination in Tibouchina (Melastomataceae)

Floral color changes are common among Melastomataceae and have been interpreted as a warning mechanism for bees to avoid old flowers, albeit increasing long-distance flower display. Here the reproductive systems of Tibouchina pulchra and T. sellowiana were investigated by controlled pollinations. Their pollinators were identified, and experiments on floral color and fragrance changes were conduced to verify if those changes affect the floral visitation. Both Tibouchina species are self compatible. The flowers lasted three days or more, and the floral color changed from white in the 1st day to pink in the following days. Pollen deposition on stigma induced floral color change. The effectiveness of the pollination is dependent on bees’ size; only large bees were regarded as effective pollinators. In experimental tests, the bees in T. pulchra preferred the natural white flowers while the visitors of T. sellowiana were attracted by both natural and mimetic 1st-day flowers (2nd-day flowers with experimentally attached 1st-day flower petals). During the experiments on floral fragrance, the bees visited both natural and mimetic 1st-day flowers (2nd-day flowers with 1st-day flower scents). In both experiments, the bees avoided natural 2nd-day flowers, but seldom visited modified 2nd-day flowers. The attractiveness of T. pulchra and T. sellowiana flowers cannot be attributed exclusively to the color or the fragrance separately, both factors seemingly act together.     

Genetic and linkage analysis of purple-blue flower in soybean

Flower color of soybean is primarily controlled by genes W1, W3, W4, Wm, and Wp. In addition, the soybean gene symbol W2, w2 produces purple-blue flower in combination with W1. This study was conducted to determine the genetic control of purple-blue flower of cultivar (cv). Nezumisaya. F(1) plants derived from a cross between Nezumisaya and purple flower cv. Harosoy had purple flowers. Segregation of the F(2) plants fitted a ratio of 3 purple:1 purple-blue. F(3) lines derived from F(2) plants with purple-blue flowers were fixed for purple-blue flowers, whereas those from F(2) plants with purple flowers fitted a ratio of 1 fixed for purple flower:2 segregating for flower color. These results indicated that the flower color of Nezumisaya is controlled by a single gene whose recessive allele is responsible for purple-blue flower. Complementation analysis revealed that flower color of Nezumisaya is controlled by W2. Linkage mapping revealed that W2 is located in molecular linkage group B2. Sap obtained from banner petals of cvs. with purple flower had a pH value of 5.73-5.77, whereas that of cvs. with purple-blue flower had a value of 6.07-6.10. Our results suggested that W2 is responsible for vacuolar acidification of flower petals.     

Florivores prefer white versus pink petal color morphs in wild radish, Raphanus sativus

Many hypotheses suggest that pollinators act to maintain or change floral color morph frequencies in nature, although pollinator preferences do not always match color morph frequencies in the field. Therefore, non-pollinating agents may also be responsible for color morph frequencies. To test this hypothesis, we examined whether Raphanus sativus plants with white flowers received different amounts of florivory than plants with pink flowers, and whether florivores preferred one floral color over the other. We found that white-flowered plants received significantly more floral damage than pink-flowered plants in eight populations over 4 years in northern California. Both generalists and specialists on Brassicaceae preferred white petals in choice and short-term no choice tests. In performance tests, generalists gained more weight on white versus pink petals whereas specialists gained similar amounts of weight on pink and white morphs. Because our results suggest that florivores prefer and perform better on white versus pink flowers, these insects may have the opportunity to affect the frequency of color morphs in the field.     

Flower Color Modification by Engineering of the Flavonoid Biosynthetic Pathway: Practical Perspectives

The status quo of flavonoid biosynthesis as it relates to flower color is reviewed together with a success in modifying flower color by genetic engineering. Flavonoids and their colored class compounds, anthocyanins, are major contributors to flower color. Many plant species synthesize limited kinds of flavonoids, and thus exhibit a limited range of flower color. Since genes regulating flavonoid biosynthesis are available, it is possible to alter flower color by overexpressing heterologous genes and/or down regulating endogenous genes. Transgenic carnations and a transgenic rose that accumulate delphinidin as a result of expressing a flavonoid 3′,5′-hydroxylase gene and have novel blue hued flowers have been commercialized. Transgenic Nierembergia accumulating pelargonidin, with novel pink flowers, has also been developed. Although it is possible to generate white, yellow, and pink-flowered torenia plants from blue cultivars by genetic engineering, field trial observations indicate difficulty in obtaining stable phenotypes.     

Genetic engineering of the anthocyanin biosynthetic pathway with flavonoid-3′,5′-hydroxylase: specific switching of the pathway in petunia

Flavonoid-3',5'-hydroxylase (F3'5'H) is the key enzyme in the synthesis of 3',5'-hydroxylated anthocyanins, which are generally required for the expression of blue or purple flower color. It has been predicted that the introduction of this enzyme into a plant species that lacks it would enable the production of blue or purple flowers by altering the anthocyanin composition. We present here the results of the genetic engineering of petunia flower color, pigmentation patterns and anthocyanin composition with sense or antisense constructs of the F3'5'H gene under the control of the CaMV 35S promoter. When sense constructs were introduced into pink flower varieties that are deficient in the enzyme, transgenic plants showed flower color changes from pink to magenta along with changes in anthocyanin composition. Some transgenic plants showed novel pigmentation patterns, e.g. a star-shaped pattern. When sense constructs were introduced into blue flower petunia varieties, the flower color of the transgenic plants changed from deep blue to pale blue or even pale pink. Pigment composition analysis of the transgenic plants suggested that the F3'5'H transgene not only created or inhibited the biosynthetic pathway to 3',5'-hydroxylated anthocyanins but switched the pathway to 3',5'-hydroxylated or 3'-hydroxylated anthocyanins.     

菊花不同花色品种中花青素苷代谢分析

应用高效液相色谱和多级质谱联用技术（HPLC-ESI-MSn）,分析菊花（Chrysanthemum×morifolium）白色、粉色、红色、紫色、红紫色和墨色6个色系共计82个品种中花青素苷合成过程的中间产物和最终产物,发现从白色、粉色、红色、紫色、红紫色到墨色花青素苷含量快速增加,分别为4.68、111.60、366.89、543.56、1220.36和2674.95μg·g-1,不同色系间花青素苷的含量差异显著（P〈0.01）,花青素苷含量越高花色越深;墨色菊花品种中总类黄酮含量显著高于其它花色品种（P〈0.01）,其它不同色系间总类黄酮含量差异不显著（P〉0.05）;随着菊花花色变深,从柚皮素分支到圣草酚的代谢流,以及从圣草酚分支到矢车菊素苷的代谢流比例增加。花青素苷成分分析发现：菊花中只含有矢车菊素苷类化合物。根据花青素苷代谢成分分析结果绘制了菊花中花青素苷代谢路径图,即在菊花类黄酮代谢途径中只存在矢车菊素苷代谢分支途径;菊花不同色系在柚皮素和圣草酚2个关键代谢分支点上向不同方向代谢流的分配比例不同,造成花青素苷产物含量不同,导致不同花色。以上研究结果为菊花花色改良的分子育种提供了理论依据。     

欧报春（Primula vulgaris）不同花色与色素关系及花色遗传初步分析

为了掌握欧报春各花色遗传规律服务于良种生产,通过对欧报春各色花进行色素吸收光谱和薄层层析分析,进行不同花色杂交研究,分析了欧报春各色花所含色素类型及各花色遗传规律。结果显示欧报春群体含多种花色素,单株也可含有多种花色素,形成多变的粉色、红色及蓝色花。黄色深浅主要由类胡萝卜素含量决定。白色对粉色及黄色为隐性遗传,黄色、粉色为显性遗传并有数量遗传特征,黄色与粉色独立遗传。蓝色为多基因控制的隐性遗传,并具有数量遗传特征。     

Sexual Dimorphism of Staminate- and Pistillate-Phase Flowers of Saponaria officinalis (Bouncing Bet) Affects Pollinator Behavior and Seed Set

The sequential separation of male and female function in flowers of dichogamous species allows for the evolution of differing morphologies that maximize fitness through seed siring and seed set. We examined staminate- and pistillate-phase flowers of protandrous Saponaria officinalis for dimorphism in floral traits and their effects on pollinator attraction and seed set. Pistillate-phase flowers have larger petals, greater mass, and are pinker in color, but due to a shape change, pistillate-phase flowers have smaller corolla diameters than staminate-phase flowers. There was no difference in nectar volume or sugar content one day after anthesis, and minimal evidence for UV nectar guide patterns in staminate- and pistillate-phase flowers. When presented with choice arrays, pollinators discriminated against pistillate-phase flowers based on their pink color. Finally, in an experimental garden, in 2012 there was a negative correlation between seed set of an open-pollinated, emasculated flower and pinkness (as measured by reflectance spectrometry) of a pistillate-phase flower on the same plant in plots covered with shade cloth. In 2013, clones of genotypes chosen from the 2012 plants that produced pinker flowers had lower seed set than those from genotypes with paler flowers. Lower seed set of pink genotypes was found in open-pollinated and hand-pollinated flowers, indicating the lower seed set might be due to other differences between pink and pale genotypes in addition to pollinator discrimination against pink flowers. In conclusion, staminate- and pistillate-phase flowers of S. officinalis are dimorphic in shape and color. Pollinators discriminate among flowers based on these differences, and individuals whose pistillate-phase flowers are most different in color from their staminate-phase flowers make fewer seeds. We suggest morphological studies of the two sex phases in dichogamous, hermaphroditic species can contribute to understanding the evolution of sexual dimorphism in plants without the confounding effects of genetic differences between separate male and female individuals.     

Floral and vegetative morphometrics of three Platonia insignis Mart. (Clusiaceae) populations,a native tree from the Brazilian Amazon

Platonia insignis Mart. (Clusiaceae), the bacurizeiro, is a native tree species from the Brazilian Amazon forests. Three populations of P. insignis have been observed in the north-east region of the state of Maranhão that differ in flower color: the red population that produces dark pink flowers, the pink population that produces light pink flowers, and the white population with yellowish-white flowers. From multivariate statistical analysis, we aimed at characterizing such populations using morpho-anatomical leaf and flower morphology parameters. A total of 40 P. insignis individuals have been sampled in the cities of São Luís and Chapadinha. The morphological traits varied more than the anatomical traits. Area, fresh mass, and dry mass were the leaf parameters that show more variations. Platonia insignis have hypostomatic or amphihypostomatic leaves. The length of the gynoecium+the length of the nectary, the total length and the length of gynoecium were the principal components considering flower analysis. The three populations did not show significant differences nor did they group using Ward's method. Individuals from the Chapadinha and São Luís red population have been separated according to leaf and flower morphological traits, and the morphological difference between individuals may represent early stages of geographical speciation.     

Genetic engineering of flavonoid pigments to modify flower color in floricultural plants

Recent advances in genetic transformation techniques enable the production of desirable and novel flower colors in some important floricultural plants. Genetic engineering of novel flower colors is now a practical technology as typified by commercialization of a transgenic blue rose and blue carnation. Many researchers exploit knowledge of flavonoid biosynthesis effectively to obtain unique flower colors. So far, the main pigments targeted for flower color modification are anthocyanins that contribute to a variety of colors such as red, pink and blue, but recent studies have also utilized colorless or faint-colored compounds. For example, chalcones and aurones have been successfully engineered to produce yellow flowers, and flavones and flavonols used to change flower color hues. In this review, we summarize examples of successful flower color modification in floricultural plants focusing on recent advances in techniques.     

Flower color affects tri-trophic-level biocontrol interactions

The adults of many parasitoid species require nectar for optimal fitness, but very little is known of flower recognition. Flight cage experiments showed that the adults of an egg parasitoid (Trichogramma carverae Oatman and Pinto) benefited from alyssum (Lobularia maritima L.) bearing white flowers to a greater extent than was the case for light pink, dark pink or purple flowered cultivars, despite all cultivars producing nectar. Survival and realised parasitism on all non-white flowers were no greater than when the parasitoids were caged on alyssum shoots from which flowers had been removed. The possibility that differences between alyssum cultivars were due to factors other than flower color, such as nectar quality, was excluded by dying white alyssum flowers by placing the roots of the plants in 5% food dye (blue or pink) solution. Survival of T. carverae was lower on dyed alyssum flowers than on undyed white flowers. Mixing the same dyes with honey in a third experiment conducted in the dark showed that the low level of feeding on dyed flowers was unlikely to be the result of olfactory or gustatory cues. Flower color appears, therefore, to be a critical factor in the choice of plants used to enhance biocontrol, and is likely also to be a factor in the role parasitoids play in structuring invertebrate communities.     

Inheritance of flower color in pickerelweed (Pontederia cordata L.)

Pickerelweed (Pontederia cordata L.) is a diploid (2n = 2x = 16), erect, emergent, herbaceous aquatic perennial. The showy inflorescences of pickerelweed make this species a prime candidate for inclusion in water gardens and aquascapes. The objective of this experiment was to determine the number of loci, number of alleles, and gene action controlling flower color (blue vs. white) in pickerelweed. Two blue-flowered and one white-flowered parental lines were used in this experiment to create S(1) and F(1) populations. F(2) populations were produced through self-pollination of F(1) plants. Evaluation of S(1), F(1), and F(2) generations revealed that flower color in these populations was controlled by 2 alleles at one locus with blue flower color completely dominant to white. We propose that this locus be named white flower with alleles W and w.     

Inheritance of flower color and spininess in safflower (Carthamus tinctorius L.)

Safflower (Carthamus tinctorius L.) flowers are used for coloring and flavoring food and also as fresh-cut and dried flowers. The most important characteristics which contribute to the ornamental value of safflower are flower color and spinelessness. The objective of this study was to determine the inheritance mode and the number of genes controlling spininess and flower color in some Iranian genotypes of safflower. The results indicated that the existence of spines on the leaves and bracts of safflower is controlled by a single dominant gene in which the spiny phenotype was completely dominant to spineless. In some crosses, flower color was controlled by two epistatic loci each with two alleles, resulting in a ratio of 13:3 in the segregating F2 population for plants with orange and yellow flowers. Also, other mechanisms of genetic control, such as duplicate dominance and duplicate recessive types of epistasis, were observed for flower color in other crosses that led to ratios of 7:9 and 15:1 for plants with orange and yellow flowers, respectively. The results suggest that for ornamental use or in the food dying industry, genotypes with orange or yellow flowers and without spines on the leaves and bracts can be produced.