SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Asteraceae

319

Recent advances in molecular phylogenetics and a series of important palaeobotanical discoveries have revolutionized our understanding of angiosperm diversification. Yet, the origin and early evolution of their most characteristic feature, the flower, remains poorly understood. In particular, the structure of the ancestral flower of all living angiosperms is still uncertain. Here we report model-based reconstructions for ancestral flowers at the deepest nodes in the phylogeny of angiosperms, using the largest data set of floral traits ever assembled. We reconstruct the ancestral angiosperm flower as bisexual and radially symmetric, with more than two whorls of three separate perianth organs each (undifferentiated tepals), more than two whorls of three separate stamens each, and more than five spirally arranged separate carpels. Although uncertainty remains for some of the characters, our reconstruction allows us to propose a new plausible scenario for the early diversification of flowers, leading to new testable hypotheses for future research on angiosperms.

Concepts: Pollination, Flowering plant, Flower, Pollen, Plant sexuality, Petal, Sepal, Asteraceae

168

BACKGROUND: The tick Rhipicephalus sanguineus is the species with the largest worldwide distribution and is proven to be involved in the transmission of pathogens such as Babesia canis, Ehrlichia canis, Coxiella burnetii, Rickettsia ricketsii, Rickettsia conorii, among others. Studies have demonstrated acquisition of resistance to some of the active principles used in commercial formulations of acaricides. Tagetes patula (Asteraceae) is a plant with highlighted economic and commercial importance due to the production of secondary metabolites with insecticide and acaricide potential, mainly flavonoids, thiophenes and terpenes. METHODS: The in vitro acaricide action of the ethanolic 70% extract from aerial parts of T. patula, obtained by percolation, was evaluated against larvae and engorged adult females of Rhipicephalus sanguineus by immersion test for 5 minutes. The chemical characterization of this extract was done by liquid chromatography coupled with mass spectrometry (LC-MS), using direct injection of sample. RESULTS: Despite T. patula not proving lethal to adults in any of the concentrations tested, at 50.0 mg/mL oviposition rate decreased by 21.5% and eliminated 99.78% of the larvae. Also it was determined that the best results were obtained with 5 minutes of immersion. From the chromatographic analysis twelve O-glycosylated flavonoids were identified. CONCLUSIONS: This is the first report on the acaricidal activity of T. patula extract against Rh. sanguineus. If we consider the application of the product in the environment, we could completely eliminate the larval stage of development of the ixodid Rh. sanguineus.

Concepts: Larva, Coxiella burnetii, Q fever, Chromatography, Analytical chemistry, Rhipicephalus sanguineus, Asteraceae, Tagetes patula

167

Flowering time of the short-day plant Chrysanthemum morifolium is largely dependent upon daylength, but it is also distinctly influenced by other environmental factors. Flowering is delayed by summer heat. Here, the underlying basis for this phenomenon was investigated. Heat-induced flowering retardation occurred similarly in C. morifolium and C. seticuspe, a wild-type diploid chrysanthemum. In both plants, this flowering retardation occurred mainly because of inhibition of capitulum development. Concurrently, expression of flowering-related genes in the shoot tip was delayed under high temperature conditions. In chrysanthemums, FLOWERING LOCUS T-like 3 (FTL3) has been identified as a floral inducer produced in the leaves after short-day stimuli and transported to the shoot tip. In C. seticuspe, heat-induced flowering retardation was accompanied by a reduction in FTL3 expression in the leaves. Two C. morifolium cultivars with flowering times that are differently affected by growth temperature were also examined. High temperature-induced FTL3 repression was observed in the leaves of both cultivars, although the degree of repression was greater in the heat-sensitive cultivar than in the heat-tolerant cultivar. When a scion of the heat-sensitive cultivar was grafted onto the stock of the heat-tolerant cultivar, flowering in the shoot tip was less sensitive to heat. Conversely, a scion of the heat-tolerant cultivar grafted onto the heat-sensitive cultivar showed increased heat sensitivity. Thus, several lines of evidence suggest that the reduction of FTL3 signalling from the leaves to the shoot tip at high temperatures is involved in flowering retardation in chrysanthemums.

Concepts: Gene, Temperature, Thermodynamics, Grafting, Flower, Chrysanthemum, Asteraceae, Cultivar

92

Various colored cultivars of ornamental flowers have been bred by hybridization and mutation breeding; however, the generation of blue flowers for major cut flower plants, such as roses, chrysanthemums, and carnations, has not been achieved by conventional breeding or genetic engineering. Most blue-hued flowers contain delphinidin-based anthocyanins; therefore, delphinidin-producing carnation, rose, and chrysanthemum flowers have been generated by overexpression of the gene encoding flavonoid 3',5'-hydroxylase (F3'5'H), the key enzyme for delphinidin biosynthesis. Even so, the flowers are purple/violet rather than blue. To generate true blue flowers, blue pigments, such as polyacylated anthocyanins and metal complexes, must be introduced by metabolic engineering; however, introducing and controlling multiple transgenes in plants are complicated processes. We succeeded in generating blue chrysanthemum flowers by introduction of butterfly pea UDP (uridine diphosphate)-glucose:anthocyanin 3',5'-O-glucosyltransferase gene, in addition to the expression of the Canterbury bells F3'5'H. Newly synthesized 3',5'-diglucosylated delphinidin-based anthocyanins exhibited a violet color under the weakly acidic pH conditions of flower petal juice and showed a blue color only through intermolecular association, termed “copigmentation,” with flavone glucosides in planta. Thus, we achieved the development of blue color by a two-step modification of the anthocyanin structure. This simple method is a promising approach to generate blue flowers in various ornamental plants by metabolic engineering.

Concepts: Color, PH, Flowering plant, Flower, Flowers, Chrysanthemum, Asteraceae, Garden plants

28

Helichrysum italicum (Roth) G. Don fil. (family Asteraceae) has been used for its medicinal properties for a long time and, even nowadays, continues to play an important role in the traditional medicine of Mediterranean countries. Based on this traditional knowledge, its different pharmacological activities have been the focus of active research.

Concepts: Scientific method, Medicine, Ayurveda, Data, Alternative medicine, Asteraceae, Helichrysum italicum, Helichrysum

27

The flowers of African marigold (Tagetes erecta L), a medicinal plant widely cultivated in Thailand, were subjected to evaluation for total phenolics, DPPH scavenging and thiobarbituric acid-reactive substance (TBARs) assays as well as tyrosinase inhibitory activity. In preliminary studies, the ethyl acetate (EA) extract obtained by continuous extraction showed the highest activities with highest phenolic content among all extracts. Bioassay-guided fractionation of EA extract led to isolation of a flavonoid identified as quercetagetin. Interestingly, it was found that quercetagetin exhibited potent DPPH scavenging activity with IC50 of 3.70 μg/ml which is about 2-3 times higher activity than standard quercetin (IC50 5.07 μg/ml) and trolox (IC50 9.93 μg/ml). Moreover, it exhibited tyrosinase inhibitory activity on L-tyrosine (IC50 89.31 μg/ml), higher than α- and β-arbutins (IC50 157.77 and 222.35 μg/ml) and slightly higher (IC50 128.41 μg/ml) than ellagic acid (IC50 151.1 μg/ml) when using L-DOPA as substrate. Testing with skin fibroblasts, all the extracts and quercetagetin demonstrated no toxic effect. These finding strongly indicate that African marigold flower is a promising source of natural antioxidative and tyrosinase inhibitory substances with safe to skin.

Concepts: Quercetin, Flowers, Phenols, Asteraceae, Calendula, Tagetes erecta, Tagetes, Tageteae

27

In the year 2012 leaf curl disease was observed on Marigold (Tagetes patula) in Lakshmangrh, Sikar province of India. Affected plants were severely stunted with apical leaf curl and crinkled leaves, symptoms typical of begomovirus infection. This is the first report of complete nucleotide sequence of a begomovirus associated with satellites molecules infecting a new host Tagetes patula in India.

Concepts: Disease, Infectious disease, Infection, Fern, Asteraceae, Tagetes patula, Tagetes, Tageteae

26

Plants produce large amounts of secondary metabolites in their shoots and roots and store them in specialized secretory structures. Although secondary metabolites and their secretory structures are commonly assumed to have a defensive function, evidence that they benefit plant fitness under herbivore attack is scarce, especially below ground. Here, we tested whether latex secondary metabolites produced by the common dandelion (Taraxacum officinale agg.) decrease the performance of its major native insect root herbivore, the larvae of the common cockchafer (Melolontha melolontha), and benefit plant vegetative and reproductive fitness under M. melolontha attack. Across 17 T. officinale genotypes screened by gas and liquid chromatography, latex concentrations of the sesquiterpene lactone taraxinic acid β-D-glucopyranosyl ester (TA-G) were negatively associated with M. melolontha larval growth. Adding purified TA-G to artificial diet at ecologically relevant concentrations reduced larval feeding. Silencing the germacrene A synthase ToGAS1, an enzyme that was identified to catalyze the first committed step of TA-G biosynthesis, resulted in a 90% reduction of TA-G levels and a pronounced increase in M. melolontha feeding. Transgenic, TA-G-deficient lines were preferred by M. melolontha and suffered three times more root biomass reduction than control lines. In a common garden experiment involving over 2,000 T. officinale individuals belonging to 17 different genotypes, high TA-G concentrations were associated with the maintenance of high vegetative and reproductive fitness under M. melolontha attack. Taken together, our study demonstrates that a latex secondary metabolite benefits plants under herbivore attack, a result that provides a mechanistic framework for root herbivore driven natural selection and evolution of plant defenses below ground.

Concepts: Evolution, Metabolism, Plant, Asteraceae, Taraxacum officinale, Taraxacum, Cockchafer, Melolontha

26

In this investigation, morphological, phytochemical and ISSR markers were used to estimate the relationships among and within seven populations of white savory (Satureja mutica), belonging to four provinces in Iran. The individuals were phenotypically diverse, which stamen length, corolla length, corolla diameter, calyx length, bract length, inflorescence length, calyx length and bracteole width were characteristics with the highest variation. Leaf dimensions were in significant correlation with flower and inflorescence characteristics. Chemical compounds of essential oils were found variable in various individuals and all samples were principally composed of phenolic constituents (carvacrol and/or thymol). As a consequence, the plants were classified into two major chemotypes including carvacrol and thymol. A total of 197 band positions were produced by 14 ISSR primers, of which 176 were found polymorphic with 88.91% polymorphism. ISSR genetic similarity values among individuals ranged between 0.45 and 0.94 which was indicative of a high level of genetic variation. Multiple regression analysis (MRA) revealed that phytochemical compositions as dependent variable, showed statistically significant correlation and in association with leaf and flower traits as independent variable, indicating a main role of leaf and flower on production of these compounds. Also, several ISSR fragments were found associated with some morphological traits and phytochemical compositions. The high diversity within and among populations of S. mutica according to different data systems could provide useful information for conservation and selection of cross-parents in breeding programs.

Concepts: Regression analysis, Statistics, Plant morphology, Flower, Trait, Asteraceae, Inflorescence, Bract

25

Trichomes are widespread in plants and develop from surface cells on different tissues(1). They have many forms and functions, from defensive spines to physical barriers that trap layers of air to insulate against desiccation, but there is growing evidence that trichomes can also have developmental roles in regulating flower structure(2,3). We report here that the trichomes on petals of cotton, Gossypium hirsutum L., are essential for correct flower bud shape through a mechanical entanglement of the trichomes on adjacent petals that anchor the edges to counter the opposing force generated by asymmetric expansion of overlapping petals. Silencing a master regulator of petal trichomes, GhMYB-MIXTA-Like10 (GhMYBML10), by RNA interference (RNAi) suppressed petal trichome growth and resulted in flower buds forming into abnormal corkscrew shapes that exposed developing anthers and stigmas to desiccation damage. Artificially gluing petal edges together could partially restore correct bud shape and fertility. Such petal ‘Velcro’ is present in other Malvaceae and perhaps more broadly in other plant families, although it is not ubiquitous. This mechanism for physical association between separate organs to regulate flower shape and function is different from the usual organ shape control(4) exerted through cell-to-cell communication and differential cell expansion within floral tissues(5,6).

Concepts: Bud, Organ, Pollination, Plant morphology, Flower, Plant stem, Sepal, Asteraceae