The fittest versus the flattest: experimental confirmation of the quasispecies effect with subviral pathogens.
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The "survival of the fittest" is the paradigm of Darwinian evolution in which the best-adapted replicators are favored by natural selection. However, at high mutation rates, the fittest organisms are not necessarily the fastest replicators but rather are those that show the greatest robustness against deleterious mutational effects, even at the cost of a low replication rate. This scenario, dubbed the "survival of the flattest", has so far only been shown to operate in digital organisms. We show that "survival of the flattest" can also occur in biological entities by analyzing the outcome of competition between two viroid species coinfecting the same plant. Under optimal growth conditions, a viroid species characterized by fast population growth and genetic homogeneity outcompeted a viroid species with slow population growth and a high degree of variation. In contrast, the slow-growth species was able to outcompete the fast species when the mutation rate was increased. These experimental results were supported by an in silico model of competing viroid quasispecies. (+info)
Structural and mutational studies of anthocyanin malonyltransferases establish the features of BAHD enzyme catalysis.
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The BAHD family is a class of acyl-CoA-dependent acyltransferases that are involved in plant secondary metabolism and show a diverse range of specificities for acyl acceptors. Anthocyanin acyltransferases make up an important class of the BAHD family and catalyze the acylation of anthocyanins that are responsible for most of the red-to-blue colors of flowers. Here, we describe crystallographic and mutational studies of three similar anthocyanin malonyltransferases from red chrysanthemum petals: anthocyanidin 3-O-glucoside-6''-O-malonyltransferase (Dm3MaT1), anthocyanidin 3-O-glucoside-3'', 6''-O-dimalonyltransferase (Dm3MaT2), and a homolog (Dm3MaT3). Mutational analyses revealed that seven amino acid residues in the N- and C-terminal regions are important for the differential acyl-acceptor specificity between Dm3MaT1 and Dm3MaT2. Crystallographic studies of Dm3MaT3 provided the first structure of a BAHD member, complexed with acyl-CoA, showing the detailed interactions between the enzyme and acyl-CoA molecules. The structure, combined with the results of mutational analyses, allowed us to identify the acyl-acceptor binding site of anthocyanin malonyltransferases, which is structurally different from the corresponding portion of vinorine synthase, another BAHD member, thus permitting the diversity of the acyl-acceptor specificity of BAHD family to be understood. (+info)
Effect of different extracting methods on quality of Chrysanthemum Morifolium Ramat. Infusion.
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The flower of Chrysanthemum Morifolium Ramat. (CM) is a useful food and folk medicine in China. Effects of Chrysanthemum Morifolium extracting (CME) conditions, including extraction temperature, extraction time and the ratio of flower to water on infusion quality were investigated. The extractability, liquor color differences and the major flavonoids of luteolin-7-O-beta-D-glucoside and luteolin of various CME methods were evaluated. The results indicated that CME temperature was the most important factors affecting quality of CM infusion. Based on the extractability and chemical compositions, the best CME conditions were the 90 to approximately 100 degrees C, 20-30 min and the ratio of flower to water of 1:40 (w/v). High-performance liquid chromatography (HPLC) of Chrysanthemum Morifolium chemical compositions including luteolin-7-O-beta-D-glucoside and luteolin was also discussed in the present paper. (+info)
Intake of vitamin A-rich foods and lung cancer risk in Taiwan: with special reference to garland chrysanthemum and sweet potato leaf consumption.
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A case-control study was conducted to investigate the association between the consumption of local common foods that are rich in vitamin A and the risk of lung cancer in Taiwan. A total of 301 incident lung cancer cases, 602 hospital controls, and 602 neighborhood controls were recruited. The consumption of 13 food items and vitamin supplements was estimated by use of a food frequency questionnaire. The conditional logistic regression models were used to estimate the adjusted odds ratios (AOR) and 95% confidence intervals (CI) for lung cancer risk with each control group as reference by adjustment of covariates. A reduced risk for lung cancer was found to be associated with increased intakes of vitamin A, alpha-carotene, and beta-carotene from 13 food items. More servings of vegetables (AOR for the highest versus the lowest quartile = 0.67-0.70, 95% CI = 0.42-1.08, (plinear trend )= 0.04), garland chrysanthemum (AOR for the highest versus the lowest tertile = 0.58-0.74, 95% CI = 0.37-1.14, (plinear trend )<= 0.04) and sweet potato leaves (AOR for the highest versus the lowest tertile = 0.43-0.65, 95% CI = 0.28-0.96, (plinear trend )<= 0.03) were associated with the reduced risk for lung cancer. In conclusion, higher consumption of vitamin A-rich vegetables, especially garland chrysanthemum and sweet potato leaves might provide potential protection from lung cancer. (+info)
Double-stranded RNA interferes in a sequence-specific manner with the infection of representative members of the two viroid families.
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Infection by viroids, non-protein-coding circular RNAs, occurs with the accumulation of 21-24 nt viroid-derived small RNAs (vd-sRNAs) with characteristic properties of small interfering RNAs (siRNAs) associated to RNA silencing. The vd-sRNAs most likely derive from dicer-like (DCL) enzymes acting on viroid-specific dsRNA, the key elicitor of RNA silencing, or on the highly structured genomic RNA. Previously, viral dsRNAs delivered mechanically or agroinoculated have been shown to interfere with virus infection in a sequence-specific manner. Here, we report similar results with members of the two families of nuclear- and chloroplast-replicating viroids. Moreover, homologous vd-sRNAs co-delivered mechanically also interfered with one of the viroids examined. The interference was sequence-specific, temperature-dependent and, in some cases, also dependent on the dose of the co-inoculated dsRNA or vd-sRNAs. The sequence-specific nature of these effects suggests the involvement of the RNA induced silencing complex (RISC), which provides sequence specificity to RNA silencing machinery. Therefore, viroid titer in natural infections might be regulated by the concerted action of DCL and RISC. Viroids could have evolved their secondary structure as a compromise between resistance to DCL and RISC, which act preferentially against RNAs with compact and relaxed secondary structures, respectively. In addition, compartmentation, association with proteins or active replication might also help viroids to elude their host RNA silencing machinery. (+info)
Characterization of volatile components in dry chrysanthemum flowers using headspace-liquid-phase microextraction-gas chromatography.
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A headspace-liquid-phase microextraction (HS-LPME)-GC (gas chromatography) method for the characterization of volatile components in dry chrysanthemum flowers has been developed. In the proposed method, two extraction solvents, n-hexadecane and benzyl alcohol, are used for preconcentrating volatiles in the sample. A droplet of the extraction solvent is squeezed from the GC syringe and inserted in the headspace of the sample bottle with the dry flower, immersed in deionized water, and warmed in a water bath. The optimum HS-LPME parameters in terms of extraction solvent type, droplet magnitude, equilibrium (water bath) temperature, equilibrium time, extraction time, and ionic strength are achieved using GC-FID (flame ionization detection) by varying several levels of the factors that affect the HS-LPME procedure. After extraction under the optimized conditions, the extraction droplet is retracted into the syringe and injected for GC-MS (mass spectrometry) analysis. Thirty-three volatile components are extracted and identified using this HS-LPME-GC-MS method, with the aid of chemometric methods. It is shown that the volatiles in dry chrysanthemum flowers are mainly unsaturated organic compounds, such as monoterpenes, sesquiterpenes and their oxygenous derivatives, triterpenoids, and aliphatic compounds. Several representative components, in order of precedence of the retention time, are pinene (106.3 microg/g), camphene (112.7 microg/g), eucapyptol (52.1 microg/g), camphor (29.4 microg/g), borneol (4.2 microg g), bornyl acetate (67.3 microg/g), caryophyllene (0.7 microg/g), and caryophyllene oxide (20.0 microg/g). The relative standard error and detection limit of this method is 5-9% and 0.4 microg/g, respectively. (+info)
Involvement of the ethylene response pathway in dormancy induction in chrysanthemum.
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