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21.
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Giuliani C Bini LM Papa F Cristalli G Sagratini G Vittori S Lucarini D Maggi F 《化学与生物多样性》2011,8(12):2179-2194
Sideritis italica (Mill.) Greuter et Burdet belongs to the Lamiaceae family and is endemic to Italy. The glandular trichomes (morphology, distribution, histochemistry, and ultrastructure) of the plant were studied for the first time, along with the chemical composition of the essential oils. Abundant non-glandular hairs and peltate (type A) and capitate (types B, C(1), and C(x)) glandular trichomes were observed both on the vegetative and reproductive organs. The histochemical procedures and the ultrastructural investigation enabled specific location of the main site of essential oil production mainly in type-A peltate hairs. Particular emphasis is given to the release mechanism of the secreted material in all of the types of glands, and the potential taxonomic value of the indumentum in the Lamiaceae family is briefly discussed. Essential oils were hydrodistilled from flowering aerial parts of S. italica, and 136 compounds (112 in flowerheads, 79 in vegetative parts) were identified. The quantitative prevalence of diterpenoids (43.4% in flowerheads and 22.3% in vegetative parts) was the most significant characteristic of the essential oil of S. italica that could be classified as a diterpene-rich essential oil according to the classification of Kirimer. 相似文献
23.
Laurence Carvalho Angelo G. Solimini Geoff Phillips Olli-Pekka Pietiläinen Jannicke Moe Ana Cristina Cardoso Anne Lyche Solheim Ingmar Ott Martin Søndergaard Gianni Tartari Seppo Rekolainen 《Hydrobiologia》2009,633(1):59-66
The Water Framework Directive (WFD) requires EU Member States to assess the “ecological status” of surface waters. As a component of ecological status, many European countries are developing a classification scheme for chlorophyll concentrations as a measure of phytoplankton biomass. The chlorophyll classification must be based on the degree of divergence of a water body from an appropriate baseline or ‘reference condition’. This article describes the development of a series of regression models for predicting reference chlorophyll concentrations on a site-specific basis. For model development, a large dataset of European lakes considered to be in reference condition, 466 lakes in total, was assembled. Data were included from 12 European countries, but lakes from Northern and Western Europe dominated and made up 92% of all reference lakes. Data have been collated on chlorophyll concentration, altitude, mean depth, alkalinity, humic type, surface area and geographical region. Regression models were developed for estimating site-specific reference chlorophyll concentrations from significant predictor ‘typology’ variables. Reference chlorophyll concentrations were found to vary along a number of environmental gradients. Concentrations increased with colour and alkalinity and decreased with lake depth and altitude. Forward selection was used to identify independent explanatory variables in regression models for predicting site-specific reference chlorophyll concentrations. Depth was selected as an explanatory variable in all models. Alkalinity was included in models for low colour and humic lakes and altitude was included in models for low colour and very humic lakes. Uncertainty in the models was quite high and arises from errors in the data used to develop the models (including natural temporal and spatial variability in data) and also from additional explanatory variables not considered in the models, particularly nutrient concentrations, retention time and grazing. Despite these uncertainties, site-specific reference conditions are still recommended in preference to type-specific reference conditions, as they use the individual characteristics of a site known to influence phytoplankton biomass, rather than adopt standards set to generally represent a large population of lakes of a particular type. For this reason, site-specific reference conditions should result in reduced error in ecological status classifications, particularly for lakes close to typology boundaries. 相似文献
24.
Hermjakob H Montecchi-Palazzi L Bader G Wojcik J Salwinski L Ceol A Moore S Orchard S Sarkans U von Mering C Roechert B Poux S Jung E Mersch H Kersey P Lappe M Li Y Zeng R Rana D Nikolski M Husi H Brun C Shanker K Grant SG Sander C Bork P Zhu W Pandey A Brazma A Jacq B Vidal M Sherman D Legrain P Cesareni G Xenarios I Eisenberg D Steipe B Hogue C Apweiler R 《Nature biotechnology》2004,22(2):177-183
25.
Apomixis is desirable in agriculture as a reproductive strategy for cloning plants by seeds. Because embryos derive from the parthenogenic development of apomeiotic egg cells, apomixis excludes fertilization in addition to meiotic segregation and recombination, resulting in offspring that are exact replicas of the parent. Introgression of apomixis from wild relatives to crop species and transformation of sexual genotypes into apomictically reproducing ones are long-held goals of plant breeding. In fact, it is generally accepted that the introduction of apomixis into agronomically important crops will have revolutionary implications for agriculture. This review deals with the current genetic and molecular findings that have been collected from model species to elucidate the mechanisms of apomeiosis, parthenogenesis and apomixis as a whole. Our goal is to critically determine whether biotechnology can combine key genes known to control the expression of the processes miming the main components of apomixis in plants. Two natural apomicts, as the eudicot Hypericum perforatum L. (St. John's wort) and the monocot Paspalum spp. (crowngrass), and the sexual model species Arabidopsis thaliana are ideally suited for such investigations at the genomic and biotechnological levels. Some novel views and original concepts have been faced on this review, including (i) the parallel between Y-chromosome and apomixis-bearing chromosome (e.g., comparative genomic analyses revealed common features as repression of recombination events, accumulation of transposable elements and degeneration of genes) from the most primitive (Hypericum-type) to the most advanced (Paspalum-type) in evolutionary terms, and (ii) the link between apomixis and gene-specific silencing mechanisms (i.e., likely based on chromatin remodelling factors), with merging lines of evidence regarding the role of auxin in cell fate specification of embryo sac and egg cell development in Arabidopsis. The production of engineered plants exhibiting apomictic-like phenotypes is critically reviewed and discussed. 相似文献
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28.
Daniele Balducci Ilaria Lazzari Magda Monari Fabio Piccinelli Gianni Porzi 《Amino acids》2010,38(3):829-837
A new and convenient stereocontrolled synthesis of the optically pure (S)-α-methyl,α-amino acids 6(a–d) that exploits the chiral synthon 1,4-N,N-[(S)-1-phenylethyl]-piperazine-2,5-dione (1) is described. The (S)-1-phenylethyl group, bonded to each of the N-atoms of the 2,5-diketopiperazine, acts as a chiral inductor in the first alkylation, while the steric hindrance appears
to be the determining factor of stereocontrol in third and forth alkylation. 相似文献
29.
Giampaolo Manao Luigia Pazzagli Paolo Cirri Anna Caselli Guido Camici Gianni Cappugi Ahmad Saeed Giampietro Ramponi 《Journal of Protein Chemistry》1992,11(3):333-345
Two lowM
r phosphotyrosine protein phosphatases have been isolated from rat liver. The enzymes were previously known as lowM
r acid phosphatases, but several recent studies have demonstrated that this family of enzymes possesses specific phosphotyrosine protein phosphatase activity. We determined the complete amino acid sequences of the two isoenzymes and named them AcP1 and AcP2. Both consist of 157 amino acid residues, are acetylated at the NH2-terminus, and have His as the COOH-terminus. The molecular weights calculated from the sequences are 18,062 for AcP1 and 17,848 for AcP2. They are homologous except in the 40–73 zone, where about 50% of residues are different. This fact suggests that the two isoenzymes are produced by an alternative splicing mechanism. There is no homology between these two isoenzymes and the receptor-like phosphotyrosine protein phosphatases LAR, CD45, human placenta PTPase 1B, and rat brain PTPase-1. AcP1 and AcP2 are also distinct from rat liver PTPase-1 and PTPase-2, since these last enzymes have higher molecular weights. AcP1 differs from AcP2 with respect to (1) substrate affinity and (2) its sensitivity to activators and inhibitors, thus suggesting a their different physiological function. 相似文献
30.
Pierre Theroux Bernard R Chaitman Leif Erhardt Andreas Jessel Thomas Meinertz Wolf-Ulrich Nickel John S Schroeder Gianni Tognoni Harvey White James T Willerson 《Trials》2000,1(1):59-9