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1.
Plant–plant facilitation increases with reduced phylogenetic relatedness along an elevation gradient
Environmental conditions can modify the intensity and sign of ecological interactions. The stress gradient hypothesis (SGH) predicts that facilitation becomes more important than competition under stressful conditions. To properly test this hypothesis, it is necessary to account for all (not a subset of) interactions occurring in the communities and consider that species do not interact at random but following a specific pattern. We aim to assess elevational changes in facilitation, in terms of species richness, frequency and intensity of the interaction as a function of the evolutionary relatedness between nurses and their associated species. We sampled nurse and their facilitated plant species in two 1000–2000 m. elevation gradients in Mediterranean Chile where low temperature imposes a mortality filter on seedlings. We first estimated the relative importance of facilitation as a mechanism adding new species to communities distributed along these gradients. We then tested whether the frequency and intensity of facilitation increases with elevation, taking into account the evolutionary relatedness of the nurse species and the facilitated species. We found that nurses increase the species richness of the community by up to 35%. Facilitative interactions are more frequent than competitive interactions (56% versus 44%) and facilitation intensity increased with elevation for interactions involving distantly related lineages. Our results highlight the importance of including an evolutionary dimension in the study of facilitation to have a clearer picture of the mechanisms enabling species to coexist and survive under stressful conditions. This knowledge is especially relevant to conserve vulnerable and threatened communities facing new climate scenarios, such as those located in Mediterranean-type ecosystems. 相似文献
2.
Milen Georgiev Vasil Georgiev Plamen Penchev Daniela Antonova Atanas Pavlov Mladenka Ilieva Simeon Popov 《Engineering in Life Science》2010,10(2):148-157
Cell suspension cultures of Lavandula vera (Lamiaceae), Nicotiana tabacum (Solanaceae), and Helianthus annuus (Asteraceae) were cultivated in three different ways: in shake flasks both as free suspensions and in two‐phase systems (in the presence of Amberlite XAD‐4 resin as a second phase), as well as in 3‐L stirred tank reactor, and their volatile metabolic profiles were studied using GC‐MS. A number of compounds, some of them having allelochemical and biological activities, were identified in all the three cell suspension cultures under study. Also the presence of some compounds, unusual for the intact plants, was observed. It was found that the cultivation mode strongly influences the production and the transport (secretion into the culture medium) of the low‐molecular‐mass volatile metabolites. Principal component analyses of 12 common hydrocarbons showed discrimination between the different cultivation modes (shake flasks and two‐phase systems cultivation) by first principal component (PC1) and second principal component (PC2). 相似文献
3.
Germ line transmission and expression of an RNAi cassette in mice generated by a lentiviral vector system 总被引:1,自引:0,他引:1
We have used a lentiviral delivery system (LentiLox3.7) to generate transgenic mice harbouring RNA interference (RNAi) against
the hepatocyte nuclear factor 4 gamma (HNF4γ). HNF4γ is a nuclear receptor with unknown function. Our analyses performed on
founder (F0) and first generation (F1) mice revealed mosaicism in F0 founders and a low efficiency of transgenesis (6%) in F1 mice. These data, together with the observation of multiple silenced transgenes, do not favour the use of LentiLox3.7 lentivirus
for transgenesis. Despite the low efficiency of transgenesis, we achieved a tissue-dependent knockdown of HNF4γ expression
in some mice.
Milen Kirilov and Minqiang Chai contributed equally to this work. 相似文献
4.
Bogdanov MG Kandinska MI Dimitrova DB Gocheva BT Palamareva MD 《Zeitschrift für Naturforschung. C, Journal of biosciences》2007,62(7-8):477-482
Preliminary differentiating screening of the antibacterial and antifungal activity of a series of diastereomeric cis/trans-3-aryl(heteroaryl)-3,4-dihydroisocoumarin-4-carboxylic acids (3a-i) was performed by the agar diffusion method against twelve microorganism strains of different taxonomic groups. S. aureus and A. niger were the most sensitive strains to the antibiotic effect of the tested compounds, both inhibited by 10 of 12 compounds. The most potent antibacterial agent was cis-3-phenyl-3,4-dihydroisocoumarin-4-carboxylic acid (cis-3a), exhibiting activity against all seven bacterial test strains. 相似文献
5.
Roldan M de Guia Adam J Rose Anke Sommerfeld Oksana Seibert Daniela Strzoda Annika Zota Yvonne Feuchter Anja Krones‐Herzig Tjeerd Sijmonsma Milen Kirilov Carsten Sticht Norbert Gretz Geesje Dallinga‐Thie Sven Diederichs Nora Klöting Matthias Blüher Mauricio Berriel Diaz Stephan Herzig 《The EMBO journal》2015,34(3):344-360
In mammals, glucocorticoids (GCs) and their intracellular receptor, the glucocorticoid receptor (GR), represent critical checkpoints in the endocrine control of energy homeostasis. Indeed, aberrant GC action is linked to severe metabolic stress conditions as seen in Cushing's syndrome, GC therapy and certain components of the Metabolic Syndrome, including obesity and insulin resistance. Here, we identify the hepatic induction of the mammalian conserved microRNA (miR)‐379/410 genomic cluster as a key component of GC/GR‐driven metabolic dysfunction. Particularly, miR‐379 was up‐regulated in mouse models of hyperglucocorticoidemia and obesity as well as human liver in a GC/GR‐dependent manner. Hepatocyte‐specific silencing of miR‐379 substantially reduced circulating very‐low‐density lipoprotein (VLDL)‐associated triglyceride (TG) levels in healthy mice and normalized aberrant lipid profiles in metabolically challenged animals, mediated through miR‐379 effects on key receptors in hepatic TG re‐uptake. As hepatic miR‐379 levels were also correlated with GC and TG levels in human obese patients, the identification of a GC/GR‐controlled miRNA cluster not only defines a novel layer of hormone‐dependent metabolic control but also paves the way to alternative miRNA‐based therapeutic approaches in metabolic dysfunction. 相似文献
6.
7.
Vasil Georgiev Ivan Ivanov Strahil Berkov Mladenka Ilieva Milen Georgiev Tatiana Gocheva Atanas Pavlov 《Engineering in Life Science》2012,12(5):534-543
Shoot culture of summer snowflake (Leucojum aestivum L.) was successfully cultivated in an advanced modified glass‐column bioreactor with internal sections for production of Amaryllidaceae alkaloids. The highest amounts of dry biomass (20.8 g/L) and galanthamine (1.7 mg/L) were achieved when shoots were cultured at 22°C and 18 L/(L·h) flow rate of inlet air. At these conditions, the L. aestivum shoot culture possessed mixotrophic‐type nutrition, synthesizing the highest amounts of chlorophyll (0.24 mg/g DW (dry weight) chlorophyll A and 0.13 mg/g DW chlorophyll B). The alkaloids extract of shoot biomass showed high acetylcholinesterase inhibitory activity (IC50 = 4.6 mg). The gas chromatography–mass spectrometry (GC/MS) profiling of biosynthesized alkaloids revealed that galanthamine and related compounds were presented in higher extracellular proportions while lycorine and hemanthamine‐type compounds had higher intracellular proportions. The developed modified bubble‐column bioreactor with internal sections provided conditions ensuring the growth and galanthamine production by L. aestivum shoot culture. 相似文献
8.
Frederick D Lewis Huihe Zhu Pierre Daublain Karsten Sigmund Torsten Fiebig Milen Raytchev Qiang Wang Vladimir Shafirovich 《Photochemical & photobiological sciences》2008,7(5):534-539
The mechanism and dynamics of charge separation and charge recombination in synthetic DNA hairpins possessing a stilbenedicarboxamide linker and a single guanine-cytosine base pair have been reinvestigated. The combination of femtosecond broad-band pump probe spectroscopy, nanosecond transient absorption experiments, and picosecond fluorescence decay measurements permits analysis of the formation and decay of the stilbene anion radical. Reversible hole injection resulting in the formation of the stilbene-adenine contact radical ion pair is found to occur on the picosecond time scale. The mechanism for charge separation across two or more base pairs is revised from single step superexchange to a multi-step process: hole injection followed by hole transport and hole trapping. The mechanism of charge recombination remains assigned to a superexchange process. 相似文献
9.
Thomas Heuser Milen Raytchev Jeremy Krell Mary E. Porter Daniela Nicastro 《The Journal of cell biology》2009,187(6):921-933
Cilia and flagella are highly conserved microtubule (MT)-based organelles with motile and sensory functions, and ciliary defects have been linked to several human diseases. The 9 + 2 structure of motile axonemes contains nine MT doublets interconnected by nexin links, which surround a central pair of singlet MTs. Motility is generated by the orchestrated activity of thousands of dynein motors, which drive interdoublet sliding. A key regulator of motor activity is the dynein regulatory complex (DRC), but detailed structural information is lacking. Using cryoelectron tomography of wild-type and mutant axonemes from Chlamydomonas reinhardtii, we visualized the DRC in situ at molecular resolution. We present the three-dimensional structure of the DRC, including a model for its subunit organization and intermolecular connections that establish the DRC as a major regulatory node. We further demonstrate that the DRC is the nexin link, which is thought to be critical for the generation of axonemal bending. 相似文献
10.
Nina Stancheva Jost Weber Josef Schulze Kalina Alipieva Jutta Ludwig-Müller Christiane Haas Vasil Georgiev Thomas Bley Milen Georgiev 《Plant Cell, Tissue and Organ Culture》2011,105(1):79-84
A cell suspension culture of Devil’s claw (Harpagophytum procumbens), a South African plant with high medicinal value, cultivated under submerged conditions showed stable growth and accumulated
high amounts of biomass (18.2 g l−1). Flow cytometry analyses of the suspension’s cell cycle kinetics showed that proportions of cells in G0/G1 and S phases varied insignificantly (between 69–76% and 9–13%, respectively) during the cultivation, while the proportion
of G2/M-phase cells increased until day 8 of cultivation, when the exponential phase of cell growth ended. Metabolite production
in the culture was studied through simultaneous determination of three bioactive phenylethanoid glycosides (verbascoside,
β-OH-verbascoside and leucosceptoside A) by high performance liquid chromatography. It was found that suspended Devil’s claw
cells accumulated mainly verbascoside (517.3 mg l−1), followed by leucosceptoside A (107.1 mg l−1) and β-OH-verbascoside (80.3 mg l−1). In addition, several fatty acids and β-sitosterol were identified in the cell suspension by gas chromatographic-mass spectrometry
analysis. Comparison of the results with previously acquired data for Harpagophytum procumbens transformed roots indicate that cell suspensions cultures are more promising as potential commercial sources of metabolites
such as phenylethanoid glycosides. 相似文献