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121.
122.
Soulat D Jault JM Geourjon C Gouet P Cozzone AJ Grangeasse C 《FEMS microbiology letters》2007,274(2):252-259
The catalytic mechanism of bacterial tyrosine-kinases (PTK) is poorly understood. These enzymes possess Walker A and B ATP-binding motifs, which are effectively required for their autophosphorylation whereas these motifs are usually found in ATP-binding proteins but not in eukaryotic protein-kinases. It was previously shown that the PTK Wzc in Escherichia coli undergoes intra- and interphosphorylation. In this work, it is shown that, in addition to its kinase activity, Wzc produces free inorganic phosphate. It is demonstrated that this ATPase activity is increased significantly by intraphosphorylation of Wzc. The fact that intraphosphorylation of Wzc does not affect Wzc affinity for ATP was also demonstrated and it was suggested that it could rather modify the local environment of the ATP molecule in the catalytic site so as to render Wzc more liable to catalyze ATP hydrolysis and interphosphorylation. These results should contribute to better understanding of the catalytic mechanism of this particular class of tyrosine-kinases, which seems, so far, restricted to bacteria. 相似文献
123.
Tony Robinet Eric Feunteun Philippe Keith Gérard Marquet Jean-Michel Olivier Elodie Réveillac Pierre Valade 《Environmental Biology of Fishes》2007,78(2):93-105
Anguillid eels were sampled from permanent rivers in the Réunion and Mauritius islands, western Indian Ocean, with a standardized
electrofishing method. A. marmorata was very dominant, corresponding to 91.7 and 90.7% of all the eels collected in Réunion and Mauritius, respectively. Three
other species (A. mossambica, A. bicolor bicolor and A. nebulosa labiata) were also present in both islands. A. marmorata showed a strong altitudinal gradient of densities from the lower to upper zones, especially in the younger stages (TL <250 mm),
while A. mossambica was only found in the upper zones and A. bicolor bicolor occurred only in the lower zones (A. nebulosa labiata was rare). The eel species composition in freshwaters of both islands is very similar because these two adjoining islands
are located in the same trail of drifting marine larvae. Mean estimated eel biomasses were noticeably low (11.1 and 22.2 kg ha−1 in Réunion and Mauritius islands, respectively), especially when compared to those of other tropical insular systems without
any eel fishery (Comoros or Polynesia, more than 100 kg ha−1). Nevertheless, the fluvial recruitment of A. marmorata seemed to be regular during the surveyed period, staggering from October to April. The obvious lack of large eels in Mauritius
but more significantly in Réunion suggests a high pressure from traditional fishery, and the local reproductive turnover is
uncertain. Because sexual maturation seems to occur at a large body size for A. marmorata, as for temperate species, the Réunion and Mauritius rivers may only have a weak contribution to the regional production
of spawners. However, the giant mottled eel population in the western Indian Ocean is believed to be panmictic at the regional
scale, and may not rely exclusively on these islands’ contribution. A comparison is made with those of freshwater systems
in other tropical islands. 相似文献
124.
125.
Jongho Sun J. Benjamin Miller Emma Granqvist Audrey Wiley-Kalil Enrico Gobbato Fabienne Maillet Sylvain Cottaz Eric Samain Muthusubramanian Venkateshwaran Sébastien Fort Richard J. Morris Jean-Michel Ané Jean Dénarié Giles E.D. Oldroyd 《The Plant cell》2015,27(3):823-838
Establishment of arbuscular mycorrhizal interactions involves plant recognition of diffusible signals from the fungus, including lipochitooligosaccharides (LCOs) and chitooligosaccharides (COs). Nitrogen-fixing rhizobial bacteria that associate with leguminous plants also signal to their hosts via LCOs, the so-called Nod factors. Here, we have assessed the induction of symbiotic signaling by the arbuscular mycorrhizal (Myc) fungal-produced LCOs and COs in legumes and rice (Oryza sativa). We show that Myc-LCOs and tetra-acetyl chitotetraose (CO4) activate the common symbiosis signaling pathway, with resultant calcium oscillations in root epidermal cells of Medicago truncatula and Lotus japonicus. The nature of the calcium oscillations is similar for LCOs produced by rhizobial bacteria and by mycorrhizal fungi; however, Myc-LCOs activate distinct gene expression. Calcium oscillations were activated in rice atrichoblasts by CO4, but not the Myc-LCOs, whereas a mix of CO4 and Myc-LCOs activated calcium oscillations in rice trichoblasts. In contrast, stimulation of lateral root emergence occurred following treatment with Myc-LCOs, but not CO4, in M. truncatula, whereas both Myc-LCOs and CO4 were active in rice. Our work indicates that legumes and non-legumes differ in their perception of Myc-LCO and CO signals, suggesting that different plant species respond to different components in the mix of signals produced by arbuscular mycorrhizal fungi. 相似文献
126.
Fanny Jaudon Fabrice Raynaud Rosine Wehrlé Jean-Michel Bellanger Mohamed Doulazmi Guilan Vodjdani Stéphane Gasman Laurent Fagni Isabelle Dusart Anne Debant Susanne Schmidt 《Molecular biology of the cell》2015,26(11):2112-2127
By regulating actin cytoskeleton dynamics, Rho GTPases and their activators RhoGEFs are implicated in various aspects of neuronal differentiation, including dendritogenesis and synaptogenesis. Purkinje cells (PCs) of the cerebellum, by developing spectacular dendrites covered with spines, represent an attractive model system in which to decipher the molecular signaling underlying these processes. To identify novel regulators of dendritic spine morphogenesis among members of the poorly characterized DOCK family of RhoGEFs, we performed gene expression profiling of fluorescence-activated cell sorting (FACS)-purified murine PCs at various stages of their postnatal differentiation. We found a strong increase in the expression of the Cdc42-specific GEF DOCK10. Depleting DOCK10 in organotypic cerebellar cultures resulted in dramatic dendritic spine defects in PCs. Accordingly, in mouse hippocampal neurons, depletion of DOCK10 or expression of a DOCK10 GEF-dead mutant led to a strong decrease in spine density and size. Conversely, overexpression of DOCK10 led to increased spine formation. We show that DOCK10 function in spinogenesis is mediated mainly by Cdc42 and its downstream effectors N-WASP and PAK3, although DOCK10 is also able to activate Rac1. Our global approach thus identifies an unprecedented function for DOCK10 as a novel regulator of dendritic spine morphogenesis via a Cdc42-mediated pathway. 相似文献
127.
128.
Effects of intensified forestry on the landscape-scale extinction risk of dead wood dependent species 总被引:1,自引:0,他引:1
In the future, a significant proportion of Northern forests may become intensively managed through the planting of monospecific
stands of native or introduced trees, and the use of multiple silvicultural treatments such as forest fertilization. Such
an intensification of management in selected parts of the landscape is suggested by different zoning models, for example the
Triad approach, which is under evaluation in some regions of North America. In this study, based on Fennoscandian conditions,
we predicted landscape-scale extinction risks of five hypothetical model insect species dependent on fresh dead wood from
Norway spruce (Picea abies), by simulating colonizations and local extinctions in forest stands. Intensified forestry applied to 50% of the spruce stands
led to strongly increased extinction risks of all species during the following 150 years. For one species—the sun-exposure
specialist—there were strong effects already after 50 years. The negative effects of intensive plantation forestry could be
compensated for by taking greater biodiversity conservation measures in other managed forests or by setting aside more forests.
This is consistent with the Triad model, which is according to our analyzes an effective way to decrease extinction risks,
especially for the short-dispersing species and the species associated with closed forest. A zoning of forest land into intensive
forestry, conventional forestry, and set asides may be better at combining increased timber production and maintenance of
biodiversity in comparison to landscapes where all production forests are managed in the same way. 相似文献
129.
Enhancing the combustible properties of bamboo by torrefaction 总被引:1,自引:0,他引:1
Bamboo has wide range of moisture content, low bulk energy density and is difficult to transport, handle, store and feed into existing combustion and gasification systems. Because of its important fuel characteristics such as low ash content, alkali index and heating value, bamboo is a promising energy crop for the future. The aim of this study was to evaluate the effects of torrefaction on the main energy properties of Bambusavulgaris. Three different torrefaction temperatures were employed: 220, 250 and 280 °C. The elemental characteristics of lignite and coal were compared to the torrefied bamboo. The characteristics of the biomass fuels tend toward those of low rank coals. Principal component analysis of FTIR data showed a clear separation between the samples by thermal treatment. The loadings plot indicated that the bamboo samples underwent chemical changes related to carbonyl groups, mostly present in hemicelluloses, and to aromatic groups present in lignin. 相似文献
130.
A preliminary experimental investigation of dry reforming of methane with carbon dioxide, that has been performed on an iron bed activated with an electric current is reported. Operating conditions for the reaction included temperature ranging from 700 to 800° C and pressure close to 1 atm. The reaction, involving an excess of pure methane and carbon dioxide, was performed with and without addition of water vapour, provided by hot water saturation of the gaseous feed. According to syngas compositions, the electron flow has a dramatic effect on the conversion of both methane and carbon dioxide. It was shown also that hot water saturation of the CO(2) and CH(4) mixture allowed very good conversion, giving a syngas with a composition very close to what was expected from equilibrium calculations. 相似文献