Temperature responses of NO and N₂O emissions from boreal organic soil     

Hannu T. Koponen  Claudia Escudé Duran  Jyrki Hytönen 《Soil biology & biochemistry》2006,38(7):1779-1787

Both NO and N₂O are produced in soil microbial processes and have importance in atmospheric physics and chemistry. In recent years several studies have shown that N₂O emissions from organic soils can be high at low temperatures. However, the effects of low temperature on NO emissions from soil are unknown. We studied in laboratory conditions, using undisturbed soil cores, the emissions of NO and N₂O from organic soils at various temperatures, with an emphasis on processes and emissions during soil freezing and thawing periods. We found no soil freezing- or thawing-related emission maxima for NO, while the N₂O emissions were higher both during soil freezing and thawing periods. The results suggest that different factors are involved in the regulation of NO and N₂O emissions at low temperatures.  相似文献   

Microtubule stabilization reduces scarring and causes axon regeneration after spinal cord injury     

Hellal F  Hurtado A  Ruschel J  Flynn KC  Laskowski CJ  Umlauf M  Kapitein LC  Strikis D  Lemmon V  Bixby J  Hoogenraad CC  Bradke F 《Science (New York, N.Y.)》2011,331(6019):928-931

Hypertrophic scarring and poor intrinsic axon growth capacity constitute major obstacles for spinal cord repair. These processes are tightly regulated by microtubule dynamics. Here, moderate microtubule stabilization decreased scar formation after spinal cord injury in rodents through various cellular mechanisms, including dampening of transforming growth factor-β signaling. It prevented accumulation of chondroitin sulfate proteoglycans and rendered the lesion site permissive for axon regeneration of growth-competent sensory neurons. Microtubule stabilization also promoted growth of central nervous system axons of the Raphe-spinal tract and led to functional improvement. Thus, microtubule stabilization reduces fibrotic scarring and enhances the capacity of axons to grow.  相似文献   

A predator unmasked: life cycle of Bdellovibrio bacteriovorus from a genomic perspective     

Rendulic S  Jagtap P  Rosinus A  Eppinger M  Baar C  Lanz C  Keller H  Lambert C  Evans KJ  Goesmann A  Meyer F  Sockett RE  Schuster SC 《Science (New York, N.Y.)》2004,303(5658):689-692

Predatory bacteria remain molecularly enigmatic, despite their presence in many microbial communities. Here we report the complete genome of Bdellovibrio bacteriovorus HD100, a predatory Gram-negative bacterium that invades and consumes other Gram-negative bacteria. Its surprisingly large genome shows no evidence of recent gene transfer from its prey. A plethora of paralogous gene families coding for enzymes, such as hydrolases and transporters, are used throughout the life cycle of B. bacteriovorus for prey entry, prey killing, and the uptake of complex molecules.  相似文献   

The BRCT domain is a phospho-protein binding domain     

Yu X  Chini CC  He M  Mer G  Chen J 《Science (New York, N.Y.)》2003,302(5645):639-642

The carboxyl-terminal domain (BRCT) of the Breast Cancer Gene 1 (BRCA1) protein is an evolutionarily conserved module that exists in a large number of proteins from prokaryotes to eukaryotes. Although most BRCT domain-containing proteins participate in DNA-damage checkpoint or DNA-repair pathways, or both, the function of the BRCT domain is not fully understood. We show that the BRCA1 BRCT domain directly interacts with phosphorylated BRCA1-Associated Carboxyl-terminal Helicase (BACH1). This specific interaction between BRCA1 and phosphorylated BACH1 is cell cycle regulated and is required for DNA damage-induced checkpoint control during the transition from G2 to M phase of the cell cycle. Further, we show that two other BRCT domains interact with their respective physiological partners in a phosphorylation-dependent manner. Thirteen additional BRCT domains also preferentially bind phospho-peptides rather than nonphosphorylated control peptides. These data imply that the BRCT domain is a phospho-protein binding domain involved in cell cycle control.  相似文献   

The chemistry of sexual deception in an orchid-wasp pollination system     

Schiestl FP  Peakall R  Mant JG  Ibarra F  Schulz C  Franke S  Francke W 《Science (New York, N.Y.)》2003,302(5644):437-438

The "sexually deceptive" orchid Chiloglottis trapeziformis attracts males of its pollinator species, the thynnine wasp Neozeleboria cryptoides, by emitting a unique volatile compound, 2-ethyl-5-propylcyclohexan-1,3-dione, which is also produced by female wasps as a male-attracting sex pheromone.  相似文献   

Deep human genealogies reveal a selective advantage to be on an expanding wave front     

Moreau C  Bhérer C  Vézina H  Jomphe M  Labuda D  Excoffier L 《Science (New York, N.Y.)》2011,334(6059):1148-1150

Since their origin, human populations have colonized the whole planet, but the demographic processes governing range expansions are mostly unknown. We analyzed the genealogy of more than one million individuals resulting from a range expansion in Quebec between 1686 and 1960 and reconstructed the spatial dynamics of the expansion. We find that a majority of the present Saguenay Lac-Saint-Jean population can be traced back to ancestors having lived directly on or close to the wave front. Ancestors located on the front contributed significantly more to the current gene pool than those from the range core, likely due to a 20% larger effective fertility of women on the wave front. This fitness component is heritable on the wave front and not in the core, implying that this life-history trait evolves during range expansions.  相似文献   

Geology. An uncertain future for soil carbon   总被引：1，自引：0，他引：1  

Trumbore SE  Czimczik CI 《Science (New York, N.Y.)》2008,321(5895):1455-1456

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Failure of bone marrow cells to transdifferentiate into neural cells in vivo     

Castro RF  Jackson KA  Goodell MA  Robertson CS  Liu H  Shine HD 《Science (New York, N.Y.)》2002,297(5585):1299

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Bypass of DNA lesions generated during anticancer treatment with cisplatin by DNA polymerase eta     

Alt A  Lammens K  Chiocchini C  Lammens A  Pieck JC  Kuch D  Hopfner KP  Carell T 《Science (New York, N.Y.)》2007,318(5852):967-970

DNA polymerase eta (Pol eta) is a eukaryotic lesion bypass polymerase that helps organisms to survive exposure to ultraviolet (UV) radiation, and tumor cells to gain resistance against cisplatin-based chemotherapy. It allows cells to replicate across cross-link lesions such as 1,2-d(GpG) cisplatin adducts (Pt-GG) and UV-induced cis-syn thymine dimers. We present structural and biochemical analysis of how Pol eta copies Pt-GG-containing DNA. The damaged DNA is bound in an open DNA binding rim. Nucleotidyl transfer requires the DNA to rotate into an active conformation, driven by hydrogen bonding of the templating base to the dNTP. For the 3'dG of the Pt-GG, this step is accomplished by a Watson-Crick base pair to dCTP and is biochemically efficient and accurate. In contrast, bypass of the 5'dG of the Pt-GG is less efficient and promiscuous for dCTP and dATP as a result of the presence of the rigid Pt cross-link. Our analysis reveals the set of structural features that enable Pol eta to replicate across strongly distorting DNA lesions.  相似文献   

Synchrony dynamics during initiation, failure, and rescue of the segmentation clock     

Riedel-Kruse IH  Müller C  Oates AC 《Science (New York, N.Y.)》2007,317(5846):1911-1915

The "segmentation clock" is thought to coordinate sequential segmentation of the body axis in vertebrate embryos. This clock comprises a multicellular genetic network of synchronized oscillators, coupled by intercellular Delta-Notch signaling. How this synchrony is established and how its loss determines the position of segmentation defects in Delta and Notch mutants are unknown. We analyzed the clock's synchrony dynamics by varying strength and timing of Notch coupling in zebra-fish embryos with techniques for quantitative perturbation of gene function. We developed a physical theory based on coupled phase oscillators explaining the observed onset and rescue of segmentation defects, the clock's robustness against developmental noise, and a critical point beyond which synchrony decays. We conclude that synchrony among these genetic oscillators can be established by simultaneous initiation and self-organization and that the segmentation defect position is determined by the difference between coupling strength and noise.  相似文献