The Physcomitrella genome reveals evolutionary insights into the conquest of land by plants     

Rensing SA  Lang D  Zimmer AD  Terry A  Salamov A  Shapiro H  Nishiyama T  Perroud PF  Lindquist EA  Kamisugi Y  Tanahashi T  Sakakibara K  Fujita T  Oishi K  Shin-I T  Kuroki Y  Toyoda A  Suzuki Y  Hashimoto S  Yamaguchi K  Sugano S  Kohara Y  Fujiyama A  Anterola A  Aoki S  Ashton N  Barbazuk WB  Barker E  Bennetzen JL  Blankenship R  Cho SH  Dutcher SK  Estelle M  Fawcett JA  Gundlach H  Hanada K  Heyl A  Hicks KA  Hughes J  Lohr M  Mayer K  Melkozernov A  Murata T  Nelson DR  Pils B  Prigge M  Reiss B  Renner T  Rombauts S  Rushton PJ 《Science (New York, N.Y.)》2008,319(5859):64-69

We report the draft genome sequence of the model moss Physcomitrella patens and compare its features with those of flowering plants, from which it is separated by more than 400 million years, and unicellular aquatic algae. This comparison reveals genomic changes concomitant with the evolutionary movement to land, including a general increase in gene family complexity; loss of genes associated with aquatic environments (e.g., flagellar arms); acquisition of genes for tolerating terrestrial stresses (e.g., variation in temperature and water availability); and the development of the auxin and abscisic acid signaling pathways for coordinating multicellular growth and dehydration response. The Physcomitrella genome provides a resource for phylogenetic inferences about gene function and for experimental analysis of plant processes through this plant's unique facility for reverse genetics.  相似文献   

Microscopic view of structural phase transitions induced by shock waves     

Kadau K  Germann TC  Lomdahl PS  Holian BL 《Science (New York, N.Y.)》2002,296(5573):1681-1684

Multimillion-atom molecular-dynamics simulations are used to investigate the shock-induced phase transformation of solid iron. Above a critical shock strength, many small close-packed grains nucleate in the shock-compressed body-centered cubic crystal growing on a picosecond time scale to form larger, energetically favored grains. A split two-wave shock structure is observed immediately above this threshold, with an elastic precursor ahead of the lagging transformation wave. For even higher shock strengths, a single, overdriven wave is obtained. The dynamics and orientation of the developing close-packed grains depend on the shock strength and especially on the crystallographic shock direction. Orientational relations between the unshocked and shocked regions are similar to those found for the temperature-driven martensitic transformation in iron and its alloys.  相似文献   

Phosphorylation by p38 MAPK as an alternative pathway for GSK3beta inactivation     

Thornton TM  Pedraza-Alva G  Deng B  Wood CD  Aronshtam A  Clements JL  Sabio G  Davis RJ  Matthews DE  Doble B  Rincon M 《Science (New York, N.Y.)》2008,320(5876):667-670

Glycogen synthase kinase 3beta (GSK3beta) is involved in metabolism, neurodegeneration, and cancer. Inhibition of GSK3beta activity is the primary mechanism that regulates this widely expressed active kinase. Although the protein kinase Akt inhibits GSK3beta by phosphorylation at the N terminus, preventing Akt-mediated phosphorylation does not affect the cell-survival pathway activated through the GSK3beta substrate beta-catenin. Here, we show that p38 mitogen-activated protein kinase (MAPK) also inactivates GSK3beta by direct phosphorylation at its C terminus, and this inactivation can lead to an accumulation of beta-catenin. p38 MAPK-mediated phosphorylation of GSK3beta occurs primarily in the brain and thymocytes. Activation of beta-catenin-mediated signaling through GSK3beta inhibition provides a potential mechanism for p38 MAPK-mediated survival in specific tissues.  相似文献   

Toward inherently secure and resilient societies   总被引：3，自引：0，他引：3  

Allenby B  Fink J 《Science (New York, N.Y.)》2005,309(5737):1034-1036

Recent years have seen a number of challenges to social stability and order, ranging from terrorist attacks and natural disasters to epidemics such as AIDS and SARS. Such challenges have generated specific policy responses, such as enhanced security at transportation hubs and planned deployment of a global tsunami detection network. However, the range of challenges and the practical impossibility of adequately addressing each in turn argue for adoption of a more comprehensive systems perspective. This should be based on the principle of enhancing social and economic resiliency as well as meeting security and emergency response needs and, to the extent possible, developing and implementing dual-use technologies that offer societal benefits even if anticipated disasters never occur.  相似文献   

Challenges of modeling ocean basin ecosystems   总被引：1，自引：0，他引：1  

deYoung B  Heath M  Werner F  Chai F  Megrey B  Monfray P 《Science (New York, N.Y.)》2004,304(5676):1463-1466

With increasing pressure for a more ecological approach to marine fisheries and environmental management, there is a growing need to understand and predict changes in marine ecosystems. Biogeochemical and physical oceanographic models are well developed, but extending these further up the food web to include zooplankton and fish is a major challenge. The difficulty arises because organisms at higher trophic levels are longer lived, with important variability in abundance and distribution at basin and decadal scales. Those organisms at higher trophic levels also have complex life histories compared to microbes, further complicating their coupling to lower trophic levels and the physical system. We discuss a strategy that builds on recent advances in modeling and observations and suggest a way forward that includes approaches to coupling across trophic levels and the inclusion of uncertainty.  相似文献   

Measuring Eastern Redcedar (Juniperus virginiana L.) Mass With the Use of Satellite Imagery     

Patrick J. Starks  Brad C. Venuto  John A. Eckroat  Tom. Lucas 《Strength and Conditioning Journal》2011,64(2):178-186

Eastern redcedar (Juniperus virginiana L.) is an aggressively spreading native species in Oklahoma grasslands. It decreases rangeland forage production, and has been implicated in reducing stream flow and groundwater recharge. Industrial-scale plans to use redcedar as a biofuel source are being considered. Optimal placement of redcedar-based industries requires determination of redcedar availability. Such large-area inventories of redcedar mass can be practically addressed via aircraft or satellite remote sensing. Therefore, we conducted a study in central and western Oklahoma to develop and test a remote-sensing–based allometric equation relating redcedar canopy area to aboveground dry mass (AGM). We used automated methods to measure tree canopy area from georectified, pan-sharpened, multispectral QuickBird images having a spatial resolution of 0. 45 m² per pixel ground sample area. We also measured the canopy area and fresh and dry mass of these trees with the use of destructive sampling techniques. Regression analysis showed that satellite-derived measurements of canopy coverage explained about 85% of field-measured redcedar dry AGM in the study plots. The resulting allometric equation was applied to an independent data set, yielding dry AGM of 38.2 metric tons ? ha^?1, which was well within the field-measured range of 36–43 metric tons ? ha^?1. The allometric equation was then applied to Natural Resources Conservation Service measurements of redcedar canopy coverage for 17 counties in Oklahoma, to determine that the area of interest contains a median value of about 11.5 million metric tons of redcedar AGM. These results indicate that 0.45-m² spatial resolution multispectral imagery can be a useful tool for rapid and reliable measurement of redcedar dry AGM.  相似文献   

Timing of large movement events of pond-breeding amphibians in Western Massachusetts, USA     

Brad C. Timm  Kevin McGarigal 《Biological conservation》2007,136(3):442-454

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Effect of cortisol on luteinizing hormone release during sexual behavior in the boar.          下载免费PDF全文

L X Wang  P Huether  E Doble    R M Liptrap 《Canadian journal of veterinary research》1986,50(4):540-542

The effect of inhibiting the rise in cortisol concentrations that occurs at copulation upon luteinizing hormone release was studied in seven adult boars. Plasma samples were collected for assay of luteinizing hormone, testosterone and cortisol on a control day and before, during and after exposure to an estrous sow. The area under the curve was used to evaluate hormone production and treatment effects were evaluated by a paired Student's t-test. The 11 beta-hydroxylase inhibitor, metyrapone, was used to suppress glucocorticoid hormone production. Cortisol concentrations increased significantly (p less than 0.05) after breeding compared to values on the control day while treatment with metyrapone prior to breeding prevented the cortisol increase (p greater than 0.05). Although luteinizing hormone production increased significantly after copulation in both breeding experiments, metyrapone pretreatment resulted in a reduction of luteinizing hormone secretion (p less than 0.05). Testosterone production was also reduced in boars pretreated with metyrapone. The results suggest that the increased levels of cortisol occurring at copulation may enhance luteinizing hormone release in boars.  相似文献   

Development of a computerized systems model for health management decision support in growing hogs     

James W. Lloyd  Stephen B. Harsh  John B. Kaneene  Gerald D. Schwab  Brad J. Thacker  Andrew J. Thulin 《Preventive veterinary medicine》1994,19(3-4):249-265

A study was designed to provide decision support for health management in growing hogs. A dynamic, stochastic systems model for a confinement, continuous production hog growing enterprise (including nursery, grower and finisher phases) was developed to simulate the economic effects of disease, available floor space and feed additives using farm- specific data. Modeling techniques included: discrete and distributed (continuous) delays; triangular probability density functions; autocorrelation; table look-up functions; an alpha-beta tracker; non-linear, constrained optimization. The model was designed to be initialized with the system's current status, using an accompanying production/financial database to achieve individual-farm specificity. Initialization of rate variables required ‘reverse optimization’ of historical system performance. Model predictions are based on an adjustment approach, where changes in current performance are dictated by changes in disease rates, available floor space and feed additive use. These effects vary randomly, but are autocorrelated between production phases, between similar diseases and over time.  相似文献   

Loss of a harvested fish species disrupts carbon flow in a diverse tropical river   总被引：1，自引：0，他引：1  

Taylor BW  Flecker AS  Hall RO 《Science (New York, N.Y.)》2006,313(5788):833-836

Harvesting threatens many vertebrate species, yet few whole-system manipulations have been conducted to predict the consequences of vertebrate losses on ecosystem function. Here, we show that a harvested migratory detrital-feeding fish (Prochilodontidae: Prochilodus mariae) modulates carbon flow and ecosystem metabolism. Natural declines in and experimental removal of Prochilodus decreased downstream transport of organic carbon and increased primary production and respiration. Thus, besides its economic value, Prochilodus is a critical ecological component of South American rivers. Lack of functional redundancy for this species highlights the importance of individual species and, contrary to theory, suggests that losing one species from lower trophic levels can affect ecosystem functioning even in species-rich ecosystems.  相似文献