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Import
Kinds of Import Terms modified by Import Selected AbstractsA HYPOTHESIS FOR IMPORT OF THE NUCLEAR-ENCODED PsaE PROTEIN OF PAULINELLA CHROMATOPHORA (CERCOZOA, RHIZARIA) INTO ITS CYANOBACTERIAL ENDOSYMBIONTS/PLASTIDS VIA THE ENDOMEMBRANE SYSTEM,JOURNAL OF PHYCOLOGY, Issue 5 2010Mackiewicz The cyanobacterial endosymbionts of Paulinella chromatophora can shed new light on the process of plastid acquisition. Their genome is devoid of many essential genes, suggesting gene transfer to the host nucleus and protein import back into the endosymbionts/plastids. Strong evidence for such gene transfer is provided by the psaE gene, which encodes a PSI component that was efficiently transferred to the Paulinella nucleus. It remains unclear, however, how this protein is imported into the endosymbionts/plastids. We reanalyzed the sequence of Paulinella psaE and identified four potential non-AUG translation initiation codons upstream of the previously proposed start codon. Interestingly, the longest polypeptide, starting from the first UUG, contains a clearly identifiable signal peptide with very high (90%) predictability. We also found several downstream hairpin structures that could enhance translation initiation from the alternative codon. These results strongly suggest that the PsaE protein is targeted to the outer membrane of Paulinella endosymbionts/plastids via the endomembrane system. On the basis of presence of respective bacterial homologs in the Paulinella endosymbiont/plastid genome, we discuss further trafficking of PsaE through the peptidoglycan wall and the inner envelope membrane. It is possible that other nuclear-encoded proteins of P. chromatophora also carry signal peptides, but, alternatively, some may be equipped with transit peptides. If this is true, Paulinella endosymbionts/plastids would possess two distinct targeting systems, one cotranslational and the second posttranslational, as has been found in higher plant plastids. Considering the endomembrane system-mediated import pathway, we also discuss homology of the membranes surrounding Paulinella endosymbionts/plastids. [source] ESTIMATING IMPORT AND EXPORT DEMAND ELASTICITIES FOR MAURITIUS AND SOUTH AFRICAAUSTRALIAN ECONOMIC PAPERS, Issue 3 2010SEEMA NARAYAN In this paper, we re-estimate the import and the export demand functions for Mauritius and South Africa using time series data. We use the bounds tests for cointegration and find evidence of a long-run relationship between import demand, income and prices for both countries. Our long run elasticities reveal that domestic income and relative prices have significant effects on the import demand for both countries, with income being the most important determinant. Furthermore, we find that while South Africa's export demand is not responsive to relative prices or income; for Mauritius income is statistically significant. [source] Gnathostomiasis: Import from LaosJOURNAL DER DEUTSCHEN DERMATOLOGISCHEN GESELLSCHAFT, Issue 5 2006Felix Hennies Creeping eruption; Gnathostomiasis; Wangenschwellung Summary Gnathostomiasis is a nematode infestation endemic in Southeast Asia, which can involve multiple organs including the liver, eyes, gastrointestinal tract and CNS. The most common manifestation is recurrent migratory subcutaneous swellings which can appear anywhere on the body and are accompanied by pruritus and systemic symptoms such as low-grade fever, loss of appetite and nausea. The diagnosis is based on the clinical picture, history of travel, peripheral blood eosinophilia and the determination of agent-specific antibody levels. The standard treatment is albendazole. We present a 37-year-old Laotian woman, who had lived in Germany for 17 years, but developed recurrent swelling of the cheek following a visit to Laos. Because of the typical clinical findings, the history of a visit to Laos, and the presence of specific anti- Gnathostoma antibodies on Western blot, the diagnosis of cutaneous gnathostomiasis was made. Zusammenfassung Die Gnathostomiasis ist eine hauptsächlich in Südost-Asien endemisch vorkommende Nematodenerkrankung, die zu einem Befall multipler Organe wie Leber, Auge, Gastrointestinaltrakt und zentralem Nervensystem führen kann. Am häufigsten kommt es jedoch zu rezidivierenden, wandernden, subkutanen Schwellungen, die am gesamten Körper auftreten können und häufig von Juckreiz und Allgemeinsymptomen wie leichtem Fieber, Appetitlosigkeit und Übelkeit begleitet werden. Die Diagnose wird anhand des klinischen Bildes, der Reiseanamnese, einer Bluteosinophilie sowie der Bestimmung Erreger-spezifischer Antikörper gestellt. Als medikamentöse Therapie hat sich das Anthelminthikum Albendazol bewährt. Vorgestellt wird eine 37-jährige, seit 17 Jahren in Deutschland lebende Patientin aus Laos, die seit einem Jahr nach Rückkehr von einem Besuch in ihrer alten Heimat unter rezidivierenden Wangenschwellungen litt. Anhand der typischen Klinik, der positiven Reiseanamnese sowie des Nachweises spezifischer Anti- Gnathostoma -Antikörper im Western-Blot wurde die Diagnose einer kutanen Gnathostomiasis gestellt. [source] Morgan Stanley Roundtable on Private Equity and Its Import for Public CompaniesJOURNAL OF APPLIED CORPORATE FINANCE, Issue 3 2006Article first published online: 4 OCT 200 The role of private equity in global capital markets appears to be expanding at an extraordinary rate. Morgan Stanley estimates that there are now some 2,700 private equity funds that either have raised, or are in the process of raising, a total of $500 billion. With this abundance of available equity capital, the willingness of private equity firms to participate in "club" deals, and the leverage that can be put on top of the equity, private equity buyers now appear able and willing to pay higher prices for assets than ever before. And thanks in part to this new purchasing power, private equity transactions reportedly account for a quarter of all global M&A activity as well as a third of the high yield and IPO markets. The stock of capital now devoted to private equity reflects the demonstrated ability of at least the most reputable buyout firms to produce consistently high rates of returns for their limited partners. Although a talent for identifying and purchasing undervalued assets may be part of the story, the ability to produce such returns on a consistent basis implies an ability to add value, to improve the performance of the operating companies they invest in and control. And in this round-table, a small group of academics and practitioners address two main questions: How does private equity add value? And are there lessons for public companies in the success of private companies? According to the panelists, the answer to the first question appears to have changed somewhat over time. The consensus was that most of the value added by the LBO firms of the,80s was created during the initial structuring of the deals, a process described by Steve Kaplan as "financial and governance engineering," which includes not only aggressive use of leverage and powerful equity incentives for operating managements, but active oversight by a small, intensely interested board of directors. In the past ten years, however, these standard LBO features have been complemented by increased attention to "operational engineering," to the point where today's buyout firms feel obligated, like classic venture capitalists, to acquire and tout their own operating expertise. In response to the second of the two questions, Michael Jensen argues that much of the approach and benefits of private equity-particularly the adjustments of financial policies and stronger managerial incentives-can be replicated by public companies. And although some of these benefits have already been realized, much more remains to be done. Perhaps the biggest challenge, however, is finding a way to transfer to public companies the board-level expertise, incentives, and degree of engagement that characterize companies run by private equity investors. [source] Assessing the distortionary impact of state trading in ChinaAGRICULTURAL ECONOMICS, Issue 3-4 2010Steve McCorriston Trade policy; State trading enterprises; China Abstract State trading is a common feature in the management of imports and exports of agricultural products and it has been a long-standing feature of China's agricultural trade regime. While the use of state trading was modified by China's accession to the WTO, it remains a dominant feature for some commodities, even though there have been recent attempts to diminish its importance. In this article, we review the role that the state trading enterprise (STE), China National Cereals, Oils and Foodstuffs Import and Export Company (COFCO), continues to play in the importing and exporting of some agricultural commodities. We then review the economic theory that has been developed to measure the tariff equivalent of importing STEs. Finally, we apply that theory through a calibration exercise to measure the tariff equivalent of COFCO in China's import market for wheat. The distortionary impact of COFCO depends on the bias in government policy toward agriculture, the competitiveness of the domestic procurement market, and also the number of firms that are allocated licenses to import alongside COFCO. [source] The law of ownership and control of meteoritesMETEORITICS & PLANETARY SCIENCE, Issue S12 2002Douglas G. SCHMITT This article reviews the law in several countries, international law, and considers the legal and ethical issues facing curators wanting to bring finds to the research community and not divert them to a black market. A survey was made of scientists involved in meteorite acquisition in over 20 countries to determine how well various systems work. Meteorite ownership law is non-uniform. English Common Law, from which the law in former British colonies including the United States evolved, provides that meteorites are the landowner's property; buried meteorites might be part of the mineral rights. Find reporting is not mandatory. Most Western European countries, and former colonies, have civil codes providing that meteorites are owned by the landowner. In many countries legislation about archaeological treasures modifies earlier meteorite law. The UNESCO Convention on the Means of Prohibiting and Preventing the Illicit Import, Export and Transfer of Ownership of Cultural Property provides for tracking and retrieving from reciprocating states, cultural property including meteorites. The Antarctic Treaty does not deal with samples exported. In July 2001 the Antarctic Treaty Consultative parties adopted a resolution to discourage non-scientific collection. Curators should exercise caution if acquiring specimens of questionable legal ownership. Governments should be urged to enact laws to (1) discourage non-scientific collection in pristine areas; (2) encourage collection in populated areas by reasonable incentives to finders, with mandatory find reporting; (3) create efficient export permitting systems allowing exchange of research samples; and (4) retrieve illegally exported meteorites under the UNESCO Cultural Property Convention. [source] Influence of Serine O -Glycosylation or O -Phoshorylation Close to the vJun Nuclear Localisation Sequence on Nuclear ImportCHEMBIOCHEM, Issue 1 2006Stefanie Schlummer Dr. Abstract Nuclear import triggered by the nuclear-localisation sequence (NLS) of the viral Jun (vJun) protein is mediated by phosphorylation of a serine close to the NLS. Since phosphorylation and glycosylation of serine residues are often in a reciprocal "yin,yang" relationship, we investigated whether glycosylation of this serine with O-linked N -acetylglucosamine (O -GlcNAc) would also regulate nuclear import via the vJun NLS. Peptides containing the vJun NLS with an adjacent O -phosphorylated, O -GlcNAc-functionalised or unmodified serine, and equipped with an N-terminal biotin or a 7-nitrobenz-2-oxa-1,3-diazolyl (NBD) fluorescent label, were synthesised on the solid phase by means of an Fmoc/Boc strategy and a Pd0 -sensitive HYCRON linker. Fluorescence-polarisation measurements on the NBD-labelled peptides indicated that modification with phosphate or O -GlcNAc leads to a decrease in affinity to the import-mediating adapter protein, importin,, of about one order of magnitude compared to the unmodified NLS. Microinjection of biotinylated NLS peptide conjugated with fluorescently labelled avidin into NIH/3T3 and MDCK cells, revealed that avidin,unmodified-NLS peptide was rapidly imported into the nucleus. However, either phosphate or O -GlcNAc next to the NLS caused almost complete exclusion of the protein conjugate from nuclear import. These findings indicate that nuclear import by the vJun NLS might not be regulated by a "yin,yang" modification of an adjacent serine with phosphate or O -GlcNAc. Rather, negative regulation of binding between the polybasic NLS and importin by a negatively charged or a bulky, uncharged residue appears likely. [source] The production and consumption of bar iron in early modern England and WalesECONOMIC HISTORY REVIEW, Issue 1 2005PETER KING Errata. The Economic History Review 59: 1, 64 The production and consumption of bar iron in early modern England and Wales. An estimate made of the bar iron production in England shows two periods when production grew rapidly, 1540-1620 and 1785-1810. Both of these were related to the adoption of new technology-the finery forge in the first case, and potting and stamping and then puddling in the second. Imports of iron from Spain declined sharply after 1540, but those from Sweden became significant from the mid-seventeenth century, and those from Russia after 1730. Consumption grew rapidly in the late sixteenth century, and again during the eighteenth. Hence, the industrial revolution was the culmination of a long period of growth. [source] Are Imports and Exports Cointegrated?METROECONOMICA, Issue 1 2004An International Comparison ABSTRACT In this paper we use the Johansen and Juselius cointegration technique to examine the long-run convergence between imports and exports for a number of industrialized countries. The results indicate that there exists a long-run steady-state relationship between imports and exports for most countries in the sample. The policy implications of our findings are that the countries are not in violation of their international budget constraints and, more importantly, there is no productivity gap between the domestic economy and the rest of the world, implying a lack of permanent technological shocks to the domestic economy. [source] Copyright, Parallel Imports and National Welfare: The Australian Market for Sound RecordingsTHE AUSTRALIAN ECONOMIC REVIEW, Issue 4 2000Theo Papadopoulos For more than a decade now there has been considerable, often heated, debate over the issue of the parallel importation of sound recordings into Australia. Citing anti-competitive monopolistic distribution, an increasingly integrated global market and the challenges of new technologies, the Australian government recently passed the Copyright Amendment Act (No.2) 1998, which permits the parallel importation of ,non-infringing' copies of a sound recording. This paper investigates the economic rationale underpinning this regulatory change and, using a partial equilibrium model, attempts to measure the likely welfare effects on consumers, copyright owners and the nation. In addition the paper examines the likely welfare impact of piracy within the new regulatory framework. This paper demonstrates that in a global music market characterised by exclusive territorial licences and price discrimination, the removal of parallel import restrictions by a small net-importer of intellectual property may be welfare enhancing for the nation. This welfare gain is at the expense of largely foreign copyright owners. [source] The Chinese Enigma: Impacts of WTO Accession Upon Canadian and U.S. Exports and ImportsCANADIAN JOURNAL OF AGRICULTURAL ECONOMICS, Issue 4 2000Xiao-Yuan Dong China's accession to the World Trade Organization (WTO) is an important milestone in the integration of this nation into the world economy. Substantial reduction in trade barriers by China, one of the world's largest and most rapidly growing economies, is expected to have a significant impact, both on China itself and on the global economy. In assessing likely impacts on trade between China and North America of China joining the WTO, a priori one might expect new opportunities for China in labor intensive activities/products, while for the United States and for Canada one might expect added export market opportunities, as China grows, in activities/products that require land, resources and capital. However, the extent to which China and its trading partners will benefit from China's increasing integration into the global economy will largely depend on the internal changes in policy and infrastructure that may be adopted by China. China has embarked on a process of economic reform, but the speed and extent to which this continues to be pursued will affect this nation's ability to capitalize on its comparative advantages and to meet new challenges that are associated with the opportunities of access to a larger market. The difficulty of forecasting such internal changes means that China continues to be a major source of uncertainty in projecting world markets and trade flows. This uncertainty is particularly evident for trade in agricultural products [source] OCTN2 is associated with carnitine transport capacity of rat skeletal musclesACTA PHYSIOLOGICA, Issue 1 2010Y. Furuichi Abstract Aim:, Carnitine plays an essential role in fat oxidation in skeletal muscles; therefore carnitine influx could be crucial for muscle metabolism. OCTN2, a sodium-dependent solute carrier, is assumed to transport carnitine into various organs. However, OCTN2 protein expression and the functional importance of carnitine transport for muscle metabolism have not been studied. We tested the hypothesis that OCTN2 is expressed at higher levels in oxidative muscles than in other muscles, and that the carnitine uptake capacity of skeletal muscles depends on the amount of OCTN2. Methods:, Rat hindlimb muscles (soleus, plantaris, and the surface and deep portions of gastrocnemius) were used for Western blotting to detect OCTN2. Tissue carnitine uptake was examined by an integration plot analysis using l -[3H]carnitine as a tracer. Tissue carnitine content was determined by enzymatic cycling methods. The percentage of type I fibres was determined by histochemical analysis. Results:, OCTN2 was detected in all skeletal muscles although the amount was lower than that in the kidney. OCTN2 expression was significantly higher in soleus than in the other skeletal muscles. The amount of OCTN2 was positively correlated with the percentage of type I fibres in hindlimb muscles. The integration plot analysis revealed a positive correlation between the uptake clearance of l -[3H]carnitine and the amount of OCTN2 in skeletal muscles. However, the carnitine content in soleus was lower than that in other skeletal muscles. Conclusion:, OCTN2 is functionally expressed in skeletal muscles and is involved in the import of carnitine for fatty acid oxidation, especially in highly oxidative muscles. [source] Examination stress in Singapore primary schoolchildren: how compliance by subjects can impact on study resultsACTA PSYCHIATRICA SCANDINAVICA, Issue 3 2003G. Parker Objective: Examinations are anecdotally viewed as extremely stressful to Singapore schoolchildren. We test this postulate by obtaining parental ratings of children's emotional stress levels longitudinally in a large representative sample of sixth (P6) and fifth (P5) class primary schoolchildren, respectively, exposed and unexposed to a streaming examination. Method: Children's stress levels were rated monthly by a parent for 10 months. Results: Analyses failed to find evidence of any differential stress impact across P6 and P5 comparison groups, apart from a subset of P6 children whose parents complied with every monthly survey. Conclusion: The streaming examination in the final year of primary school did not emerge as a general stressor to children, but achieved salience within a defined subset of children whose parents were highly study compliant. Study compliance may be a proxy variable of some import, and have wider relevance to other cohort studies and to intervention trials. [source] Direct Reference and Definite DescriptionsDIALECTICA, Issue 1 2008Genoveva Marti According to Donnellan the characteristic mark of a referential use of a definite description is the fact that it can be used to pick out an individual that does not satisfy the attributes in the description. Friends and foes of the referential/attributive distinction have equally dismissed that point as obviously wrong or as a sign that Donnellan's distinction lacks semantic import. I will argue that, on a strict semantic conception of what it is for an expression to be a genuine referential device, Donnellan is right: if a use of a definite description is referential, it must be possible for it to refer to an object independently of any attributes associated with the description, including those that constitute its conventional meaning. [source] Contextualism, Scepticism, and the Problem of Epistemic DescentDIALECTICA, Issue 4 2001Duncan Pritchard Perhaps the most dominant anti-sceptical proposal in recent literature ,advanced by such figures as Stewart Cohen, Keith DeRose and David Lewis ,is the contextualist response to radical scepticism. Central to the contextualist thesis is the claim that, unlike other non-contextualist anti-sceptical theories, contextualism offers a dissolution of the sceptical paradox that respects our common sense epistemological intuitions. Taking DeRose's view as representative of the contextualist position, it is argued that instead of offering us an intuitive response to scepticism, contextualism is actually committed to a revisionist stance as regards our everyday usage of epistemic terms. In particular, it is argued that the thesis fails to present a satisfactory explication of a notion ,that of,epistemic descent', that is pivotal to the anti-sceptical import of the account. On the positive side, however, it is claimed that although the contextualist response to scepticism is ultimately unsatisfying, DeRose's theory does contain within it the framework for a completely different - and far more persuasive - account of the,phenomenology'of scepticism which runs along non-contextualist lines. [source] Precipitation control over inorganic nitrogen import,export budgets across watersheds: a synthesis of long-term ecological researchECOHYDROLOGY, Issue 2 2008E. S. Kane Abstract We investigated long-term and seasonal patterns of N imports and exports, as well as patterns following climate perturbations, across biomes using data from 15 watersheds from nine Long-Term Ecological Research (LTER) sites in North America. Mean dissolved inorganic nitrogen (DIN) import,export budgets (N import via precipitation,N export via stream flow) for common years across all watersheds was highly variable, ranging from a net loss of , 0·17 ± 0·09 kg N ha,1mo,1 to net retention of 0·68 ± 0·08 kg N ha,1mo,1. The net retention of DIN decreased (smaller import,export budget) with increasing precipitation, as well as with increasing variation in precipitation during the winter, spring, and fall. Averaged across all seasons, net DIN retention decreased as the coefficient of variation (CV) in precipitation increased across all sites (r2 = 0·48, p = 0·005). This trend was made stronger when the disturbed watersheds were withheld from the analysis (r2 = 0·80, p < 0·001, n = 11). Thus, DIN exports were either similar to or exceeded imports in the tropical, boreal, and wet coniferous watersheds, whereas imports exceeded exports in temperate deciduous watersheds. In general, forest harvesting, hurricanes, or floods corresponded with periods of increased DIN exports relative to imports. Periods when water throughput within a watershed was likely to be lower (i.e. low snow pack or El Niño years) corresponded with decreased DIN exports relative to imports. These data provide a basis for ranking diverse sites in terms of their ability to retain DIN in the context of changing precipitation regimes likely to occur in the future. Copyright © 2008 John Wiley & Sons, Ltd. [source] Regional Income Inequality and International TradeECONOMIC GEOGRAPHY, Issue 3 2004Julie A. Silva Abstract: This study investigates the effects of trade on income inequality across regions in the United States. Using both structural and price-based measures of regional trade involvement, we evaluate the effects of trade on inequality within and across states, the metropolitan and nonmetropolitan portions of the states, and the major census regions. Across all states and metropolitan and nonmetropolitan areas, we found that trade affects inequality primarily via import and export prices. In contrast to our expectations, however, a weaker dollar,more expensive imports and cheaper exports,is associated with the worsening of a state's position relative to other states and greater inequality within the state. Across the census regions, both our price and orientation measures had significant effects, but the direction of these effects varied by region. Whereas many regions benefited from cheaper imports, states in regions that are traditionally home to low-wage sectors, including the Southeast and South Central regions, were made relatively worse off by lower import prices and by greater orientation toward import-competing goods. Our findings reinforce notions about the uneven impacts of globalization and suggest that policy measures are needed to ensure that both the benefits and costs of involvement in international trade are shared across regions. [source] WHO'S AFRAID OF THE MARSHALL-LERNER CONDITION?ECONOMIC PAPERS: A JOURNAL OF APPLIED ECONOMICS AND POLICY, Issue 4 2005Gordon D. Menzies The Marshall-Lerner condition,that the sum of the elasticities of import and export demand exceeds unity,has been put forward as a condition that is required for a depreciation to make the trade balance more positive. Based on recently estimated trade equations, the more appropriate condition for Australia is that the sum of the import elasticity of demand and the elasticity of the export price with respect to the exchange rate exceeds unity. I call this the Small Economy Marshall,Lerner (SEML) condition. In recent history, this condition was fulfilled in 1999,2001, when the (unstable) relationship between the terms of trade and the exchange rate broke down. [source] Harmonizing External Quotas in an FTA: A Step Backward?ECONOMICS & POLITICS, Issue 3 2002Olivier Cadot This paper explores how political,economy forces shape quantitative barriers against the rest of the world in an FTA. We show that whereas the dilution of lobbying power in an FTA typically leads to a relaxation of external quotas, this result is likely to be overturned as integration deepens. In particular, we show that cooperation among member countries on the level of their external quotas, cross,border lobbying by import,competing interests in the free,trade area, and the consolidation of national external quotas into a single one, all lead to stiffer restrictions against imports from the rest of the world. We also show that, unlike tariffs, endogenous quotas are not crucially affected by the presence of rules of origin. [source] LIVING THE QUESTIONS: RILKE'S CHALLENGE TO OUR QUEST FOR CERTAINTYEDUCATIONAL THEORY, Issue 1 2007Mordechai Gordon The quest for certainty in education refers to our desire to gain a sense of psychological security and more control over a field that is fundamentally indeterminate. This quest implies an unwillingness to live with the inherent complexities and risks of education. After exploring the meaning and import of Rilke's challenge and comparing it to the position of Socrates, Gordon uses Rilke's insight to analyze a specific educational experience and then discusses some of its educational implications for teacher education. [source] Interpreting sustainable development and societal utility in Norwegian GMO assessmentsENVIRONMENTAL POLICY AND GOVERNANCE, Issue 4 2008G. Kristin Rosendal Abstract This article examines the process of assessing applications for genetically modified (GM) crops or plants for import or commercial planting in Norway. GMO legislation in Norway is closely linked to the EU through the Agreement on the European Economic Area (EEA), to which Norway is a party. A central difference with the EU processes emanates from specific clauses in the Norwegian Gene Technology Act on ,sustainable development' and ,societal utility', which provide a potentially wider leverage for Norwegian authorities to turn down the applications. Research material indicates evidence of an increasingly restrictive practice in the Norwegian evaluations, raising the question of how this can be explained in the face of increasing global acceptance of GMOs. A related question is to what extent and how this result is affected by the trends in the EU. An increasingly restrictive practice may be explained by changes in the access structure to the evaluating body, or it may be due to learning and a growing acceptance of the precautionary principle in this sector. Third, a higher number of rejections may largely be associated with the interest structure pertaining to GMOs in Norway. Final decisions are pending and there are uncertainties concerning how Norwegian authorities will apply the specific criteria of the Gene Technology Act. Copyright © 2008 John Wiley & Sons, Ltd and ERP Environment. [source] Guidelines for the management of invasive alien plants or potentially invasive alien plants which are intended for import or have been intentionally importedEPPO BULLETIN, Issue 3 2006Article first published online: 15 DEC 200 No abstract is available for this article. [source] EVOLUTIONARY ANALYSIS OF A KEY FLORAL TRAIT IN AQUILEGIA CANADENSIS (RANUNCULACEAE): GENETIC VARIATION IN HERKOGAMY AND ITS EFFECT ON THE MATING SYSTEMEVOLUTION, Issue 7 2007Christopher R. Herlihy The mating system of flowering plant populations evolves through selection on genetically based phenotypic variation in floral traits. The physical separation of anthers and stigmas within flowers (herkogamy) is expected to be an important target of selection to limit self-fertilization. We investigated the pattern of phenotypic and genetic variation in herkogamy and its effect of self-fertilization in a broad sample of natural populations of Aquilegia canadensis, a species that is highly selfing despite strong inbreeding depression. Within natural populations, plants exhibit substantial phenotypic variation in herkogamy caused primarily by variation in pistil length rather than stamen length. Compared to other floral traits, herkogamy is much more variable and a greater proportion of variation is distributed among rather than within individuals. We tested for a genetic component of this marked phenotypic variation by growing naturally pollinated seed families from five populations in a common greenhouse environment. For three populations, we detected a significant variation in herkogamy among families, and a positive regression between parental herkogamy measured in the field and progeny herkogamy in the greenhouse, suggesting that there is often genetic variation in herkogamy within natural populations. We estimated levels of self-fertilization for groups of flowers that differed in herkogamy and show that, as expected, herkogamy was associated with reduced selfing in 13 of 19 populations. In six of these populations, we performed floral emasculations to show that this decrease in selfing is due to decreased autogamy (within-flower selfing), the mode of selfing that herkogamy should most directly influence. Taken together, these results suggest that increased herkogamy should be selected to reduce the production of low-quality selfed seed. The combination of high selfing and substantial genetic variation for herkogamy in A. canadensis is enigmatic, and reconciling this observation will require a more integrated analysis of how herkogamy influences not only self-fertilization, but also patterns of outcross pollen import and export. [source] The allene oxide cyclase family of Arabidopsis thaliana , localization and cyclizationFEBS JOURNAL, Issue 10 2008Florian Schaller Jasmonates are derived from oxygenated fatty acids (oxylipins) via the octadecanoid pathway and are characterized by a pentacyclic ring structure. They have regulatory functions as signaling molecules in plant development and adaptation to environmental stress. Recently, we solved the structure of allene oxide cyclase 2 (AOC2) of Arabidopsis thaliana, which is, together with the other three AOCs, a key enzyme in the biosynthesis of jasmonates, in that it releases the first cyclic and biologically active metabolite , 12-oxo-phytodienoic acid (OPDA). On the basis of models for the bound substrate, 12,13(S)-epoxy-9(Z),11,15(Z)-octadecatrienoic acid, and the product, OPDA, we proposed that a conserved Glu promotes the reaction by anchimeric assistance. According to this hypothesis, the transition state with a pentadienyl carbocation and an oxyanion is stabilized by a strongly bound water molecule and favorable ,,, interactions with aromatic residues in the cavity. Stereoselectivity results from steric restrictions to the necessary substrate isomerizations imposed by the protein environment. Here, site-directed mutagenesis was used to explore and verify the proposed reaction mechanism. In a comparative analysis of the AOC family from A. thaliana involving enzymatic characterization, in vitro import, and transient expression of AOC,enhanced green fluorescent protein fusion proteins for analysis of subcellular targeting, we demonstrate that all four AOC isoenzymes may contribute to jasmonate biosynthesis, as they are all located in chloroplasts and, in concert with the allene oxide synthase, they are all able to convert 13(S)-hydroperoxy-9(Z),11(E),15(Z)-octadecatrienoic acid into enantiomerically pure cis(+)-OPDA. [source] Human ATP-dependent RNA/DNA helicase hSuv3p interacts with the cofactor of survivin HBXIPFEBS JOURNAL, Issue 19 2005Michal Minczuk The human SUV3gene encodes an NTP-dependent DNA/RNA DExH box helicase predominantly localized in mitochondria. Its orthologue in yeast is a component of the mitochondrial degradosome complex involved in the mtRNA decay pathway. In contrast to this, the physiological function of human SUV3 remains to be elucidated. In this report we demonstrate that the hSuv3 protein interacts with HBXIP, previously identified as a cofactor of survivin in suppression of apoptosis and as a protein that binds the HBx protein encoded by the hepatitis B virus. Using deletion analysis we identified the region within the hSuv3 protein, which is responsible for binding to HBXIP. The HBXIP binding domain was found to be important for mitochondrial import and stability of the Suv3 protein in vivo. We discuss the possible involvement of the hSuv3p,HBXIP interaction in the survivin-dependent antiapoptotic pathway. [source] Bioenergetics of the formyl-methanofuran dehydrogenase and heterodisulfide reductase reactions in Methanothermobacter thermautotrophicusFEBS JOURNAL, Issue 1 2003Linda M. I. De Poorter The synthesis of formyl-methanofuran and the reduction of the heterodisulfide (CoM-S-S-CoB) of coenzyme M (HS-CoM) and coenzyme B (HS-CoB) are two crucial, H2 -dependent reactions in the energy metabolism of methanogenic archaea. The bioenergetics of the reactions in vivo were studied in chemostat cultures and in cell suspensions of Methanothermobacter thermautotrophicus metabolizing at defined dissolved hydrogen partial pressures (,pH2). Formyl-methanofuran synthesis is an endergonic reaction (,G°, = +16 kJ·mol,1). By analyzing the concentration ratios between formyl-methanofuran and methanofuran in the cells, free energy changes under experimental conditions (,G,) were found to range between +10 and +35 kJ·mol,1 depending on the pH2 applied. The comparison with the sodium motive force indicated that the reaction should be driven by the import of a variable number of two to four sodium ions. Heterodisulfide reduction (,G°, = ,40 kJ·mol,1) was associated with free energy changes as high as ,55 to ,80 kJ·mol,1. The values were determined by analyzing the concentrations of CoM-S-S-CoB, HS-CoM and HS-CoB in methane-forming cells operating under a variety of hydrogen partial pressures. Free energy changes were in equilibrium with the proton motive force to the extent that three to four protons could be translocated out of the cells per reaction. Remarkably, an apparent proton translocation stoichiometry of three held for cells that had been grown at pH2<0.12 bar, whilst the number was four for cells grown above that concentration. The shift occurred within a narrow pH2 span around 0.12 bar. The findings suggest that the methanogens regulate the bioenergetic machinery involved in CoM-S-S-CoB reduction and proton pumping in response to the environmental hydrogen concentrations. [source] Nuclear import and DNA-binding activity of RFX1FEBS JOURNAL, Issue 10 2001Evidence for an autoinhibitory mechanism RFX1 binds and regulates the enhancers of a number of viruses and cellular genes. RFX1 belongs to the evolutionarily conserved RFX protein family that shares a DNA-binding domain and a conserved C-terminal region. In RFX1 this conserved region mediates dimerization, and is followed by a unique C-terminal tail, containing a highly acidic stretch. In HL-60 cells nuclear translocation of RFX1 is regulated by protein kinase C with unknown mechanisms. By confocal fluorescence microscopy, we have identified a nonclassical nuclear localization signal (NLS) at the extreme C-terminus. The adjacent ,acidic region', which showed no independent NLS activity, potentiated the function of the NLS. Subcellular fractionation showed that the tight association of RFX1 with the nucleus is mediated by its DNA-binding domain and enhanced by the dimerization domain. In contrast, the acidic region inhibited nuclear association, by down-regulating the DNA-binding activity of RFX1. These data suggest an autoinhibitory interaction, which may regulate the function of RFX1 at the level of DNA binding. The C-terminal tail thus constitutes a composite localization domain, which on the one hand mediates nuclear import of RFX1, and on the other hand inhibits its association with the nucleus and binding to DNA. The participation of the acidic region in both activities suggests a mechanism by which the nuclear import and DNA-binding activity of RFX1 may be coordinately regulated by phosphorylation by kinases such as PKC. [source] Assembly of cytochrome f into the cytochrome bf complex in isolated pea chloroplastsFEBS JOURNAL, Issue 3 2001Ruth M. Mould Structural features of cytochrome f necessary for assembly into the cytochrome bf complex were examined in isolated pea chloroplasts following import of 35S-labelled chimeric precursor proteins, consisting of the presequence of the small subunit of Rubisco fused to the turnip cytochrome f precursor. Assembly was detected by nondenaturing gel electrophoresis of dodecyl maltoside-solubilized thylakoid membranes. A cytochrome f polypeptide unable to bind haem because of mutagenesis of Cys21 and Cys24 to alanine residues was assembled into the complex and had similar stability to the wild-type polypeptide. This indicates that covalent haem binding to cytochrome f is not necessary for assembly of the protein into the cytochrome bf complex. A truncated protein lacking the C-terminal 33 amino acid residues, including the transmembrane span and the stroma-exposed region, was translocated across the thylakoid membrane, had a similar stability to wild-type cytochrome f but was not assembled into the complex. This indicates that the C-terminal region of cytochrome f is important for assembly into the complex. A mutant cytochrome f unable to bind haem and lacking the C-terminal region was also translocated across the thylakoid membrane but was extremely labile, indicating that, in the absence of the C-terminal membrane anchor, haem-less cytochrome f is recognized by a thylakoid proteolytic system. [source] Biogenesis of the yeast frataxin homolog Yfh1pFEBS JOURNAL, Issue 11 2000Tim44-dependent transfer to mtHsp70 facilitates folding of newly imported proteins in mitochondria Tim44 is an essential component of the mitochondrial inner membrane protein import machinery. In this study we asked if Tim44 is of relevance in intramitochondrial protein folding. We investigated the role of Tim44 in the biogenesis of the authentic mitochondrial protein Yfh1p, the yeast homolog of mammalian frataxin, which was recently implicated in Friedreich ataxia. After inactivation of Tim44, binding of mitochondrial heat shock protein (mtHsp)70 to translocating Yfh1p and subsequent folding to the native state was nearly completely blocked. Residual amounts of imported Yfh1p showed an increased tendency to aggregate. To further characterize the functions of Tim44 in the matrix, we imported dihydrofolate reductase (DHFR) as a model protein. Depletion of Tim44 allowed import of DHFR, although folding of the newly imported DHFR was delayed. Moreover, the depletion of Tim44 caused a strongly reduced binding of mtHsp70 and Mge1 to the translocating polypeptide. Subsequent dissociation of mtHsp70 from imported DHFR was delayed, indicating that mtHsp70,substrate complexes formed independently of Tim44 differ from the complexes that form under the control of Tim44. We conclude that Tim44 not only plays a role in protein translocation but also in the pathways of mitochondrial protein folding. [source] Intracellular trafficking and release of intact edible mushroom lectin from HT29 human colon cancer cellsFEBS JOURNAL, Issue 7 2000Lu-Gang Yu Our previous studies have shown that the Gal,1,3GalNAc,- (Thomsen,Friedenreich antigen)-binding lectin from the common edible mushroom Agaricus bisporus (ABL) reversibly inhibits cell proliferation, and this effect is a consequence of inhibition of nuclear localization sequence-dependent nuclear protein import after ABL internalization [Yu, L.G., Fernig, D.G., White, M.R.H., Spiller, D.G., Appleton, P., Evans, R.C., Grierson, I., Smith, J.A., Davies, H., Gerasimenko, O.V., Petersen, O.H., Milton, J.D. & Rhodes, J.M. (1999) J. Biol. Chem.274, 4890,4899]. Here, we have investigated further the intracellular trafficking and fate of ABL after internalization in HT29 human colon cancer cells. Internalization of 125I-ABL occurred within 30 min of the lectin being bound to the cell surface. Subcellular fractionation after pulse labelling of the cells with 125I-ABL for 2 h at 4 °C followed by culture of the cells at 37 °C demonstrated a steady increase in radioactivity in a crude nuclear extract. The radioactivity in this extract reached a maximum after 10 h and declined after 20 h. Release of ABL from the cell, after pulse labelling, was assessed using both fluorescein isothiocyanate-labelled ABL and 125I-ABL and was slow, with a t1/2 of 48 h. Most of the 125I-ABL both inside cells and in the medium remained intact, as determined by trichloroacetic acid precipitation and SDS/PAGE, and after 48 h only 22 ± 2% of ABL in the medium and 14 ± 2% inside the cells was degraded. This study suggests that the reversibility of the antiproliferative effect of ABL is associated with its release from cells after internalization. The internalization and subsequent slow release, with little degradation of ABL, reflects the tendency of lectins to resist biodegradation and implies that other endogenous or exogenous lectins may be processed in this way by intestinal epithelial cells. [source] | ||||||||||||||||||||||||||||||||||||||||||||||