Direct and indirect selection on flowering time, water-use efficiency (WUE, δ (13)C), and WUE plasticity to drought in Arabidopsis thaliana.

Flowering time and water-use efficiency (WUE) are two ecological traits that are important for plant drought response. To understand the evolutionary significance of natural genetic variation in flowering time, WUE, and WUE plasticity to drought in Arabidopsis thaliana, we addressed the following questions: (1) How are ecophysiological traits genetically correlated within and between different soil moisture environments? (2) Does terminal drought select for early flowering and drought escape? (3) Is WUE plasticity to drought adaptive and/or costly? We measured a suite of ecophysiological and reproductive traits on 234 spring flowering accessions of A. thaliana grown in well-watered and season-ending soil drying treatments, and quantified patterns of genetic variation, correlation, and selection within each treatment. WUE and flowering time were consistently positively genetically correlated. WUE was correlated with WUE plasticity, but the direction changed between treatments. Selection generally favored early flowering and low WUE, with drought favoring earlier flowering significantly more than well-watered conditions. Selection for lower WUE was marginally stronger under drought. There were no net fitness costs of WUE plasticity. WUE plasticity (per se) was globally neutral, but locally favored under drought. Strong genetic correlation between WUE and flowering time may facilitate the evolution of drought escape, or constrain independent evolution of these traits. Terminal drought favored drought escape in these spring flowering accessions of A. thaliana. WUE plasticity may be favored over completely fixed development in environments with periodic drought

Deregulating and liberalizing the North-American telecommunications market: Explaining the US-approach

This paper examines the substantial regulatory changes in North American telecommunications markets over the past decade. We argue that a combination of U.S. domestic politics and the logic of international strategic positioning produced substantial and far-reaching reform driven primarily by multilateral actions at the WTO and a set of unilateral U.S. initiatives (primarily benchmarks). Internationally, although NAFTA played an important role as a „building block“ for the WTO agreement, we argue the lack of market coverage and more far-reaching WTO agreement ultimately limited NAFTA's role in driving reform. The logic of U.S. domestic politics also played a central role by putting certain constraints on what the U.S. would accept in a telecommunications trade deal. Specifically, there was broad political support for a deal, but the particular problems facing U.S. carriers in competitive international markets meant any deal had to cover all major telecommunications markets and had to address the very real anti-competitive opportunities open to foreign monopolists. Our argument suggests continued reform is likely to be driven primarily by the framework established at the WTO, although the U.S. will continue to use unilateral initiatives to drive reform acceptable to key U.S. political actors.Dieses Papier untersucht die erheblichen Regulierungsänderungen auf dem nordamerikanischen Telekommunikationsmarkt während der letzten Dekade. Wir argumentieren, dass die Kombination von amerikanischer Innenpolitik und internationalen strategischen Interessen bedeutende und weit reichende Reformen erzeugte, ausgelöst vor allem von multilateralen Aktivitäten in der WTO und einseitigen Initiativen der USA (insbesondere Benchmarks). Die NAFTA war zwar ein wichtiger ?Baustein? für das WTO-Abkommen, ihr begrenzter Wirkungsbereich und die weiter gehenden WTO-Vereinbarungen beeinträchtigten aber letztlich ihre Rolle als Triebkraft für Reformen. Die amerikanische Innenpolitik spielte einen zentralen Part, da sich hieraus Grenzen bezüglich der Inhalte eines Telekommunikationsabkommens ableiteten, das die USA zu akzeptieren bereit waren. Zwar gab es eine breite politische Unterstützung für ein Abkommen. Angesichts der spezifischen Probleme der amerikanischen Anbieter im internationalen Wettbewerb musste aber jede Vereinbarung alle großen Telekommunikationsmärkte umfassen, und sie musste den sehr konkreten Möglichkeiten ausländischer Monopolanbieter zur Beschränkung des Wettbewerbs Rechnung tragen. Unsere Überlegungen führen zu dem Ergebnis, dass weitere Reformen im Wesentlichen im Rahmen der WTO vorangetrieben werden dürften. Allerdings werden die USA auch in Zukunft einseitig Initiativen ergreifen, um Reformen durchzusetzen, die für ihre politischen Hauptakteure akzeptabel sind

Long-range electron transfer in structurally engineered pentaammineruthenium (histidine-62) cytochrome c

In many biological processes, long-range electron transfer (ET) plays a key role. When the three-dimensional structures of proteins are accurately known, use of modified proteins and protein-protein complexes provides an experimental approach to study ET rates between two metal centers. For Ru(His)- modified proteins, the introduction of histidine residues at any desired surface location by site-directed mutagenesis opens the way for systematic investigations of ET pathways

The physiological basis for genetic variation in water use efficiency and carbon isotope composition in Arabidopsis thaliana.

Ecologists and physiologists have documented extensive variation in water use efficiency (WUE) in Arabidopsis thaliana, as well as association of WUE with climatic variation. Here, we demonstrate correlations of whole-plant transpiration efficiency and carbon isotope composition (δ(13)C) among life history classes of A. thaliana. We also use a whole-plant cuvette to examine patterns of co-variation in component traits of WUE and δ(13)C. We find that stomatal conductance (g s) explains more variation in WUE than does A. Overall, there was a strong genetic correlation between A and g s, consistent with selection acting on the ratio of these traits. At a more detailed level, genetic variation in A was due to underlying variation in both maximal rate of carboxylation (V cmax) and maximum electron transport rate (Jmax). We also found strong effects of leaf anatomy, where lines with lower WUE had higher leaf water content (LWC) and specific leaf area (SLA), suggesting a role for mesophyll conductance (g m) in variation of WUE. We hypothesize that this is due to an effect through g m, and test this hypothesis using the abi4 mutant. We show that mutants of ABI4 have higher SLA, LWC, and g m than wild-type, consistent with variation in leaf anatomy causing variation in g m and δ(13)C. These functional data also add further support to the central, integrative role of ABI4 in simultaneously altering ABA sensitivity, sugar signaling, and CO2 assimilation. Together our results highlight the need for a more holistic approach in functional studies, both for more accurate annotation of gene function and to understand co-limitations to plant growth and productivity

Pleiotropy of FRIGIDA enhances the potential for multivariate adaptation.

An evolutionary response to selection requires genetic variation; however, even if it exists, then the genetic details of the variation can constrain adaptation. In the simplest case, unlinked loci and uncorrelated phenotypes respond directly to multivariate selection and permit unrestricted paths to adaptive peaks. By contrast, 'antagonistic' pleiotropic loci may constrain adaptation by affecting variation of many traits and limiting the direction of trait correlations to vectors that are not favoured by selection. However, certain pleiotropic configurations may improve the conditions for adaptive evolution. Here, we present evidence that the Arabidopsis thaliana gene FRI (FRIGIDA) exhibits 'adaptive' pleiotropy, producing trait correlations along an axis that results in two adaptive strategies. Derived, low expression FRI alleles confer a 'drought escape' strategy owing to fast growth, low water use efficiency and early flowering. By contrast, a dehydration avoidance strategy is conferred by the ancestral phenotype of late flowering, slow growth and efficient water use during photosynthesis. The dehydration avoidant phenotype was recovered when genotypes with null FRI alleles were transformed with functional alleles. Our findings indicate that the well-documented effects of FRI on phenology result from differences in physiology, not only a simple developmental switch

Natural variation in abiotic stress responsive gene expression and local adaptation to climate in Arabidopsis thaliana.

Gene expression varies widely in natural populations, yet the proximate and ultimate causes of this variation are poorly known. Understanding how variation in gene expression affects abiotic stress tolerance, fitness, and adaptation is central to the field of evolutionary genetics. We tested the hypothesis that genes with natural genetic variation in their expression responses to abiotic stress are likely to be involved in local adaptation to climate in Arabidopsis thaliana. Specifically, we compared genes with consistent expression responses to environmental stress (expression stress responsive, "eSR") to genes with genetically variable responses to abiotic stress (expression genotype-by-environment interaction, "eGEI"). We found that on average genes that exhibited eGEI in response to drought or cold had greater polymorphism in promoter regions and stronger associations with climate than those of eSR genes or genomic controls. We also found that transcription factor binding sites known to respond to environmental stressors, especially abscisic acid responsive elements, showed significantly higher polymorphism in drought eGEI genes in comparison to eSR genes. By contrast, eSR genes tended to exhibit relatively greater pairwise haplotype sharing, lower promoter diversity, and fewer nonsynonymous polymorphisms, suggesting purifying selection or selective sweeps. Our results indicate that cis-regulatory evolution and genetic variation in stress responsive gene expression may be important mechanisms of local adaptation to climatic selective gradients

Investigating Developmental Changes in Scalp-To-Cortex Correspondence Using Diffuse Optical Tomography Sensitivity in Infancy

Significance: Diffuse optical tomography (DOT) uses near-infrared light spectroscopy (NIRS) to measure changes in cerebral hemoglobin concentration. Anatomical interpretations of NIRS data require accurate descriptions of the cranio-cerebral relations and DOT sensitivity to the underlying cortical structures. Such information is limited for pediatric populations because they undergo rapid head and brain development. Aim: We aim to investigate age-related differences in scalp-to-cortex distance and mapping between scalp locations and cortical regions of interest (ROIs) among infants (2 weeks to 24 months with narrow age bins), children (4 and 12 years), and adults (20 to 24 years). Approach: We used spatial scalp projection and photon propagation simulation methods with age-matched realistic head models based on MRIs. Results: There were age-group differences in the scalp-to-cortex distances in infancy. The developmental increase was magnified in children and adults. There were systematic age-related differences in the probabilistic mappings between scalp locations and cortical ROIs. Conclusions: Our findings have important implications in the design of sensor placement and making anatomical interpretations in NIRS and fNIRS research. Age-appropriate, realistic head models should be used to provide anatomical guidance for standalone DOT data in infants

Cortical Source Analysis of Event-Related Potentials: A Developmental Approach

Cortical source analysis of electroencephalographic (EEG) signals has become an important tool in the analysis of brain activity. The aim of source analysis is to reconstruct the cortical generators (sources) of the EEG signal recorded on the scalp. The quality of the source reconstruction relies on the accuracy of the forward problem, and consequently the inverse problem. An accurate forward solution is obtained when an appropriate imaging modality (i.e., structural magnetic resonance imaging - MRI) is used to describe the head geometry, precise electrode locations are identified with 3D maps of the sensor positions on the scalp, and realistic conductivity values are determined for each tissue type of the head model. Together these parameters contribute to the definition of realistic head models. Here, we describe the steps necessary to reconstruct the cortical generators of the EEG signal recorded on the scalp. We provide an example of source reconstruction of event-related potentials (ERPs) during a face-processing task performed by a 6-month-old infant. We discuss the adjustments necessary to perform source analysis with measures different from the ERPs. The proposed pipeline can be applied to the investigation of different cognitive tasks in both younger and older participants

Hail to the Chief: Former Law Clerks for William Rehnquist Recall What They Learned and How He Touched Their Lives

Chief Justice William H. Rehnquist, who died Sept. 3, is remembered for his disarming warmth and humor, breadth of knowledge about the law, and insistence that there is life outside the office. Few knew him better than the legions of clerks who tolled with and learned from him. Indeed, the sheer number who attended his funeral testifies to how highly he was regarded. Here, four former clerks from the decades of the 1970s, \u2780s and \u2790s write about their own particular memories of the late chief justice