ALBERT

Description: RNA editing of miRNAs, especially in the seed region, adds another layer to miRNA mediated gene regulation which can modify its targets, altering cellular signaling involved in important processes such as differentiation. In this study, we have explored the role of miRNA editing in CD4 + T cell differentiation. CD4 + T cells are an integral component of the adaptive immune system. Naïve CD4 + T cells, on encountering an antigen, get differentiated either into inflammatory subtypes like Th1, Th2 or Th17, or into immunosuppressive subtype Treg, depending on the cytokine milieu. We found C-to-U editing at fifth position of mature miR-100, specifically in Treg. The C-to-U editing of miR-100 is functionally associated with at least one biologically relevant target change, from MTOR to SMAD2. Treg cell polarization by TGFβ1 was reduced by both edited and unedited miR-100 mimics, but percentage of Treg in PBMCs was only reduced by edited miR-100 mimics, suggesting a model in which de-repression of MTOR due to loss of unedited mir-100, promotes tolerogenic signaling, while gain of edited miR-100 represses SMAD2, thereby limiting the Treg. Such delicately counterbalanced systems are a hallmark of immune plasticity and we propose that miR-100 editing is a novel mechanism toward this end.

Description: Abstract Inducible defense is a common form of phenotypic plasticity, and inducibility (change in defense after herbivore‐attack) has long been predicted to trade off with constitutive (or baseline) defense to manage resource allocation. Although such trade‐offs likely constrain evolution within species, the extent to which they influence divergence among species is unresolved. We studied cardenolide toxins among genetic families in eight North American Asclepias species, spanning the full range of defense in the genus. Using common environment experiments and chemical assays, we report a consistent trade‐off (negative genetic correlation) between concentrations of constitutive cardenolides and their inducibility within each species. However, no trade‐off was found in a phylogenetic analysis across species. To investigate factors driving differences in defense allocation among species we used latitude as a proxy for growing season and herbivore pressure and found that divergence into lower latitudes resulted in evolution of higher cardenolides overall. Next we used an enzymatic assay of the cellular target of cardenolides (sodium‐potassium ATPase) and confirm that higher cardenolides resulted in stronger toxicity to a sensitive species, but not to specialized monarch butterflies. Thus, plant speciation into biogeographic regions with alternative resources or pest pressure resulted in the macroevolution of cardenolide defense, especially against unspecialized herbivores. Nonetheless, trade‐offs persist in the extent to which this defense is allocated constitutively or is inducible among genotypes within each species. This article is protected by copyright. All rights reserved.

Description: Abstract Biodiversity is defined by trait‐differences between organisms, and biologists have long sought to predict associations among ecologically important traits: why do some traits trade off while others are co‐expressed? Why might some trait associations hold across levels of organization, from individuals and genotypes to populations and species, while others only occur at one level? Understanding such scaling is a core biological problem, bearing on the evolution of ecological strategies as well as forecasting responses to environmental change. Explicitly considering the hierarchy of biodiversity and expectations at each scale (individual change, evolution within and among populations, and species turn‐over) is necessary as we work towards a predictive framework in evolutionary ecology. Within species, a trait may have an association with another trait due to phenotypic plasticity, genetic correlation, or population‐level local adaptation. Plastic responses are often adaptive and yet individuals have a fixed pool of resources; thus, positive and negative trait associations can be generated by immediate environmental needs and energetic demands. Genetic variation and covariation for traits within a population are typically shaped by varying natural selection in space and time. Although genetic correlations are infrequently long‐term constraints, they may indicate competing organismal demands. Traits are often quantitatively differentiated (local adaptation) among populations, although selection rarely favors qualitatively different strategies until populations become reproductively isolated. Across species, niche specialization to particular habitats or biotic interactions may determine trait correlations, a subset of which are termed “strategic trade‐offs” because they are a consequence of adaptive specialization. Across scales, constraints within species often do not apply as new species evolve, and conversely, trait correlations observed across populations or species may not be reflected within populations. I give examples of such scale‐dependent trait associations and their causes across taxonomic groups and ecosystems, and in the final section of the paper I specifically evaluate leaf economic spectrum traits and their associations with plant defense against herbivory. Scale‐dependent predictions emerge for understanding plant ecology holistically, and this approach can be fruitfully applied more generally in evolutionary ecology. Adaptive specialization and community context are two of the primary drivers of trade‐offs and syndromes across biological scales.

Description: In this paper, we attempt to find out the ‘spectro-temporal’ characteristics during the jet ejection, of several outbursting Galactic black hole sources based on RXTE -Proportional Counter Array (PCA)/High Energy X-ray Timing Experiment (HEXTE) data in the energy band of 2–100 keV. We present results of detailed analysis of these sources during the rising phase of their outburst, whenever simultaneous or near-simultaneous X-ray and radio observations are ‘available’. We find that before the peak radio flare (transient jet) a few of the sources (in addition to those reported earlier) exhibit ‘local’ softening within the soft intermediate state itself. Except the duration, all the properties of the ‘local’ softening (Quasi Periodic Oscillation (QPO) not observed, reduction in total rms, soft spectra) are observed to be similar to the canonical soft state. We find similar ‘local’ softening for the recent outburst of V404 Cyg also based on SWIFT observations. Fast changes in the ‘spectro-temporal’ properties during the ‘local’ softening imply that it may not be occurring due to change in Keplerian accretion rate. We discuss these results in the framework of the magnetized two component advective flow model.

Description: We study the spectral and temporal characteristics of the source GS 2023+338 (V404 Cyg) during the initial phase of its 2015 June outburst, over the energy range of 0.5–150 keV. This is the first detailed study of the characteristics of this source based on SWIFT observations, being reported. Based on our analysis, we understand that the source existed in the hard, intermediate and soft spectral states. We find that the evolution of the spectral parameters, the hardness-intensity diagram and the rms-intensity diagram are not similar to those observed for most of the outbursting black hole sources. We also observe presence of weak peaked components in the power density spectra during the intermediate state of the source. Dramatic changes in the spectral and temporal properties are also exhibited before the ejection of a radio jet suggesting it to be associated with the coronal mass ejection. It seems that may be due to evacuation of the inner part of the Keplerian disc for a short duration, the disc component is not observed after the huge radio flare. The absorption features observed in the low-energy spectra suggest the presence of wind emission and the evolution of the characteristics of the variable Fe line emission during both hard and intermediate states, indicate its origin to be probably related to the wind/outflow.

Description: Attraction of mutualists and defense against antagonists are critical challenges for most organisms and can be especially acute for plants with pollinating and non-pollinating flower visitors. Secondary compounds in flowers have been hypothesized to adaptively mediate attraction of mutualists and defense against antagonists, but this hypothesis has rarely been tested. The tissues of milkweeds ( Asclepias spp.) contain toxic cardenolides that have long been studied as chemical defenses against herbivores. Milkweed nectar also contains cardenolides, and we have examined the impact of manipulating cardenolides in nectar on the foraging choices of two flower visitors: generalist bumblebees, Bombus impatiens , which are mutualistic pollinators, and specialist monarch butterflies, Danaus plexippus , which are herbivores as larvae and ineffective pollinators as adults. Although individual bumblebees in single foraging bouts showed no avoidance of cardenolides at the highest natural concentrations reported for milkweeds, a pattern of deterrence did arise when entire colonies were allowed to forage for several days. Monarch butterflies were not deterred by the presence of cardenolides in nectar when foraging from flowers, but laid fewer eggs on plants paired with cardenolide-laced flowers compared to controls. Thus, although deterrence of bumblebees by cardenolides may only occur after extensive foraging, a primary effect of nectar cardenolides appears to be reduction of monarch butterfly oviposition. This article is protected by copyright. All rights reserved.

Description: Computational classification of mitochondrial shapes reflects stress and redox state Cell Death and Disease 4, e461 (January 2013). doi:10.1038/cddis.2012.213 Authors: T Ahmad, K Aggarwal, B Pattnaik, S Mukherjee, T Sethi, B K Tiwari, M Kumar, A Micheal, U Mabalirajan, B Ghosh, S Sinha Roy & A Agrawal

Description: Abstract More than five decades ago, Ehrlich and Raven proposed a revolutionary idea–that the evolution of novel plant defense could spur adaptive radiation in plants. Despite motivating much work on plant–herbivore coevolution and defense theory, Ehrlich and Raven never proposed a mechanism for their "escape and radiate" model. Recent intriguing mechanisms proposed by Marquis et al. include sympatric divergence, pleiotropic effects of plant defense traits on reproductive isolation, and strong postzygotic isolation, but these may not be general features of herbivore‐mediated speciation. An alternate view is that herbivores may impose strong divergent selection on defenses in allopatric plant populations, with plant–herbivore coevolution driving local adaptation resulting in plant speciation. Building on these ideas, we propose three scenarios that consider the role of herbivores in plant speciation. These include (1) vicariance, subsequent coevolution within populations and adaptive divergence between geographically isolated populations, (2) colonization of a new habitat lacking effective herbivores followed by loss of defense and then re‐evolution and coevolution of defense in response to novel herbivores, and (3) evolution of a new defense followed by range expansion, vicariance, and coevolution. We discuss the general role of coevolution in plant speciation and consider outstanding issues related to understanding: (1) the mechanisms behind cospeciation of plants and insects, (2) geographic variation in defense phenotypes, (3) how defensive traits and geography map on plant phylogenies, and (4) the role of herbivores in driving character displacement in defense phenotypes of related species in sympatry.

Description: Author(s): B. Meredig, A. Agrawal, S. Kirklin, J. E. Saal, J. W. Doak, A. Thompson, K. Zhang, A. Choudhary, and C. Wolverton Typically, computational screens for new materials sharply constrain the compositional search space, structural search space, or both, for the sake of tractability. To lift these constraints, we construct a machine learning model from a database of thousands of density functional theory (DFT) calcul... [Phys. Rev. B 89, 094104] Published Fri Mar 14, 2014