An Endogenous F-Box Protein Regulates ARGONAUTE1 in \u3cem\u3eArabidopsis thaliana\u3c/em\u3e

ARGONAUTE1 (AGO1) mediates microRNA- and small interfering RNA-directed posttranscriptional gene silencing in Arabidopsis thaliana,. Mutant alleles of SQUINT (SQN) slightly reduce AGO1 activity and have weak effects on shoot morphology. A screen for mutations that suppress the sqn phenotype produced loss-of-function mutations in the F-box gene FBW2. Mutations in FBW2 not only suppress sqn but also suppress many of the developmental phenotypes of weak, but not null, alleles of AGO1 by increasing AGO1 protein levels. Conversely, over-expression of FBW2 decreases the abundance of the AGO1 protein but not AGO1 messenger RNA, further indicating that FBW2 regulates AGO1 protein levels. fbw2 mutants have no obvious morphological phenotype, but display a reduced sensitivity to abscisic acid (ABA) that can be attributed to increased AGO1 activity. Our results indicate that FBW2 is a novel negative regulator of AGO1 and suggest that it plays a role in ABA signalling and/or response

Structural characterization of nanofiber silk produced by embiopterans (webspinners)

Embiopterans produce silken galleries and sheets using exceptionally fine silk fibers in which they live and breed. In this study, we use electron microscopy (EM), Fourier-transform infrared (FT-IR) spectroscopy, wide angle X-ray diffraction (WAXD) and solid-state nuclear magnetic resonance (ssNMR) techniques to elucidate the molecular level protein structure of webspinner (embiid) silks. Silks from two species Antipaluria urichi and Aposthonia ceylonica are studied in this work. Electron microscopy images show that the fibers are about 90–100 nm in diameter, making webspinner silks among the finest of all known animal silks. Structural studies reveal that the silk protein core is dominated by β-sheet structures, and that the protein core is coated with a hydrophobic alkane-rich surface coating. FTIR spectra of native embiid silk shows characteristic alkane CH2 stretchings near 2800–2900 cm−1, which decrease approximately 50% after washing the silk with 2 : 1 CHCl3 : MeOH. Furthermore, 13C ssNMR data shows a significant CH2 resonance that is strongly affected by the presence of water, supporting the idea that the silk fibers are coated with a hydrocarbon-rich layer. Such a layer is likely used to protect the colonies from rain. FTIR data also suggests that embiid silks are dominated by β-sheet secondary structures similar to spider and silkworm silk fibers. NMR data confirms the presence of β-sheet nanostructures dominated by serine-rich repetitive regions. A deconvolution of the serine Cβ NMR resonance reveals that approximately 70% of all seryl residues exist in a β-sheet structure. This is consistent with WAXD results that suggest webspinner silks are 70% crystalline, which is the highest crystalline fraction reported for any animal silks. The work presented here provides a molecular level structural picture of silk fibers produced by webspinners

Scintillation of tantalate compounds

A screening of 63 metal-tantalate-oxides was conducted in search of heavy scintillator materials operating at ambient temperature. While tantalates are known to have slow scintillation decay times, the high atomic number of tantalum (73) provides good stopping power for gamma rays. Screened samples were synthesized by solid state reactions. Scintillation properties of these materials were evaluated by X-ray diffraction, X-ray excited luminescence and pulsed X-ray luminescence. Of the 63 synthesized tantalates examined only 12 had luminosity values greater than 1000 ph/MeV at room temperature. From these, ScTaO4, YTa3O9, and Zn3Ta2O8 have greater than 40% of their emission in the first μs. The brightest and fastest compound of those tested was Zn3Ta2O8 with an estimated luminosity of 26,000 ph/MeV and a main decay time of 600 ns from its crystalline powder. Further attention is given to Zn3Ta2O8 and Mg4Ta2O9 scintillation properties, demonstrating their potential for scintillation applications

ACE-ASIA - Regional climatic and atmospheric chemical effects of Asian dust and pollution

Although continental-scale plumes of Asian dust and pollution reduce the amount of solar radiation reaching the earth's surface and perturb the chemistry of the atmosphere, our ability to quantify these effects has been limited by a lack of critical observations, particularly of layers above the surface. Comprehensive surface, airborne, shipboard, and satellite measurements of Asian aerosol chemical composition, size, optical properties, and radiative impacts were performed during the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) study. Measurements within a massive Chinese dust storm at numerous widely spaced sampling locations revealed the highly complex structure of the atmosphere, in which layers of dust, urban pollution, and biomass-burning smoke may be transported long distances as distinct entities or mixed together. The data allow a first-time assessment of the regional climatic and atmospheric chemical effects of a continental-scale mixture of dust and pollution. Our results show that radiative flux reductions during such episodes are sufficient to cause regional climate change

Planet Migration and Disk Destruction due to Magneto-Centrifugal Stellar Winds

This paper investigates the influence of magneto-centrifugally driven or simply magnetic winds of rapidly-rotating, strongly-magnetized T Tauri stars in causing the inward or outward migration of close-in giant planets. The azimuthal ram pressure of the magnetized wind acting on the planet tends to increase the planet's angular momentum and cause outward migration if the star's rotation period $P_*$ is less than the planet's orbital period $P_p$. In the opposite case, $P_* > P_p$, the planet migrates inward. Thus, planets orbiting at distances larger (smaller) than $0.06 {\rm AU}(P_*/5{\rm d})^{2/3}$ tend to be pushed outward (inward), where $P_*$ is the rotation period of the star assumed to have the mass of the sun. The magnetic winds are likely to occur in T Tauri stars where the thermal speed of the gas close to the star is small, where the star's magnetic field is strong, and where the star rotates rapidly. The time-scale for appreciable radial motion of the planet is estimated as $\sim 2 - 20$ Myr. A sufficiently massive close-in planet may cause tidal locking and once this happens the radial migration due to the magnetic wind ceases. The magnetic winds are expected to be important for planet migration for the case of a multipolar magnetic field rather than a dipole field where the wind is directed away from the equatorial plane and where a magnetospheric cavity forms. The influence of the magnetic wind in eroding and eventually destroying the accretion disk is analyzed. A momentum integral is derived for the turbulent wind/disk boundary layer and this is used to estimate the disk erosion time-scale as $\sim 1-10^2$ Myr, with the lower value favored.Comment: 8 pages, 6 figure

Transcriptome analysis of egg viability in rainbow trout, Oncorhynchus mykiss

Background Maternal transcripts are accumulated in the oocyte during oogenesis to provide for protein synthesis from oocyte maturation through early embryonic development, when nuclear transcription is silenced. The maternal mRNAs have short poly(A) tails after undergoing post-transcriptional processing necessary for stabilizing them for storage. The transcripts undergo cytoplasmic polyadenylation when they are to be translated. Transcriptome analyses comparing total mRNA and elongated poly(A) mRNA content among eggs of different quality can provide insight into molecular mechanisms affecting egg developmental competence in rainbow trout. The present study used RNA-seq to compare transcriptomes of unfertilized eggs of rainbow trout females yielding different eyeing rates, following rRNA removal and poly(A) retention for construction of the libraries. Results The percentage of embryos to reach the 32-cell stage at 24 h post fertilization was significantly correlated to family eyeing rate, indicating that inviable embryos were developmentally compromised before zygotic genome activation. RNA sequencing identified 2 differentially expressed transcripts (DETs) from total mRNA sequencing comparing females with low-quality ( 80% eyeing) eggs. In contrast, RNA sequencing from poly(A) captured transcripts identified 945 DETs between low- and high-quality eggs, 1012 between low- and medium-quality eggs, and only 2 between medium- and high-quality eggs. The transcripts of mitochondrial genes were enriched with polyadenylated transcript sequencing and they were significantly reduced in low-quality eggs. Similarly, mitochondrial DNA was reduced in low-quality eggs compared with medium- and high-quality eggs. The functional gene analysis classified the 945 DETs between low- and high-quality eggs into 31 functional modules, many of which were related to ribosomal and mitochondrial functions. Other modules involved transcription, translation, cell division, apoptosis, and immune responses. Conclusions Our results indicate that differences in egg quality may be derived from differences in maternal nuclear transcript activation and cytoplasmic polyadenylation before ovulation, as opposed to accumulation and storage of maternal nuclear transcripts during oogenesis. Transcriptome comparisons suggest low-quality eggs suffered from impaired oxidative phosphorylation and translation. The DETs identified in this study provide insight into developmental competence in rainbow trout eggs.Ope

Contemporaneous Imaging Comparisons of the Spotted Giant sigma Geminorum Using Interferometric, Spectroscopic, and Photometric Data

Nearby active stars with relatively rapid rotation and large starspot structures offer the opportunity to compare interferometric, spectroscopic, and photometric imaging techniques. In this paper, we image a spotted star with three different methods for the first time. The giant primary star of the RS Canum Venaticorum binary sigma. Geminorum (sigma Gem) was imaged for two epochs of interferometric, high-resolution spectroscopic, and photometric observations. The light curves from the reconstructions show good agreement with the observed light curves, supported by the longitudinally consistent spot features on the different maps. However, there is strong disagreement in the spot latitudes across the methods.Peer reviewe

PU.1 controls fibroblast polarization and tissue fibrosis

Fibroblasts are polymorphic cells with pleiotropic roles in organ morphogenesis, tissue homeostasis and immune responses. In fibrotic diseases, fibroblasts synthesize abundant amounts of extracellular matrix, which induces scarring and organ failure. By contrast, a hallmark feature of fibroblasts in arthritis is degradation of the extracellular matrix because of the release of metalloproteinases and degrading enzymes, and subsequent tissue destruction. The mechanisms that drive these functionally opposing pro-fibrotic and pro-inflammatory phenotypes of fibroblasts remain unknown. Here we identify the transcription factor PU.1 as an essential regulator of the pro-fibrotic gene expression program. The interplay between transcriptional and post-transcriptional mechanisms that normally control the expression of PU.1 expression is perturbed in various fibrotic diseases, resulting in the upregulation of PU.1, induction of fibrosis-associated gene sets and a phenotypic switch in extracellular matrix-producing pro-fibrotic fibroblasts. By contrast, pharmacological and genetic inactivation of PU.1 disrupts the fibrotic network and enables reprogramming of fibrotic fibroblasts into resting fibroblasts, leading to regression of fibrosis in several organs