Characterising the seasonal cycle of dissolved organic nitrogen using Cefas SmartBuoy high-resolution time-series samples from the southern North Sea

The Cefas SmartBuoy network provides a unique insight into the biogeochemical dynamics of the Northern European shelf seas, particularly the North Sea, through high-resolution automated offshore water sampling. We present total dissolved nitrogen and dissolved organic nitrogen (DON) from the Dowsing SmartBuoy site (53.531° N, 1.053° E) from January to October 2010, the first high resolution seasonal (winter-autumn) cycle of DON from the open North Sea. On top of a refractory background DON concentration of approximately 5 μM, a rapid increase in DON of a further ～5 μM is observed over the course of the spring bloom. This rapidly produced DON declines at an estimated net decay rate of between 0.6 and 1.8 μM month^?1. The slow decay suggests that the majority of the additional DON produced during the spring bloom is of semi-labile nature and has a lifetime of weeks to months. The dataset allows us to tightly constrain the budget for water column nitrogen over the winter, spring and summer of 2010 and clearly demonstrates the ‘sawtooth’ nature of the seasonal cycle of DON in the open North Sea, which has been impossible to resolve with a more traditional ship-based mode of operation. This work highlights the importance of autonomous sampling approaches in better understanding shelf sea biogeochemistry in the future.     

Mitophagy is required for mitochondrial biogenesis and myogenic differentiation of C2C12 myoblasts

Myogenesis is a crucial process governing skeletal muscle development and homeostasis. Differentiation of primitive myoblasts into mature myotubes requires a metabolic switch to support the increased energetic demand of contractile muscle. Skeletal myoblasts specifically shift from a highly glycolytic state to relying predominantly on oxidative phosphorylation (OXPHOS) upon differentiation. We have found that this phenomenon requires dramatic remodeling of the mitochondrial network involving both mitochondrial clearance and biogenesis. During early myogenic differentiation, autophagy is robustly upregulated and this coincides with DNM1L/DRP1 (dynamin 1-like)-mediated fragmentation and subsequent removal of mitochondria via SQSTM1 (sequestosome 1)-mediated mitophagy. Mitochondria are then repopulated via PPARGC1A/PGC-1α (peroxisome proliferator-activated receptor gamma, coactivator 1 alpha)-mediated biogenesis. Mitochondrial fusion protein OPA1 (optic atrophy 1 [autosomal dominant]) is then briskly upregulated, resulting in the reformation of mitochondrial networks. The final product is a myotube replete with new mitochondria. Respirometry reveals that the constituents of these newly established mitochondrial networks are better primed for OXPHOS and are more tightly coupled than those in myoblasts. Additionally, we have found that suppressing autophagy with various inhibitors during differentiation interferes with myogenic differentiation. Together these data highlight the integral role of autophagy and mitophagy in myogenic differentiation.     

Identifying populations for management: fine-scale population structure in the New Zealand alpine rock wren (<Emphasis Type="Italic">Xenicus gilviventris</Emphasis>)

Examining the spatial genetic structure of cryptic species occupying challenging terrain can afford otherwise unattainable insights into ecological and evolutionary processes, such as population dynamics and dispersal patterns; information important for optimising conservation management. Using 13 microsatellite markers, we evaluated patterns of fine-scale gene flow and the spatial extent of genetic structuring of rock wren (Xenicus gilviventris), a threatened alpine passerine endemic to mountainous regions of the South Island, New Zealand. Through spatial autocorrelation analysis, we found that the ‘genetic patch size’, i.e. the distance over which individuals were not genetically independent, was surprisingly large (c. 70 km), given the rock wren’s limited flight ability. By estimating recent migration rates among sampling locations we also found asymmetries in gene flow indicative of source–sink dynamics. An area with intensive deer and predator control, in the Murchison Mountains, Fiordland, appears to be a particularly important source of migrants for other populations. These findings suggest that management to maintain connectivity is required across relatively large spatial scales and source populations may be those where introduced mammals are managed.     

Nanocrystalline SrS:Ce3+ system for the generation of white light‐emitting diodes

Nanocrystalline SrS phosphors doped with Ce³⁺ ions at different concentrations (0.5, 1, 1.5 and 2 mol%) are synthesized via the solid‐state diffusion method (SSDM), which is suitable for the large‐scale production of phosphors in industrial applications. The as‐prepared samples are characterized using an X‐ray diffraction (XRD) technique, field emission scanning electron microscopy (FESEM), high‐resolution transmission electron microscopy (HRTEM) and energy‐dispersive X‐ray (EDX) analysis. The optical properties of these phosphors are analyzed using reflectance spectra, photoluminescence spectra and afterglow decay curves. The cubic structure of the SrS phosphor is confirmed by XRD analysis and the crystallite size calculated by Scherer's formula using XRD data shows the nanocrystalline nature of the phosphors. No phase change is observed with increasing concentrations of Ce³⁺ ions. The surface morphology of the prepared phosphors is determined by FESEM, which shows a sphere‐like structure and good connectivity of the grains. The authenticity of the formation of nanocrystalline phosphors is examined by HRTEM analysis. Elemental compositional information for the prepared phosphors is gathered by EDX analysis. Photoluminescence studies reveal that the emission spectra of the prepared phosphor shows broad band emission centered at 458 and 550 nm due to the transition of electrons from the 5d → 4f energy levels. The afterglow decay characteristics of different as‐synthesized SrS:Ce³⁺ nanophosphors are conceptually described. Copyright © 2016 John Wiley & Sons, Ltd.     

Experimental warming alters the community composition,diversity, and N2 fixation activity of peat moss (Sphagnum fallax) microbiomes

Sphagnum‐dominated peatlands comprise a globally important pool of soil carbon (C) and are vulnerable to climate change. While peat mosses of the genus Sphagnum are known to harbor diverse microbial communities that mediate C and nitrogen (N) cycling in peatlands, the effects of climate change on Sphagnum microbiome composition and functioning are largely unknown. We investigated the impacts of experimental whole‐ecosystem warming on the Sphagnum moss microbiome, focusing on N₂ fixing microorganisms (diazotrophs). To characterize the microbiome response to warming, we performed next‐generation sequencing of small subunit (SSU) rRNA and nitrogenase (nifH) gene amplicons and quantified rates of N₂ fixation activity in Sphagnum fallax individuals sampled from experimental enclosures over 2 years in a northern Minnesota, USA bog. The taxonomic diversity of overall microbial communities and diazotroph communities, as well as N₂ fixation rates, decreased with warming (p < 0.05). Following warming, diazotrophs shifted from a mixed community of Nostocales (Cyanobacteria) and Rhizobiales (Alphaproteobacteria) to predominance of Nostocales. Microbiome community composition differed between years, with some diazotroph populations persisting while others declined in relative abundance in warmed plots in the second year. Our results demonstrate that warming substantially alters the community composition, diversity, and N₂ fixation activity of peat moss microbiomes, which may ultimately impact host fitness, ecosystem productivity, and C storage potential in peatlands.     

Biometric evidence that sexual selection has shaped the hominin face

We consider sex differences in human facial morphology in the context of developmental change. We show that at puberty, the height of the upper face, between the lip and the brow, develops differently in males and females, and that these differences are not explicable in terms of sex differences in body size. We find the same dimorphism in the faces of human ancestors. We propose that the relative shortening in men and lengthening in women of the anterior upper face at puberty is the mechanistic consequence of extreme maxillary rotation during ontogeny. A link between this developmental model and sexual dimorphism is made for the first time, and provides a new set of morphological criteria to sex human crania. This finding has important implications for the role of sexual selection in the evolution of anthropoid faces and for theories of human facial attractiveness.     

On-line capillary column immobilised metal affinity chromatography/electrospray ionisation mass spectrometry for the selective analysis of histidine-containing peptides

Capillary column immobilised metal affinity chromatography (IMAC) has been combined on-line with electrospray ionisation/quadrupole time-of-flight mass spectrometry for the fractionation of histidine-containing peptides. IMAC beads (Poros 20MC, 20 microm) containing imidodiacetate chelating groups on a cross-linked poly(styrene-divinylbenzene) support were packed into a fused silica column (250 microm i.d.), which was interfaced to the electrospray ion source of the spectrometer. A Cu(II) activated column was used to isolate histidine-containing peptides from tryptic and other peptide mixtures with an average breakthrough of 9.1%, to reduce the complexity of the mass spectral analysis. The analysis cycle time was reduced to less than 15 min, at an optimum flow rate of 7.5 microL/min, without sacrificing peptide selectivity. Direct coupling of capillary IMAC with MS allows on-line separation, using MS compatible loading and elution buffers, and detection in a high-throughput fashion when compared to off-line strategies.     

Semi-supervised learning for peptide identification from shotgun proteomics datasets

Shotgun proteomics uses liquid chromatography-tandem mass spectrometry to identify proteins in complex biological samples. We describe an algorithm, called Percolator, for improving the rate of confident peptide identifications from a collection of tandem mass spectra. Percolator uses semi-supervised machine learning to discriminate between correct and decoy spectrum identifications, correctly assigning peptides to 17% more spectra from a tryptic Saccharomyces cerevisiae dataset, and up to 77% more spectra from non-tryptic digests, relative to a fully supervised approach.     

Screen for mutations affecting development of zebrafish neural crest

The neural crest provides a useful model to learn how cell fate diversification is regulated during vertebrate development. Our approach is to isolate zebrafish mutations in which the development of neural crest derivatives is disrupted, in order to learn about the underlying genetic mechanisms. We describe a screen in which parthenogenetic diploid embryos are examined both for visible phenotypes and for cellular defects in neural crest-derived sensory neurons recognized immunohistochemically. We present preliminary results from this screen and briefly describe a few representative mutations. We also discuss the general utility of our strategy and comment on the future directions of this approach. © 1996 Wiley-Liss, Inc.     

Barentsz is essential for the posterior localization of oskar mRNA and colocalizes with it to the posterior pole

The localization of Oskar at the posterior pole of the Drosophila oocyte induces the assembly of the pole plasm and therefore defines where the abdomen and germ cells form in the embryo. This localization is achieved by the targeting of oskar mRNA to the posterior and the localized activation of its translation. oskar mRNA seems likely to be actively transported along microtubules, since its localization requires both an intact microtubule cytoskeleton and the plus end-directed motor kinesin I, but nothing is known about how the RNA is coupled to the motor. Here, we describe barentsz, a novel gene required for the localization of oskar mRNA. In contrast to all other mutations that disrupt this process, barentsz-null mutants completely block the posterior localization of oskar mRNA without affecting bicoid and gurken mRNA localization, the organization of the microtubules, or subsequent steps in pole plasm assembly. Surprisingly, most mutant embryos still form an abdomen, indicating that oskar mRNA localization is partially redundant with the translational control. Barentsz protein colocalizes to the posterior with oskar mRNA, and this localization is oskar mRNA dependent. Thus, Barentsz is essential for the posterior localization of oskar mRNA and behaves as a specific component of the oskar RNA transport complex.