Open membranes are the precursors for assembly of large DNA viruses

Nucleo cytoplasmic large DNA viruses (NCLDVs) are a group of double‐stranded DNA viruses that replicate their DNA partly or entirely in the cytoplasm in association with viral factories (VFs). They share about 50 genes suggesting that they are derived from a common ancestor. Using transmission electron microscopy (TEM) and electron tomography (ET) we showed that the NCLDV vaccinia virus (VACV) acquires its membrane from open membrane intermediates, derived from the ER. These open membranes contribute to the formation of a single open membrane of the immature virion, shaped into a sphere by the assembly of the viral scaffold protein on its convex side. We now compare VACV with the NCLDV Mimivirus by TEM and ET and show that the latter also acquires its membrane from open membrane intermediates that accumulate at the periphery of the cytoplasmic VF. In analogy to VACV this membrane is shaped by the assembly of a layer on the convexside of its membrane, likely representing the Mimivirus capsid protein. By quantitative ET we show for both viruses that the open membrane intermediates of assembly adopt an ‘open‐eight’ conformation with a characteristic diameter of 90 nm for Mimi‐ and 50 nm for VACV. We discuss these results with respect to the common ancestry of NCLDVs and propose a hypothesis on the possible origin of this unusual membrane biogenesis.     

Source pools and disharmony of the world's island floras

Island disharmony refers to the biased representation of higher taxa on islands compared to their mainland source regions and represents a central concept in island biology. Here, we develop a generalizable framework for approximating these source regions and conduct the first global assessment of island disharmony and its underlying drivers. We compiled vascular plant species lists for 178 oceanic islands and 735 mainland regions. Using mainland data only, we modelled species turnover as a function of environmental and geographic distance and predicted the proportion of shared species between each island and mainland region. We then quantified the over‐ or under‐representation of families on individual islands (representational disharmony) by contrasting the observed number of species against a null model of random colonization from the mainland source pool, and analysed the effects of six family‐level functional traits on the resulting measure. Furthermore, we aggregated the values of representational disharmony per island to characterize overall taxonomic bias of a given flora (compositional disharmony), and analysed this second measure as a function of four island biogeographical variables. Our results indicate considerable variation in representational disharmony both within and among plant families. Examples of generally over‐represented families include Urticaceae, Convolvulaceae and almost all pteridophyte families. Other families such as Asteraceae and Orchidaceae were generally under‐represented, with local peaks of over‐representation in known radiation hotspots. Abiotic pollination and a lack of dispersal specialization were most strongly associated with an insular over‐representation of families, whereas other family‐level traits showed minor effects. With respect to compositional disharmony, large, high‐elevation islands tended to have the most disharmonic floras. Our results provide important insights into the taxon‐ and island‐specific drivers of disharmony. The proposed framework allows overcoming the limitations of previous approaches and provides a quantitative basis for incorporating functional and phylogenetic approaches into future studies of island disharmony.     

Quantifying the potential impact of alien plants of Iran using the Generic Impact Scoring System (GISS) and Environmental Impact Classification for Alien Taxa (EICAT)

Biological Invasions - Assessing the impacts of alien plant species is scientifically important and critical for supporting invasion-related policies. Generic Impact Scoring System (GISS) and...     

Estimation of pea (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.) microsatellite mutation rate based on pedigree and single-seed descent analyses

Microsatellites, or simple sequence repeats (SSRs) are widespread class of repetitive DNA sequences, used in population genetics, genetic diversity and mapping studies. In spite of the SSR utility, the genetic and evolutionary mechanisms are not fully understood. We have investigated three microsatellite loci with different position in the pea (Pisum sativum L.) genome, the A9 locus residing in LTR region of abundant retrotransposon, AD270 as intergenic and AF016458 located in 5′untranslated region of expressed gene. Comparative analysis of a 35 pair samples from seven pea varieties propagated by single-seed descent for ten generations, revealed single 4 bp mutation in 10th generation sample at AD270 locus corresponding to stepwise increase in one additional ATCT repeat unit. The estimated mutation rate was 4.76 × 10^-3 per locus per generation, with a 95% confidence interval of 1.2 × 10^-4 to 2.7 × 10^-2. The comparison of cv. Bohatyr accessions retrieved from different collections, showed intra-, inter-accession variation and differences in flanking and repeat sequences. Fragment size and sequence alternations were also found in long term in vitro organogenic culture, established at 1983, indicative of somatic mutation process. The evidence of homoplasy was detected across of unrelated pea genotypes, which adversaly affects the reliability of diversity estimates not only for diverse germplasm but also highly bred material. The findings of this study have important implications for Pisum phylogeny studies, variety identification and registration process in pea breeding where mutation rate influences the genetic diversity and the effective population size estimates.     

The Association of Dispersal and Persistence Traits of Plants with Different Stages of Succession in Central European Man-Made Habitats

Traits related to seed dispersal, clonality and bud bank affect the success or failure of plant species. Using data from 13 successional seres in various human-made habitats the spectra of traits associated with dispersal and persistence were compared to determine the traits that can be used to predict the occurrence of particular plant species at each stage in a succession and how the importance of these traits changes over time. Differences in the traits of species associated with primary and secondary successions were also studied. Species with seeds that are dispersed by water (hydrochory) decreased in abundance during the course of succession. Species with a splitting main root, monocyclic and dicyclic shoots also decreased in abundance. Species capable of forming a potential below-ground bud bank, hypogeogenous rhizome and retaining a long-term connection with clonal offspring increased in abundance. The results indicate that seed dispersal is more important in determining the species composition in the early stages of succession whereas bud banks and clonal traits are more important in the later stages and for colonizing a locality. Primary and secondary seres did not remarkably differ in the trait spectra of the species present indicating that these trends occur in both types of succession.     

Molecular architecture of mouse activating NKR-P1 receptors

Receptors belonging to NKR-P1 family and their specific Clr ligands form an alternative missing self recognition system critical in immunity against tumors and viruses, elimination of tumor cells subjected to genotoxic stress, activation of T cell dependent immune response, and hypertension. The three-dimensional structure of the extracellular domain of the mouse natural killer (NK) cell receptor mNKR-P1Aex has been determined by X-ray diffraction. The core of the C-type lectin domain (CTLD) is homologous to the other CTLD receptors whereas one quarter of the domain forms an extended loop interacting tightly with a neighboring loop in the crystal. This domain swapping mechanism results in a compact interaction interface. A second dimerization interface resembles the known arrangement of other CTLD NK receptors. A functional dimeric form of the receptor is suggested, with the loop, evolutionarily conserved within this family, proposed to participate in interactions with ligands.     

Ecological impacts of invasive alien plants: a meta-analysis of their effects on species, communities and ecosystems

Biological invasions cause ecological and economic impacts across the globe. However, it is unclear whether there are strong patterns in terms of their major effects, how the vulnerability of different ecosystems varies and which ecosystem services are at greatest risk. We present a global meta-analysis of 199 articles reporting 1041 field studies that in total describe the impacts of 135 alien plant taxa on resident species, communities and ecosystems. Across studies, alien plants had a significant effect in 11 of 24 different types of impact assessed. The magnitude and direction of the impact varied both within and between different types of impact. On average, abundance and diversity of the resident species decreased in invaded sites, whereas primary production and several ecosystem processes were enhanced. While alien N-fixing species had greater impacts on N-cycling variables, they did not consistently affect other impact types. The magnitude of the impacts was not significantly different between island and mainland ecosystems. Overall, alien species impacts are heterogeneous and not unidirectional even within particular impact types. Our analysis also reveals that by the time changes in nutrient cycling are detected, major impacts on plant species and communities are likely to have already occurred.     

FTLD-TDP with motor neuron disease,visuospatial impairment and a progressive supranuclear palsy-like syndrome: broadening the clinical phenotype of TDP-43 proteinopathies. A report of three cases

Background  

Frontotemporal lobar degeneration with ubiquitin and TDP-43 positive neuronal inclusions represents a novel entity (FTLD-TDP) that may be associated with motor neuron disease (FTLD-MND); involvement of extrapyramidal and other systems has also been reported.     

Luminescent properties of europium complexes with bis(diphenylphosphino)alkane dioxides

Eu(NO₃)₃?5H₂O and EuCl₃?6H₂O were allowed to react with bis(diphenylphosphino)alkane dioxides Ph₂P(O)(CH₂)_nP(O)Ph₂ (n = 2, 4, 6) to obtain polymeric and binuclear complexes. The prepared compounds were structurally characterized by X‐ray diffraction. Luminescence measurements (emission and excitation spectra, quantum yields, lifetimes) were compared with crystallographic data in order to find a relationship between luminescent properties of the Eu(III) complexes and their structures. The Eu(III) polymers, especially [Eu(dpphO₂)₂Cl₂]⁺Cl^–}_n, have shown extremely long luminescence lifetimes, up to 3.73 ms, as a result of a highly protecting hydrophobic shield. Copyright © 2011 John Wiley & Sons, Ltd.