Personality-dependent inter- and intraspecific foraging competition in the invasive round goby,Neogobius melanostomus

This study examines the impact of boldness on foraging competition of the highly invasive round goby Neogobius melanostomus Pallas 1815. Individual risk tolerance, or boldness, was measured as the time to resume movement after a simulated predation strike. Fish that resumed movement faster were categorized as “bold,” fish that took more time to resume movement were categorized as “shy” and those that fell in between these two categories were determined to have “intermediate” boldness. Competitive impacts of boldness in N. melanostomus were determined in a laboratory foraging experiment in which interspecific (juvenile Atlantic cod Gadus morhua Linnaeus 1758) and intraspecific (intermediate N. melanostomus) individuals were exposed to either bold or shy N. melanostomus competitors. G. morhua consumed fewer prey when competing with bold N. melanostomus than when competing with shy N. melanostomus, whereas intermediately bold N. melanostomus foraging was not affected by competitor boldness. Bold and shy N. melanostomus consumed similar amounts of prey, and the number of interactions between paired fish did not vary depending on the personality of N. melanostomus individuals. Therefore, intraspecific foraging competition was not found to be personality dependent. This study provides evidence that individual differences in boldness can mediate competitive interactions in N. melanostomus; nonetheless, results also show that competition is also governed by other mechanisms that require further study.     

Confronting Death in Legal Disputes About Treatment-Limitation in Children

Most legal analyses of selective nontreatment of seriously ill children centre on the question of whether it is in a child’s best interests to be kept alive in the face of extreme suffering and/or an intolerable quality of life. Courts have resisted any direct confrontation with the question of whether the child’s death is in his or her best interests. Nevertheless, representations of death may have an important role to play in this field of jurisprudence. The prevailing philosophy is to configure death as a release from a futile or painful existence and/or as a dignified end in an objectively hopeless situation. However, there can be disagreement about the meaning of death in these settings. Some parents object that death would be premature or that it represents a culpable neglect of their child. A closer examination of these discordant interpretations allows for a better comprehension of the cultural understandings that underscore clinical and legal accounts of death following end-of-life decisions.     

The RNR motif of B. subtilis RNase P protein interacts with both PRNA and pre-tRNA to stabilize an active conformer

Ribonuclease P (RNase P) catalyzes the metal-dependent 5′ end maturation of precursor tRNAs (pre-tRNAs). In Bacteria, RNase P is composed of a catalytic RNA (PRNA) and a protein subunit (P protein) necessary for function in vivo. The P protein enhances pre-tRNA affinity, selectivity, and cleavage efficiency, as well as modulates the cation requirement for RNase P function. Bacterial P proteins share little sequence conservation although the protein structures are homologous. Here we combine site-directed mutagenesis, affinity measurements, and single turnover kinetics to demonstrate that two residues (R60 and R62) in the most highly conserved region of the P protein, the RNR motif (R60–R68 in Bacillus subtilis), stabilize PRNA complexes with both P protein (PRNA•P protein) and pre-tRNA (PRNA•P protein•pre-tRNA). Additionally, these data indicate that the RNR motif enhances a metal-stabilized conformational change in RNase P that accompanies substrate binding and is essential for efficient catalysis. Stabilization of this conformational change contributes to both the decreased metal requirement and the enhanced substrate recognition of the RNase P holoenzyme, illuminating the role of the most highly conserved region of P protein in the RNase P reaction pathway.     

A biochemical screen for identification of small-molecule regulators of the Wnt pathway using Xenopus egg extracts

Misregulation of the Wnt pathway has been shown to be responsible for a variety of human diseases, most notably cancers. Screens for inhibitors of this pathway have been performed almost exclusively using cultured mammalian cells or with purified proteins. We have previously developed a biochemical assay using Xenopus egg extracts to recapitulate key cytoplasmic events in the Wnt pathway. Using this biochemical system, we show that a recombinant form of the Wnt coreceptor, LRP6, regulates the stability of two key components of the Wnt pathway (β-catenin and Axin) in opposing fashion. We have now fused β-catenin and Axin to firefly and Renilla luciferase, respectively, and demonstrate that the fusion proteins behave similarly as their wild-type counterparts. Using this dual luciferase readout, we adapted the Xenopus extracts system for high-throughput screening. Results from these screens demonstrate signal distribution curves that reflect the complexity of the library screened. Of several compounds identified as cytoplasmic modulators of the Wnt pathway, one was further validated as a bona fide inhibitor of the Wnt pathway in cultured mammalian cells and Xenopus embryos. We show that other embryonic pathways may be amendable to screening for inhibitors/modulators in Xenopus egg extracts.     

Selective IgA deficiency in autoimmune diseases

Selective immunoglobulin A deficiency (IgAD) is the most common primary immunodeficiency in Caucasians. It has previously been suggested to be associated with a variety of concomitant autoimmune diseases. In this review, we present data on the prevalence of IgAD in patients with Graves disease (GD), systemic lupus erythematosus (SLE), type 1 diabetes (T1D), celiac disease (CD), myasthenia gravis (MG) and rheumatoid arthritis (RA) on the basis of both our own recent large-scale screening results and literature data. Genetic factors are important for the development of both IgAD and various autoimmune disorders, including GD, SLE, T1D, CD, MG and RA, and a strong association with the major histocompatibility complex (MHC) region has been reported. In addition, non-MHC genes, such as interferon-induced helicase 1 (IFIH1) and c-type lectin domain family 16, member A (CLEC16A), are also associated with the development of IgAD and some of the above diseases. This indicates a possible common genetic background. In this review, we present suggestive evidence for a shared genetic predisposition between these disorders.     

Interaction with the histone chaperone Vps75 promotes nuclear localization and HAT activity of Rtt109 in vivo

Modification of histones is critical for the regulation of all chromatin-templated processes. Yeast Rtt109 is a histone acetyltransferase (HAT) that acetylates H3 lysines 9, 27 and 56. Rtt109 associates with and is stabilized by Nap1 family histone chaperone Vps75. Our data suggest Vps75 and Nap1 have some overlapping functions despite their different cellular localization and histone binding specificity. We determined that Vps75 contains a classical nuclear localization signal and is imported by Kap60-Kap95. Rtt109 nuclear localization depends on Vps75, and nuclear localization of the Vps75-Rtt109 complex is not critical for Rtt109-dependent functions, suggesting Rtt109 may be able to acetylate nascent histones before nuclear import. To date, the effects of VPS75 deletion on Rtt109 function had not been separated from the resulting Rtt109 degradation; thus, we used an Rtt109 mutant lacking the Vps75-interaction domain that is stable without Vps75. Our data show that in addition to promoting Rtt109 stability, Vps75 binding is necessary for Rtt109 acetylation of the H3 tail. Direct interaction of Vps75 with H3 likely allows Rtt109 access to the histone tail. Furthermore, our genetic interaction data support the idea of Rtt109-independent functions of Vps75. In summary, our data suggest that Vps75 influences chromatin structure by regulating histone modification and through its histone chaperone functions.     

Stability of pollination services decreases with isolation from natural areas despite honey bee visits

Sustainable agricultural landscapes by definition provide high magnitude and stability of ecosystem services, biodiversity and crop productivity. However, few studies have considered landscape effects on the stability of ecosystem services. We tested whether isolation from florally diverse natural and semi-natural areas reduces the spatial and temporal stability of flower-visitor richness and pollination services in crop fields. We synthesised data from 29 studies with contrasting biomes, crop species and pollinator communities. Stability of flower-visitor richness, visitation rate (all insects except honey bees) and fruit set all decreased with distance from natural areas. At 1 km from adjacent natural areas, spatial stability decreased by 25, 16 and 9% for richness, visitation and fruit set, respectively, while temporal stability decreased by 39% for richness and 13% for visitation. Mean richness, visitation and fruit set also decreased with isolation, by 34, 27 and 16% at 1 km respectively. In contrast, honey bee visitation did not change with isolation and represented > 25% of crop visits in 21 studies. Therefore, wild pollinators are relevant for crop productivity and stability even when honey bees are abundant. Policies to preserve and restore natural areas in agricultural landscapes should enhance levels and reliability of pollination services.