Evolution and intraspecific exploitative competition I. One-locus theory for small additive gene effects

Using the model of exploitative competition of R. H. MacArthur and R. Levins (1967, Amer. Natur. 101, 377–385), evolution at a gene locus which influences the niche position is considered. The locus has multiple alleles, and the contributions of the alleles to the genotypic value are additive. The resource spectrum and the utilization functions of the genotypes are assumed to be Gaussian. Evolution will make the mode of the niche converge to the resource optimum, as long as the allele contributions are small compared to the distance between the mode of the niche and the resource optimum. When this distance is of the same order of magnitude as the allele contributions, then the globally stable equilibrium will maintain at most two alleles in the population, unless the allele contributions are large. Classical overdominance is not needed to maintain polymorphism. This result predicts high linkage disequilibrium in similar multilocus models. It is concluded that intraspecific competition can be a powerful force in maintaining two-allele polymorphisms, and that it can maintain high linkage disequilibrium among closely linked loci.     

Notch signaling in the pigmented epithelium of the anterior eye segment promotes ciliary body development at the expense of iris formation

The ciliary body and iris are pigmented epithelial structures in the anterior eye segment that function to maintain correct intra‐ocular pressure and regulate exposure of the internal eye structures to light, respectively. The cellular and molecular factors that mediate the development of the ciliary body and iris from the ocular pigmented epithelium remain to be fully elucidated. Here, we have investigated the role of Notch signaling during the development of the anterior pigmented epithelium by using genetic loss‐ and gain‐of‐function approaches. Loss of canonical Notch signaling results in normal iris development but absence of the ciliary body. This causes progressive hypotony and over time leads to phthisis bulbi, a condition characterized by shrinkage of the eye and loss of structure/function. Conversely, Notch gain‐of‐function results in aniridia and profound ciliary body hyperplasia, which causes ocular hypertension and glaucoma‐like disease. Collectively, these data indicate that Notch signaling promotes ciliary body development at the expense of iris formation and reveals novel animal models of human ocular pathologies.     

Cantareus aspersus metallothionein metal binding abilities: The unspecific CaCd/CuMT isoform provides hints about the metal preference determinants in metallothioneins

In Proteomics, gene/protein families including both specialized and non-specialized paralogs are an invaluable tool to study the evolution of structure/function relationships in proteins. Metallothioneins (MTs) of the pulmonate gastropod molluscs (snails) offer one of the best materials to study the metal-binding specificity of proteins, because they consist of a polymorphic system that includes members with extremely distinct metal preferences but with a high protein sequence similarity. Cantareus aspersus was the first snail where three paralogous MTs were isolated: the highly specific cadmium (CaCdMT) and copper (CaCuMT) isoforms, and an unspecific CaCd/CuMT isoform, so called because it was natively isolated as a mixed Cd and Cu complex. In this work, we have thoroughly analyzed the Zn^2 +-, Cd^2 +- and Cu⁺-binding abilities of these three CaMTs by means of the spectroscopic and spectrometric characterization of the respective recombinant, as well as in vitro-substituted, metal-complexes. The comparison with the orthologous HpMTs and the study of the isoform-determinant residues allow correlating the protein sequence variability with the coordination capabilities of these MTs. Surprisingly, the CaCuMT isoform exhibits a stronger Cu-thionein character than the HpCuMT ortholog, and the CaCd/CuMT isoform could be defined as a non-optimized Cu-thionein, which has not attained any defined functional differentiation in the framework of the snail MT gene/protein family.     

Global phylogeography of sailfish: deep evolutionary lineages with implications for fisheries management

Hydrobiologia - Since the Miocene profound climatic changes have influenced the biology and ecology of species worldwide, such as their connectivity, genetic population structure, and biogeography....     

Tissue-specific Salmonella Typhimurium gene expression during persistence in pigs

Salmonellosis caused by Salmonella Typhimurium is one of the most important bacterial zoonotic diseases. The bacterium persists in pigs resulting in asymptomatic 'carrier pigs', generating a major source for Salmonella contamination of pork. Until now, very little is known concerning the mechanisms used by Salmonella Typhimurium during persistence in pigs. Using in vivo expression technology (IVET), a promoter-trap method based on ΔpurA attenuation of the parent strain, we identified 37 Salmonella Typhimurium genes that were expressed 3 weeks post oral inoculation in the tonsils, ileum and ileocaecal lymph nodes of pigs. Several genes were expressed in all three analyzed organs, while other genes were only expressed in one or two organs. Subsequently, the identified IVET transformants were pooled and reintroduced in pigs to detect tissue-specific gene expression patterns. We found that efp and rpoZ were specifically expressed in the ileocaecal lymph nodes during Salmonella peristence in pigs. Furthermore, we compared the persistence ability of substitution mutants for the IVET-identified genes sifB and STM4067 to that of the wild type in a mixed infection model. The ΔSTM4067::kanR was significantly attenuated in the ileum contents, caecum and caecum contents and faeces of pigs 3 weeks post inoculation, while deletion of the SPI-2 effector gene sifB did not affect Salmonella Typhimurium persistence. Although our list of identified genes is not exhaustive, we found that efp and rpoZ were specifically expressed in the ileocaecal lymph nodes of pigs and we identified STM4067 as a factor involved in Salmonella persistence in pigs. To our knowledge, our study is the first to identify Salmonella Typhimurium genes expressed during persistence in pigs.     

Targeting vascular NADPH oxidase 1 blocks tumor angiogenesis through a PPARα mediated mechanism

Reactive oxygen species, ROS, are regulators of endothelial cell migration, proliferation and survival, events critically involved in angiogenesis. Different isoforms of ROS-generating NOX enzymes are expressed in the vasculature and provide distinct signaling cues through differential localization and activation. We show that mice deficient in NOX1, but not NOX2 or NOX4, have impaired angiogenesis. NOX1 expression and activity is increased in primary mouse and human endothelial cells upon angiogenic stimulation. NOX1 silencing decreases endothelial cell migration and tube-like structure formation, through the inhibition of PPARα, a regulator of NF-κB. Administration of a novel NOX-specific inhibitor reduced angiogenesis and tumor growth in vivo in a PPARα dependent manner. In conclusion, vascular NOX1 is a critical mediator of angiogenesis and an attractive target for anti-angiogenic therapies.