Cryopreservation of the coccolithophore, <Emphasis Type="Italic">Emiliania huxleyi</Emphasis> (Haptophyta,Prymnesiophyceae)

We studied the cryopreservation of the most common coccolithophore, Emiliania huxleyi which is considered as one of the main global carbon cycle participants. Both stages of this complex life cycle species were submitted to gradual addition of three distinct cryoprotectants: dimethylsulfoxide (7.5% v/v), methanol (5% v/v) and proline (0.5 M). They were then control-rate cooled (−5 °C min⁻¹) to −50 °C before plunging into liquid nitrogen. Free radical oxygen species have been proposed to occur in cells subjected to pre-freezing manipulation or to cooling. Therefore, catalase (preventing accumulation of hydroxyl radicals) was evaluated for its ability to improve cell viability before and after freezing-thawing challenge. With the exception of proline which induced a decrease in diploid cell proliferation, cryoprotectants had no deleterious effects. On the contrary, growth of the haploid stage was enhanced by each CPA treatment, suggesting mixotrophic growth. Cryopreservation succeeded when dimethylsulfoxide was used, and the late exponential phase was obtained as soon as the 15th post-thawing day. Cell densities were then similar to the unfrozen controls. Catalase had no beneficial effect on the ability of cells to grow, neither prior freezing nor after thawing. In comparison with former attempts to cryopreserve E. huxleyi in other culture collection centers, our protocols allowed faster recovery.     

Nationwide molecular surveillance of pandemic H1N1 influenza A virus genomes: Canada, 2009

Background

In April 2009, a novel triple-reassortant swine influenza A H1N1 virus (“A/H1N1pdm”; also known as SOIV) was detected and spread globally as the first influenza pandemic of the 21^st century. Sequencing has since been conducted at an unprecedented rate globally in order to monitor the diversification of this emergent virus and to track mutations that may affect virus behavior.

Methodology/Principal Findings

By Sanger sequencing, we determined consensus whole-genome sequences for A/H1N1pdm viruses sampled nationwide in Canada over 33 weeks during the 2009 first and second pandemic waves. A total of 235 virus genomes sampled from unique subjects were analyzed, providing insight into the temporal and spatial trajectory of A/H1N1pdm lineages within Canada. Three clades (2, 3, and 7) were identifiable within the first two weeks of A/H1N1pdm appearance, with clades 5 and 6 appearing thereafter; further diversification was not apparent. Only two viral sites displayed evidence of adaptive evolution, located in hemagglutinin (HA) corresponding to D222 in the HA receptor-binding site, and to E374 at HA2-subunit position 47. Among the Canadian sampled viruses, we observed notable genetic diversity (1.47×10⁻³ amino acid substitutions per site) in the gene encoding PB1, particularly within the viral genomic RNA (vRNA)-binding domain (residues 493–757). This genome data set supports the conclusion that A/H1N1pdm is evolving but not excessively relative to other H1N1 influenza A viruses. Entropy analysis was used to investigate whether any mutated A/H1N1pdm protein residues were associated with infection severity; however no virus genotypes were observed to trend with infection severity. One virus that harboured heterozygote coding mutations, including PB2 D567D/G, was attributed to a severe and potentially mixed infection; yet the functional significance of this PB2 mutation remains unknown.

Conclusions/Significance

These findings contribute to enhanced understanding of Influenza A/H1N1pdm viral dynamics.     

Absolute Configuration and Enantiodifferentiation of a Hemicryptophane Incorporating an Azaphosphatrane Moiety

The hemicryptophane racemate (±)‐ M-1 , P-1 was optically resolved by semipreparative HPLC on Chiralpak IC column. The absolute configuration of each isolated enantiomer was established from the analysis of their electronic circular dichroism spectra. Enantiodifferentiation of the chiral cationic cage (±)‐ M-1 , P-1 was evidenced in solution using Δ‐TRISPHAT as chiral solvating agent, and the diastereomeric associations were observed in ¹H and ³¹P NMR spectra. Chirality 24:1077–1081, 2012. © 2012 Wiley Periodicals, Inc.     

A Re-Appraisal of the Early Andean Human Remains from Lauricocha in Peru

The discovery of human remains from the Lauricocha cave in the Central Andean highlands in the 1960’s provided the first direct evidence for human presence in the high altitude Andes. The skeletons found at this site were ascribed to the Early to Middle Holocene and represented the oldest known population of Western South America, and thus were used in several studies addressing the early population history of the continent. However, later excavations at Lauricocha led to doubts regarding the antiquity of the site. Here, we provide new dating, craniometric, and genetic evidence for this iconic site. We obtained new radiocarbon dates, generated complete mitochondrial genomes and nuclear SNP data from five individuals, and re-analyzed the human remains of Lauricocha to revise the initial morphological and craniometric analysis conducted in the 1960’s. We show that Lauricocha was indeed occupied in the Early to Middle Holocene but the temporal spread of dates we obtained from the human remains show that they do not qualify as a single contemporaneous population. However, the genetic results from five of the individuals fall within the spectrum of genetic diversity observed in pre-Columbian and modern Native Central American populations.     

Development of a one-step embryonic stem cell-based assay for the screening of sprouting angiogenesis

Background  

Angiogenesis assays are important tools for the identification of regulatory molecules and the potential development of therapeutic strategies to modulate neovascularization. Although numerous in vitro angiogenesis models have been developed in the past, they exhibit limitations since they do not recapitulate the entire angiogenic process or correspond to multi-step procedures that are not easy to use. Convenient, reliable, easily quantifiable and physiologically relevant assays are still needed for pharmacological screenings of angiogenesis.     

Novel insights into genome plasticity in Eukaryotes: mosaic aneuploidy in Leishmania

Leishmania are unicellular eukaryotes that have many markedly original molecular features compared with other uni‐ or multicellular eukaryotes like yeasts or mammals. Genome plasticity in this parasite has been the subject of many publications, and has been associated with drug resistance or adaptability. Aneuploidy has been suspected by several authors and it is now confirmed using state‐of‐the‐art technologies such as high‐throughput DNA sequencing. The analysis of genome contents at the single cell level using fluorescence in situ hybridization (FISH) has brought a new light on the genome organization: within a cell population, every chromosome, in every cell, may be present in at least two ploidy states (being either monosomic, disomic or trisomic), and the chromosomal content varies greatly from cell to cell, thus generating a constitutive intra‐strain genomic heterogeneity, here termed ‘mosaic aneuploidy’. Mosaic aneuploidy deeply affects the genetics of these organisms, leading, for example, to an extreme degree of intra‐strain genomic diversity, as well as to a clearance of heterozygous cells in the population without however affecting genetic heterogeneity. Second, mosaic aneuploidy might be considered as a powerful strategy evolved by the parasite for adapting to modifications of environment conditions as well as for the emergence of drug resistance. On the whole, mosaic aneuploidy may be considered as a novel mechanism for generating phenotypic diversity driven by genomic plasticity.     

Genomic regions involved in productivity of two interspecific poplar families in Europe. 1. Stem height, circumference and volume

Interspecific hybrids of Populus species are known for their superior growth. In this study, we examined the effect of the genetic background and contrasting environmental conditions on growth and searched for quantitative trait loci (QTL) affecting growth traits. To this end, two hybrid poplar families resulting from controlled crosses, Populus deltoides ‘S9-2’ × P. nigra ‘Ghoy’ (D × N, 180 F₁) and P. deltoides ‘S9-2’ × P. trichocarpa ‘V24’ (D × T, 182 F₁), were grown at two contrasting sites, Northern Italy and Central France. At the end of the second growing season, tree dimensions (stem height, circumference, and volume) were assessed. The performances of both families significantly differed within and between sites. Tree volume was significantly larger at the Italian site as compared to the French site. Genotype by environment interactions were significant but low for both families and for all growth traits. Tight correlations among the individual growth traits indicated that there may be a common genetic mechanism with pleiotropic effects on these growth traits. In line with previous studies, linkage groups I, VII, IX, X, XVI, XVII, and XIX appeared to have genomic regions with the largest effects on growth traits. This study revealed that (1) both families have high potential for selection of superior poplar hybrids due to the pronounced heterosis (hybrid vigor) and the large genetic variability in terms of growth and (2) the choice of site is crucial for poplar cultivation. Dillen and Storme contributed equally to the work. An erratum to this article can be found at     

Enantiopure encaged Verkade's superbases: Synthesis,chiroptical properties,and use as chiral derivatizing agent

Verkade's superbases, entrapped in the cavity of enantiopure hemicryptophane cages, have been synthesized with enantiomeric excess (ee) superior to 98%. Their absolute configuration has been determined by using electronic circular dichroism (ECD) spectroscopy. These enantiopure encaged superbases turned out to be efficient chiral derivatizing agents for chiral azides, underlining that the chirality of the cycloveratrylene (CTV) macrocycle induces different magnetic and chemical environments around the phosphazide functions.     

Genetic diversity increases insect herbivory on oak saplings

A growing body of evidence from community genetics studies suggests that ecosystem functions supported by plant species richness can also be provided by genetic diversity within plant species. This is not yet true for the diversity-resistance relationship as it is still unclear whether damage by insect herbivores responds to genetic diversity in host plant populations. We developed a manipulative field experiment based on a synthetic community approach, with 15 mixtures of one to four oak (Quercus robur) half-sib families. We quantified genetic diversity at the plot level by genotyping all oak saplings and assessed overall damage caused by ectophagous and endophagous herbivores along a gradient of increasing genetic diversity. Damage due to ectophagous herbivores increased with the genetic diversity in oak sapling populations as a result of higher levels of damage in mixtures than in monocultures for all families (complementarity effect) rather than because of the presence of more susceptible oak genotypes in mixtures (selection effect). Assemblages of different oak genotypes would benefit polyphagous herbivores via improved host patch location, spill over among neighbouring saplings and diet mixing. By contrast, genetic diversity was a poor predictor of the abundance of endophagous herbivores, which increased with individual sapling apparency. Plant genetic diversity may not provide sufficient functional contrast to prevent tree sapling colonization by specialist herbivores while enhancing the foraging of generalist herbivores. Long term studies are nevertheless required to test whether the effect of genetic diversity on herbivory change with the ontogeny of trees and local adaptation of specialist herbivores.