Broad-scale adaptive genetic variation in alpine plants is driven by temperature and precipitation

Identifying adaptive genetic variation is a challenging task, in particular in non-model species for which genomic information is still limited or absent. Here, we studied distribution patterns of amplified fragment length polymorphisms (AFLPs) in response to environmental variation, in 13 alpine plant species consistently sampled across the entire European Alps. Multiple linear regressions were performed between AFLP allele frequencies per site as dependent variables and two categories of independent variables, namely Moran's eigenvector map MEM variables (to account for spatial and unaccounted environmental variation, and historical demographic processes) and environmental variables. These associations allowed the identification of 153 loci of ecological relevance. Univariate regressions between allele frequency and each environmental factor further showed that loci of ecological relevance were mainly correlated with MEM variables. We found that precipitation and temperature were the best environmental predictors, whereas topographic factors were rarely involved in environmental associations. Climatic factors, subject to rapid variation as a result of the current global warming, are known to strongly influence the fate of alpine plants. Our study shows, for the first time for a large number of species, that the same environmental variables are drivers of plant adaptation at the scale of a whole biome, here the European Alps.     

Requirement of transmembrane domain for CD154 association to lipid rafts and subsequent biological events

Interaction of CD40 with CD154 leads to recruitment of both molecules into lipid rafts, resulting in bi-directional cell activation. The precise mechanism by which CD154 is translocated into lipid rafts and its impact on CD154 signaling remain largely unknown. Our aim is to identify the domain of CD154 facilitating its association to lipid rafts and the impact of such association on signaling events and cytokine production. Thus, we generated Jurkat cell lines expressing truncated CD154 lacking the cytoplasmic domain or chimeric CD154 in which the transmembrane domain was replaced by that of transferrin receptor I, known to be excluded from lipid rafts. Our results show that cell stimulation with soluble CD40 leads to the association of CD154 wild-type and CD154-truncated, but not CD154-chimera, with lipid rafts. This is correlated with failure of CD154-chimera to activate Akt and p38 MAP kinases, known effectors of CD154 signaling. We also found that CD154-chimera lost the ability to promote IL-2 production upon T cell stimulation with anti-CD3/CD28 and soluble CD40. These results demonstrate the implication of the transmembrane domain of CD154 in lipid raft association, and that this association is necessary for CD154-mediated Akt and p38 activation with consequent enhancement of IL-2 production.     

Ecological and historical drivers of diversification in the fly genus Chiastocheta Pokorny

Coevolution is among the main forces shaping the biodiversity on Earth. In Eurasia, one of the best-known plant-insect interactions showing highly coevolved features involves the fly genus Chiastocheta and its host-plant Trollius. Although this system has been widely studied from an ecological point of view, the phylogenetic relationships and biogeographic history of the flies have remained little investigated. In this integrative study, we aim to test the monophyly of the five Chiastocheta eco-morphological groups, defined by Pellmyr in 1992, by inferring a mitochondrial phylogeny. We further apply a new approach to assess the effect of (i) different molecular substitution rates and (ii) phylogenetic uncertainty on the inference of the spatio-temporal evolution of the group. From a taxonomic point of view, we demonstrate that only two of Pellmyr's groups (rotundiventris and dentifera) are phylogenetically supported, the other species appearing para- or polyphyletic. We also identify the position of C. lophota, which was not included in previous surveys. From a spatio-temporal perspective, we show that the genus arose during the Pliocene in Europe. Our results also indicate that at least four large-scale dispersal events are required to explain the current distribution of Chiastocheta. Moreover, each dispersal to or from Asia is associated with a host-shift and seems to correspond to an increase in speciation rates. Finally, we highlight the correlation between diversification and climatic fluctuations, which indicate that the cycles of global cooling over the last million years had an influence on the radiation of the group.     

History or ecology? Substrate type as a major driver of patial genetic structure in Alpine plants

Climatic history and ecology are considered the most important factors moulding the spatial pattern of genetic diversity. With the advent of molecular markers, species' historical fates have been widely explored. However, it has remained speculative what role ecological factors have played in shaping spatial genetic structures within species. With an unprecedented, dense large-scale sampling and genome-screening, we tested how ecological factors have influenced the spatial genetic structures in Alpine plants. Here, we show that species growing on similar substrate types, largely determined by the nature of bedrock, displayed highly congruent spatial genetic structures. As the heterogeneous and disjunctive distribution of bedrock types in the Alps, decisive for refugial survival during the ice ages, is temporally stable, concerted post-glacial migration routes emerged. Our multispecies study demonstrates the relevance of particular ecological factors in shaping genetic patterns, which should be considered when modelling species projective distributions under climate change scenarios.     

Quantitative immunodetection of key elements of polyphosphoinositide signal transduction in osteoblasts from arthritic patients shows a direct correlation with cell proliferation

Phosphoinositides play an essential role in diverse cellular functions such as cell proliferation, cytoskeletal regulation, intracellular vesicle trafficking, motility, cell metabolism and death. Alteration of these pathways is common to many diseases. In this study, we show that osteoblasts from patients affected by osteoarthritis (OA) and by rheumatoid arthritis (RA) present a decreased cell proliferation and a reduced expression of the key elements of polyphosphoinositide signal transduction such as phosphatidylinositol-3-kinase (PI 3K), phospholipase C γ₁ (PLCγ₁), and protein kinase C ζ (PKCζ) compared to the post-traumatic (PT) patients. Our results suggest that a correlation may exist between the reduced osteoblast proliferation observed in OA and RA patients and the lowered expression of PI 3K, PLCγ₁, and PKCζ enzymes. The reduced proliferation rate of osteoblasts in response to these signal transduction effectors could counteract the evolution of arthritic disease.     

Bioprospecting of indigenous resources for the exploration of exopolysaccharide producing lactic acid bacteria

Exploration of biodiversity lead towards the discovery of novel exopolysaccharide (EPS) producing microbes that have multiple applications. The safety compatibility status of lactic acid bacteria (LAB) makes it an attractive candidate for the production of EPS in industries. Therefore, new bacterial isolates are continuously being identified from different habitats. Current research was conducted to explore indigenous biodiversity for the production of dextransucrase, which is involved in the synthesis of dextran. Dextran is an EPS which is used in different industries. In this study, thirty-nine LAB were isolated from different food samples. The isolates were identified as genus Leuconostoc, Weissella and Streptococcus based on genotypic and phenotypic characteristics. Screening revealed that only eight isolates can produce dextransucrase in high titres. Fermentation conditions of dextran producing LAB was optimized. The results indicated that Weissella confusa exhibited maximum specific activity (1.50?DSU?mg^?1) in 8?h at 25?°C with pH 7.5. Dextran produced from Weissella proved to be a useful alternative to commercially used dextran produced by Leuconostoc mesenteroides in industries for various applications.     

Genetic heterogeneity, modes of inheritance, and risk estimates for a joint study of caucasians with insulin-dependent diabetes mellitus

From 11 studies, a total of 1,792 Caucasian probands with insulin-dependent diabetes mellitus (IDDM) are analyzed. Antigen genotype frequencies in patients, transmission from affected parents to affected children, and the relative frequencies of HLA-DR3 and -DR4 homozygous patients all indicate that DR3 predisposes in a "recessive"-like and DR4 in a "dominant"-like or "intermediate" fashion, after allowing for the DR3/DR4 synergistic effect. Removal of DR3 and DR4 reveals an overall protective effect of DR2, predisposing effects of DR1 and DRw8, and a slight protective effect of DR5 and a predisposing effect of DRw6. Analysis of affected-parent-to-affected-child data indicates that a subset of DR2 may predispose. The non-DR3, non-DR4 antigens are not independently associated with DR3 and DR4; the largest effect is a deficiency of DR2, followed by excesses of DR1, DRw8, and DRw6, in DR4 individuals, as compared with DR3 individuals. HLA-B locus distributions on patient haplotypes indicate that only subsets of both DR3 and DR4 are predisposing. The presence or absence of Asp at position 57 of the DQ beta gene, recently implicated in IDDM predisposition, is not by itself sufficient to explain the inheritance of IDDM. At a minimum, the distinguishing features of the DR3-associated and DR4-associated predisposition remain to be identified at the molecular level. Risk estimates for sibs of probands are calculated based on an overall sibling risk of 6%; estimates for those sharing two, one, or zero haplotypes are 12.9%, 4.5%, and 1.8%, respectively. Risk estimates subdivided by the DR type of the proband are also calculated, the highest being 19.2% for sibs sharing two haplotypes with a DR3/DR4 proband.     

Preparation of chromosome spreads for electron (TEM,SEM, STEM), light and confocal microscopy

In the past, ultrastructural studies on chromosome morphology have been carried out using light microscopy, scanning electron microscopy and transmission electron microscopy of whole mounted or sectioned samples. Until now, however, it has not been possible to use all of these techniques on the same specimen. In this paper we describe a specimen preparation method that allows one to study the same chromosomes by transmission, scanning-transmission and scanning electron microscopy, as well as by standard light microscopy and confocal microscopy. Chromosome plates are obtained on a carbon coated glass slide. The carbon film carrying the chromosomes is then transferred to electron microscopy grids, subjected to various treatments and observed. The results show a consistent morphological correspondence between the different methods. This method could be very useful and important because it makes possible a direct comparison between the various techniques used in chromosome studies such as banding, in situ hybridization, fluorescent probe localization, ultrastructural analysis, and colloidal gold cytochemical reactionsAbbreviations CLSM confocal laser scanning microscope - EM electron microscopy - kV kilovolt(s) - LM light microscope - SEM scanning electron microscope - STEM scanning-transmission electron microscope - TEM transmission electron microscope     

Phylogeography and population genomics of a lotic water beetle across a complex tropical landscape

The habitat template concept applied to a freshwater system indicates that lotic species, or those which occupy permanent habitats along stream courses, are less dispersive than lentic species, or those that occur in more ephemeral aquatic habitats. Thus, populations of lotic species will be more structured than those of lentic species. Stream courses include both flowing water and small, stagnant microhabitats that can provide refuge when streams are low. Many species occur in these microhabitats but remain poorly studied. Here, we present population genetic data for one such species, the tropical diving beetle Exocelina manokwariensis (Dytiscidae), sampled from six localities along a ~300 km transect across the Birds Head Peninsula of New Guinea. Molecular data from both mitochondrial (CO1 sequences) and nuclear (ddRAD loci) regions document fine‐scale population structure across populations that are ~45 km apart. Our results are concordant with previous phylogenetic and macroecological studies that applied the habitat template concept to aquatic systems. This study also illustrates that these diverse but mostly overlooked microhabitats are promising study systems in freshwater ecology and evolutionary biology. With the advent of next‐generation sequencing, fine‐scale population genomic studies are feasible for small nonmodel organisms to help illuminate the effect of habitat stability on species’ natural history, population structure and geographic distribution.