A habitat suitability analysis at multi-spatial scale of two sympatric flying fox species reveals the urgent need for conservation action

In this study we used a multi-spatial scale approach to investigate habitat suitability, roosting characteristics, and ecological niche in two flying fox species on the Comoros Islands—Pteropus livingstonii and Pteropus seychellensis comorensis. At a broad scale, we assessed the ecological niche and habitat suitability for both species using the Species Distribution Modeling method based on the recent ensembles of small models (ESM) approach. At a fine scale, Ecological Niche Factor Analysis (ENFA) was applied to assess habitat selection by each species. Direct observation was used at each roost to estimate the total number of individuals and to identify the roost characteristics. At both broad and fine scales, the analyses highlighted clear niche partitioning by the two species. We found that P. livingstonii has a very limited distribution, restricted to steep, high-elevation slopes of the islands’ remaining natural forests, and the patterns were the same for roosting, foraging sites and the entire habitat. By contrast, P. s. comorensis has a relatively large geographic range that extends over low-elevation farmlands and villages and it was negatively correlated to natural forest across the entire area and all roosting sites, but its foraging areas were positively correlated to natural forest and high elevation areas. Both species selected large, tall trees for roosting. The total number of individuals in the studied area was estimated to be 1243 P. livingstonii and 11,898 P. s. comorensis. The results of our study demonstrated that these two species use different habitat types and ensure different ecosystem services in pollination and seed dispersion and thus are both critical for maintaining overall ecosystem dynamics. However, the currently high level of hunting pressure and roost disturbance makes them vulnerable to extinction. To ensure the viability of both species, conservation measures need to be taken by the Comoros government.     

Cellular senescence induces replication stress with almost no affect on DNA replication timing

Organismal aging entails a gradual decline of normal physiological functions and a major contributor to this decline is withdrawal of the cell cycle, known as senescence. Senescence can result from telomere diminution leading to a finite number of population doublings, known as replicative senescence (RS), or from oncogene overexpression, as a protective mechanism against cancer. Senescence is associated with large-scale chromatin re-organization and changes in gene expression. Replication stress is a complex phenomenon, defined as the slowing or stalling of replication fork progression and/or DNA synthesis, which has serious implications for genome stability, and consequently in human diseases. Aberrant replication fork structures activate the replication stress response leading to the activation of dormant origins, which is thought to be a safeguard mechanism to complete DNA replication on time. However, the relationship between replicative stress and the changes in the spatiotemporal program of DNA replication in senescence progression remains unclear.

Here, we studied the DNA replication program during senescence progression in proliferative and pre-senescent cells from donors of various ages by single DNA fiber combing of replicated DNA, origin mapping by sequencing short nascent strands and genome-wide profiling of replication timing (TRT).

We demonstrate that, progression into RS leads to reduced replication fork rates and activation of dormant origins, which are the hallmarks of replication stress. However, with the exception of a delay in RT of the CREB5 gene in all pre-senescent cells, RT was globally unaffected by replication stress during entry into either oncogene-induced or RS. Consequently, we conclude that RT alterations associated with physiological and accelerated aging, do not result from senescence progression. Our results clarify the interplay between senescence, aging and replication programs and demonstrate that RT is largely resistant to replication stress.     

Interleukin-7-aggravated joint inflammation and tissue destruction in collagen-induced arthritis is associated with T-cell and B-cell activation

Introduction

We sought to investigate the capacity of interleukin (IL)-7 to enhance collagen-induced arthritis and to study by what mechanisms this is achieved.

Methods

Mice received multiple injections with IL-7 or phosphate-buffered saline (PBS) as a control. Arthritis severity and incidence were determined by visual examination of the paws. Joint destruction was determined by assessing radiographs and immunohistochemistry of the ankle joints. Total cellularity and numbers of T-cell and B-cell subsets were assessed, as well as ex vivo production of interferon-γ (IFN-γ), IL-17, and IL-4. Proinflammatory mediators were measured in serum with multianalyte profiling.

Results

IL-7 increased arthritis severity and radiology-assessed joint destruction. This was consistent with IL-7-increased intensity of cell infiltrates, bone erosions, and cartilage damage. Splenic CD19⁺ B cells and CD19⁺/GL7⁺ germinal center B cells, as well as CD4 and CD8 numbers, were increased by IL-7. IL-7 expanded memory T cells, associated with increased percentages of IFN-γ-, IL-4-, and IL-17-producing CD4⁺ T cells. On antigen restimulation of draining lymph node cells in vitro IL-7 treatment was found to increase IFN-γ and IL-17 production, whereas IL-4 was reduced. IL-7 also increased concentrations of proinflammatory mediators, indicative of T-cell activation (sCD40L), vascular activation (VCAM-1, VEGF), tissue destruction (fibroblast growth factor-basic (FGF-b), LIF), and chemotaxis (MIP-1γ, MIP-3β, lymphotactin, MDC, and MCP-5).

Conclusions

In arthritic mice, IL-7 causes expansion of T and B cells, associated with increased levels of proinflammatory mediators. IL-7 intensifies arthritis severity and joint destruction, accompanied by increased Th1 and Th17 activity. These data indicate that IL-7 could be an important mediator in arthritic conditions and that targeting IL-7 or its receptor represent novel therapeutic strategies.     

Combination of chloroplast and mitochondrial DNA polymorphisms to study cytoplasm genetic differentiation in the olive complex ( Olea europaea L.)

Four hundred and four individuals belonging to the species Olea europaea were characterised using mitochondrial DNA (mtDNA) RFLPs. Twelve mitotypes were distinguished. The combination of mtDNA information with cpDNA polymorphism (characterised in a previous study) led us to recognise 20 cytoplasmic lineages of which seven were found in the Mediterranean area (oleasters, cultivars and O. e. subsp. maroccana). In the olive complex, strong cytoplasm genetic differentiation was revealed ( F(st) = 0.73). Very strong linkage disequilibrium between cpDNA and mtDNA polymorphisms was observed, particularly in the Mediterranean subspecies europaea. This high congruence between genetic structure based on cpDNA or mtDNA sustains a low level of recurrent mutation in both organelle DNAs and, thus, the polymorphisms used in this study were pertinent to reconstruct olive phylogeography. In the Mediterranean area, genetic drift due to population regression during Quaternary glaciations, and founder effects associated with the postglacial seed dissemination, have probably contributed to the existence of a high genetic linkage disequilibrium between cpDNA and mtDNA polymorphisms. Thus, four Mediterranean cytoplasmic lineages, clearly distinguished both by cpDNA and mtDNA polymorphisms, most likely reflect four distinct relic populations during Quaternary glaciations. Finally, O. e. subsp. maroccana from South Morocco, which also displayed specific cytoplasmic lineages, should be considered as another relic Mediterranean population.     

Initial preference for plant species and state during oviposition site selection by an odonate

Endophytic egg‐laying odonates use an ovipositor to insert their eggs inside plant tissues. Before egg deposition, oviposition site selection consists of two crucial steps: (i) the initial choice, typically decided in species that oviposit in tandem within vertical substrates by the male when landing and then by the female by staying on the substrate or flying to another; and (ii) the insertion site choice, made by the female who uses her ovipositor to palpate the substrate. Some odonates prefer to deposit their eggs within specific plant species. Some are able to discriminate between living and dead substrates during the initial choice. However, the extent to which odonates discriminate among distinct plant species during the initial choice is unknown. We studied the initial site preference in Lestes macrostigma (Odonata: Lestidae) to determine whether the males and/or females show a distinct preference among five types of shoots when landing on or when palpating the substrate, respectively. Male L. macrostigma preferred to land on Bolboschoenus maritimus and dead Juncus spp. When focusing on J. maritimus, females preferentially palpated the substrate when the male landed on dead shoots. We suggest that the male preference for these substrates is consistent with that of the female during insertion site choice but also during egg deposition. Such behavior should reduce the duration of oviposition, with benefits of reducing the predation risk and increasing available time for foraging. The advantage in preferring these substrates should be linked to a selection pressure acting on egg development and/or survival.     

Prospects on the evolutionary mitogenomics of plants: A case study on the olive family (Oleaceae)

The mitogenome is rarely used to reconstruct the evolutionary history of plants, contrary to nuclear and plastid markers. Here, we evaluate the usefulness of mitochondrial DNA for molecular evolutionary studies in Oleaceae, in which cases of cytoplasmic male sterility (CMS) and of potentially contrasted organelle inheritance are known. We compare the diversity and the evolution of mitochondrial and chloroplast genomes by focusing on the olive complex and related genera. Using high‐throughput techniques, we reconstructed complete mitogenomes (ca. 0.7 Mb) and plastomes (ca. 156 kb) for six olive accessions and one Chionanthus. A highly variable organization of mitogenomes was observed at the species level. In olive, two specific chimeric genes were identified in the mitogenome of lineage E3 and may be involved in CMS. Plastid‐derived regions (mtpt) were observed in all reconstructed mitogenomes. Through phylogenetic reconstruction, we demonstrate that multiple integrations of mtpt regions have occurred in Oleaceae, but mtpt regions shared by all members of the olive complex derive from a common ancestor. We then assembled 52 conserved mitochondrial gene regions and complete plastomes of ten additional accessions belonging to tribes Oleeae, Fontanesieae and Forsythieae. Phylogenetic congruence between topologies based on mitochondrial regions and plastomes suggests a strong disequilibrium linkage between both organellar genomes. Finally, while phylogenetic reconstruction based on plastomes fails to resolve the evolutionary history of maternal olive lineages in the Mediterranean area, their phylogenetic relationships were successfully resolved with complete mitogenomes. Overall, our study demonstrates the great potential of using mitochondrial DNA in plant phylogeographic and metagenomic studies.     

Oxidative stress in skin fibroblasts cultures from patients with Parkinson's disease

Background  

In the substantia nigra of Parkinson's disease (PD) patients, increased lipid peroxidation, decreased activities of the mitochondrial complex I of the respiratory chain, catalase and glutathione-peroxidase, and decreased levels of reduced glutathione have been reported. These observations suggest that oxidative stress and mitochondrial dysfunction play a role in the neurodegeneration in PD. We assessed enzymatic activities of respiratory chain and other enzymes involved in oxidative processes in skin fibroblasts cultures of patients with PD.