Patterns of island treeline elevation – a global perspective

Treeline research has strongly focused on mountain systems on the mainland. However, island treelines offer the opportunity to contribute to the global framework on treeline elevation due to their island‐specific attributes such as isolation, small area, low species richness and relative youth. We hypothesize that, similar to the mainland, latitude‐driven temperature variation is the most important determinant of island treeline elevation on a global scale. To test this hypothesis, we compared mainland with island treeline elevations. Then we focused 1) on the global effects of latitude, 2) on the regional effects of island type (continental vs oceanic islands) and 3) the local effects of several specific island characteristics (age, area, maximum island elevation, isolation and plant species richness). We collected a global dataset of islands (n = 86) by applying a stratified design using GoogleEarth and the Global Island Database. For each island we extracted data on latitude and local characteristics. Treeline elevation decreased from the mainland through continental to oceanic islands. Island treeline elevation followed a hump‐shaped latitudinal distribution, which is fundamentally different from the mainland double‐hump. Higher maximum island elevation generated higher treeline elevation and was found the best single predictor of island treeline elevation, even better than latitude. Lower island treeline elevation may be the result of a low mass elevation effect (MEE) influencing island climates and an increasingly impoverished species pool but also trade wind inversion‐associated aridity. The maximum island elevation effect possibly results from an increasing mass elevation effect (MEE) with increasing island elevation but also range shifts during climatic fluctuations and the summit syndrome (i.e. high wind speeds and poor soils in peak regions). Investigating islands in treeline research has enabled disentangling the global effect of latitude from regional and local effects and, at least for islands, a comprehensive quantification of the MEE.     

Antigen-driven interactions with dendritic cells and expansion of Foxp3+ regulatory T cells occur in the absence of inflammatory signals

Foxp3+ regulatory T cells (Tregs) play a pivotal role in the maintenance of peripheral T cell tolerance and are thought to interact with dendritic cells (DC) in secondary lymphoid organs. We analyzed here the in vivo requirements for selective expansion of Ag-specific Treg vs CD4+CD25- effector T cells and engagement of Ag-specific Treg-DC interactions in secondary lymphoid organs. Using i.v. Ag delivery in the absence of inflammation, we found that CD4+CD25+Foxp3+ Tregs undergo vigorous expansion and accumulate whereas naive CD4+CD25-Foxp3- T cells undergo abortive activation. Quantifying directly the interactions between Tregs and CD11c+ DC, we found that Tregs establish cognate contacts with endogenous CD11c+ DC in spleen and lymph nodes at an early time point preceding their expansion. Importantly, we observed that as few as 10(3) Tregs selectively expanded by i.v. Ag injection are able to suppress B and T cell immune responses in mouse recipients challenged with the Ag. Our results demonstrate that Tregs are selectively mobilized by Ag recognition in the absence of inflammatory signals, and can induce thereafter potent tolerance to defined Ag targets.     

Mapping of a spontaneous mutation for early flowering time in maize highlights contrasting allelic series at two-linked QTL on chromosome 8

Only a few mutations affecting flowering time have been detected in maize. We analyzed a spontaneous early mutation, vgt-f7p, which appeared during production of the inbred line F7. This mutation shortens the time from planting to flowering by about 100 growing degree days (GDD), and reduces the number of nodes. It therefore seems to affect the timing of meristem differentiation from a vegetative to a reproductive state. It was mapped to a 6 cM confidence interval on chromosome 8, using a QTL mapping approach. QTL analysis of a mapping population generated by crossing the mutant F7 line (F7p) and the Gaspé flint population showed that vgt-f7p is probably allelic to vgt1, a QTL described in previous studies, and affects earliness more strongly than the Gaspé allele at vgt1. Global analysis of the QTL in the region suggested that there may be two consensus QTL, vgt1 and vgt2. These two QTL have contrasting allelic effects: rare alleles conferring extremely early flowering at vgt1 vs. greater diversity and milder effects at locus vgt2. Finally, detailed syntenic analysis showed that the vgt1 region displays a highly conserved duplicated region on chromosome 6, which also plays an important role in maize flowering time variation. The cloning of vgt1 should, therefore, also facilitate the analysis of the molecular basis of variation due to this second region.     

MPK9 and MPK12 function in SA-induced stomatal closure in Arabidopsis thaliana

Salicylic acid (SA) induces stomatal closure sharing several components with abscisic acid (ABA) and methyl jasmonate (MeJA) signaling. We have previously shown that two guard cell-preferential mitogen-activated protein kinases (MAPKs), MPK9 and MPK12, positively regulate ABA signaling and MeJA signaling in Arabidopsis thaliana. In this study, we examined whether these two MAPKs are involved in SA-induced stomatal closure using genetic mutants and a pharmacological, MAPKK inhibitor. Salicylic acid induced stomatal closure in mpk9 and mpk12 single mutants but not in mpk9 mpk12 double mutants. The MAPKK inhibitor PD98059 inhibited SA-induced stomatal closure in wild-type plants. Salicylic acid induced extracellular reactive oxygen species (ROS) production, intracellular ROS accumulation, and cytosolic alkalization in the mpk9, mpk12, and mpk9 mpk12 mutants. Moreover, SA-activated S-type anion channels in guard cells of wild-type plants but not in guard cells of mpk9 mpk12 double mutants. These results imply that MPK9 and MPK12 are positive regulators of SA signaling in Arabidopsis guard cells.     

Low species diversity and high interindividual variability in faeces of preterm infants as revealed by sequences of 16S rRNA genes and PCR-temporal temperature gradient gel electrophoresis profiles

Little information regarding the composition of the gut microbiota in preterm infants is available. The purpose of this study was to investigate the bacterial diversity in faeces of preterm infants, using analysis of randomly cloned 16S rRNA genes and PCR-TTGE (temporal temperature gradient gel electrophoresis) profiles, to determine whether noncultivated bacteria represented an important part of the community. The 288 clones obtained from faecal samples of 16 preterm infants were classified into 25 molecular species. All but one molecular species had a cultivated representative in public databases: molecular tools did not reveal any unexplored diversity. The mean number of molecular species per infant was 3.25, ranging from one to eight. There was a high interindividual variability. The main groups encountered were the Enterobacteriaceae family and the genera Enterococcus, Streptococcus and Staphylococcus. Seven preterm infants were colonized by anaerobes and only four by bifidobacteria. TTGE profiles were composed of one to nine bands (mean value: 4.3). Furthermore, 51 of 59 clones (86%) comigrated with a band of the corresponding faecal sample. This study will form a comparative framework for other studies, e.g. on the faecal microbiota of preterm infants with different pathologies or the impact of diet on colonization.     

Role of Phosphorylation in Moesin Interactions with PIP2-Containing Biomimetic Membranes

Moesin, a protein of the ezrin, radixin, and moesin family, which links the plasma membrane to the cytoskeleton, is involved in multiple physiological and pathological processes, including viral budding and infection. Its interaction with the plasma membrane occurs via a key phosphoinositide, the phosphatidyl(4,5)inositol-bisphosphate (PIP₂), and phosphorylation of residue T558, which has been shown to contribute, in cellulo, to a conformationally open protein. We study the impact of a double phosphomimetic mutation of moesin (T235D, T558D), which mimics the phosphorylation state of the protein, on protein/PIP₂/microtubule interactions. Analytical ultracentrifugation in the micromolar range showed moesin in the monomer and dimer forms, with wild-type (WT) moesin containing a slightly larger fraction (～30%) of dimers than DD moesin (10–20%). Only DD moesin was responsive to PIP₂ in its micellar form. Quantitative cosedimentation assays using large unilamellar vesicles and quartz crystal microbalance on supported lipid bilayers containing PIP₂ reveal a specific cooperative interaction for DD moesin with an ability to bind two PIP₂ molecules simultaneously, whereas WT moesin was able to bind only one. In addition, DD moesin could subsequently interact with microtubules, whereas WT moesin was unable to do so. Altogether, our results point to an important role of these two phosphorylation sites in the opening of moesin: since DD moesin is intrinsically in a more open conformation than WT moesin, this intermolecular interaction is reinforced by its binding to PIP₂. We also highlight important differences between moesin and ezrin, which appear to be finely regulated and to exhibit distinct molecular behaviors.     

Lasuén's pterodactyl: An early use of a pterosaur in plastic arts

Among the sculptures adorning the former building of the Faculties of Medicine and Sciences (1893) in Saragossa (Spain) is one that represents a pterosaur. It is a work by D. Lasuén based on one of the first, but little known, restorations of these animals, drawn and engraved by T. Susemihl more than half a century before. Although it seems out of place, this sculpture was simply seen as a symbol of zoology. We suggest that it may have several significations. Besides embodying the animal kingdom, it may have been a surrogate of the dragon and thus a reference to the House of Aragon through its dragon-slaying holy patron, Saint George.     

Vesicular stomatitis virus glycoprotein: a transducing coat for SFV-based RNA vectors

BACKGROUND: Semliki Forest virus (SFV) vectors have a great potential for the induction of protective immunity in a large number of clinical conditions including cancer. Such a potential accounts for the huge efforts made to improve the in vivo expression from SFV vectors. It is noteworthy that efficient in vivo expression strongly relies on the ability to deliver high-titre vectors. To achieve this, the generation of recombinant SFV particles, using independent expression systems for structural SFV genes, has been proposed. However, despite several modifications in the production process, a risk of contamination with replication-competent, or partially recombined, virus has remained. METHODS: Here, we exploit the ability of the vesicular stomatitis virus glycoprotein (VSV-G), expressed in trans, to hijack full-length genomic SFV RNA into secreted virus-like particles (VLPs). To allow SFV vector mobilisation, we designed a CMV driven SFV vector in which the internal 26S promoter has been extensively mutated. With this vector, mobilisation events were monitored using the Green Fluorescent Protein (GFP). The production procedure involves a sequential transfection protocol, of plasmids expressing the VSV-G and the SFV vector respectively. RESULTS: We show that the VLPs are effective for cellular delivery of SFV vectors in a broad range of human and non-human cellular targets. Furthermore, production of VLPs is easy and allows, through concentration, the harvest of high-titre vector. CONCLUSIONS: The present paper describes a convenient process aimed at mobilising full length SFV vectors. A major issue to consider, while developing clinically relevant gene transfer vectors, is the risk of undesirable generation of replication competent by-products. Importantly, as the VSV-G gene shares no homology with the SFV genome, our VLPs offer a strong guarantee of biosafety.     

Carbon flux analysis in a pantothenate overproducing Corynebacterium glutamicum strain

Carbon flux analysis during a pseudo-stationary phase of metabolite accumulation in a genetically engineered strain of Corynebacterium glutamicum, containing plasmids leading to over-expression of the ilvBNCD and panBC operons, has identified the basic metabolic constraints governing the potential of this bacterium to produce pantothenate. Carbon flux converging on pyruvate (75% of glucose uptake) is controlled by anabolic precursor requirements and NADPH demand provoking high carbon loss as CO₂ via the pentose pathway. Virtually all the flux of pyruvate is directed into the branched pathway leading to both valine and pantothenate production, but flux towards valine is tenfold higher than that transformed to pantothenate, indicating that significant improvements will only be obtained if carbon flux at the ketoisovalerate branchpoint can be modulated.