Expression and function of junctional adhesion molecule-C in myelinated peripheral nerves

JAM-C is an adhesion molecule that is expressed on cells within the vascular compartment and epithelial cells and, to date, has been largely studied in the context of inflammatory events. Using immunolabeling procedures in conjunction with confocal and electron microscopy, we show here that JAM-C is also expressed in peripheral nerves and that this expression is localized to Schwann cells at junctions between adjoining myelin end loops. Sciatic nerves from JAM-C-deficient [having the JAM-C gene knocked out (KO)] mice exhibited loss of integrity of the myelin sheath and defective nerve conduction as indicated by morphological and electrophysiological studies, respectively. In addition, behavioral tests showed motor abnormalities in the KO animals. JAM-C was also expressed in human sural nerves with an expression profile similar to that seen in mice. These results demonstrate that JAM-C is a component of the autotypic junctional attachments of Schwann cells and plays an important role in maintaining the integrity and function of myelinated peripheral nerves.     

CB1 cannabinoid receptors and on-demand defense against excitotoxicity

Abnormally high spiking activity can damage neurons. Signaling systems to protect neurons from the consequences of abnormal discharge activity have been postulated. We generated conditional mutant mice that lack expression of the cannabinoid receptor type 1 in principal forebrain neurons but not in adjacent inhibitory interneurons. In mutant mice,the excitotoxin kainic acid (KA) induced excessive seizures in vivo. The threshold to KA-induced neuronal excitation in vitro was severely reduced in hippocampal pyramidal neurons of mutants. KA administration rapidly raised hippocampal levels of anandamide and induced protective mechanisms in wild-type principal hippocampal neurons. These protective mechanisms could not be triggered in mutant mice. The endogenous cannabinoid system thus provides on-demand protection against acute excitotoxicity in central nervous system neurons.     

Amyloid fibrils of the HET-s(218-289) prion form a beta solenoid with a triangular hydrophobic core

Prion and nonprion forms of proteins are believed to differ solely in their three-dimensional structure, which is therefore of paramount importance for the prion function. However, no atomic-resolution structure of the fibrillar state that is likely infectious has been reported to date. We present a structural model based on solid-state nuclear magnetic resonance restraints for amyloid fibrils from the prion-forming domain (residues 218 to 289) of the HET-s protein from the filamentous fungus Podospora anserina. On the basis of 134 intra- and intermolecular experimental distance restraints, we find that HET-s(218-289) forms a left-handed beta solenoid, with each molecule forming two helical windings, a compact hydrophobic core, at least 23 hydrogen bonds, three salt bridges, and two asparagine ladders. The structure is likely to have broad implications for understanding the infectious amyloid state.     

Identification of QTLs for BYDV tolerance in bread wheat

We searched for QTLs involved in tolerance to barley yellow dwarf (BYD), a serious viral disease of small grain cereals in two wheat populations, Opata × Synthetic (ITMI)and Frontana × INIA66 (F × I), for which marker data had previously been generated. The populations were evaluated in replicated field trials under artificial inoculation with a BYDV-PAV-Mex isolate and under disease-free conditions. Disease symptoms (yellowing, dwarfism and biomass reduction) were visually recorded and agronomic traits (number of tillers,height, biomass, yield and thousand-kernel weight) were measured on five plants per plot. Phenotypic data on all evaluated traits showed normal distribution with high correlation between visual estimates and measured values. Heritabilities were mostly moderate to high in the 114 lines of the ITMI population, and from low to moderate in the 117 lines of the F × I population. QTL analyses were based on genetic maps containing 443 loci for the ITMI population and 317 loci for the F × I population. Using composite interval mapping, 22 QTLs in the ITMI population and seven in the F × I population were detected, explaining9.8–43.3% of total phenotypic variation (σ² _P)per agronomic trait in the first population, and 4.1–13.7% in the second. Individual QTLs explained less than 15.8%of σ² _P. In the F × I population a minor QTL explaining 7% of σ² _P for yellowing was detected on the short arm of 7D, linked to leaf tip necrosis, a morphological marker for linked genes Bdv1, Yr18 andLr34. A QTL consistently detected for several traits on 2D in the ITMI population and on the short arm of group 6 chromosome(6S) in F × I explained 10–15% of σ² _P. The large number of QTLs having mostly small effects and the continuous distribution of all evaluated traits confirmed the polygenic nature and complexity of BYD tolerance in wheat. This revised version was published online in August 2006 with corrections to the Cover Date.     

Approaches for breeding apples with durable disease resistance

Summary In most apple breeding programmes resistance to diseases has a high priority. The main emphasis is put on scab and mildew resistance. Recent evidence about the risk of breakdown of the Vf scab resistance demonstrates the need to search for new approaches in disease resistance breeding. The following options might be considered: discover and exploit new sources of resistance to enlarge the genetic basis of resistance; accumulate different functional resistances in one genotype; develop orchard designs in order to increase diversity in the host-pathogen interactions and establish a resistance management system. To implement these strategies the genetic structure of the resistance must be examined by using modern methods of molecular biology. Resistance donors and advanced selections should be examined under high natural inoculum pressure at several locations around the world. We examined the possibility of identifying polygenic or partial scab resistance in apple. Nineteen apple varieties and selections, among them the differential hosts for scab races 1 to 5, were artificially inoculated in the glasshouse with scab conidia. The leaf symptoms were analysed macroscopically and microscopically There were significant differences which are actually exploited in our breeding programme. Conclusions are drawn towards new approaches for breeding and growing apples with durable disease resistance.     

Freshwater biodiversity under climate warming pressure: Identifying the winners and losers in temperate standing waterbodies

Climate warming is affecting the biodiversity all around the world, resulting in the expansion or contraction of the geographical range of species, and leading to colonisation (winners) and extinction (losers) events in ecosystems. It is crucial for the conservation of biodiversity to identify these potential winners and losers.We focus here on small standing waterbodies in Switzerland and on five taxonomic groups: vascular plants, snails, beetles, dragonflies and amphibians. We first assessed the sensitivity of each species to climate warming through their thermal preferences, using current altitudinal and latitudinal distribution, as a surrogate for temperature. We then evaluated the resilience of species to perturbations through five ecological and biogeographical criteria applicable to the perturbation “warming”: dispersal ability, degree of habitat specialisation, geographical extent in the study area, future trend in geographical extent, and future trend of habitat availability for species.Potential winners and losers of a warming climate could be quantified through their thermal preferences. The proportion of potential losers ranged from zero species for snails to 33% of the regional species pool for dragonflies. The set of potential winners was much larger, ranging from 53% for amphibians to 61% for dragonflies. A multimetric index combining the five resilience criteria enabled the further prioritisation of the species along a gradient of extinction risk.This potential threat from climate warming is not reflected by the current Red Lists of dragonflies and amphibians, suggesting that conservation management could gain from a complementary label indicating the degree of sensitivity to warming.     

Multispecies Phytophthora disease patterns in declining beech stands

Decline diseases are typically caused by complex abiotic and biotic interactions and characterized by a suite of symptoms indicative of low plant vigour. Diseased trees are frequently infected by Phytophthora, but the complex interactions between pathogen, host and the heterogeneous forest environment mask a comprehensive understanding of the aetiology. In the present study, we surveyed European beech (Fagus sylvatica) stands in Swiss forests with recent increases in bleeding lesions for the presence of Phytophthora. We used a combined approach of analysing soil and bark samples from trees displaying bleeding lesions and trees free from bleeding lesions. Soil baiting revealed a higher prevalence of Phytophthora spp. around trees with bleeding lesions than around trees without bleeding lesions. For the bark samples from bleeding lesions, we used several detection methods. Phytophthora spp. were detected in 74% of the trees by an immunological on‐site diagnostic kit, in 64% by a specific PCR assay, and 38% by isolation on selective media. All samples tested were negative for P. ramorum using qPCR. Overall, nine Phytophthora species were identified by ITS sequencing, the most common of which were P. plurivora, P. gonapodyides, P. × cambivora and P. syringae. We identified distinct species in bleeding lesions and the rhizosphere of the same host tree which suggests a multispecies Phytophthora disease patterns in these declining beech. Among the recovered species, P. × cambivora and P. × serendipita were identified as hybrid genotypes with the former abundant in bleeding lesions.     

Female biased mortality caused by anthropogenic nest loss contributes to population decline and adult sex ratio of a meadow bird

Meadow breeding birds such as the whinchat Saxicola rubetra have been declining due to increased farming intensity. In modern grassland management, the first mowing and the bird’s breeding cycle coincide, causing high nest destruction rates and low productivity of grassland bird populations. However, it is virtually unknown whether the mowing process directly affects adult survival by accidentally killing incubating females. We studied adult survival of an Alpine whinchat population during two breeding seasons using either colour-ringing or radio-tracking of 71 adults. Assessing territories, mowing phenology and nest destruction from 1988 to 2007 allowed changes in the factors associated with female mowing mortality to be estimated. Adult survival over 5-day-periods was Φ = 0.986, but during the period of mowing female survival was strongly reduced (Φ = 0.946). As a result, 80.6% of the males, but only 68.4% of the females survived the breeding season. Mowing undoubtedly killed two of 20 radio-tagged females when they were laying or incubating. In the 20-year period, an increasing proportion of nests were destroyed before the chicks hatched and this change was associated with an increased distortion of the adult sex ratio. Modelling the population growth rate showed that including the additional effect of mowing on female mortality resulted in a 1.7 times faster local population decline. These results are consistent with the hypothesis that the extinction of whinchat populations in the lowlands of central Europe was caused not only by habitat degradation and low productivity, but also by increased man-made female mortality.