Y chromosome haplotyping in Scandinavian wolves (Canis lupus) based on microsatellite markers

The analysis of mitochondrial DNA sequences has for a long time been the most extensively used genetic tool for phylogenetic, phylogeographic and population genetic studies. Since this approach only considers female lineages, it tends to give a biased picture of the population history. The use of protein polymorphisms and microsatellites has helped to obtain a more unbiased view, but complementing population genetic studies with Y chromosome markers could clarify the role of each sex in natural processes. In this study we analysed genetic variability at four microsatellite loci on the canid Y chromosome. With these four microsatellites we constructed haplotypes and used them to study the genetic status of the Scandinavian wolf population, a population that now contains 60-70 animals but was thought to have been extinct in the 1970s. In a sample of 100 male wolves from northern Europe we found 17 different Y chromosome haplotypes. Only two of these were found in the current Scandinavian population. This indicates that there should have been at least two males involved in the founding of the Scandinavian wolf population after the bottleneck in the 1970s. The two Scandinavian Y chromosome haplotypes were not found elsewhere in northern Europe, which indicates low male gene flow between Scandinavia and the neighbouring countries.     

The Rate of Tau Synthesis Is Differentially Regulated During Postnatal Development in Mouse Cerebellum

1. Tau, which is a microtubule-associated protein, with mRNA targeted to the axon and growth cone, is involved in axonal elongation. During postnatal development in mouse, Tau expression in cerebellar granule cells is reduced after the second postnatal week. The aim of this work was to study the regulation of the rate of the synthesis of Tau protein during the period of granule cell axonal growth in mouse cerebellum.2. We found four [³⁵S]methionine-labeled isoforms of Tau synthesized postnataly. Their levels remain constant from postnatal day 9 to 12 (P9–P12), and decreased by P20.3. The rate of Tau synthesis showed differences with the rate of synthesis of total proteins. They also differ from proteins phosphatases 2A and 2B, both associated with the regulation of Tau function. In addition, the turnover of newly synthesized Tau increased at P20, compared with P9 and P12.4. These results imply a specific developmental regulation of mRNA translation of Tau, and indicate that, after the period of synapse formation is complete, and therefore axonal growth has finished (P20), only a limited number of new Tau molecules are synthesized. This might reflect that, after synapse formation is complete, newly synthesized Tau molecules are not longer needed.     

Regional assessment of plant invasions across different habitat types

Questions: 1. Which habitats have the highest degree of invasion? 2. Do native species-rich communities have also a high degree of invasion? 3. Do the patterns of association between native and alien species richness vary between habitats. Location: Catalonia region (NE Spain). Methods: We conducted a large regional analysis of 15655 phytosociological relevés to detect differences in the degree of invasion between European Nature Information System (EUNIS) habitats representative of temperate and Mediterranean European areas. Results: Alien species were present in less than 17 % of the relevés and represented less than 2% of the total number of species per habitat. The EUNIS habitats with the highest alien species richness were arable land and gardens followed by anthropogenic forb-rich habitats, riverine and lakeshore scrubs, southern riparian galleries and thickets and trampled areas. In contrast, the following habitats had never any alien species: surface running waters, raised and blanket bogs, valley mires, poor fens and transition mires, base-rich fens, alpine and sub-alpine grasslands, sub-alpine moist or wet tall-herb and fern habitats, alpine and sub-alpine scrub habitats and spiny Mediterranean heaths. There was a unimodal relationship between the mean native and mean alien species richness per EUNIS habitat with a high number of aliens in habitats with intermediate number of native species and a low number of aliens at both extremes of the native species gradient. Within EUNIS habitats, the relationship was positive, negative or non-significant depending on the habitat type without any clear pattern related to the number of native species. Alien species richness was not related to plot size, neither between habitats nor within habitats. Conclusions: The analysis emphasised that the habitats with a higher degree of invasion were the most disturbed ones and that in general habitats rich in native species did not harbour less invaders than habitats poor in native species.     

Biodiversity influences invasion success of a facultative epiphytic seaweed in a marine forest

The biotic resistance hypothesis predicts that more diverse communities should have greater resistance to invasions than species-poor communities. However for facultative and obligate epiphytic invaders a high native species richness, abundance and community complexity might provide more resources for the invader to thrive to. We conducted surveys across space and time to test for the influence of native algal species abundance and richness on the abundance of the invasive facultative epiphytic filamentous alga Lophocladia lallemandii in a Mediterranean Cystoseira balearica seaweed forest. By removing different functional groups of algae, we also tested whether these relationships were dependent on the complexity and abundance of the native algal community. When invasion was first detected, Lophocladia abundance was positively related to species richness, but the correlation became negative after two years of invasion. Similarly, a negative relationship was also observed across sites. The removal experiment revealed that more complex native communities were more heavily invaded, where also a positive relationship was found between native algal richness and Lophocladia, independently of the native algal abundance. Our observational and experimental data show that, at early stages of invasion, species-rich seaweed forests are not more resistant to invasion than species-poor communities. Higher richness of native algal species may increase resource availability (i.e. substrate) for invader establishment, thus facilitating invasion. After the initial invasion stage, native species richness decreases with time since invasion, suggesting negative impacts of invasive species on native biodiversity.     

Production of lipids and formation and mobilization of lipid bodies in Chlorella vulgaris

We investigated the formation of lipid bodies in the microalga Chlorella vulgaris CCALA 256 under lipid-induction conditions in autotrophically grown cultures. We found that cell division ceased after depletion of nitrates from the growth medium within the first days of cultivation. The growth of non-dividing cells subsequently led to the rapid accumulation of lipids. We describe in detail both biogenesis and mobilization of lipid bodies using fluorescence and transmission electron microscopy. Small lipid bodies fused very soon after their creation in the cytosol, forming, eventually, one huge lipid body. In stationary growth phase, lipids were present in the form of a large lipid body occupying most of the cell volume. After replenishment of nitrogen, lipid content decreased rapidly and, within 24 hours, the large lipid body was fragmented into smaller ones. This mobilization of the cellular lipid store occurred independently of light.     

Disentangling Biodiversity and Climatic Determinants of Wood Production

Background

Despite empirical support for an increase in ecosystem productivity with species diversity in synthetic systems, there is ample evidence that this relationship is dependent on environmental characteristics, especially in structurally more complex natural systems. Empirical support for this relationship in forests is urgently needed, as these ecosystems play an important role in carbon sequestration.

Methodology/Principal Findings

We tested whether tree wood production is positively related to tree species richness while controlling for climatic factors, by analyzing 55265 forest inventory plots in 11 forest types across five European countries. On average, wood production was 24% higher in mixed than in monospecific forests. Taken alone, wood production was enhanced with increasing tree species richness in almost all forest types. In some forests, wood production was also greater with increasing numbers of tree types. Structural Equation Modeling indicated that the increase in wood production with tree species richness was largely mediated by a positive association between stand basal area and tree species richness. Mean annual temperature and mean annual precipitation affected wood production and species richness directly. However, the direction and magnitude of the influence of climatic variables on wood production and species richness was not consistent, and vary dependent on forest type.

Conclusions

Our analysis is the first to find a local scale positive relationship between tree species richness and tree wood production occurring across a continent. Our results strongly support incorporating the role of biodiversity in management and policy plans for forest carbon sequestration.     

An antibody directed against PDGF receptor beta enhances the antitumor and the anti-angiogenic activities of an anti-VEGF receptor 2 antibody

Platelet-derived growth factor (PDGF) and its receptors (PDGFR) play important roles in tumorigenesis through stimulating tumor growth and promoting angiogenesis via enhancing pericyte recruitment and vessel maturation. Here we produced a neutralizing antibody, 1B3, directed against mouse PDGFRbeta. 1B3 binds to PDGFRbeta with high affinity (9x10(-11)M) and blocks PDGF-BB from binding to the receptor with an IC(50) of approximately 1.2 nM. The antibody also blocks ligand-stimulated activation of PDGFRbeta and downstream signaling molecules, including Akt and MAPK p42/44, in tumor cells. In animal studies, 1B3 significantly enhanced the antitumor and the anti-angiogenic activities of DC101, an antibody directed against mouse vascular endothelial growth factor receptor 2, in a pancreatic (BxPC-3) and a non-small cell lung (NCI-H460) tumor xenograft models. Treatment with the combination of 1B3 and DC101 in BxPC-3 xenograft-bearing mice resulted in tumor regression in 58% of mice compared to that in 18% of mice treated with DC101 alone. Taken together, these results lend great support to use PDGFRbeta antagonists in combinations with other antitumor and/or anti-angiogenic agents in the treatment of a variety of cancers.     

Genome Sequencing Highlights the Dynamic Early History of Dogs

To identify genetic changes underlying dog domestication and reconstruct their early evolutionary history, we generated high-quality genome sequences from three gray wolves, one from each of the three putative centers of dog domestication, two basal dog lineages (Basenji and Dingo) and a golden jackal as an outgroup. Analysis of these sequences supports a demographic model in which dogs and wolves diverged through a dynamic process involving population bottlenecks in both lineages and post-divergence gene flow. In dogs, the domestication bottleneck involved at least a 16-fold reduction in population size, a much more severe bottleneck than estimated previously. A sharp bottleneck in wolves occurred soon after their divergence from dogs, implying that the pool of diversity from which dogs arose was substantially larger than represented by modern wolf populations. We narrow the plausible range for the date of initial dog domestication to an interval spanning 11–16 thousand years ago, predating the rise of agriculture. In light of this finding, we expand upon previous work regarding the increase in copy number of the amylase gene (AMY2B) in dogs, which is believed to have aided digestion of starch in agricultural refuse. We find standing variation for amylase copy number variation in wolves and little or no copy number increase in the Dingo and Husky lineages. In conjunction with the estimated timing of dog origins, these results provide additional support to archaeological finds, suggesting the earliest dogs arose alongside hunter-gathers rather than agriculturists. Regarding the geographic origin of dogs, we find that, surprisingly, none of the extant wolf lineages from putative domestication centers is more closely related to dogs, and, instead, the sampled wolves form a sister monophyletic clade. This result, in combination with dog-wolf admixture during the process of domestication, suggests that a re-evaluation of past hypotheses regarding dog origins is necessary.     

The potential for indirect effects between co‐flowering plants via shared pollinators depends on resource abundance,accessibility and relatedness

Co‐flowering plant species commonly share flower visitors, and thus have the potential to influence each other's pollination. In this study we analysed 750 quantitative plant–pollinator networks from 28 studies representing diverse biomes worldwide. We show that the potential for one plant species to influence another indirectly via shared pollinators was greater for plants whose resources were more abundant (higher floral unit number and nectar sugar content) and more accessible. The potential indirect influence was also stronger between phylogenetically closer plant species and was independent of plant geographic origin (native vs. non‐native). The positive effect of nectar sugar content and phylogenetic proximity was much more accentuated for bees than for other groups. Consequently, the impact of these factors depends on the pollination mode of plants, e.g. bee or fly pollinated. Our findings may help predict which plant species have the greatest importance in the functioning of plant–pollination networks.