Diversification, biotic interchange, and the universal trade-off hypothesis

Competition theory predicts that multispecies coexistence requires that species have traits that fall on the same interspecific trade-off surface. Fossil records for mollusks, mammals, trees, and other taxa show that with rare exception, ecologically similar species have coexisted for a million years or more after interchange between formerly isolated realms. This coexistence suggests the possibility, termed the universal trade-off hypothesis, that ecologically similar species of different realms have been bound to the same interspecific trade-off surface despite millions of years of independent evolution. Such persistence fails to support the biogeographic superiority hypothesis, which posits that genetic drift, recombination, mutation, and selection would cause taxa of one realm to gain superiority over those of another realm during long periods of isolation. Analysis of the lengths of time that species have persisted once in contact suggests that the trade-off surfaces of realms differed by <0.1% at the time of interchange. This implies that macroevolutionary patterns of differentiation and speciation within and between realms were more likely the movement of traits on a common trade-off surface rather than directional selection achieved without compensatory trade-offs and costs. The existence of transrealm trade-offs, should further work support this possibility, has deep implications for ecology and evolution.     

Community diversity outweighs effect of warming on plant colonization

Abiotic environmental change, local species extinctions and colonization of new species often co‐occur. Whether species colonization is driven by changes in abiotic conditions or reduced biotic resistance will affect community functional composition and ecosystem management. We use a grassland experiment to disentangle effects of climate warming and community diversity on plant species colonization. Community diversity had dramatic impacts on the biomass, richness and traits of plant colonists. Three times as many species colonized the monocultures than the high diversity 17 species communities (~30 vs. 10 species), and colonists collectively produced 10 times as much biomass in the monocultures than the high diversity communities (~30 vs. 3 g/m²). Colonists with resource‐acquisitive strategies (high specific leaf area, light seeds, short heights) accrued more biomass in low diversity communities, whereas species with conservative strategies accrued most biomass in high diversity communities. Communities with higher biomass of resident C4 grasses were more resistant to colonization by legume, nonlegume forb and C3 grass colonists, but not by C4 grass colonists. Compared with effects of diversity, 6 years of 3°C‐above‐ambient temperatures had little impact on plant colonization. Warmed subplots had ~3 fewer colonist species than ambient subplots and selected for heavier seeded colonists. They also showed diversity‐dependent changes in biomass of C3 grass colonists, which decreased under low diversity and increased under high diversity. Our findings suggest that species colonization is more strongly affected by biotic resistance from residents than 3°C of climate warming. If these results were extended to invasive species management, preserving community diversity should help limit plant invasion, even under climate warming.     

Resistance of soil biota and plant growth to disturbance increases with plant diversity

Plant diversity is critical to the functioning of ecosystems, potentially mediated in part by interactions with soil biota. Here, we characterised multiple groups of soil biota across a plant diversity gradient in a long‐term experiment. We then subjected soil samples taken along this gradient to drought, freezing and a mechanical disturbance to test how plant diversity affects the responses of soil biota and growth of a focal plant to these disturbances. High plant diversity resulted in soils that were dominated by fungi and associated soil biota, including increased arbuscular mycorrhizal fungi and reduced plant‐feeding nematodes. Disturbance effects on the soil biota were reduced when plant diversity was high, resulting in higher growth of the focal plant in all but the frozen soils. These results highlight the importance of plant diversity for soil communities and their resistance to disturbance, with potential feedback effects on plant productivity.     

Characterization of Microcirculation in Multiple Sclerosis Lesions by Dynamic Texture Parameter Analysis (DTPA)

Objective

Texture analysis is an alternative method to quantitatively assess MR-images. In this study, we introduce dynamic texture parameter analysis (DTPA), a novel technique to investigate the temporal evolution of texture parameters using dynamic susceptibility contrast enhanced (DSCE) imaging. Here, we aim to introduce the method and its application on enhancing lesions (EL), non-enhancing lesions (NEL) and normal appearing white matter (NAWM) in multiple sclerosis (MS).

Methods

We investigated 18 patients with MS and clinical isolated syndrome (CIS), according to the 2010 McDonald''s criteria using DSCE imaging at different field strengths (1.5 and 3 Tesla). Tissues of interest (TOIs) were defined within 27 EL, 29 NEL and 37 NAWM areas after normalization and eight histogram-based texture parameter maps (TPMs) were computed. TPMs quantify the heterogeneity of the TOI. For every TOI, the average, variance, skewness, kurtosis and variance-of-the-variance statistical parameters were calculated. These TOI parameters were further analyzed using one-way ANOVA followed by multiple Wilcoxon sum rank testing corrected for multiple comparisons.

Results

Tissue- and time-dependent differences were observed in the dynamics of computed texture parameters. Sixteen parameters discriminated between EL, NEL and NAWM (pAVG = 0.0005). Significant differences in the DTPA texture maps were found during inflow (52 parameters), outflow (40 parameters) and reperfusion (62 parameters). The strongest discriminators among the TPMs were observed in the variance-related parameters, while skewness and kurtosis TPMs were in general less sensitive to detect differences between the tissues.

Conclusion

DTPA of DSCE image time series revealed characteristic time responses for ELs, NELs and NAWM. This may be further used for a refined quantitative grading of MS lesions during their evolution from acute to chronic state. DTPA discriminates lesions beyond features of enhancement or T2-hypersignal, on a numeric scale allowing for a more subtle grading of MS-lesions.     

Protein lysine‐Nζ alkylation and O‐phosphorylation mediated by DTT‐generated reactive oxygen species

Reactive oxygen species (ROS) play crucial roles in physiology and pathology. In this report, we use NMR spectroscopy and mass spectrometry (MS) to demonstrate that proteins (galectin-1, ubiquitin, RNase, cytochrome c, myoglobin, and lysozyme) under reducing conditions with dithiothreitol (DTT) become alkylated at lysine-N_ζ groups and O-phosphorylated at serine and threonine residues. These adduction reactions only occur in the presence of monophosphate, potassium, trace metals Fe/Cu, and oxygen, and are promoted by reactive oxygen species (ROS) generated via DTT oxidation. Superoxide mediates the chemistry, because superoxide dismutase inhibits the reaction, and hydroxyl and phosphoryl radicals are also likely involved. While lysine alkylation accounts for most of the adduction, low levels of phosphorylation are also observed at some serine and threonine residues, as determined by western blotting and MS fingerprinting. The adducted alkyl group is found to be a fragment of DTT that forms a Schiff base at lysine N_ζ groups. Although its exact chemical structure remains unknown, the DTT fragment includes a SH group and a –CHOH–CH₂– group. Chemical adduction appears to be promoted in the context of a well-folded protein, because some adducted sites in the proteins studied are considerably more reactive than others and the reaction occurs to a lesser extent with shorter, unfolded peptides and not at all with small organic molecules. A structural signature involving clusters of positively charged and other polar groups appears to facilitate the reaction. Overall, our findings demonstrate a novel reaction for DTT-mediated ROS chemistry with proteins.     

Lipofuscin inhibits the proteasome by binding to surface motifs

Lipofuscin, a highly oxidized aggregate, consists of covalently cross-linked proteins, lipids, and sugar residues and is one of the major life-span-limiting factors in postmitotic aging cells. An artificial model of this material, showing characteristics and effects comparable to those of the natural form, has turned out to be very useful for in vitro studies. Artificial lipofuscin was used to investigate its effects on the viability of human fibroblasts, its rate of uptake, and its ability to inhibit the proteasomal system. The inhibition of the proteasomal system is one of the major aspects of the cytotoxic effects of lipofuscin. We present here that this proteasomal inhibition is due to proteasomal binding to the lipofuscin surface motifs, degradable by protease K. Furthermore, removal of the surface peptide structures by protease K strongly reduces the cytotoxic effects of lipofuscin and binding of cellular proteins and proteasomes to intracellular protein aggregates.     

The inhibition of TNF-alpha anti-tumoral properties by blocking antibodies promotes tumor growth in a rat model

Tumor necrosis factor (TNF) antagonists represent a milestone in the therapy of autoimmune conditions. Anti-TNF antibodies have been approved for clinical use and during the last eight years thousands of patients have been treated. However, the long-term sequelae of anti-TNF agents in promoting carcinogenesis remain unclear. This study sought to define the role of intra-tumor TNF-alpha production on cancer cell progression and to determine whether TNF-alpha antibodies can suppress anti-tumoral immunity. Using an experimental animal tumor model we demonstrate that anti-TNF-alpha antibodies hinder anti-tumor immune responses and promote growth of immunogenic rat colon tumors (REG) that are always rejected by immunocompetent untreated rats. The major role of TNF-alpha in the anti-tumoral immune response was confirmed by transfecting progressive and tolerogenic rat colon tumor cells (PRO) with the TNF-alpha gene. PRO tumor cells secreting TNF-alpha induce tumor-infiltrating dendritic cell (DC) activation. This triggers a potent immune response leading to tumor rejection and long-lasting immunity. Therefore, the prominent role of TNF-alpha in anti-tumoral immune responses underscores the need for caution and close surveillance following the administration of TNF inhibitors.     

Structural characterization and molecular identification of arbuscular mycorrhiza morphotypes of <Emphasis Type="Italic">Alzatea verticillata</Emphasis> (Alzateaceae), a prominent tree in the tropical mountain rain forest of South Ecuador

The vast majority of the highly diverse trees in the tropical mountain rain forest of South Ecuador form arbuscular mycorrhizas, and previous molecular investigations revealed a high diversity of fungi. In this study, we present a first trial to link fungal DNA-sequences with defined morphotypes characterized on the basis of partly new mycelial features obtained from field material of one tree species, Alzatea verticillata. Fine roots were halved lengthwise to study the mycelium anatomy on one half and to obtain fungal nuclear rDNA coding for the small subunit rRNA of Glomeromycota from the other half. Light microscopy revealed conspicuously large amounts of mycelium attaching to the surface of the rootlets. The mycelium formed fine- or large-branched appressoria-like plates, vesicles of regular or irregular shape, and very fine, multibranched structures ensheathed by septate hyphae. These previously undescribed features of the supraradical mycelia combined with intraradical mycelium structures were used for distinguishing of four main morphogroups and subordinate 14 morphotypes. DNA sequences of Glomus group A, Acaulospora and Gigaspora, were obtained and linked to three morphogroups. Two sequence types within Glomus group A could be tentatively associated to subordinate morphotypes. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.