Lost in diversity Mommer, Liesje; Cotton, T. E. Anne; Raaijmakers, Jos M. ...
New phytologist,
April 2018, Letnik:
218, Številka:
2
Journal Article
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There is consensus that plant species richness enhances plant productivity within natural grasslands, but the underlying drivers remain debated. Recently, differential accumulation of soil-borne ...fungal pathogens across the plant diversity gradient has been proposed as a cause of this pattern. However, the below-ground environment has generally been treated as a ‘black box’ in biodiversity experiments, leaving these fungi unidentified.
Using next generation sequencing and pathogenicity assays, we analysed the community composition of root-associated fungi from a biodiversity experiment to examine if evidence exists for host specificity and negative density dependence in the interplay between soil-borne fungi, plant diversity and productivity.
Plant species were colonised by distinct (pathogenic) fungal communities and isolated fungal species showed negative, species-specific effects on plant growth. Moreover, 57% of the pathogenic fungal operational taxonomic units (OTUs) recorded in plant monocultures were not detected in eight plant species plots, suggesting a loss of pathogenic OTUs with plant diversity.
Our work provides strong evidence for host specificity and negative density-dependent effects of root-associated fungi on plant species in grasslands. Our work substantiates the hypothesis that fungal root pathogens are an important driver of biodiversity-ecosystem functioning relationships.
1. Plant diversity has profound effects on primary production. Plant diversity has been shown to correlate with increased primary production in nutrient-limited grassland ecosystems. This ...overyielding has been attributed to vertical niche differentiation among species below-ground, allowing for complementarity in resource capture. However, a rigorous test of this longstanding hypothesis is lacking because roots of different species could not be distinguished in diverse communities. 2. Here, we present the first application of a DNA-based technique that quantifies species abundances in multispecies root samples. We were thus able to compare root distributions in monocultures of two grasses and two forbs with root distributions in four-species mixtures. In order to investigate if vertical niche differentiation is driven by soil nutrient depletion, the topsoil layer of the communities were either nutrient-rich or -poor. 3. Immediately in the first year, 40% more root biomass was produced in mixtures than expected from the monocultures, together with significant below-ground complementarity effects, probably preceding above-ground overyielding. This below-ground overyielding appeared not to be the result of vertical niche differentiation, as rooting depth of the community tended to decrease, rather than increase in mixtures compared to monocultures. Roots thus tended to clump in the very dense topsoil layer rather than segregate over the whole profile in mixtures. The below-ground overyielding was mainly driven by enhanced root investments of one species, Anthoxanthum odoratum, in the densely rooted topsoil layer without retarding the growth of the other species. 4. Synthesis. Conventional ecological mechanisms, such as competition for nutrients, do not seem to be able to explain the increased root investments of A. odoratum in mixtures compared to monocultures, with apparently little effect on the root growth of the other species. Instead, the observed root responses are consistent with species-specific root recognition responses. From a community perspective, the observed early below-ground overyielding may initiate the recently reported increased soil organic matter, mineralization and N availability and thus may ultimately be responsible for the higher productivity at high plant species diversity.
•Persons with tinnitus might display altered auditory predictions for unexpected auditory input.•Position predictions did not differ between persons with tinnitus and without.•Temporal predictability ...facilitated deviance processing for the P50-like activity.•Parallel assessment of three sound predictability levels can be disentangled by tsPCA.
Tinnitus denotes the perception of a non-environmental sound and might result from aberrant auditory prediction. Successful prediction of formal (e.g., type) and temporal sound characteristics facilitates the filtering of irrelevant information, also labelled as ‘sensory gating’ (SG). Here, we explored if and how parallel manipulations of formal prediction violations and temporal predictability affect SG in persons with and without tinnitus. Age-, education- and sex-matched persons with and without tinnitus (N = 52) participated and listened to paired-tone oddball sequences, varying in formal (standard vs. deviant pitch) and temporal predictability (isochronous vs. random timing). EEG was recorded from 128 channels and data were analyzed by means of temporal spatial principal component analysis (tsPCA). SG was assessed by amplitude suppression for the 2nd tone in a pair and was observed in P50-like activity in both timing conditions and groups. Correspondingly, deviants elicited overall larger amplitudes than standards. However, only persons without tinnitus displayed a larger N100-like deviance response in the isochronous compared to the random timing condition. This result might imply that persons with tinnitus do not benefit similarly as persons without tinnitus from temporal predictability in deviance processing. Thus, persons with tinnitus might display less temporal sensitivity in auditory processing than persons without tinnitus.
1. Below-ground resource partitioning is often proposed as the underlying mechanism for the positive relationship between plant species richness and productivity. For example, if species have ...different root distributions, a mixture of plant species may be able to use the available resources more completely than the individual species in a monoculture. However, there is little experimental evidence for differentiation in vertical root distributions among species and its contribution to biodiversity effects. 2. We determined species-specific root standing biomass over depth using molecular techniques (real-time qPCR) in a large grassland biodiversity experiment (one to eight plant species mixtures), in 2 years. Species-specific root biomass data were used to disentangle the effects of positive interactions between species (complementarity effects) and effects due to dominance of productive species (selection effects) on root biomass in mixtures. In a next step, these biodiversity effects were linked to the diversity of rooting depths and the averaged rooting depth of the community. 3. Root biomass increased with species richness. This was mainly due to positive interactions (the complementarity effect), which increased with species richness below-ground. In contrast, the selection effect decreased with species richness. Although there was considerable variation in vertical root distribution between species in monocultures, the diversity of rooting strategies did not explain the complementarity effect. Rather, the abudance of deep-rooting species in mixtures (i.e. high community-weighted mean) was significantly related to the complementarity effect. Comparing the "predicted" root distribution (based on monocultures) to the actual distribution in mixtures, we found that mixtures rooted deeper than expected, but this did not better explain the complementarity effect. 4. Synthesis. This study demonstrates that vertical root distributions of species provide only subtle evidence for resource partitioning. W e found no evidence that functional diversity in vertical rooting patterns was important for the complementarity effect, in contrast to our expectation that the enhancement of productivity was due to resource partitioning. Alternatively, we found significant but weak relationships between the complementarity effect and deep-rooting communities, based on the communityweighted mean root distribution. This suggests that factors other than below-ground resource partitioning alone may drive the biodiversity-productivity relationship.
Glycosaminoglycans (GAGs) are linear negatively charged polysaccharides and important components of extracellular matrices and cell surface glycan layers such as the endothelial glycocalyx. The GAG ...family includes sulfated heparin, heparan sulfate (HS), dermatan sulfate (DS), chondroitin sulfate (CS), keratan sulfate, and non-sulfated hyaluronan. Because relative expression of GAGs is dependent on cell-type and niche, isolating GAGs from cell cultures and tissues may provide insight into cell- and tissue-specific GAG structure and functions. In our objective to obtain structural information about the GAGs expressed on a specialized mouse glomerular endothelial cell culture (mGEnC-1) we adapted a recently published GAG isolation protocol, based on cell lysis, proteinase K and DNase I digestion. Analysis of the GAGs contributing to the mGEnC-1 glycocalyx indicated a large HS and a minor CS content on barium acetate gel. However, isolated GAGs appeared resistant to enzymatic digestion by heparinases. We found that these GAG extracts were heavily contaminated with RNA, which co-migrated with HS in barium acetate gel electrophoresis and interfered with 1,9-dimethylmethylene blue (DMMB) assays, resulting in an overestimation of GAG yields. We hypothesized that RNA may be contaminating GAG extracts from other cell cultures and possibly tissue, and therefore investigated potential RNA contaminations in GAG extracts from two additional cell lines, human umbilical vein endothelial cells and retinal pigmental epithelial cells, and mouse kidney, liver, spleen and heart tissue. GAG extracts from all examined cell lines and tissues contained varying amounts of contaminating RNA, which interfered with GAG quantification using DMMB assays and characterization of GAGs by barium acetate gel electrophoresis. We therefore recommend routinely evaluating the RNA content of GAG extracts and propose a robust protocol for GAG isolation that includes an RNA digestion step.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Better biomarkers are needed to predict treatment outcome in non-small cell lung cancer (NSCLC) patients treated with anti-programmed death-1/programmed death-ligand 1 (PD-1/PD-L1) checkpoint ...inhibitors. PD-L1 immunohistochemistry has limited predictive value, possibly because of tumor heterogeneity of PD-L1 expression. Noninvasive PD-L1 imaging using
Zr-durvalumab might better reflect tumor PD-L1 expression.
NSCLC patients eligible for second-line immunotherapy were enrolled. Patients received 2 injections of
Zr-durvalumab: one without a preceding dose of unlabeled durvalumab (tracer dose only) and one with a preceding dose of 750 mg of durvalumab, directly before tracer injection. Up to 4 PET/CT scans were obtained after tracer injection. After imaging acquisition, patients were treated with 750 mg of durvalumab every 2 wk. Tracer biodistribution and tumor uptake were visually assessed and quantified as SUV, and both imaging acquisitions were compared. Tumor tracer uptake was correlated with PD-L1 expression and clinical outcome, defined as response to durvalumab treatment.
Thirteen patients were included, and 10 completed all scheduled PET scans. No tracer-related adverse events were observed, and all patients started durvalumab treatment. Biodistribution analysis showed
Zr-durvalumab accumulation in the blood pool, liver, and spleen. Serial imaging showed that image acquisition 120 h after injection delivered the best tumor-to-blood pool ratio. Most tumor lesions were visualized with the tracer dose only versus the coinjection imaging acquisition (25% vs. 13.5% of all lesions). Uptake heterogeneity was observed within (SUV
range, 0.2-15.1) and between patients. Tumor uptake was higher in patients with treatment response or stable disease than in patients with disease progression according to RECIST 1.1. However, this difference was not statistically significant (median SUV
, 4.9 vs. 2.4;
= 0.06). SUV
correlated better with the combined tumor and immune cell PD-L1 score than with PD-L1 expression on tumor cells, although neither was statistically significant (
= 0.06 and
= 0.93, respectively).
Zr-durvalumab was safe, without any tracer-related adverse events, and more tumor lesions were visualized using the tracer dose-only imaging acquisition.
Zr-durvalumab tumor uptake was higher in patients with a response to durvalumab treatment but did not correlate with tumor PD-L1 immunohistochemistry.
ObjectiveAlthough the role of artificial intelligence (AI) in medicine is increasingly studied, most patients do not benefit because the majority of AI models remain in the testing and prototyping ...environment. The development and implementation trajectory of clinical AI models are complex and a structured overview is missing. We therefore propose a step-by-step overview to enhance clinicians’ understanding and to promote quality of medical AI research.MethodsWe summarised key elements (such as current guidelines, challenges, regulatory documents and good practices) that are needed to develop and safely implement AI in medicine.ConclusionThis overview complements other frameworks in a way that it is accessible to stakeholders without prior AI knowledge and as such provides a step-by-step approach incorporating all the key elements and current guidelines that are essential for implementation, and can thereby help to move AI from bytes to bedside.
Summary
Advances in root ecology have revealed that root standing biomass is higher in species‐rich plant communities than in species‐poor communities. Currently, we do not know whether this ...below‐ground diversity effect is the result of enhanced root production or reduced root mortality or both, which is essential information to understand ecosystem functioning, as it determines C sequestration and N dynamics in soil.
Minirhizotron observations were combined with root coring in five different plant communities (four monocultures and the respective mixture). Molecular markers were used to quantitatively determine species abundance in mixed root biomass samples in order to track shifts in below‐ground species composition. In addition, a litterbag experiment was performed to study root decomposition independent of root mortality.
Root length production was greater and root length loss was lower in the mixture than expected from monocultures in all years. Simulations suggest that at least two species must have had reduced losses in mixture compared to monoculture. However, the diversity effects on root mortality may partially be explained by selection effects as the species with the longest root life span became dominant in the mixtures. Root length loss from minirhizotrons was very low; the combination of minirhizotron length measurements with root biomass estimates from coring suggested underestimation of root loss in minirhizotrons over time. Root decomposition was not affected by diversity.
Diversity enhanced root length production and decreased root loss, resulting in below‐ground overyielding. With decomposition unaffected, our results suggest that root mortality is reduced with increasing diversity. Future studies have to reveal the generality of our observations in larger scale biodiversity experiments by using species having a wider variety of root traits.
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