Single cell analysis is crucial for elucidating cellular diversity and heterogeneity as well as for medical diagnostics operating at the ultimate detection limit. Although superbly sensitive ...biosensors have been developed using the strongly enhanced evanescent fields provided by optical microcavities, real-time quantification of intracellular molecules remains challenging due to the extreme low quantity and limitations of the current techniques. Here, we introduce an active-mode optical microcavity sensing stage with enhanced sensitivity that operates via Förster resonant energy transferring (FRET) mechanism. The mutual effects of optical microcavity and FRET greatly enhances the sensing performance by four orders of magnitude compared to pure Whispering gallery mode (WGM) microcavity sensing system. We demonstrate distinct sensing mechanism of FRET-WGM from pure WGM. Predicted lasing wavelengths of both donor and acceptor by theoretical calculations are in perfect agreement with the experimental data. The proposed sensor enables quantitative molecular analysis at single cell resolution, and real-time monitoring of intracellular molecules over extended periods while maintaining the cell viability. By achieving high sensitivity at single cell level, our approach provides a path toward FRET-enhanced real-time quantitative analysis of intracellular molecules.
Black phosphorus (BP) has attracted much attention as a new member of 2D materials due to its unique electronic and optical properties and a wide range of promising applications. Here, for the first ...time, we report the photoluminescence lifetime of BP nanomaterial and its applications as an efficient agent for live cell imaging. With a lateral size of ∼35 nm and a thickness of ∼6 nm, the fabricated BP nanoparticles (BPNPs) exhibited a unique photoluminescent (PL) emission at ∼690 nm. The photoluminescence lifetime (PLT) of BPNPs was determined to be 110.5 ps. Coating a layer of mesoporous silica on the surface of BPNPs (BPNPs@mSiO
) extended the lifetime to 267 ps, suggesting a change in the microenvironment. The lifetime was also influenced by ionic strength and intracellular microenvironment, which implies BPNPs as valuable probes for sensing variations in the microenvironment. Live cell imaging was achieved via directly probing the photoluminescence intensity or the photoluminescence lifetime. Our findings are significant, implying that BPNPs can be of large value in sensing variations of the cellular microenvironment and in probing cells with distinct cytosolic contents. This research leads to promising prospects for BPNPs in multiple biomedical applications.
Promyelocytic leukemia nuclear bodies (PML-NBs) are mobile subnuclear organelles formed by PML and Sp100 protein. They have been reported to have a role in transcription, DNA replication and repair, ...telomere lengthening, cell cycle control and tumor suppression. We have conducted high-resolution 4Pi fluorescence laser-scanning microscopy studies complemented with correlative electron microscopy and investigations of the accessibility of the PML-NB subcompartment. During interphase PML-NBs adopt a spherical organization characterized by the assembly of PML and Sp100 proteins into patches within a 50- to 100-nm-thick shell. This spherical shell of PML and Sp100 imposes little constraint to the exchange of components between the PML-NB interior and the nucleoplasm. Post-translational SUMO modifications, telomere repeats and heterochromatin protein 1 were found to localize in characteristic patterns with respect to PML and Sp100. From our findings, we derived a model that explains how the three-dimensional organization of PML-NBs serves to concentrate different biological activities while allowing for an efficient exchange of components.
This article examines the possibilities of implementing race- and gender-separated organisational models within institutional participatory mechanisms in the light of the concept of discretion. Based ...on an investigation carried out within a participatory mechanism in a French working-class neighbourhood, the text shows how discretion allows the existence of a homogeneous public in terms of gender and race, despite the French colourblind political context marked by the valorisation of the norm of 'social mix'. The article highlights the effects of this discreet non-mixed organisation both in terms of individual empowerment processes for the participants and in terms of the acknowledgment of this group as a legitimate audience by local institutions.
Practical 4Pi microscopy has so far exclusively relied on multiphoton excitation of fluorescence, because the nonlinear suppression of contributions from higher-order sidelobes was mandatory for ...unambiguous axial superresolution. We show that novel lenses of 74 degrees semiaperture angle enable biological 4Pi microscopy with regular one-photon fluorescence excitation, thus increasing the signal and reducing system complexity and cost. An axial resolution of 95 nm, corresponding to a more than fourfold improvement over confocal microscopy, is verified in the imaging of microtubules in mammalian cells.
Vegetation of arable fields has changed significantly over the past decades as indicated by a marked decline in the abundance and diversity of arable plants. Thus, beyond the preservation of remnant ...populations, introduction of autochthonous seeds is a necessary measure to promote threatened arable plants and to restore agro-ecosystems. However, there is a lack of knowledge on the most suitable agricultural methods for plant establishment. This topic was investigated for three winter annuals (Legousia speculum-veneris, Consolida regalis, Lithospermum arvense) in a three-year field experiment in southern Germany. We established 14 management treatments with five replicates in a completely randomized block design. In year 1, arable plants were sown in a mixture of 850 seeds m−2 either without crop or with cereal crops in different sowing densities (25 %, 100 %). After crop harvest different types of soil tillage were applied (rotary cultivator, mouldboard plough). In year 2, four different crop types (autumn-sown spelt, spring-sown triticale, pea, clover-grass) were sown, and in year 3, rye was cultivated. Establishment was measured yearly as seed production of the rare arable plants, and their overall population growth rates were calculated at the end of the study period. Highest population growth rates were observed in L. speculum-veneris, followed by C. regalis and L. arvense. Population growth of the target plants decreased significantly with crop and weed cover averaged over the study period. Initial crop sowing densities had a significant impact on first-year establishment, with persisting effects in years 2 and 3. Best results were obtained without cover crop compared to cereals sown with 25 or 100 % sowing density. The establishment of target plants was also affected by crop type in year 2 (spelt > pea > spring triticale > clover-grass). However, establishment was overall high in year 3, when all plots were cultivated with rye. Type of soil tillage had no effect within the crop rotation ‘rye–clover-grass–rye’, while rotary cultivation in ‘without crop–rye–rye’ was positive for the establishment of L. speculum-veneris and L. arvense. The results indicate good opportunities for the reintroduction of rare arable plants under different crop rotations with best results for extensively managed fields with low crop competition.
•Greenhouse and reciprocal transplant experiments with rare arable plant species.•Low population differentiation in phenology and biomass production.•No evidence for local adaptation but high ...phenotypic variability.•Species-specific responses to drought stress with minor provenance effects.•Results confirm current seed zones for seed transfer in the study region.
A better understanding of regional differentiation and local adaptation of rare arable plants is essential for the development of suitable methods for the reintroduction of these species. We set up F1 and F2 greenhouse experiments with 4–12 source populations of five rare arable plant species to test for genetically based differentiation in biomass production and phenology in South Germany. For three species, i.e. Arnoseris minima, Consolida regalis and Teesdalia nudicaulis, reciprocal transplant experiments were performed in arable fields to investigate local adaptation in plant establishment as well as biomass production to the northern or southern regions of three seed transfer zones. We found low regional differentiation, but provenance-specific responses to drought stress in Legousia speculum-veneris biomass and A. minima phenology. Moreover, little evidence was identified for local adaptation, while significant differences were seen in the performance between the transplant sites and study years, indicating a high phenotypic variability. Our results suggest that the current seed zones are suitable for the seed transfer of rare arable plants in the study region. Thus, there is a low risk of maladaptation when using autochthonous seed sources within the seed zones, but a high extinction risk of these species and their respective ecosystem functions if no active restoration is done, including transplant measures.
Competition is ubiquitous in plant communities with various effects on plant fitness and community structure. A long‐standing debate about different approaches to explain competition is the ...controversy between David Tilman and Philip Grime. Grime stated that the importance of competition relative to the impact of the environment increases along a productivity gradient, while Tilman argued that the intensity of competition is independent of productivity. To revisit this controversy, we assumed that the effects of plant–plant interactions are additive and applied the new competition indices by Díaz‐Sierra et al. (2017) in a field experiment along a productivity gradient in S‐Germany, using the rare arable plant Arnoseris minima as a study species. The ‘target technique' was applied, to separate the effects of root and shoot competition. The study plants were exposed to five competition treatments with three replicates in 18 sites, respectively. We investigated the expectation that root competition is more intense in unproductive sites than shoot competition. Additionally, we predicted survival to be less affected by competition than growth‐related plant parameters. Using the biomass of individuals without competition as a proxy for site productivity there was a positive relationship with competition importance but no relationship with competition intensity when plants experienced full competition. Survival of the target plants was unaffected by competition. Root competition was the main mechanism determining the performance of the target plants, whereas the effect of shoot competition was relatively low albeit increasing with productivity. We conclude that when considering plant–plant interactions additive both Grime's and Tilman's theories can be supported.
Diversity of arable plants in Europe has markedly declined during the past decades and many species have become threatened. Low‐intensity farming can offer potential retreats for these species, while ...spontaneous dispersal between such fields is unlikely. Thus, reintroduction of endangered species is necessary to restore agrobiodiversity. To test the applicability under real farm conditions, we seeded a mixture of three winter annuals (Legousia speculum‐veneris, Consolida regalis, Lithospermum arvense) at 850 seeds/m2 on four organic farms near Munich, Germany, in autumn 2011. Seed production and soil seed banks were investigated on four plots within one field on each farm for 3 years. In addition, we evaluated seed dispersal caused by arable management along the main machining direction. In the first year, winter cereals were cultivated and the study species emerged at all sites with a seed production mostly exceeding the initial sowing rates. In the third year, species establishment varied depending on crop rotations. Seed production of L. speculum‐veneris was higher than in the two other species, and exceeded the number of originally sown seeds up to 20 times. While L. speculum‐veneris became very common in the seed bank, C. regalis was less abundant and L. arvense hardly developed a soil seed bank. Seeds of L. speculum‐veneris and L. arvense were found up to 15 m and seeds of C. regalis up to 13 m away from the sown plots. We suggest using seed production, seed bank, and dispersal as key indicators to evaluate establishment of reintroduced arable plants.
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